Biology Vocabulary

Front 1

Organism's modification in structure, function, or behavior suitable to the environment

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adaptation

Front 2

Multicellular, heterotrophic organism belonging to the kingdom Animalia

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animal

Front 3

Scientific name of an organism, the first part of which designates the genus and the second part of which designates the specific epithet

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binomial nomenclature

Front 4

Total number of species, the variability of their genes, and the communities in which they live.

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biodiversity

Front 5

Scientific study of life

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biology

Front 6

Zone of air, land, and water at the surface of the Earth in which living organisms are found

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biosphere

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Smallest unit that displays the properties of life; composed of cytoplasm surrounded by a plasma membrane

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cell

Front 8

One of the categories, or taxa, used by taxonomists to group species; class is the taxon above the order level

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class

Front 9

Assemblage of populations interacting with one another within the same environment

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community

Front 10

Statement made following an experiment as to whether or not the results support the hypothesis

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conclusion

Front 11

Sample that goes through all the steps of an experiment but does not contain the variable being tested; a standard against which the results of an experiment are checked

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control

Front 12

Facts or information collected through observation and / or experimentation

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data

Front 13

Process of logic and reasoning, using "if…then" statements

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deductive reasoning

Front 14

Largest of the categories, or taxa, used by taxonomists to group species; the three domains are Archaeia, Bacteria, and Eukarya

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domain

Front 15

One of the three domains of life; contains prokaryotic cells that often live in extreme habitats and have unique genetic, biochemical, and physiological characteristics; its members are sometimes referred to as archaea

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domain Archaea

Front 16

One of the three domains of life; contains prokaryotic cells that differ from archaea because they have their own unique genetic, biochemical, and physiological characteristics

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domain Bacteria

Front 17

One of the three domains of life, consisting of organisms with eukaryotic cells and further classified into the kingdoms Protista, Fungi, Plantae, and Animalia

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domain Eukarya

Front 18

Biological community together with the associated abiotic environment; characterized by a flow of energy and a cycling of inorganic nutrients

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ecosystem

Front 19

Quality that appears as biological complexity increases

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emergent property

Front 20

Capacity to do work and bring about change; occurs in a variety of forms

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energy

Front 21

Descent of organisms from common ancestors with the development of genetic and phenotypic changes over time that make them more suited to the environment

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evolution

Front 22

Artificial situation devised to test a hypothesis

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experiment

Front 23

Methodology by which an experiment will seek to support the hypothesis

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experimental design

Front 24

Factor of the experiment being tested

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experimental variable

Front 25

Total disappearance of a species or higher group

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extinction

Front 26

One of the categories, or taxa, used by taxonomists to group species; the taxon above the genus level

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family

Front 27

Saprotrophic decomposer; the body is made up of filaments called hyphae that form a mass called a mycelium

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fungus

Front 28

Unit of heredity existing as alleles on the chromosomes; in diploid organisms, typically two alleles are inherited - one from each parent

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gene

Front 29

One of the categories, or taxa, used by taxonomists to group species; contains those species that are most closely related through evolution

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genus

Front 30

Maintenance of normal internal conditions in a cell or an organism by means of self-regulating mechanism

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homeostasis

Front 31

Supposition established by reasoning after consideration of available evidence; it can be tested by obtaining more data, often by experimentation

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hypothesis

Front 32

Using specific observations and the process of logic and reasoning to arrive at a hypothesis

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inductive reasoning

Front 33

One of the categories, or taxa, used by taxonomists to group species; the taxon above the phylum

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kindgom

Front 34

See principle; Theory that is generally accepted by an overwhelming number of scientists;

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law

Front 35

All of the chemical reactions that occur in a cell during growth and repair

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metabolism

Front 36

Simulation of a process that aids conceptual understanding until the process can be studied firsthand; a hypothesis that describes how a particular process could possibly be carried out

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model

Front 37

Organism composed of many cells; usually has organized tissues, organs, and organ systems

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multicellular

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Mechanism of evolution caused by environmental selection of organisms most fit to reproduce; results in adaptation to the environment

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natural selection

Front 39

Step in the scientific method by which data are collected before a conslusion is drawn

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observation

Front 40

One of the categories, or taxa, used by taxonomists to group species; the taxon above the family level

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order

Front 41

Individual living thing

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organism

Front 42

Observable event

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phenomenon

Front 43

Process occurring usually within chloroplasts whereby chlorophyll-containing organelles trap solar energy to reduce carbon dioxide to carbohydrate

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photosynthesis

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One of the categories, or taxa, used by taxonomists to group species; the taxon above the class level

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phylum

Front 45

Multicellular, usually photosynthetic, organism belonging to the plant kingdom

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plant

Front 46

Group of organisms of the same species occupying a certain area and sharing a common gene pool

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population

Front 47

Step of the scientific process that follows the formulation of a hypothesis and assists in creating the experimental design

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prediction

Front 48

See law; Theory that is generally accepted by an overwhelming number of scientists;

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principle

Front 49

Member of the kingdom Protista

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protist

Front 50

To produce a new individual of the same kind

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reproduce

Front 51

Result or change that occurs when an experimental variable is utilized in an experiment

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responding variable

Front 52

Process by which scientists formulate a hypothesis, gather data by observation and experimentation, and come to a conclusion

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scientific process

Front 53

Concept supported by a broad range of observations, experiments, and data

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scientific theory

Front 54

Group of similarly constructed organisms capable of interbreeding and producing fertile offspring; organisms that share a common gene pool; the taxon at the lowest level of classification

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species

Front 55

Branch of biology concerned with identifying, describing, and naming organisms

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taxonomy

Front 56

Made up of but a single cell, as in the bacteria

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unicellular

Front 57

Molecules tending to raise the hydrogen ion concentration in a solution and to lower its pH numerically

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acid

Front 58

Smallest particle of an element that displays the properties of the element

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atom

Front 59

Mass of an atom equal to the number of protons plus the number of neutrons within the nucleus

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atomic mass

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Number of protons within the nucleus of an atom

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atomic number

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One or two letters that represent the name of an element -- e.g., H stands for a hydrogen atom, and Na stands for a sodium atom

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atomic symbol

Front 62

Molecules tending to lower the hydrogen ion concentration in a solution and raise the pH numerically

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base

Front 63

Substance or group of substances that tend to resist pH changes of a solution, thus stabilizing its relative acidity and basicity

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buffer

Front 64

amount of heat energy required to raise the temperature of one gram of water 1 degree Celsius

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calorie

Front 65

The product of atoms from two or more different elements bound together

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compound

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Chemical bond in which atoms share one pair of electrons

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covalent bond

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Negative subatomic particle, moving about in an energy level around the nucleus of an atom

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electron

Front 68

The ability of an atom to attract elecrons toward itself in a chemical bond

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electronegativity

Front 69

Concentric energy levels in which electrons orbit

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electron shell

Front 70

Substance that cannot be broken down into substances with different properties; composed of only one type of atom

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element

Front 71

Weak bond that arises between a slightly positive hydrogen atom of one molecule and a slightly negative atom of another molecule or between parts of the same molecule

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hydrogen bond

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Hydrogen atom that has lost its electron and therefore bears a positive charge

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hydrogen ion (H+)

Front 73

Type of molecule that interacts with water by dissolving in water and / or by forming hydrogen bonds with water molecules

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hydrophilic

Front 74

Type of molecule that does not interact with water because it is nonpolar

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hydrophobic

Front 75

One of the wtwo ions that results when a water molecule dissociates; it has gained an electron and therefore bears a negative charge

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hydroxide ion (OH-)

Front 76

Charged particle that carries a negative or positive charge

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ion

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chemical bond in which ions are attracted to one another by opposite charges

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ionic bond

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Atom of the same element having the same atomic number but a different mass number due to the number of neutrons

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isotope

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Anything that takes up space and has mass

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matter

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Union of two or more atoms of the same element; also, the smallest part of a compound that retains the properties of the compound

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molecule

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Neutral subatomic particle, located in the nucleus and assigned one atomic mass unit

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neutron

Front 82

Bond in which the sharing of electrons between atoms is fairly equal

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nonpolar covalent bond

Front 83

States that an atom other than hydrogen tends to form bonds until it has eight electrons in its outer shell; an atom that already has eight electrons in its outer shell does not react and is inert

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octet rule

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volume of space around a nucleus where elecrons can be found most of the time

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orbital

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Measurement scale for hydrogen ion concentration

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pH scale

Front 86

Bond in which the sharing of electrons between atoms is unequal

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polar covalent bond

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Positive subatomic particle located in the nucleus and assigned one atomic mass unit

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proton

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Ionic compound that results from a classical acid-base reaction

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salt

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Substance that is dissolved in a solvent, forming a solution

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solute

Front 90

Fluid (the solvent) that contains a dissolved solid (the solute)

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solution

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Substance having an attached radioactive isotope that allows a researcher to track its whereabouts in a biological system

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tracer

Front 92

Portion of ATP and ADP that is composed of the base adenine and the sugar ribose

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adenosine

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Nucleotide with two phosphate groups that can accept another phosphate group and become ATP

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ADP (adenosine diphosphate)

Front 94

Organic molecule composed of an amino group and an acid group; covalently bonds to produce peptide molecules

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amino acid

Front 95

Complex formed of enzymes and their carrier proteins; functions in the production of ATP in chloroplasts and mitochondria

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ATP (adenosine triphosphate)

Front 96

Class of organic compounds that includes monosaccharides, disaccharides, and polysaccharides

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carbohydrate

Front 97

Polysaccharide that is the major complex carbohydrate in plant cell walls

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cellulose

Front 98

Molecule that binds to a protein during synthesis and keeps it from making incorrect interactions

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chaperone protein

Front 99

Strong but flexible nitrogenous polysaccharide found in the exoskeleton of arthropods

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chitin

Front 100

Nonprotein organic molecule that aids the action of the enzyme to which it is loosely bound

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coenzyme

Front 101

Hydrogen bonding between particular purines and pyrimidines in DNA

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complementary base pairing

Front 102

Chemical reaction resulting in a covalent bond with the accompanying loss of a water molecule

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dehydration reaction

Front 103

Loss of an enzyme's normal shape so that it no longer functions; caused by a less than optimal pH and temperature

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denatured

Front 104

Pentose sugar found in DNA

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deoxyribose

Front 105

Sugar that contains two units of a monosaccharide; e.g., maltose

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disaccharide

Front 106

Nucleic acid polymer produced from covalent bonding of nucleotide monomers that contain the sugar deoxyribose; the genetic material of nearly all organisms

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DNA (deoxyribonucleic acid)

Front 107

Organic catalyst, usually a protein, that speeds a reaction in cells due to its particular shape

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enzyme

Front 108

Organic molecule that contains glycerol and fatty acids and is found in adipose tissue of vertebrates

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fat

Front 109

Molecule that contains a hydrocarbon chain and ends with an acid group

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fatty acid

Front 110

Principle structural proteins of the body; generally insoluble; include collagens, elastins, keratins, and actin and myosin

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fibrous protein

Front 111

Specific cluster of atoms attached to the carbon skeleton of organic molecules that enters into reactions and behaves in a predictable way.

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functional group

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Most of the proteins in the body; soluble in water or salt solution; includes albumins, globulins, histones

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globular protein

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Six-carbon sugar that organisms degrade as a source of energy during cellular respiration

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glucose

Front 114

Three-carbon carbohydrate with three hydroxyl groups attached; a component of fats and oils

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glycerol

Front 115

Storage polysaccharide found in animals; composed of glucose molecules joined in a linear fashion but having numerous branches

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glycogen

Front 116

Iron-containing respiratory pigment occurring in vertebrate red blood cells and in the blood plasma of some invertebrates

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hemoglobin

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Six-carbon sugar

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hexose

Front 118

Splitting of a compound by the addition of water, with the H^+ being incorporated in one fragment and the OH^- in the other

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hydrolysis reaction

Front 119

Type of molecule that interacts with water by dissolving in water and / or by forming hydrogen bonds with water molecules

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hydrophilic

Front 120

Type of molecule that does not interact with water because it is nonpolar

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hydrophobic

Front 121

Branch of science which deals with compounds that do not occur in the plant or animal worlds

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inorganic chemistry

Front 122

Molecules with the same molecular formula but a different structure, and therefore a different shape

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isomer

Front 123

Class of organic compounds that tends to be soluble in nonpolar solvents; includes fats and oils

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lipid

Front 124

Small molecule that is a subunit of a polymer -- e.g., glucose is a monomer of starch

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monomer

Front 125

Simple sugar; a carbohydrate that cannot be decomposed by hydrolysis -- e.g., glucose

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monosaccharide

Front 126

Polymer of nucleotides; both DNA and RNA are nucleic acids

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nucleic acid

Front 127

Monomer of DNA and RNA consisting of a 5-carbon sugar bonded to a nitrogenous base and a phosphate group

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nucleotide

Front 128

Triglyceride, usually of plant origin, that is composed of glycerol and three fatty acids and is liquid in consistency due to many unsaturated bonds in the hydrocarbon chains of the fatty acids

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oil

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Branch of science which deals with compounds that contain carbon

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organic chemistry

Front 130

Molecule that always contains carbon and hydrogen, and often contains oxygen as well; organic molecules are associated with living things

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organic molecule

Front 131

Five-carbon sugar. Deoxyribose is the pentose sugar found in DNA; ribose is the pentose sugar found in RNA

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pentose

Front 132

Two or more amino acids joined together by covalent bonding

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peptide

Front 133

Type of covalent bond that joins two amino acids

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peptide bond

Front 134

Unique molecule found in bacterial cells walls

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peptidoglycan

Front 135

Molecule that forms the bilayer of the cell's membranes; has a polar, hydrophilic head bonded to two nonpolar, hydrophobic tails

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phospholipid

Front 136

Macromolecule consisting of covalently bonded monomers; for example, a polypeptide is a polymer of monomers called amino acids

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polymer

Front 137

Polymer of many amino acids linked by peptide bonds

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polypeptide

Front 138

Polymer made from sugar monomers; the polysaccharides starch and glycogen are polymers of glucose monomers

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polysaccharide

Front 139

Infectious particle consisting of protein only and no nucleic acid

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prion

Front 140

Molecule consisting of one or more polypeptides

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protein

Front 141

Pentose sugar found in RNA

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ribose

Front 142

Nucleic acid produced from covalent bonding of nucleotide monomers that contain the sugar ribose; occurs in three forms: messenger RNA, ribosomal RNA, and transfer RNA

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RNA (ribonucleic acid)

Front 143

Fatty acid molecule that lacks double bonds between the carbons of its hydrocarbon chain. The chain bears the maximum number of hydrogens possible

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saturated fatty acid

Front 144

Storage polysaccharide found in plants that is composed of glucose molecules joined in a linear fashion with few side chains

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starch

Front 145

Type of lipid molecule having a complex of four carbon rings -- e.g., cholesterol, estrogen, progesterone, and testosterone

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steroid

Front 146

Neutral fat composed of glycerol and three fatty acids

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triglyceride

Front 147

Fatty acid molecule that has one or more double bonds between the carbons of its hydrocarbon chain. The chain bears fewer hydrogens than the maximum number possible

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unsaturated fatty acid

Front 148

Sticky, solid, waterproof lipid consisting of many long-chain fatty acids usually linked to long-chain alcohols

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wax

Front 149

Muscle protein filament in a sarcomere; its movement shortens the sarcomere, yielding muscle contraction. Actin filaments play a role in the movement of the cell and its organelles

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actin filament

Front 150

Programmed cell death involving a cascade of specific cellular events leading to death and destruction of the cell

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apoptosis

Front 151

A rod-shaped bacterium

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bacillus

Front 152

A cytoplasmic structure that is located at the base of - and may organize - cilia or flagella

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basal body

Front 153

Gelatinous layer surrounding the cells of blue-green algae and certain bacteria

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capsule

Front 154

Smallest unit that displays the properties of life; composed of cytoplasm surrounded by a plasma membrane

Back 154

cell

Front 155

In a prokaryotic cell, the portion composed of the plasma membrane, the cell wall, and the glycocalyx

Back 155

cell envelope (of prokaryotes)

Front 156

One of the major theories of biology, which states that all organisms are made up of cells; cells are capable of self-reproduction and come only from preexisting cells.

Back 156

cell theory

Front 157

Structure that surrounds a plant, protistan, fungal, or bacterial cell and maintains the cell's shape and rigidity.

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cell wall

Front 158

In a plant cell, a large, fluid-filled sac that stores metabolites. During growth, it enlarges, forcing the primary cell wall to expand and the cell surface-area-to-volume ratio to increase.

Back 158

central vacuole (of plant cell)

Front 159

Cell organelle, existing in pairs, that occurs in the centrosome and may help organize a mitotic spindle for chromosome movement during animal cell division.

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centriole

Front 160

Central microtubule organizing center of cells. In animal cells, it contains two centrioles.

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centrosome

Front 161

Membrane-bounded organelle in algae and plants with chlorophyll-containing membranous thylakoids; where photosynthesis takes place.

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chloroplast

Front 162

network of fibrils consisting of DNA and associated proteins observed within a nucleus that is not dividing.

Back 162

chromatin

Front 163

Organelles that contain pigments that result in a yellow, orange, or red color. C___________ are responsible for the color of autumn leaves, fruits, carrots, and some flowers.

Back 163

chromoplast

Front 164

Coiled, rodlike structures of condensed chromatin.

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chromosome

Front 165

Short, hairlike projection from the plasma membrane, occurring usually in larger numbers (cilia)

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cilium

Front 166

A spherical-shaped bacterium

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coccus

Front 167

Short, fingerlike projections formed by the folding of the inner membrane of mitochondria

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cristae

Front 168

Photosynthetic bacteria that contain chlorophyll and release oxygen; formerly called blue-green algae.

Back 168

cyanobacteria

Front 169

Contents of a cell between the nucleus (nucleoid region of bacteria) and the plasma membrane

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cytoplasm

Front 170

Internal framework of the cell, consisting of microtubules, actin filaments, and intermediate filaments

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cytoskeleton

Front 171

Cellular system that consists of the nuclear envelope, endoplasmic reticulum, Golgi apparatus, and vesicles.

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endomembrane system

Front 172

System of membranous saccules and channels in the cytoplasm, often with attached ribosomes.

Back 172

endoplasmic reticulum (ER)

Front 173

Type of cell that has a membrane-bounded nucleus and membranous organelles; found in organisms within the domain Eukarya.

Back 173

eukaryotic cell

Front 174

Small, bristlelike fiber on the surface of a bacterial cell, which attaches bacteria to a surface; also fingerlike extension from the oviduct near the ovary.

Back 174

fimbriae

Front 175

Long, slender extension used for locomotion by some bacteria, protozoans, and sperm.

Back 175

flagellum (pl., flagella)

Front 176

Gel-like coating outside the cell wall of a bacterium. If compact, it is called a capsule; if diffuse, it is called a slime layer.

Back 176

glycocalyx

Front 177

Organelle consisting of saccules and vesicles that processes, packages, and distributes molecules about or from the cell.

Back 177

Golgi apparatus

Front 178

Stack of chlorophyll-containing thylakoids in a chloroplast.

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granum

Front 179

In a bacterium, stored nutrients for later use.

Back 179

inclusion body

Front 180

Ropelike assemblies of fibrous polypeptides in the cytoskeleton that provide support and strength to cells; so called because they are intermediate in size between actin filaments and microtubules.

Back 180

intermediate filament

Front 181

Plastid, generally colorless, that synthesizes and stores starch and oils.

Back 181

leucoplast

Front 182

Membrane-bounded vesicle that contains hydrolytic enzymes for digesting macromolecules

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lysosome

Front 183

Unstructured semifluid substance that fills the space between cells in connective tissues or inside organelles.

Back 183

matrix

Front 184

In a bacterium, plasma membrane that folds into the cytoplasm and increases surface area.

Back 184

mesosome

Front 185

Small cylindrical organelle composed of tubulin protein around an empty central core; present in the cytoplasm, centrioles, cilia, and flagella.

Back 185

microtubule

Front 186

Membrane-bounded organelle in which ATP molecules are produced during the process of cellular respiration.

Back 186

mitochondrion

Front 187

Protein that moves along either actin filaments or microtubules and translocates organelles.

Back 187

motor molecule

Front 188

Double membrane that surrounds the nucleus in eukaryotic cells and is connected to the endoplasmic reticulum; has pores that allow substances to pass between the nucleus and the cytoplasm.

Back 188

nuclear envelope

Front 189

Opening in the nuclear envelope that permits the passage of proteins into the nucleus and ribosomal subunits out of the nucleus.

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nuclear pore

Front 190

Region of prokaryotic cells where DNA is located; it is not bounded by a nuclear envelope.

Back 190

nucleoid

Front 191

Dark-staining, spherical body in the nucleus that produces ribosomal subunits.

Back 191

nucleolus

Front 192

Semifluid medium of the nucleus containing chromatin

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nucleoplasm

Front 193

Membrane-bounded organelle within a eukaryotic cell that contains chromosomes and controls the structure and function of the cell.

Back 193

nucleus

Front 194

Small, often membranous structure in the cytoplasm having a specific structure and function.

Back 194

organelle

Front 195

Enzyme-filled vesicle in which fatty acids and amino acids are metabolized to hydrogen peroxide that is broken down to harmless products.

Back 195

peroxisome

Front 196

Membrane surrounding the cytoplasm that consists of a phospholipid bilayer with embedded proteins; functions to regulate the entrance and exit of molecules from cell.

Back 196

plasma membrane

Front 197

Self-duplicating ring of accessory DNA in the cytoplasm of bacteria.

Back 197

plasmid

Front 198

Organelles of plants and algae that are bounded by a double membrane and contain internal membranes and/or vesicles (i.e., chloroplasts, chromoplasts, leucoplasts).

Back 198

plastid

Front 199

String of ribosomes simultaneously translating regions of the same mRNA strand during protein synthesis.

Back 199

polyribosome

Front 200

Lacking a membrane-bounded nucleus and organelles; the cell type within the domains Bacteria and Archaea.

Back 200

prokaryotic cell

Front 201

Cytoplasmic extension of amoeboid protists; used for locomotion and engulfing food.

Back 201

pseudopod

Front 202

RNA and protein in two subunits; site of protein synthesis in the cytoplasm.

Back 202

ribosome

Front 203

Membranous system of tubules, vesicles, and sacs in cells; has attached ribosomes.

Back 203

rough ER

Front 204

Release of a substance by exocytosis from a cell that may be a gland or part of a gland.

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secretion

Front 205

In a bacterium, elongated, hollow appendage used to transfer DNA to other cells.

Back 205

sex pili

Front 206

Membranous system of tubules, vesicles, and sacs in eukaryotic cells; lacks attached ribosomes.

Back 206

smooth ER

Front 207

Long, rod-shaped bacterium that is twisted into a rigid spiral; if the spiral is flexible rather than rigid, it is called a spirochete.

Back 207

spirillum

Front 208

Long, rod-shaped bacterium that is twisted into a flexible spiral; if the spiral is rigid rather than flexible, it is called a spirillum.

Back 208

spirochete

Front 209

Fluid within a chloroplast that contains enzymes involved in the synthesis of carbohydrates during photosynthesis.

Back 209

stroma

Front 210

Ratio of a cell's outside area to its internal volume.

Back 210

surface - area - to - volume ratio

Front 211

Flattened sac within a granum whose membrane contains chlorophyll and where the light reactions of photosynthesis occur.

Back 211

thylakoid

Front 212

Membrane-bounded sac, larger than a vesicle; usually functions in storage and can contain a variety of substances. In plants, the central vacuole fills much of the interior of the cell.

Back 212

vacuole

Front 213

Small, membrane-bounded sac that stores substances within a cell.

Back 213

vesicle

Front 214

Use of a plasma membrane carrier protein to move a molecule or ion from a region of lower concentration to one of higher concentration; it opposes equilibrium and requires energy.

Back 214

active transport

Front 215

Junction between cells in which the adjacent plasma membranes do not touch but are held together by intercellular filaments attached to buttonlike thickenings.

Back 215

adhesion junction

Front 216

Junctions that mechanically attach adjoining cells (e.g., adhesion, tight, and gap junctions).

Back 216

anchoring junction

Front 217

Protein that combines with and transports a molecule or ion across the plasma membrane.

Back 217

carrier protein

Front 218

Glycoprotein that helps the body defend itself against pathogens.

Back 218

cell recognition protein

Front 219

Structure that surrounds a plant, protistan, fungal, or bacterial cell and maintains the cell's shape and rigidity.

Back 219

cell wall

Front 220

Protein that forms a channel to allow a particular molecule or ion to cross the plasma membrane.

Back 220

channel protein

Front 221

One of the major lipids found in animal plasma membranes; makes the membrane impermeable to many molecules.

Back 221

cholesterol

Front 222

Gradual change in chemical concentration from one point to another.

Back 222

concentration gradient

Front 223

In animal cells, shriveling of the cell due to water leaving the cell when the environment is hypertonic.

Back 223

crenation

Front 224

Intercellular junction that connects cytoskeletons of adjacent cells.

Back 224

desmosome

Front 225

Ability of plasma membranes to regulate the passage of substances into and out of the cell, allowing some to pass through and preventing the passage of others.

Back 225

differentially permeable

Front 226

Movement of molecules or ions from a region of higher to lower concentration; it requires no energy and tends to lead to an equal distribution.

Back 226

diffusion

Front 227

Process by which substances are moved into the cell from the environment by phagocytosis (cellular eating) or pinocytosis (cellular drinking); includes receptor-mediated endocytosis.

Back 227

endocytosis

Front 228

Protein that catalyzes a specific reaction.

Back 228

enzymatic protein

Front 229

Process in which an intracellular vesicle fuses with the plasma membrane so that the vesicle's contents are released outside the cell.

Back 229

exocytosis

Front 230

Passive transfer of a substance into or out of a cell along a concentration gradient by a process that requires a carrier.

Back 230

facilitated transport

Front 231

Model for the plasma membrane based on the changing location and pattern of protein molecules in a fluid phospholipid bilayer.

Back 231

fluid-mosaic model

Front 232

Junction between cells formed by the joining of two adjacent plasma membranes; it lends strength and allows ions, sugars, and small molecules to pass between cells.

Back 232

gap junction

Front 233

Lipid in plasma membranes that bears a carbohydrate chain attached to a hydrophobic tail.

Back 233

glycolipid

Front 234

Protein in plasma membranes that bears a carbohydrate chain.

Back 234

glycoprotein

Front 235

Higher solute concentration (less water) than the cytoplasm of a cell; causes cell to lose water by osmosis.

Back 235

hypertonic solution

Front 236

Lower solute (more water) concentration than the cytoplasm of a cell; causes cell to gain water by osmosis.

Back 236

hypotonic solution

Front 237

Solution that is equal in solute concentration to that of the cytoplasm of a cell; causes cell to neither lose nor gain water by osmosis.

Back 237

isotonic solution

Front 238

Diffusion of water through a differentially permeable membrane

Back 238

osmosis

Front 239

Measure of the tendency of water to move across a differentially permeable membrane; visible as an increase in liquid on the side of the membrane with higher solute concentration.

Back 239

osmotic pressure

Front 240

Process by which amoeboid-type cells engulf large substances, forming an intracellular vacuole.

Back 240

phagocytosis

Front 241

Comprises the plasma membrane; each polar, hydrophilic head is bonded to two nonpolar, hydrophobic tails; contains embedded proteins.

Back 241

phospholipid bilayer

Front 242

Process by which vesicle formation brings macromolecules into the cell.

Back 242

pinocytosis

Front 243

In plants, cytoplasmic strands that extend through pores in the cell wall and connect the cytoplasm of two adjacent cells.

Back 243

plasmodesmata

Front 244

Contraction of the cell contents due to the loss of water.

Back 244

plasmolysis

Front 245

Selective uptake of molecules into a cell by vacuole formation after they bind to specific receptor proteins in the plasma membrane.

Back 245

receptor-mediated endocytosis

Front 246

Protein located in the plasma membrane or within the cell; binds to a substance that alters some metabolic aspect of the cell.

Back 246

receptor protein

Front 247

Carrier protein in the plasma membrane that moves sodium ions out of and potassium ions into animal cells; important in nerve and muscle cells.

Back 247

sodium-potassium pump

Front 248

Substance that is dissolved in a solvent, forming a solution.

Back 248

solute

Front 249

Fluid (the solvent) that contains a dissolved solid (the solute).

Back 249

solution

Front 250

Liquid portion of a solution that serves to dissolve a solute.

Back 250

solvent

Front 251

Junction between cells when adjacent plasma membrane proteins join to form an impermeable barrier.

Back 251

tight junction

Front 252

Osmolarity of a solution compared to that of a cell. If the solution is isotonic to the cell, there is no net movement of water; if the solution is hypotonic, the cell gains water; and if the solution is hypertonic, the cell loses water.

Back 252

tonicity

Front 253

Pressure of the cell contents against the cell wall; in plant cells, determined by the water content of the vacuole and provides internal support.

Back 253

turgor pressure

Front 254

Region on the surface of an enzyme where the substrate binds and where the reaction occurs.

Back 254

active site

Front 255

Nucleotide with two phosphate groups that can accept another phosphate group and become ATP.

Back 255

ADP (adenosine diphosphate)

Front 256

Nucleotide with three phosphate groups. The breakdown of ATP into ADP + P makes energy available for energy-requiring processes in cells.

Back 256

ATP (adenosine triphosphate)

Front 257

In ATP production, enzymes and their carrier proteins that span the membrane with a channel that allows hydrogen ions to flow down their electrochemical gradient. The flow of hydrogen ions through the channel provides the energy for the ATP synthase enzyme to produce ATP from ADP + P.

Back 257

ATP synthase complex

Front 258

energy associated with the interaction of atoms in a molecule.

Back 258

chemical energy

Front 259

The production of ATP due to a hydrogen ion gradient across a membrane is called chemiosmosis. Ability of certain membranes to use a hydrogen ion gradient to drive ATP formation.

Back 259

chemiosmosis

Front 260

Nonprotein organic molecule that aids the action of the enzyme to which it is loosely bound.

Back 260

coenzyme

Front 261

Nonprotein adjunct required by an enzyme in order to function; many cofactors are metal ions, others are coenzymes.

Back 261

cofactor

Front 262

Form of enzyme inhibition where the substrate and inhibitor are both able to bind to the enzyme's active site; each complexes with the enzyme. Only when the substrate is at the active site will product form.

Back 262

competitive inhibition

Front 263

Reactions that occur simultaneously; one is an exergonic reaction that releases energy, and the other is an endergonic reaction that requires an input of energy in order to occur.

Back 263

coupled reactions

Front 264

Loss of an enzyme's normal shape so that it no longer functions; caused by a less than optimal pH and temperature.

Back 264

denatured

Front 265

Passage of electrons along a series of membrane-bound electron carrier molecules from a higher to lower energy level; the energy released is used for the synthesis of ATP.

Back 265

electron transport chain

Front 266

Chemical reaction that requires an input of energy; opposite of exergonic reaction.

Back 266

endergonic reaction

Front 267

Capacity to do work and bring about change; occurs in a variety of forms.

Back 267

energy

Front 268

energy that must be added in order for molecules to react with one another.

Back 268

energy of activation

Front 269

Measure of disorder or randomness.

Back 269

entropy

Front 270

Organic catalyst, usually a protein, that speeds a reaction in cells due to its particular shape.

Back 270

enzyme

Front 271

Means by which cells regulate enzyme activity; may be competitive or noncompetitive inhibition.

Back 271

enzyme inhibition

Front 272

Chemical reaction that releases energy; opposite of endergonic reaction.

Back 272

exergonic reaction

Front 273

Mechanism for regulating metabolic pathways in which the concentration of the product is kept within a certain range until binding at an allosteric site shuts down the pathway, and no more product is produced.

Back 273

feedback inhibition

Front 274

Useful energy in a system that is capable of performing work.

Back 274

free energy

Front 275

Type of kinetic energy; captured solar energy eventually dissipates as heat in the environment.

Back 275

heat

Front 276

Change in the shape of an enzyme's active site that enhances the fit between the active site and its substrate(s).

Back 276

induced fit model

Front 277

Energy associated with motion.

Back 277

kinetic energy

Front 278

Two laws explaining energy and its relationships and exchanges. The first, also called the "law of conservation," says that energy cannot be created or destroyed but can only be changed from one form to another; the second says that energy cannot be changed from one form to another without a loss of usable energy.

Back 278

laws of thermodynamics

Front 279

A type of kinetic energy, such as walking or running.

Back 279

mechanical energy

Front 280

Series of linked reactions, beginning with a particular reactant and terminating with an end product.

Back 280

metabolic pathway

Front 281

All of the chemical reactions that occur in a cell during growth and repair.

Back 281

metabolism

Front 282

Coenzyme of oxidation-reduction that accepts electrons and hydrogen ions to become NADH + H+ as oxidation of substrates occurs. During cellular respiration, NADH carries electrons to the electron transport chain in mitochondria.

Back 282

NAD+ (nicotinamide adenine dinucleotide phosphate)

Front 283

Form of enzyme inhibition where the inhibitor binds to an enzyme at a location other than the active site; while at this site, the enzyme shape changes, the inhibitor is unable to bind to its substrate, and no product forms.

Back 283

noncompetitive inhibition

Front 284

Loss of one or more electrons from an atom or molecule; In biological systems, generally the loss of hydrogen atoms.

Back 284

oxidation

Front 285

In metabolic processes, a way to activate an enzyme in which the enzyme either attaches an inorganic phosphate to a molecule or mediates the transfer of a phosphate group from one molecule to another.

Back 285

phophorylation

Front 286

Stored energy as a result of location or spatial arrangement.

Back 286

potential energy

Front 287

Substance that forms as a result of a reaction.

Back 287

product

Front 288

Substance that participates in a reaction.

Back 288

reactant

Front 289

Gain of electrons by an atom or molecule with a concurrent storage of energy; in biological systems, the electrons are accompanied by hydrogen ions.

Back 289

reduction

Front 290

Reactant in a reaction controlled by an enzyme.

Back 290

substrate

Front 291

Essential requirement in the diet, needed in small amounts. Vitamins are often part of coenzymes.

Back 291

vitamin

Front 292

Spectrum produced when atoms absorb specific wavelengths of incoming light as they become excited from lower to higher energy levels.

Back 292

absorption spectrum

Front 293

Spectrum of light that elicits a particular response.

Back 293

action spectrum

Front 294

Complex formed of enzymes and their carrier proteins; functions in the production of ATP in chloroplasts and mitochondria.

Back 294

ATP synthase

Front 295

Organism that can capture energy and synthesize organic molecules from inorganic nutrients.

Back 295

autotroph

Front 296

Plant that fixes carbon dioxide via the Calvin cycle; the first stable product of C3 photosynthesis is a 3-carbon compound.

Back 296

C3 plant

Front 297

Plant that fixes carbon dioxide to produce a C4 molecule that releases carbon dioxide to the Calvin cycle.

Back 297

C4 plant

Front 298

Portion of photosynthesis that takes place in the stroma of chloroplasts and can occur in the dark; it uses the products of the light reactions to reduce CO2 to a carbohydrate.

Back 298

Calvin cycle reactions

Front 299

Plant that fixes carbon dioxide at night to produce a C4 molecule that releases carbon dioxide to the Calvin cycle during the day; CAM stands for crassulacean-acid metabolism.

Back 299

CAM

Front 300

Photosynthetic reaction in which carbon dioxide is attached to an organic compound.

Back 300

carbon dioxide (CO2) fixation

Front 301

Yellow or orange pigment that serves as an accessory to chlorophyll in photosynthesis.

Back 301

carotenoid

Front 302

Ability of certain membranes to use a hydrogen ion gradient to drive ATP formation.

Back 302

chemiosmosis

Front 303

Green pigment that absorbs solar energy and is important in algal and plant photosynthesis; occurs as chlorophyll a and chorophyll b.

Back 303

chlorophyll

Front 304

Membrane-bounded organelle in algae and plants with chlorophyll-containing membranous thylakoids; where photosynthesis takes place.

Back 304

chloroplast

Front 305

Portion of the light reaction that involves only photosystem I and generates ATP.

Back 305

cyclic electron pathway

Front 306

Passage of electrons along a series of membrane-bound electron carrier molecules from a higher to lower energy level; the energy released is used for the synthesis of ATP.

Back 306

electron transport chain

Front 307

Stack of chlorophyll-containing thylakoids in a chloroplast.

Back 307

grana (sing., granum)

Front 308

Organism that cannot synthesize organic compounds from inorganic substances and therefore must take in organic food.

Back 308

heterotroph

Front 309

Portion of photosynthesis that captures solar energy and takes place in thylakoid membranes of chloroplasts; it produces ATP and NADPH.

Back 309

light reactions

Front 310

Portion of the light reactions of photosynthesis that involves both photosystem I and photosystem II. It generates both ATP and NADPH.

Back 310

noncyclic electron pathway

Front 311

Series of reactions that occurs in plants when carbon dioxide levels are depleted but oxygen continues to accumulate, and the enzyme RuBP cabroxylase fixes oxygen instead of carbon dioxide.

Back 311

photorespiration

Front 312

Process occurring usually within chloroplasts whereby chlorophyll-containing organelles trap solar energy to reduce carbon dioxide to carbohydrate.

Back 312

photosynthesis

Front 313

Photosynthetic unit where solar energy is absorbed and high-energy electrons are generated; contains a pigment complex and an electron acceptor; occurs as PS (photosystem) I and PS II.

Back 313

photosystem

Front 314

An enzyme that starts the Calvin cycle rections by catalyzing attachment of the carbon atom from CO2 to RuBP.

Back 314

RuBP carboxylase

Front 315

Small openings between two guard cells on the underside of leaf epidermis through which gases pass.

Back 315

stomata

Front 316

Fluid within a chloroplast that contains enzymes involved in the synthesis of carbohydrates during photosynthesis.

Back 316

stroma

Front 317

Flattened sac within a granum whose membrane contains chlorophyll and where the light reactions of photosynthesis occur.

Back 317

thylakoid

Front 318

Portion of the electromagnetic spectrum that is visible to the human eye.

Back 318

visible light

Front 319

Molecule made up of a 2-carbon acetyl group attached to coenzyme A. During cellular repiration, the acetyl group enters the citric acid cycle for further breakdown

Back 319

acetyl CoA

Front 320

Fermentation process that produces ethanol and CO2 from sugars.

Back 320

alcoholic fermentation

Front 321

Metabolic process by which larger molecules are synthesized from smaller ones; anabolic matabolism

Back 321

anabolism

Front 322

Growing or metabolizing in the absence of oxygen

Back 322

anaerobic

Front 323

Metabolic process that breaks down large molecules into smaller ones; catabolic metabolism

Back 323

catabolism

Front 324

Metabolic reactions that use the energy from carbohydrate, fatty acid, or amino acid breakdown to produce ATP molecules

Back 324

celllular respiration

Front 325

Ability of certain membranes to use a hydrogen ion gradient to drive ATP formation

Back 325

chemiosmosis

Front 326

Cycle of reactions in mitochondria that begins with citric acid. It breaks down an acetyl group and produces CO2, ATP, NADH, and FADH2; also called the Krebs cycle

Back 326

citric acid cycle

Front 327

Any of several iron-containing protein molecules that serve as electron carriers in photosynthesis and cellular respiration

Back 327

cytochrome

Front 328

Removal of an amino group (-NH2) from an amino acid or other organic compound

Back 328

deamination

Front 329

Membrane-bound molecules that pass electrons from higher to lower energy levels during cellular respiration

Back 329

electron carrier

Front 330

Passage of electrons along a series of membrane-bound electron carrier molecules from a higher to lower energy level; the energy released is used for the synthesis of ATP

Back 330

electron transport chain

Front 331

Flavin adenine dinucleotide; a coenzyme of oxidation-reduction that becomes FADH2 as oxidation of substrates occurs, and then delivers electrons to the electron transport chain in mitochondria during cellular respiration

Back 331

FAD

Front 332

Anaerobic breakdown of glucose that results in a gain of two ATP and end products such as alcohol and lactate

Back 332

fermentation

Front 333

Anaerobic breakdown of glucose that results in a gain of two ATP and the end product pyruvate

Back 333

glycolysis

Front 334

Fermentation that produces lactic acid as the sole or primary product

Back 334

lactic acid fermentation

Front 335

Metabolites that are the products of and/or the substrates for key reactions in cells, allowing one type of molecule to be changed into another type, such as carbohydrates converted to fats.

Back 335

metabolic pool

Front 336

Membrane-bounded organelle in which ATP molecules are produced during the process of cellular respiration

Back 336

mitochondrion

Front 337

Nicotinamide adenine dinucleotide; coenzyme of oxidation-reduction that accepts electrons and hydrogen ions to become NADH + H+ as oxidation of substrates occurs. During cellular respiration, NADH carries electrons to the electron transport chain in mitochondria

Back 337

NAD+

Front 338

Process by which ATP production is tied to an electron transport system that uses oxygen as the final acceptor; occurs in mitochondria

Back 338

oxidative phophorylation

Front 339

Amount of oxygen required to oxidize lactic acid produced anaerobically during strenuous muscle activity

Back 339

oxygen debt

Front 340

Reaction that oxidizes pyruvate with the release of carbon dioxide; results in acetyl CoA and connects glycolysis to the citric acid cycle

Back 340

preparatory reaction

Front 341

End product of glycolysis; its further fate, involving fermentation or entry into a mitochondrion, depends on oxygen availability

Back 341

pyruvate

Front 342

Process in which ATP is formed by transferring a phosphate from a metabolic substrate to ADP

Back 342

substrate-level phosphorylation

Front 343

Mitotic phase during which daughter chromosomes move toward the poles of the spindle.

Back 343

anaphase

Front 344

Formation of new blood vessels; one mechanism by which cancer spreads.

Back 344

angiogenesis

Front 345

Programmed cell death involving a cascade of specific cellular events leading to death and destruction of the cell

Back 345

apoptosis

Front 346

Reproduction that requires only one parent and does not involve gametes.

Back 346

asexual reproduction

Front 347

Short, radiating fibers produced by the centrosomes on animal cells.

Back 347

aster

Front 348

Mass of cells derived from a single mutated cell that has repeatedly undergone cell division but has remained at the site of origin.

Back 348

benign

Front 349

Splitting of a parent cell into two daughter cells; serves as an asexual form of reproduction in bacteria.

Back 349

binary fission

Front 350

Malignant tumor whose nondifferentiated cells exhibit loss of contact inhibition, uncontrolled growth, and the ability to invade tissue and metastasize.

Back 350

cancer

Front 351

Development of cancer.

Back 351

carcinogenesis

Front 352

Repeating sequence of events in eukaryotes that involves cell growth and nuclear division; consists of the stages G1, S, G2, and M.

Back 352

cell cycle

Front 353

Structure across a dividing plant cell that signals the location of new plasma membranes and cell walls.

Back 353

cell plate

Front 354

Cell organelle, existing in pairs, that occurs in the centrosome and may help organize a mitotic spindle for chromosome movement during animal cell division.

Back 354

centriole

Front 355

Constriction where sister chromatids of a chromosome are held together.

Back 355

centromere

Front 356

Central microtubule organizing center of cells. In animal cells, it contains two centrioles.

Back 356

centrosome

Front 357

Before nuclear division takes place, DNA replicates, duplicating the chromosomes in the parent cell. Each chromosome now had two identical double helix molecultes; each double helix is a c________, and the two identical c_________ are called sister c_________.

Back 357

chromatid

Front 358

Network of fibrils consisting of DNA and associated proteins observed within a nucleus that is not dividing.

Back 358

chromatin

Front 359

Protein that cycles in quantity as the cell cycle progresses; combines with and activates the kinases that function to promote the events of the cycle.

Back 359

cyclin

Front 360

Division of the cytoplasm following mitosis and meiosis.

Back 360

cytokinesis

Front 361

Cell condition in which two of each type of chromosome are present.

Back 361

diploid (2n) number

Front 362

G_____ f______ are external signals received at the plasma membrane. Even cells arrested in G0 will finish the cell cycle if stimulated to do so by g_____ f______.

Back 362

growth factor

Front 363

Cell condition in which only one of each type of chromosome is present.

Back 363

haploid (n) number

Front 364

Stages of the cell cycle (G1, S, G2) during which growth and DNA synthesis occur when the nucleus is not actively dividing.

Back 364

interphase

Front 365

Disk-shaped structure within the centromere of a chromosome to which spindle microtubules become attached during mitosis and meiosis.

Back 365

kinetochore

Front 366

Cancer of the blood-forming tissues leading to the overproduction of abnormal white blood cells.

Back 366

leukemia

Front 367

The power to threaten life; cancerous.

Back 367

malignant

Front 368

Mitotic phase during which chromosomes are aligned at the metaphase plate.

Back 368

metaphase

Front 369

A disk formed during metaphase in which all of a cell's chromosomes lie in a single plane at right angles to the spindle fibers.

Back 369

metaphase plate

Front 370

Spread of cancer from the place of origin throughout the body; caused by the ability of cancer cells to migrate and invade tissues.

Back 370

metastasis

Front 371

Process in which a parent nucleus produces two daughter nuclei, each having the same number and kinds of chromosomes as the parent nucleus.

Back 371

mitosis

Front 372

Any new and abnormal growth of tissue in which the growth is uncontrolled and progressive.

Back 372

neoplasm

Front 373

Region of prokaryotic cells where DNA is located; it is not bounded by a nuclear envelope.

Back 373

nucleoid

Front 374

Cancer-causing gene.

Back 374

oncogene

Front 375

For control of cell division the p53 gene halts the cell cycle when DNA mutates and is in need of repair.

Back 375

p53 (gene)

Front 376

Phase of mitosis which generally begins with the disintegration of the nuclear membrane.

Back 376

prometaphase

Front 377

Mitotic phase during which chromatin condenses so that chromosomes appear; chromosomes are scattered.

Back 377

prophase

Front 378

Normal gene that can become an oncogene through mutation.

Back 378

proto-oncogene

Front 379

Genetically identical to the original individual.

Back 379

reproductive cloning

Front 380

A molecule that stimulates or inhibits a metabolic event.

Back 380

signal

Front 381

One of two genetically identical chromosomal units that are the result of DNA replication and are attached to each other at the centromere.

Back 381

sister chromatid

Front 382

Body cell; excludes cells that underego meiosis and become sperm or egg.

Back 382

somatic cell

Front 383

Microtubule structure that brings about chromosomal movement during nuclear division.

Back 383

spindle

Front 384

Tip of the end of a chromosome that shortens with each cell division and may thereby regulate the number of times a cell can divide.

Back 384

telomere

Front 385

Mitotic phase during which daughter cells are located at each pole.

Back 385

telophase

Front 386

Used to create mature cells of various cell types. Also, used to learn about specialization of cells and provide cells and tissue to treat human illnesses.

Back 386

therapeutic cloning

Front 387

Cells derived from a single mutated cell that has repeatedly undergone cell division; benign tumors remain at the site of origin, while malignant tumors metastasize.

Back 387

tumor

Front 388

Gene that codes for a protein that ordinarily suppresses cell division; inactivity can lead to a tumor.

Back 388

tumor suppressor gene

Front 389

Alternative form of a gene -- alleles occur at the same locus on homologous chromosomes.

Back 389

allele

Front 390

Life cycle, typical of plants, in which a diploid sporophyte alternates with a haploid gametophyte.

Back 390

alternation of generations

Front 391

Homologous chromosomes, each having sister chromatids that are joined by a nucleoprotein lattice during meiosis; also called a tetrad.

Back 391

bivalent

Front 392

Exchange of segments between nonsister chromatids of a bivalent during meiosis.

Back 392

crossing-over

Front 393

Cell condition in which two of each type of chromosome are present.

Back 393

diploid (2n) number

Front 394

Fusion of sperm and egg nuclei, producing a zygote that develops into a new individual.

Back 394

fertilization

Front 395

Haploid sex cell; e.g., egg and sperm.

Back 395

gamete

Front 396

Development of the male and female sex gametes.

Back 396

gametogenesis

Front 397

Haploid generation of the alternation of generations life cycle of a plant; produces gametes that unite to form a dipoid zygote.

Back 397

gametophyte

Front 398

Process in which new genetic information is incorporated into a chromosome or DNA fragment.

Back 398

genetic recombination

Front 399

Cell condition in which only one of each type of chromosome is present.

Back 399

haploid (n) number

Front 400

Member of a pair of chromosomes that are alike and come together in synapsis during prophase of the first meiotic division ; a homologue.

Back 400

homologous chromosome

Front 401

Mamber of a homologous pair of chromosomes.

Back 401

homologue

Front 402

Alleles of unlinked genes segregate independently of each other during meiosis so that the gametes contain all possible combinations of alleles.

Back 402

independent assortment

Front 403

Period of time between meiosis I and meiosis II during which no DNA replication takes place.

Back 403

interkinesis

Front 404

Disk-shaped structure within the centromere of a chromosome to which spindle microtubules become attached during mitosis and meiosis.

Back 404

kinetochore

Front 405

Recurring pattern of genetically programmed events by which individuals grow, develop, maintain themselves, and reproduce.

Back 405

life cycle

Front 406

Type of nuclear division that occurs as part of sexual reproduction, in which the daughter cells receive the haploid number of chromosomes in varied combinations.

Back 406

meiosis

Front 407

Production of eggs in females by the process of meiosis and maturation.

Back 407

oogenesis

Front 408

In oogenesis, a nonfunctional product; two to three meiotic products are of this type.

Back 408

polar body

Front 409

In oogenesis, the functional product of meiosis I; becomes the egg.

Back 409

secondary oocyte

Front 410

Reproduction involving meiosis, gamete formation, and fertilization; produces offspring with chromosomes inherited from each parent with a unique combination of genes.

Back 410

sexual reproduction

Front 411

Production of sperm in males by the process of meiosis and maturation.

Back 411

spermatogenesis

Front 412

Asexual reproductive or resting cell capable of developing into a new organism without fusion with another cell, in contrast to a gamete.

Back 412

spore

Front 413

Diploid generation of the alternation of generations life cycle of a plant; produces haploid spores that develop into the haploid generation.

Back 413

sporophyte

Front 414

Pairing of homologous chromosomes during meiosis I.

Back 414

synapsis

Front 415

Diploid cell formed by the union of two gametes; the product of fertilization.

Back 415

zygote

Front 416

Sexually transmitted disease caused by Gardnerella vaginalis, Mobiluncus spp., Mycoplasma hominis, and various anaerobic bacteria. Although a mild disease, it is a risk factor for obstetric infections and pelvic inflammatory disease.

Back 416

bacterial vaginosis

Front 417

Narrow end of the uterus, which leads into the vagina.

Back 417

cervix

Front 418

Under development, this birth control method immunizes against the hormone HCG, crucial to maintaining implantation of the embryo.

Back 418

contraceptive vaccine

Front 419

Sexual union between a male and a female.

Back 419

copulation

Front 420

Follicle that has released an egg and increases its secretion of progesterone.

Back 420

corpus luteum

Front 421

Presence of uterine tissue outside the utereus, which can contribute to infertility; possibly the result of irregular menstrual flow.

Back 421

endometriosis

Front 422

Mucous membrane lining the interior surface of the uterus.

Back 422

endometrium

Front 423

Female sex hormone that helps maintain sexual organs and secondary sex characteristics.

Back 423

estrogen

Front 424

Membrane that is not a part of the embryo but is necessary to the continued existence and health of the embryo.

Back 424

extraembryonic membrane

Front 425

Structure in the ovary of animals that contains an oocyte; site of oocyte production.

Back 425

follicle

Front 426

First half of the ovarian cycle, during which the follicle matures and much estrogen (and some progesterone) is produced.

Back 426

follicular phase

Front 427

Haploid sex cell; e.g., egg and sperm.

Back 427

gamete

Front 428

Organ that produces gametes; the ovary produces eggs, and the testis produces sperm.

Back 428

gonad

Front 429

Gonadotropic hormone produced by the chorion that functions to maintain the uterine lining.

Back 429

human chorionic gonadotropin (HCG)

Front 430

Virus responsible for AIDS

Back 430

human immunodeficiency virus (HIV)

Front 431

Inability to have as many children as desired.

Back 431

infertility

Front 432

Secretion of milk by mammary glands, usually for the nourishment of an infant.

Back 432

lactation

Front 433

Immature form in the life cycle of some animals; it sometimes undergoes metamorphosis to become the adult form.

Back 433

larva

Front 434

Second half of the ovarian cycle, during which the corpus luteum develops and much progesterone (and some estrogen) is produced.

Back 434

luteal phase

Front 435

Onset of menstruation

Back 435

menarche

Front 436

Termination of the ovarian and uterine cycles in older women.

Back 436

menopause

Front 437

Periodic shedding of tissue and blood from the inner lining of the uterus in primates.

Back 437

menstruation

Front 438

Change in shape and form that some animals, such as insects, undergo during development.

Back 438

metamorphosis

Front 439

Immature egg that is undergiong meiosis; upon completion of meiosis, the oocyte becomes an egg.

Back 439

oocyte

Front 440

Physiological and psychological sensations that occur at the climax of sexual stimulation.

Back 440

orgasm

Front 441

Monthly changes occurring in the ovary that determine the level of sex hormones in the blood.

Back 441

ovarian cycle

Front 442

In flowering plants, the enlarged, ovule-bearing portion of the carpel that develops into a fruit; female gonad in animals that produces an egg and female sex hormones.

Back 442

ovary

Front 443

Bursting of a follicle when a secondary oocyte is released from the ovary; if fertilization ocurs, the secondary oocyte becomes an egg.

Back 443

ovulation

Front 444

Haploid egg cell that is usualy fertilized by a sperm to form a diploid zygote.

Back 444

ovum

Front 445

Development of an egg cell into a whole organism without fertilization.

Back 445

parthenogenesis

Front 446

Male copulatory organ; in humans, the male organ of sexual intercourse.

Back 446

penis

Front 447

Organ formed during the development of placental mammals from the chorion and the uterine wall; allows the embryo, and then the fetus, to acquire nutrients and rid itself of wastes; produces hormones that regulate pregnancy.

Back 447

placenta

Front 448

Female sex hormone that helps maintain sexual organs and secondary sex characteristics.

Back 448

progesterone

Front 449

Period of life when secondary sex changes occur in humans; marked by the onset of menses in females and sperm production in males.

Back 449

puberty

Front 450

Trait that is sometimes helpful but not absolutely necessary for reproduction and is maintained by the sex hormones in males and females.

Back 450

secondary sex characteristic

Front 451

Thick, whitish fluid consisting of sperm and secretions from several glands of the male reproductive tract.

Back 451

semen (seminal fluid)

Front 452

Long, coiled structure contained within chambers of the testis where sperm are produced.

Back 452

seminiferous tubule

Front 453

Male gamete having a haploid number of chromosomes and the ability to fertilize an egg, the female gamete.

Back 453

sperm

Front 454

Male gonad that produces sperm and the male sex hormones.

Back 454

testes

Front 455

Male sex hormone that helps maintain sexual organs and secondary sex characteristics.

Back 455

testosterone

Front 456

Sexually transmitted disease caused by the parasitic protozoan Trichomonas vaginalis.

Back 456

trichomoniasis

Front 457

Cycle that runs concurrently with the ovarian cycle; it prepares the uterus to receive a developing zygote.

Back 457

uterine cycle

Front 458

In mammals, expanded portion of the female reproductive tract through which eggs pass to the environment or in which an embryo develops and is nourished before birth.

Back 458

uterus

Front 459

Animal that gives birth after partial development of offspring within mother.

Back 459

viviparous

Front 460

Dense nutrient material in the egg of a bird or reptile.

Back 460

yolk

Front 461

allele

Back 461

Alternative form of a gene -- alleles occur at the same locus on homologous chromosomes.

Front 462

autosome

Back 462

Any chromosome other than the sex-determining pair.

Front 463

carrier

Back 463

Heterozygous individual who has no apparent abnormality but can pass on an allele for a recessively inhereited genetic disordeer.

Front 464

codominance

Back 464

Inheritance pattern in which both alleles of a gene are equally expressed.

Front 465

dihybrid cross

Back 465

Cross between parents that differ in two traits.

Front 466

dominant allele

Back 466

Allele that exerts its phenotypic effect in the heterozygote; it masks the expression of the recessive allele.

Front 467

epistasis

Back 467

Inheritance pattern in which one gene masks the expression of another gene that is at a different locus and is independently inherited.

Front 468

gene locus

Back 468

Specific location of a particular gene on homologous chromosomes.

Front 469

genotype

Back 469

Genes of an organism for a particular trait or traits; often designated by letters -- for example, BB or Aa.

Front 470

heterozygous

Back 470

Possessing unlike alleles for a particular trait.

Front 471

homozygous

Back 471

Possessing two identical alleles for a particular trait.

Front 472

incomplete dominance

Back 472

Inheritance pattern in which the offspring has an intermediate phenotype, as when a red-flowered plant and a white-flowered plant produce pink-flowered offspring.

Front 473

monohybrid cross

Back 473

Cross between parents that differ in only one trait.

Front 474

multifactorial

Back 474

The result of the interaction of several genes.

Front 475

multiple alleles

Back 475

Inheritance pattern in which there are more than two alleles for a particular trait; each individual has only two of all possible alleles.

Front 476

phenotype

Back 476

Visible expression of a genotype -- e.g., brown eyes or attached earlobes.

Front 477

pleiotropy

Back 477

Inheritance pattern in which one gene affects many phenotypic characteristics of the individual.

Front 478

polygenic inheritance

Back 478

Pattern of inheritance in which a trait is controlled by several allelic pairs; each dominant allele contributes to the phenotype in an additive and like manner.

Front 479

Punnett square

Back 479

Grid used to calculate the expected results of simple genetic crosses.

Front 480

recessive allele

Back 480

Allele that exerts its phenotypic effect only in the homozygote; its expression is masked by a dominant allele.

Front 481

testcross

Back 481

Cross between an individual with the dominant phenotype and an individual with the recessive phenotype. The resulting phenotypic ratio indicates whether the dominant phenotype is homozygous or heterozygous.

Front 482

unifactorial

Back 482

One gene consisting of a single pair of alleles, one dominant and one recessive.

Front 483

wild type

Back 483

Phenotype or genotype that is characteristic of the majority of individuals of a species in a natural environment.

Front 484

amniocentesis

Back 484

Procedure for removing amniotic fluid surrounding the developing fetus for testing of the fluid or cells within the fluid.

Front 485

aneuploid

Back 485

Individual whose chromosome number is not an exact multiple of the haploid number for the species.

Front 486

autosome

Back 486

Any chromosome other than the sex-determining pair.

Front 487

carrier

Back 487

Heterozygous individual who has no apparent abnormality but can pass on an allele for a recessively inherited genetic disorder.

Front 488

chorionic villi sampling (CVS)

Back 488

Prenatal test in which a sample of chorionic villi cells is removed for diagnostic purposes.

Front 489

chromosomal mutation

Back 489

Alteration in the chromosome structure or number typical of the species.

Front 490

chromosome theory of inheritance

Back 490

The idea that chromosomes are the carriers of genes

Front 491

deletion

Back 491

Change in chromosome structure in which the end of a chromosome breaks off or two simultaneous breaks lead to the loss of an internal segment; often causes abnormalities -- e.g., cri du chat syndrome.

Front 492

duplication

Back 492

Change in chromosome structure in which a particular segment is present more than once in the same chromosome.

Front 493

euploidy

Back 493

Cells containing only complete sets of chromosomes.

Front 494

gene linkage

Back 494

Relationship between genes on the same chromosome.

Front 495

inversion

Back 495

Change in chromosome structure in which a segment of a chromosome is turned around 180°; this reversed sequence of genes can lead to altered gene activity and abnormalitites

Front 496

karyotype

Back 496

Chromosomes arranged by pairs according to their size, shape, and general appearance in mitotic metaphase.

Front 497

linkage group

Back 497

Alleles of different genes that are located on the same chromosome and tend to be inherited together.

Front 498

linkage map

Back 498

Depicts the distances between loci as well as the order in which they occur on the organism.

Front 499

locus

Back 499

The physical location of a gene withiin a chromosome.

Front 500

monosomy

Back 500

One less chromosome than usual.

Front 501

nondisjunction

Back 501

Failure of homologous chromosomes or daughter chromosomes to separate during meiosis I and meiosis II, respectively.

Front 502

polyploid

Back 502

Having a chromosome number that is a multiple greater than twice that of the monoploid number.

Front 503

sex chromosome

Back 503

Chromosome that determines the sex of an individual; in humans, females have two X chromosomes, and males have an X and a Y chromosome.

Front 504

syndrome

Back 504

Group of symptoms that appear together and tend to indicate the presence of a particular disorder.

Front 505

translocation

Back 505

Movement of a chromosomal segment from one chromosome to another nonhomologous chromosome, leading to abnormalities -- e.g., Down syndrome.

Front 506

trisomy

Back 506

Having three of a particular type of chromosome (2n + 1)

Front 507

X-linked

Back 507

Allele that is located on an X chromosome but may control a trait that has nothing to do with the sexual characteristics of an animal.

Front 508

adenine (A)

Back 508

One of four nitrogen-containing bases in nucleotides composing the structure of DNA and RNA.

Front 509

bacteriophage

Back 509

Virus that infects bacteria.

Front 510

complementary base pairing

Back 510

Hydrogen bonding between particular purines and pyrimidines in DNA.

Front 511

cytosine (C)

Back 511

One of four nitrogen-containing bases in the nucleotides composing the structure of DNA and RNA; pairs with guanine.

Front 512

DNA (deoxyribonucleic acid)

Back 512

Nucleic acid polymer produced from covalent bonding of nucleotide monomers that contain the sugar deoxyribose; the genetic material of nearly all organisms.

Front 513

DNA polymerase

Back 513

During replication, an enzyme that joins the nucleotides complementary to a DNA template.

Front 514

DNA repair enzyme

Back 514

One of several enzymes that restore the original base sequence in an altered DNA strand.

Front 515

DNA replication

Back 515

Synthesis of a new DNA double helix prior to mitosis and meiosis in eukaryotic cells and during prokaryotic fission in prokaryotic cells.

Front 516

double helix

Back 516

Double spiral; describes the three-dimensional shape of DNA.

Front 517

genetic mutation

Back 517

Altered gene whose sequence of bases differs from the previous sequence.

Front 518

guanine (G)

Back 518

One of four nitrogen-containing bases in nucleotides composing the structure of DNA and RNA; pairs with cytosine.

Front 519

nucleic acid

Back 519

Polymer of nucleotides; both DNA and RNA are nucleic acids.

Front 520

nucleotide

Back 520

Monomer of DNA and RNA consisting of a 5-carbon sugar bonded to a nitrogenous base and a phosphate group.

Front 521

proofreading

Back 521

Process used to check the accuracy of DNA replication as it occurs and to replace a mispaired base with the right one.

Front 522

purine

Back 522

Type of nitrogen-containing base, such as adenine and guanine, having a double-ring structure.

Front 523

pyrimidine

Back 523

Type of nitrogen-containing base, such as cytosine, thymine, and uracil, having a single-ring structure.

Front 524

replication fork

Back 524

In eukaryotes, the point where the two parental DNA strands separate to allow replication.

Front 525

RNA (ribonucleic acid)

Back 525

Nucleic acid produced from covalent bonding of nucleotide monomers that contain the sugar ribose; occurs in three forms: messenger RNA, ribosomal RNA, and transfer RNA.

Front 526

semiconservative replication

Back 526

Duplication of DNA resulting in two double helix molecules, each having one parental and one new strand.

Front 527

template

Back 527

Parental strand of DNA that serves as a guide for the complementary daughter strand produced during DNA replication.

Front 528

thymine (T)

Back 528

One of four nitrogen-containing bases in nucleotides composing the structure of DNA; pairs with adenine.

Front 529

anticodon

Back 529

Three-base sequence in a transfer RNA molecule base that pairs with a complementary codon in mRNA.

Front 530

codon

Back 530

Three-base sequence in messenger RNA that causes the insertion of a particular amino acid into a protein, or termination of translation.

Front 531

elongation

Back 531

The step in protein synthesis in which a polypeptide increases in length one amino acid at a time. Elongation factors, which facilitate the binding of tRNA anticodons to mRNA codons at a ribosome and tRNA participation are required.

Front 532

exon

Back 532

Coding sequence in DNA transcribed and present in primary mRNA.

Front 533

gene

Back 533

Unit of heredity existing as alleles on the chromosomes; in diploid organisms, typically two alleles are inherited -- one from each parent.

Front 534

genetic code

Back 534

Universal code in existence for eons; specifies protein synthesis. Each codon consists of three letters for the DNA nucleotides that make up amino acids found in proteins.

Front 535

initiation

Back 535

One of 3 steps in translation, this step brings all the translation components together.

Front 536

intron

Back 536

Non coding sequence in DNA transcribed and present in primary mRNA. Excised later in the process.

Front 537

messenger RNA (mRNA)

Back 537

Type of RNA formed from a DNA template and bearing coded information for the amino acid sequence of a polypeptide.

Front 538

noncoding gene

Back 538

Transcribes into any other types of RNA other than mRNA.

Front 539

polyribosome

Back 539

String of ribosomes simultaneously translating regions of the same mRNA strand during protein synthesis.

Front 540

promoter

Back 540

In an operon, a sequence of DNA where RNA polymerase binds prior to transcription.

Front 541

protein-coding gene

Back 541

Transcribes into mRNA.

Front 542

ribosomal RNA (rRNA)

Back 542

Type of RNA found in ribosomes that translate messenger RNAs to produce proteins.

Front 543

ribozyme

Back 543

Enzyme that carries out mRNA processing

Front 544

RNA (ribonucleic acid)

Back 544

Nucleic acid produced from covalent bonding of nucleotide monomers that contain the sugar ribose; occurs in three forms: messenger RNA, ribosomal RNA, and transfer RNA.

Front 545

RNA polymerase

Back 545

During transcription, an enzyme that joins nucleotides complementary to a DNA template.

Front 546

RNA transcript

Back 546

mRNA molecule formed during transcription that has a sequence of bases complementary to a gene.

Front 547

termination

Back 547

The final step in protein synthesis. The polypeptide and the assembled components that carried out protein synthesis are separated from one another.

Front 548

transcription

Back 548

Process whereby a DNA strand serves as a template for the formation of mRNA.

Front 549

transfer RNA (tRNA)

Back 549

Type of RNA that transfers a particular amino acid to a ribosome during protein synthesis; at one end, it binds to the amino acid, and at the other end it has an anticodon that binds to an mRNA codon.

Front 550

translation

Back 550

Process whereby ribosomes use the sequence of codons in mRNA to produce a polypeptide with a particular sequence of amino acids.

Front 551

triplet code

Back 551

During gene expression, each sequence of three nucleotide bases stands for a particular amino acid.

Front 552

uracil

Back 552

In RNA, this base replaces the thymine found in DNA.

Front 553

wobble hypothesis

Back 553

Ability of the 5'-most nucleotide of an anticodon to interact with more than one nucleotide at the 3'-end of codons; helps explain the degeneracy of the genetic code.

Front 554

Barr body

Back 554

Dark-staining body (discovered by M. Barr) in the nuclei of female mammals that contains a condensed, inactive X chromosome.

Front 555

carcinogen

Back 555

Environmental agent that causes mutations leading to the development of cancer.

Front 556

chromatin

Back 556

Network of fibrils consisting of DNA and associated proteins observed within a nucleus that is not dividing.

Front 557

corepressor

Back 557

Molecule that binds to a repressor, allowing the repressor to bind to an operator in a repressible operon.

Front 558

epigenetic inheritance

Back 558

Site of gene functionality that is not encoded within the DNA sequence but that is still inheritable from one generation to the next.

Front 559

euchromatin

Back 559

Chromatin that is extended and accessible for transcription.

Front 560

frameshift mutation

Back 560

Insertion or deletion of at least one base so that the reading frame of the corresponding mRNA changes.

Front 561

genetic mutation

Back 561

Altered gene whose sequence of bases differs from the previous sequence.

Front 562

heterochromatin

Back 562

Highly compacted chromatin that is not accessible for transcription.

Front 563

histone

Back 563

Small basic protein with large amounts of lysine and arginine that is associated with eukaryotic DNA in chromatin.

Front 564

inducer

Back 564

Molecule that brings about activity of an opereon by joining with a repressor and preventing it from binding to the operator.

Front 565

inducible operon

Back 565

In a catabolic pathway, an operon causes transcription of the genes controlling a group of enzymes.

Front 566

microRNA

Back 566

Introns that are processed into smaller signals; after being degraded, they combine with a protein, and the complex binds to mRNAs. These are then destroyed instead of being translated.

Front 567

nucleosome

Back 567

In the nucleus of a eukaryotic cell, a unit composed of DNA wound around a core of eight histone proteins, giving the appearance of a string of beads.

Front 568

operator

Back 568

In an operon, the sequence of DNA that binds tightly to a repressor, and thereby regulates the expression of structural genes.

Front 569

operon

Back 569

Group of structural and regulating genes that function as a single unit.

Front 570

point mutation

Back 570

Change of one base only in the sequence of bases in a gene.

Front 571

posttranscriptional control

Back 571

Gene expression following translation regulated by the way mRNA transcripts are processed.

Front 572

posttranslational control

Back 572

Gene expression following translation regulated by the activity of the newly synthesized protein.

Front 573

promoter

Back 573

In an operon, a sequence of DNA where RNA polymerase binds prior to transcription.

Front 574

regulator gene

Back 574

In an operon, a gene that codes for a protein that regulates the expression of other genes.

Front 575

repressible operon

Back 575

Operon that is normally active because the repressor is normally inactive.

Front 576

repressor

Back 576

In an operon, protein molecule that binds to an operator, preventing transcription of structural genes.

Front 577

structural gene

Back 577

Gene that codes for an enzyme in a metabolic pathway.

Front 578

transcription activator

Back 578

Protein that speeds transcription.

Front 579

transcription factor

Back 579

In eukaryotes, protein required for the initiation of transcription by RNA polymerase.

Front 580

transcriptional control

Back 580

Control of gene expression during the transcriptional phase determined by mechanisms that control whether transcription occurs or the rate at which it occurs.

Front 581

translational conrol

Back 581

Gene expression regulated by the activity of mRNA transcripts.

Front 582

transposon

Back 582

DNA sequence capable of randomly moving from one site to another in the genome.

Front 583

Computer technologies used to study the genome

Back 583

bioinformatics

Front 584

Production of identical copies. In organisms, the production of organisms with the same genes; in genetic engineering, the production of many identical copies of a gene

Back 584

cloning

Front 585

DNA that has been synthesized from mRNA by the action of transcriptase

Back 585

complementary DNA (cDNA)

Front 586

The use of DNA fragment lengths resulting from restriction enzyme cleavage to identify particular individuals

Back 586

DNA fingerprinting

Front 587

Enzyme that links DNA fragments; used during production of recombinant DNA to join foreign DNA to vector DNA

Back 587

DNA ligase

Front 588

DNA cloning to produce many identical copies of the same gene

Back 588

gene cloning

Front 589

Correction of a detrimental mutation by the addition of new DNA and its insertion in a genome

Back 589

gene therapy

Front 590

Alteration of genomes for medical or industrial purposes

Back 590

genetic engineering

Front 591

Study of whole genomes

Back 591

genomics

Front 592

Self-duplicating ring of accessory DNA in the cytoplasm of bacteria

Back 592

plasmid

Front 593

Technique that uses the enzyme DNA polymerase to produce millions of copies of a particular piece of DNA

Back 593

polymerase chain reaction (PCR)

Front 594

Study of the complete collection of proteins that an organism produces

Back 594

proteomics

Front 595

DNA that contains genes from more than one source

Back 595

recombinant DNA (rDNA)

Front 596

Bacterial enzyme that stops viral reproduction by cleaving viral DNA; used to cut DNA at specific points during production of recombinant DNA

Back 596

restriction enzyme

Front 597

Freeliving organism in the environment that has had a foreign gene inserted into it

Back 597

transgenic organism

Front 598

In genetic engineering, a means to transfer foreign genetic material into a cell -- e.g., a plasmid

Back 598

vector

Front 599

Organism's modification in structure, function, or behavior suitable to the environment

Back 599

adaptation

Front 600

Structure that has a similar function in separate lineages but differs in anatomy and ancestry

Back 600

analogous structure

Front 601

Study of the geographical distribution of organisms

Back 601

biogeography

Front 602

Belief espoused by Georges Cuvier that periods of catastrophic extinctions occurred, after which repopulation of surviving species took place, giving the appearance of change through time

Back 602

catastrophism

Front 603

Descent of organisms from common ancestors with the development of genetic and phenotypic changes over time that make them more suited to the environment

Back 603

evolution

Front 604

Total disappearance of a species or higher group

Back 604

extinct

Front 605

Ability of an organism to reproduce and pass its genes to the next fertile generation; measured against the ability of other organisms to reproduce in the same environment

Back 605

fitness

Front 606

History of life recorded from remains from the past

Back 606

fossil record

Front 607

In evolution, a structure that is similar in different types of organisms because these organisms are derived from a common ancestor

Back 607

homologous structure

Front 608

Lamarckian belief that characteristics acquired during the lifetime of an organism can be passed on to offspring

Back 608

inheritance of acquired characteristics

Front 609

Mechanism of evolution caused by environmental selection of organisms most fit to reproduce; results in adaptation to the environment

Back 609

natural selection

Front 610

Study of fossils that results in knowledge about the history of life

Back 610

peleontology

Front 611

Belief espoused by James Hutton that geological forces act at a continuous uniform rate

Back 611

uniformitarianism

Front 612

Remains of an organ that was functional in some ancestor but is no longer functional in the organism in question

Back 612

vestigial organ

Front 613

Remains of a structure that was functional in some ancestor but is no longer functional in the organism in question

Back 613

vestigial structure

Front 614

Evolution of several species from a common ancestor into new ecological or geographical zones

Back 614

adaptive radiation

Front 615

Origin of new species between populations that are separated geographically

Back 615

allopatric speciation

Front 616

Mating of individuals with similar phenotypes

Back 616

assortative mating

Front 617

Cause of genetic drift, occurs when a majority of genotypes are prevented from participating in the production of the next generation as a result of a natural disaster or human interference

Back 617

bottleneck effect

Front 618

Outcome of natural selection in which an extreme phenotype is favored, usually in a changing environment

Back 618

directional selection

Front 619

Outcome of natural selection in which the two extreme phenotypes are favored over the average phenotype, leading to more than one distinct form

Back 619

disruptive selection

Front 620

Cause of genetic drift due to colonization by a limited number of individuals who, by chance, have different gene frequencies than the parent population

Back 620

founder effect

Front 621

Sharing of genes between two populations through interbreeding

Back 621

gene flow

Front 622

Total of all the genes of all the individuals in a population

Back 622

gene pool

Front 623

Mechanism of evolution due to random changes in the allelic frequencies of a population; more likely to occur in small populations or when only a few individuals of a large population reproduce

Back 623

genetic drift

Front 624

Law stating that the gene frequencies in a population remain stable if evolution does not occur due to nonrandom mating, selection, migration, and genetic drift

Back 624

Hardy-Weinberg principle

Front 625

Increased frequency of darkly pigmented (melanic) forms in a population when soot and pollution make lightly pigmented forms easier for predators to see against a pigmented background

Back 625

industrial melanism

Front 626

Large-scale evolutionary change, such as the formation of new species

Back 626

macroevolution

Front 627

Change in gene frequencies between populations of a species over time

Back 627

microevolution

Front 628

Mechanism of evolution caused by environmental selection of organisms most fit to reproduce; results in adaptation to the environment

Back 628

natural selection

Front 629

Mating among individuals on the basis of their phenotypic similarities or differences, rather than mating on a random basis

Back 629

nonrandom mating

Front 630

Genes that have more than one wild-type allele

Back 630

polymorphic

Front 631

Group of organisms of the same species occupying a certain area and sharing a common gene pool

Back 631

population

Front 632

The study of gene frequencies and their changes within a population

Back 632

population genetics

Front 633

Anatomical or physiological difference between two species that prevents successful reproduction after mating has taken place

Back 633

postzygotic isolating mechanism

Front 634

Anatomical or behavioral difference between two species that prevents the possibility of mating

Back 634

prezygotic isolating mechanism

Front 635

Reproductive success of a genotype as measured by survival, fecundity, or other life-history parameters

Back 635

relative fitness

Front 636

Changes in males and females, often due to male competition and female selectivity, leading to increased fitness

Back 636

sexual selection

Front 637

Origin of new species due to the evolutionary process of descent with modification

Back 637

speciation

Front 638

Group of similarly constructed organisms capable of interbreeding and producing fertile offspring; organisms that share a common gene pool; the taxon at the lowest level of classification

Back 638

species

Front 639

Outcome of natural selection in which extreme phenotypes are eliminated and the average phenotype is conserved

Back 639

stabilizing selection

Front 640

Origin of new species in populations that overlap geographically

Back 640

sympatric speciation

Front 641

Determining the age of a fossil by direct measurement, usually involving radioisotope decay

Back 641

absolute dating (of fossils)

Front 642

Increase in the complexity of chemicals over time that could have led to the first cells

Back 642

chemical evolution

Front 643

An aggregate of colloidal droplets held together by electrostatic forces

Back 643

coacervate droplet

Front 644

Movement of continents with respect to one another over the Earth's surfaces

Back 644

continental drift

Front 645

Possible explanation of the evolution of eukaryotic organelles by phagocytosis of prokaryotes

Back 645

endosymbiotic hypothesis

Front 646

Total disappearance of a species or higher group

Back 646

extinction

Front 647

Any past evidence of an organism that has been preserved in the Earth's crust

Back 647

fossil

Front 648

History of the Earth based on correlations between rocks (or the fossils contained in them) and time periods of the past

Back 648

geological timescale

Front 649

Deposits found in certain layers of strata; similar fossils can be found in the same strata around the world

Back 649

index fossil

Front 650

Droplet of phospholipid molecules formed in a liquid environment

Back 650

liposome

Front 651

Episode of large-scale extinction in which large numbers of species disappear in a few million years or less

Back 651

mass extinction

Front 652

Formed from proteinoids exposed to water; has properties similar to those of today's cells

Back 652

microsphere

Front 653

Idea that the rate at which mutational changes accumulate in certain genes is constant over time and is not involved in adaptation to the environment

Back 653

molecular clock

Front 654

Ridge on the ocean floor where oceanic crust forms and from which it moves laterally in each direction

Back 654

ocean ridge

Front 655

Accumulation of O3, formed from oxygen in the upper atmosphere; a filtering layer that protects the Earth from ultraviolet radiation

Back 655

ozone shield

Front 656

Study of fossils that results in knowledge about the history of life

Back 656

paleontology

Front 657

Concept that the Earth's crust if divided into a number of fairly rigid plates whose movements account for continental drift

Back 657

plate tectonics

Front 658

In chemical evolution, the proposal that protein originated before other macromolecules and made possible the formation of protocells

Back 658

protein-first hypothesis

Front 659

Abiotically polymerized amino acids that, when exposed to water, become microspheres having cellular characteristics

Back 659

proteinoid

Front 660

Also called protocell, possible first cell

Back 660

protobiont

Front 661

In biological evolution, a possible cell forerunner that became a cells once it acquired genes

Back 661

protocell

Front 662

Determining the age of fossils by noting their sequential relationship in strata; absolute dating relies on radioactive dating techniques to assign an actual date

Back 662

relative dating (of fossils)

Front 663

In chemical evolution, the proposal that RNA originated before other macromolecules and allowed the formation of the first cell(s)

Back 663

RNA-first hypothesis

Front 664

Process by which particulate material accumulates and forms a stratum

Back 664

sedimentation

Front 665

Ancient layer of sedimentary rock; results from slow deposition of silt, volcanic ash, and other materials

Back 665

stratum

Front 666

Domed structure found in shallow seas consisting of cyanobacteria bound to calcium carbonate

Back 666

stromatolite

Front 667

Structure that has a similar function in separate lineages but differs in anatomy and ancestry

Back 667

analogous structure

Front 668

Similarity of function but not of origin

Back 668

analogy

Front 669

Structural, physiological, or behavioral trait that is present in a common ancestor and all members of a group

Back 669

ancestral characteristic

Front 670

Assignment of two names to each organism; a system developed by Carolus Linnaeus in the mid-eighteenth century

Back 670

binomial nomenclature

Front 671

Any structural, chromosomal, or molecular feature that distinguishes one group from another

Back 671

character

Front 672

Taxon or other group consisting of an ancestral species and all of its descendants, forming a distinct branch on a phylogenetic tree

Back 672

clade

Front 673

School of systematics that uses derived characters to determine monphyletic groups and construct cladograms

Back 673

cladistic systematics

Front 674

In cladistics, a branching diagram that shows the relationship among species in regard to their shared derived characters

Back 674

cladogram

Front 675

One of the categories, or taxa, used by taxonomists to group species; class is the taxon above the order level

Back 675

class

Front 676

Ancestors held in common by at least two lines of descent

Back 676

common ancestor

Front 677

Similarity in structure in distantly related groups due to adaptation to the environment

Back 677

convergent evolution

Front 678

Structural, physiological, or behavioral trait that is present in a specific lineage and is not present in the common ancestor for several lineages

Back 678

derived character

Front 679

Method to determine relatedness by allowing single DNA strands from two different species to join, and thereafter observing how well they joined

Back 679

DNA-DNA hybridization

Front 680

Largest of the categories, or taxa, used by taxonomists to group species; three members are Archaea, Bacteria, and Eukarya

Back 680

domain

Front 681

One of the three domains of life; contains prokaryotic cells that ofetn live in extreme habitats and have unique genetic, biochemical, and physiological characteristics; its members are sometimes referred to as archaea

Back 681

domain Archaea

Front 682

One of the three domains of life; contains prokaryotic cells that differ from archaea because they have their own unique genetic, biochemical, and physiological characteristics

Back 682

domain Bacteria

Front 683

One of the three domains of life, consisting of organisms with eukaryotic cells and further classified into the kingdoms Protista, Fungi, Plantae, and Animalia

Back 683

domain Eukarya

Front 684

One of the categories, or taxa, used by taxonomists to group species; the taxon above the genus level

Back 684

family

Front 685

System of classification that contains the kingdoms Monera, Protista, Plantae, Animalia, and Fungi

Back 685

five-kingdom system

Front 686

One of the categories, or taxa, used by taxonomists to group species; contains those species that are most closely related through evolution

Back 686

genus

Front 687

In evolution, a structure that is similar in different types of organisms because these organisms are derived from a common ancestor

Back 687

homologous structure

Front 688

Similarity of parts or organs of different organisms caused by evolutionary derivation from a corresponding part or organ in a remote ancestor, and usually having a similar embryonic origin

Back 688

homology

Front 689

One of the categories, or taxa, used by taxonomists to group species, the taxon above phylum

Back 689

kingdom

Front 690

Idea that the rate at which mutational changes accumulate in certain genes is constant over time and is not involved in adaptation to the environment

Back 690

molecular clock

Front 691

One of the categories, or taxa, used by taxonomists to group species; the taxon above the family level

Back 691

order

Front 692

Similarity in structure in related groups that cannot be traced to a common ancestor

Back 692

parallel evolution

Front 693

School of systematics that determines the degree of relatedness between species by counting the number of their similarities

Back 693

phenetic systematics

Front 694

Diagram that indicates common ancestors and lines of descent among a group of organisms

Back 694

phylogenetic tree

Front 695

Evolutionary history of a group of organisms

Back 695

phylogeny

Front 696

One of the categories, or taxa, used by taxonomists to group species, the taxon above the class level

Back 696

phylum

Front 697

Group of similarly constructed organisms capable of interbreeding and producing fertile offspring; organisms that share a common gene pool; the taxon at the lowest level of classification

Back 697

species

Front 698

In the binomial system of taxonomy, the second part of an organism's name; it may be descriptive

Back 698

specific epithet

Front 699

Study of the diversity of organisms to classify them and determine their evolutionary relationships

Back 699

systematics

Front 700

Group of organisms that fills a particular classification category

Back 700

taxon

Front 701

Branch of biology concerned with identifying, describing, and naming organisms

Back 701

taxonomy

Front 702

School of systematics that takes into consideration the degree of difference between derived characters to construct phylogenetic trees

Back 702

traditional systematics

Front 703

Member of the domain Archaea

Back 703

archaea

Front 704

Member of the domain Bacteria

Back 704

bacteria

Front 705

Virus that infects bacteria

Back 705

bacteriophage

Front 706

Splitting of a parent cell into two daughter cells; serves as an asexual form of reproduction in bacteria

Back 706

binary fission

Front 707

Protective protein containing the genetic material of a virus

Back 707

capsid

Front 708

Organism able to synthesize organic molecules by using carbon dioxide as the carbon source and the oxidation of an inorganic substance (such as hydrogen sulfide) as the energy source

Back 708

chemoautotroph

Front 709

Organism that is unable to produce its own organic molecules, and therefore requires organic nutrients in its diet

Back 709

chemoheterotroph

Front 710

Transfer of genetic material from one cell to another

Back 710

conjugation

Front 711

Photosynthetic bacterium that contains chlorophyll and releases oxygen; formerly called a blue-green alga.

Back 711

cyanobacteria

Front 712

Newly idenfitied viruses that are becoming more prominent

Back 712

emerging virus

Front 713

Spore formed within a cell; certain bacteria form endospores

Back 713

endospore

Front 714

Prokaryote that is able to grow in either the presence or the absence of gaseous oxygen

Back 714

facultative anaerobe

Front 715

Small, bristlelike fiber on the surface of a bacterial cell, which attaches bacteria to a surface; also fingerlike extension from the oviduct near the ovary

Back 715

fimbriae

Front 716

Long, slender extension used for locomotion by some bacteria, protozoans, and sperm

Back 716

flagellum (pl. flagella)

Front 717

Type of archaea that lives in extremely salty habitats

Back 717

halophile

Front 718

Organisms that can be infected by a virus, specifically

Back 718

host specific

Front 719

Symbiotic relationship between certain fungi and algae, in which the fungi possibly provide inorganic food or water and the algae provide organic food.

Back 719

lichen

Front 720

Bacteriophage life cycle in which the virus incorporates its DNA into that of a bacterium; occurs preliminary to the lytic cycle

Back 720

lysogenic cycle

Front 721

Bacteriophage life cycle in which the virus takes over the operation of the bacterium immediately upon entering it and subsequently destroys the bacterium

Back 721

lytic cycle

Front 722

Type of archaea that lives in oxygen-free habitats, such as swamps, and releases methane gas.

Back 722

methanogen

Front 723

Region of prokaryotic cells where DNA is located; it is not bounded by a nuclear envelope

Back 723

nucleoid

Front 724

Prokaryote unable to grow in the presence of free oxygen

Back 724

obligate anaerobe

Front 725

Disease-causing agent such as viruses, parasitic bacteria, fungi, and animals.

Back 725

pathogen

Front 726

Unique molecule found in bacterial cell walls.

Back 726

peptidoglycan

Front 727

Organism able to synthesize organic molecules by using carbon dioxide as the carbon source and sunlight as the energy source

Back 727

photoautotroph

Front 728

Self-duplicating ring of accessory DNA in the cytoplasm of bacteria.

Back 728

plasmid

Front 729

Infectious particle consisting of protein only and no nucleic acid

Back 729

prion

Front 730

Organism that lacks the membrane-bounded nucleus and membranous organelles typical of eukaryotes

Back 730

prokaryote

Front 731

RNA virus containing the enzyme reverse transcriptase that carries out RNA/DNA transcription

Back 731

retrovirus

Front 732

Organism that secretes digestive enzymes and absorbs the resulting nutrients back across the plasma membrane

Back 732

saprotroph

Front 733

Type of archaea that lives in hot, acidic, aquatic habitats, such as hot springs or near hydrothermal vents.

Back 733

thermoacidophile

Front 734

Exchange of DNA between bacteria by means of a bacteriophage.

Back 734

transduction

Front 735

Taking up of extraneous genetic material from the environment by bacteria

Back 735

transformation

Front 736

Infectious strand of RNA devoid of a capsid and much smaller than a virus.

Back 736

viroid

Front 737

Pathogenicity of an organism as indicated by ability to invade host tissues and cause disease.

Back 737

virulent

Front 738

Cell that moves and engulfs debris with pseudopods

Back 738

amoeboid

Front 739

Marine photosynthetic protist with a notable abundance of xanthophyll pigments; this group include well-known seaweeds of northern rocky shores.

Back 739

brown algae

Front 740

Free-living amoeboid cells that feed on bacteria and yeasts by phagocytosis and aggregate to form a plasmodium that produces spores.

Back 740

cellular slime mold

Front 741

Complex unicellular protist that moves by means of cilia and digests food in food vacuoles.

Back 741

ciliate

Front 742

Loose association of cells that remain independent for most functions.

Back 742

colony

Front 743

Transfer of genetic material from one cell to another.

Back 743

conjugation

Front 744

In protists and invertebrates, resting stage that contains reproductive bodies or embryos.

Back 744

cyst

Front 745

Golden-brown alga with a cell wall in two parts, or valves; significant part of phytoplankton.

Back 745

diatom

Front 746

Photosynthetic unicellular protist with two flagella, one whiplash and the other located within a groove between protective cellulose plates; significant part of phytoplankton.

Back 746

dinoflagellate

Front 747

[]]['

Back 747

euglenoid

Front 748

End-to-end chains of cells that form as cell division occurs in only one plane; in plants, the elongated stalk of a stamen.

Back 748

filament

Front 749

Member of the phylum foraminifera bearing a calcium carbonate test with many openings through which pseudopods extend.

Back 749

foraminiferan

Front 750

Members of a diverse group of photosynthetic protists; contain chlorophylls a and b and have other biochemical characteristics like those of plants.

Back 750

green algae

Front 751

Obtaining nourishment by ingesting solid food particles.

Back 751

holozoic

Front 752

To ingest extracellular particles by engulfing them, as do amoeboid cells.

Back 752

phagocytize

Front 753

Part of plankton containing organisms that photosynthesize, relesing oxygen to the atmosphere and serving as food producers in aquatic ecosystems.

Back 753

phytoplankton

Front 754

Freshwater and marine organisms that are suspended on or near the surface of the water; includes phytoplankton and zooplankton.

Back 754

plankton

Front 755

Free-living mass of cytoplasm that moves by pseudopods on a forest floor or in a field, feeding on decaying plant material by phagocytosis; reproduces by spore formation.

Back 755

plasmoidial slime mold

Front 756

Member of the kingdom Protista

Back 756

protist

Front 757

Heterotrophic, unicellular protist that moves by flagella, cilia, or pseudopodia, or is immobile.

Back 757

protozoan

Front 758

Cytoplasmic extension of amoeboid protists; used for locomotion and engulfing food.

Back 758

pseudopod

Front 759

Member of the phylum Actinopoda bearing a glassy silicon test, usually with a radial arrangement of spines; pseudopods are external to the test.

Back 759

radiolarian

Front 760

Marine photosynthetic protists with a notable abundance of phycoblilin pigments; include coralline algae of coral reefs.

Back 760

red algae

Front 761

Multicellular forms of red, green, and brown algae found in marine habitats.

Back 761

seaweed

Front 762

Structure that produces spores.

Back 762

sporangium

Front 763

Asexual reproductive or resting cell capable of developing into a new organism without fusion with another cell, in contrast to a gamete.

Back 763

spore

Front 764

Spore-forming protist that has no means of locomotion and is typically a parasite with a complex life cycle having both sexual and asexual phases.

Back 764

sporozoan

Front 765

Loose-fitting shell of a foraminiferan or a radiolarian; made of calcium carbonate or silicon, respectively.

Back 765

test

Front 766

Found in ciliates; contains long, barbed threads useful for defense and capturing prey.

Back 766

trichocyst

Front 767

Parasitic zooflagellate that causes severe disease in human beings and domestic animals, including a condition called sleeping sickness.

Back 767

trypanosome

Front 768

Filamentous organisms having cell walls made of cellulose; typically decomposers of dead freshwater organisms, but some are parasites of aquatic or terrestrial organisms.

Back 768

water mold

Front 769

Nonphotosynthetic protist that moves by flagella; typically zooflagellates enter into symbiotic relationships, and some are parasitic.

Back 769

zooflagellate

Front 770

Part of plankton containing protozoans and other types of microscopic animals.

Back 770

zooplankton

Front 771

Fingerlike sac in which nuclear fusion, meiosis, and ascospore production occur during sexual reproduction of sac fungi.

Back 771

ascus

Front 772

Clublike structure in which nuclear fusion, meiosis, and basidospore production occur during sexual reproduction of club fungi.

Back 772

basidium

Front 773

Asexual form of reproduction whereby a new organism develops as an outgrowth of the body of the parent.

Back 773

budding

Front 774

Members of the phylum Basidiomycota

Back 774

club fungi

Front 775

Spore produced by sac and club fungi during asexual reproduction.

Back 775

conidiospore

Front 776

Having two haploid nuclei that stem from different parent cells; during sexual reproduction, sace and club fungi have dikaryotic cells.

Back 776

dikaryotic

Front 777

Spore-producing and sporedisseminating structure fund in sac and club fungi.

Back 777

fruiting body

Front 778

Saprotrophic decomposer; the body is made up of filaments called hyphae that form a mass called a mycelium.

Back 778

fungus (pl., fungi)

Front 779

Filament of the vegatative body of a fungus.

Back 779

hypha

Front 780

Symbiotic relationship between certain fungi and algae, in which the fungi possibly provide inorganic food or water and the algae provide organic food.

Back 780

lichen

Front 781

Tangled mass of hyphal filaments composing the vegetative body of a fungus.

Back 781

mycelium

Front 782

Mutualistic relationship between fungal hyphae and roots of vascular plants.

Back 782

mycorrhizae

Front 783

Lacking cell walls; some fungal species have hyphae that are nonseptate.

Back 783

nonseptate

Front 784

Members of the phylum Ascomycota.

Back 784

sac fungi

Front 785

Having cell walls; some fungal species have hyphae that are septate.

Back 785

septate

Front 786

Structure that produces spores.

Back 786

sporangium

Front 787

Asexual or resting cell capable of developing into a new organism without fusion with another cell, in contrast to a gamete.

Back 787

spore

Front 788

Unicellular fungus that has a single nucleus and reproduces asexually by budding or fission, or sexually through spore formation.

Back 788

yeast

Front 789

Thick-walled resting cell formed during sexual reproduction of zygospore fungi.

Back 789

zygospore

Front 790

Members of the phylum Zygomycota.

Back 790

zygospore fungi

Front 791

Life cycle, typical of plants, in which a diploid sporophyte alternates with a haploid gametophyte

Back 791

alternation of generations

Front 792

Flowering plant; the seeds are borne within a fruit

Back 792

angiosperm

Front 793

Sperm-producing structures, as in the moss life cycle

Back 793

antheridia

Front 794

Egg-producing structures, as in the moss life cycle

Back 794

archegonia

Front 795

Member of one of three phyla of nonvascular plants -- the mosses, liverworts, and hornworts

Back 795

bryophyte

Front 796

Ovule-bearing unit that is a part of a pistil

Back 796

carpel

Front 797

Type of seedless vascular plant that is also called ground pine because it has the appearance of a miniature pine tree

Back 797

club moss

Front 798

Fossil fuel formed millions of years ago from plant material that did not decay

Back 798

coal

Front 799

Structure comprised of scales bearing sporangia; pollen cones bear microsporangia, and seed cones bear megasporangia

Back 799

cone

Front 800

Member of a group of cone-bearing gymnosperm plants that includes pine, cedar, and spruce trees

Back 800

conifer

Front 801

Seed leaf for embryo of a flowering plant; provides nutrient molecules for the developing plant before photosynthesis begins

Back 801

cotyledon

Front 802

Waxy layer covering the epidermis of plants that protects the plant against water loss and disease-causing organisms

Back 802

cuticle

Front 803

Type of gymnosperm with palmate leaves and massive cones; cycads are most often found in the tropics and subtropics

Back 803

cycad

Front 804

Having unisexual flowers or cones, with the male flowers or cones confined to certain plants and the female flowers or cones of the same species confined to other different plants

Back 804

dioecious

Front 805

Abbreviation of eudicotyledon. Flowering plant group; members have two embryonic leaves (cotyledons), net-veined leaves, vascular bundles in a ring, flower parts in fours or fives and their multiples, and other characteristics

Back 805

eudicot

Front 806

Member of a group of plants that have large fronds; in the sexual life cycle, the independent gametophyte produces flagellated sperm, and the vascular sporophyte produces windblown apores.

Back 806

fern

Front 807

Reproductive organ of a flowering plant, consisting of several kinds of modified leaves arranged in concentric rings and attached to a modified stem called the receptacle

Back 807

flower

Front 808

Leaf of a fern

Back 808

frond

Front 809

Flowering plant structure consisting of one or more ripened ovaries that usually contain seeds

Back 809

fruit

Front 810

Haploid generation of the alternation of generations life cycle of a plant; produces gametes that unite to form a diploid zygote

Back 810

gametophyte

Front 811

Member of phylum Ginkgophyte; maidenhair tree

Back 811

ginkgo

Front 812

Type of woody seed plant in which the seeds are not enclosed by fruit and are usually borne in cones, such as those of the conifers

Back 812

gymnosperm

Front 813

Seed plant that produces two types of spores -- microspores and megaspores. A plant that produces only one type of spore is homosporous.

Back 813

heterosporous

Front 814

In some plants, production of only one type of spore rather than differentiated types

Back 814

homosporous

Front 815

Member of phylum Anthocerophyta

Back 815

hornwort

Front 816

Division of seedless vascular plants having only one genus (Equisetum) in existence today; characterized by rhizomes, scale-like leaves, strobili, and tough, rigid stems

Back 816

horsetails

Front 817

Chemical that hardens the cell walls of plants

Back 817

lignin

Front 818

Type of bryophyte

Back 818

liverwort

Front 819

One of the two types of spores produced by seed plants; develops into a female gametophyte (embryo sac)

Back 819

megaspore

Front 820

One of the two types of spores produced by seed plants; develops into a male gametophyte (pollen grain)

Back 820

microspore

Front 821

Abbreviation of monocotyledon. Flowering plant group; members have one embryonic leaf (cotyledon), parallel-veined leaves, scattered vascular bundles, flower parts in threes or multiples of three, and other characteristics

Back 821

monocot

Front 822

Having unisexual male flowers or cones and unisexual female flowers or cones both on the same plant

Back 822

monoecious

Front 823

Type of bryophyte

Back 823

moss

Front 824

Bryophytes, such as mosses and liverworts, that have no vascular tissue and either occur in moist locations or have special adaptations for living in dry locations

Back 824

nonvascular plants

Front 825

In flowering plants, the enlarged, ovulebearing portion of the carpel that develops into a fruit; female gonad in animals that produces an egg and female sex hormones

Back 825

ovary

Front 826

In seed plants, a structure that contains the female gametophyte and has the potential to develop into a seed

Back 826

ovule

Front 827

Organic fuel consisting of the partially decomposed remains of peat mosses that accumulate in bogs

Back 827

peat

Front 828

Flower stalk; expands into the receptacle

Back 828

peduncle

Front 829

A flower part that occurs just inside the sepals; often conspicuously colored to attract pollinators

Back 829

petal

Front 830

Vascular tissue that conducts organic solutes in plants; contains sieve-tube members and companion cells

Back 830

phloem

Front 831

In seed plants, structure that is derived from a microspore and develops into a male gametophyte

Back 831

pollen grain

Front 832

In seed plants, a tube that forms when a pollen grain lands on the stigma and germinates. The tube grows, passing between the cells of the stigma and the style to reach the egg inside an ovule, where fertilization occurs

Back 832

pollen tube

Front 833

In gymnosperms, the transfer of pollen from pollen cone to seed cone; in angiosperms, the transfer of pollen from anther to stigma

Back 833

pollination

Front 834

Animal (e.g., a bee) that inadvertently transfers pollen from anther to stigma

Back 834

pollinator

Front 835

Area where a flower attaches to a floral stalk

Back 835

receptacle

Front 836

Rootlike hair that anchors a plant and absorbs minerals and water from the soil

Back 836

rhizoid

Front 837

Rootlike underground stem

Back 837

rhizome

Front 838

Mature ovule that contains an embryo, with stored food enclosed in a protective coat.

Back 838

seed

Front 839

Outermost, sterile, leaflike covering of the flower, usually green in color.

Back 839

sepal

Front 840

Structure that produces spores

Back 840

sporangium

Front 841

Asexual reproductive or resting cell capable of developing into a new organism without fusion with another cell, in contrast to a gamete

Back 841

spore

Front 842

Modified leaf that bears a sporangium or sporangia

Back 842

sporophyll

Front 843

Diploid generation of the alternation of generations life cycle of a plant; produces haploid spores that develop into the haploid generation

Back 843

sporophyte

Front 844

In flowering plants, the portion of the flower that consists of a filament and an anther containing pollen sacs where pollen is produced

Back 844

stamen

Front 845

In flowering plants, portion of the carpel where pollen grains adhere and germinate before fertilization can occur

Back 845

stigma

Front 846

Small opening between two guard cells on the underside of leaf epidermis through which gases pass

Back 846

stoma

Front 847

In club mosses, terminal clusters of leaves that bear sporangia

Back 847

strobilus

Front 848

Elongated, central portion of the carpel between the ovary and stigma

Back 848

style

Front 849

Transport tissue in plants, consisting of xylem and phloem

Back 849

vascular tissue

Front 850

Common name for seedless vascular plant that consists only of stems and has no leaves or roots

Back 850

whisk fern

Front 851

Vascular tissue that transports water and mineral solutes upward through the plant body; it contains vessel elements and tracheids

Back 851

xylem

Front 852

Fibrous roots that develop from stems or leaves, such as the prop roots of corn of the holdfast roots of ivy

Back 852

adventitious roots

Front 853

Layer of wood (secondary xylem) usually produced during one growing season.

Back 853

annual ring

Front 854

In vascular plants, masses of cells in the root and shoot that reproduce and elongate as primary growth occurs

Back 854

apical meristem

Front 855

Bud located in the axil of a leaf

Back 855

axillary bud

Front 856

External part of a tree, containing cork, cork cambium, and phloem

Back 856

bark

Front 857

Broad, expanded portion of a plant leaf that may be single or compound leaflets

Back 857

blade

Front 858

Layer of impermeable lignin and suberin bordering four sides of root endodermal cells; prevents water and solute transport between adjacent cells

Back 858

Casparian strip

Front 859

Plant tissue composed of cells with unevenly thickened walls; supports growth of stems and petioles

Back 859

collenchyma

Front 860

In plants, tissues composed of two or more kinds of cells (e.g., xylem, containing tracheids and vessel elements; phloem, containing sieve-tube members and companion cells)

Back 860

complex tissues

Front 861

Outer covering of the bark of trees; made of dead cells that may be sloughed off

Back 861

cork

Front 862

Lateral meristem that produces cork

Back 862

cork cambium

Front 863

In plants, ground tissue bounded by the epidermis and vascular tissue in stems and roots; in animals, outer layer of an organ, such as the cortex of the kidney or adrenal gland

Back 863

cortex

Front 864

Seed leaf for embryo of a flowering plant; provides nutrient molecules for the developing plant before photosynthesis begins

Back 864

cotyledon

Front 865

Waxy layer covering the epidermis of plants that protects the plant against water loss and disease-causing organisms

Back 865

cuticle

Front 866

Plant which sheds its leaves annually

Back 866

deciduous

Front 867

Internal plant root tissue forming a boundary between the cortex and the vascular cylinder

Back 867

endodermis

Front 868

Exterior tissue, usually one cell thick, of leaves, young stems, roots, and other parts of plants

Back 868

epidermal tissue

Front 869

In mammals, the outer, protective layer of the skin; in plants, tissue that covers roots, leaves, and stems of nonwoody organisms

Back 869

epidermis

Front 870

Abbreviation of eudicotyledon. Flowering plant group; members have two embryonic leaves (cotyledons), net-veined leaves, vascular bundles in a ring, flower parts in fours or fives and their multiples, and other characteristics

Back 870

eudicot

Front 871

In most monocots, a mass of similarly sized roots that cling to the soil

Back 871

fibrous root system

Front 872

Tissue that constitutes most of the body of a plant; consists of perenchyma, collenchyma, and sclerenchyma cells that function in storage, basic metabolism, and support

Back 872

ground tissue

Front 873

Nonwoody stem

Back 873

herbaceous stem

Front 874

In vascular plants, the region of a stem between two successive nodes

Back 874

internode

Front 875

Lateral appendage of a stem, highly variable in structure, often containing cells that carry out photosynthesis

Back 875

leaf

Front 876

Vascular tissue within a leaf

Back 876

leaf vein

Front 877

Frond of usually numerous, lightly raised, somewhat spongy, groups of cells in the bark of woody plants. Permits gas exchange between the interior of a plant and the external atmosphere

Back 877

lenticel

Front 878

Chemical that hardens the cell walls of plants

Back 878

lignin

Front 879

Undifferentiated embryonic tissue in the active growth regions of plants

Back 879

meristem

Front 880

Innere, thickest layer of a leaf consisting of palisade and spongy mesophyll; the site of most of photosynthesis

Back 880

mesophyll

Front 881

Abbreviation of monocotyledon. Flowering plant group; members have one embryonic leaf (cotyledon), parallel-veined leaves, scattered vascular bundles, flower parts in threes or multiples of three, and other characteristics

Back 881

monocot

Front 882

Mutualistic relationship between fungal hyphae and roots of vascular plants

Back 882

mycorrhizae

Front 883

In plants, the place where one or more leaves attach to a stem

Back 883

node

Front 884

Combination of two or more different tissues performing a common function

Back 884

organ

Front 885

Layer of tissue in a plant leaf containing elongated cells with many chloroplasts

Back 885

palisade mesophyll

Front 886

Plant tissue composed of the least-specialized of all plant cells; found in all organs of a plant

Back 886

parenchyma

Front 887

Flowering plant that lives more than one growing season because the underground parts regrow each season

Back 887

perennial

Front 888

Layer of cells surrounding the vascular tissue of roots; produces branch roots

Back 888

pericycle

Front 889

Protective tissue that replaces epidermis; includes cork, cork cambium

Back 889

periderm

Front 890

The part of a lant leaf that connects the blade to the stem

Back 890

petiole

Front 891

Vascular tissue that conducts organic solutes in plants; contains sieve-tube members and companion cells.

Back 891

phloem

Front 892

Paernchyma tissue in the center of some stems and roots

Back 892

pith

Front 893

Any depression or opening; usually in reference to the small openings in the cell walls of xylem cells that function in providing a continuum between adjacent xylem cells

Back 893

pit

Front 894

Original root that grows straight down and remains the dominant root of the plant; contrasts with fibrous root system

Back 894

primary root

Front 895

Rootlike underground stem

Back 895

rhizome

Front 896

Protective cover of the root tip, whose cells are constantly replaced as they are ground off when the root pushes through rough soil particles

Back 896

root cap

Front 897

Extension of a root epidermal cell that collectively increases the surface area for the absorption of water and minerals

Back 897

root hair

Front 898

Structure on plant root that contains nitrogen-fixing bacteria

Back 898

root nodule

Front 899

Includes the main root and any and all of its lateral (side) branches

Back 899

root system

Front 900

Plant tissue composed of cells with heavily lignified cell walls; functions in support

Back 900

sclerenchyma

Front 901

Group of actively dividing embryonic cells at the tips of plant shoots

Back 901

shoot apical meristem

Front 902

Aboveground portion of a plant consisting of the stem, leaves, and flowers

Back 902

shoot system

Front 903

Member that joins with others in the phloem tissue of plants as a means of transport for nutrient sap.

Back 903

sieve-tube member

Front 904

Layer of tissue in a a plant leaf containing loosely packed cells, increasing the amount of surface area for gas exchange

Back 904

spongy mesophyll

Front 905

Usually the upright, vertical portion of a plant that transports substances to and from the leaves

Back 905

stem

Front 906

Stem that grows horizontally along the ground and may give rise to new plants where it contacts the soil -- e.g., the runners of a strawberry plant.

Back 906

stolon

Front 907

Small opening between two guard cells on the underside of leaf epidermis through which gases pass.

Back 907

stoma

Front 908

Main axis of a root that penetrates deeply and is used by certain plants (such as carrots) for food storage

Back 908

taproot

Front 909

Bud that develops at the apex of a shoot

Back 909

terminal bud

Front 910

In vascular plants, type of cell in xylem that has tapered ends and pits through which water and minerals flow

Back 910

tracheid

Front 911

In plants, specialized outgrowth of the epidermis (i.e., root hairs)

Back 911

trichomes

Front 912

In plants, primary phloem and primary xylem enclosed by a bundle sheath

Back 912

vascular bundle

Front 913

In plants, lateral meristem that produces secondary phloem and secondary xylem

Back 913

vascular cambium

Front 914

In eudicots, the tissues in the middle of a root, consisting of the pericycle and vascular tissues

Back 914

vascular cylinder

Front 915

Transport tissue in plants, consisting of xylem and phloem.

Back 915

vascular tissue

Front 916

Cell that joins with others to form a major conducting tube found in xylem

Back 916

vessel element

Front 917

Secondary xylem that builds up year after year in woody plants and becomes the annual rings

Back 917

wood

Front 918

Vascular tissue that transports water and mineral solutes upward through the plant body; it contains vessel elements and tracheids

Back 918

xylem

Front 919

Layer of impermeable lignin and suberin bordering four sides of root endodermal cells; prevents water and solute transport between adjacent cells

Back 919

Casparian strip

Front 920

Explanation for upward transport of water in xylem based upon transpiration-created tension and the cohesive properties of water molecules

Back 920

cohesion-tension model

Front 921

Cell associated with sieve-tube members in phloem of vascular plants

Back 921

companion cell

Front 922

Waxy layer covering the epidermis of plants that protects the plant against water loss and disease-causing organisms

Back 922

cuticle

Front 923

Plant that takes its nourishment from the air because its placement in other plants gives it an aerial position

Back 923

epiphyte

Front 924

In plants, substance required for normal growth, development, or reproduction

Back 924

essential nutrient

Front 925

Removing a strip of bark from around a tree

Back 925

girdling

Front 926

One of two cells that surround a leaf stoma; changes in the turgor pressure of these cells cause the stoma to open or close

Back 926

guard cell

Front 927

Liberation of water droplets from the edges and tips of leaves

Back 927

guttation

Front 928

Major layer of soil visible in vertical profile; for example, topsoil is the A horizon

Back 928

horizon

Front 929

Decomposing organic matter in the soil

Back 929

humus

Front 930

Technique for growing plants by suspending them with their roots in a nutrient solution

Back 930

hydroponics

Front 931

Essential element needed in large amounts for plant growth, such as nitrogen, calcium or sulfur

Back 931

macronutrient

Front 932

Essential element needed in small amounts for plant growth, such as boron, copper, and zinc

Back 932

micronutrient

Front 933

Naturally occurring inorganic substance containing two or more elements; certain minerals are needed in the diet

Back 933

mineral

Front 934

Mutualistic relationship between fungal hyphae and roots of vascular plants

Back 934

mycorrhizae

Front 935

Vascular tissue that conducts organic solutes in plants; contains sieve-tube members and companion cells.

Back 935

phloem

Front 936

The use of plants to restore a natural area to its original condition

Back 936

phytoremediation

Front 937

Explanation for phloem transport; osmotic pressure following active transport of sugar into phloem brings a flow of sap from a source to a sink

Back 937

pressure-flow model

Front 938

Extension of a root epidermal cell that collectively increases the surface area for the absorption of water and minerals

Back 938

root hair

Front 939

Structure on plant root that contains nitrogen-fixing bacteria

Back 939

root nodule

Front 940

Osmotic pressure caused by active movement of mineral into root cells; sereves to elevate water in xylem for a short distance

Back 940

root pressure

Front 941

Member that joins with others in the phloem tissue of plants as a means of transport for nutrient sap.

Back 941

sieve-tube member

Front 942

Accumulation of inorganic rock material and organic matter that is capable of supporting the growth of vegetation

Back 942

soil

Front 943

Movement of topsoil to a new location due to the action of wind or running water.

Back 943

soil erosion

Front 944

Vertical section of soil from the ground surface to the unaltered rock below.

Back 944

soil profile

Front 945

Small opening between two guard cells on the underside of leaf epidermis through which gases pass.

Back 945

stoma

Front 946

In vascular plants, type of cell in xylem that has tapered ends and pits through which water and minerals flow

Back 946

tracheid

Front 947

Plant's loss of water to the atmosphere, mainly through evaporation at leaf stomata

Back 947

transpiration

Front 948

Cell that joins with others to form a major conducting tube found in xylem

Back 948

vessel element

Front 949

Potential energy of water; a measure of the capability to release or take up water relative to another substance.

Back 949

water potential

Front 950

Plant hormone that causes stomata to close and initiates and maintains dormancy

Back 950

abscisic acid (ABA)

Front 951

Dropping of leaves, fruits or flowers from a plant

Back 951

abscission

Front 952

Influence of a terminal bud in suppressing the growth of lateral buds

Back 952

apical dominance

Front 953

Plant hormone regulating growth, particularly cell elongation; also called indoleacetic acid (IAA)

Back 953

auxin

Front 954

Internal mechanism that maintains a biological rhythm in the absence of environmental stimuli

Back 954

biological clock

Front 955

Biological rhythm with a 24-hour cycle

Back 955

circadian rhythm

Front 956

Protective sheath that covers the young leaves of a seedling

Back 956

coleoptile

Front 957

Plant hormone that promotes cell division; often works in combination with auxin during organ development in plant embryos

Back 957

cytokinin

Front 958

Plant whose flowering is not dependent on day length -- e.g., tomato and cucumber

Back 958

day-neutral plant

Front 959

In plants, a cessation of growth under conditions that seem appropriate for growth

Back 959

dormancy

Front 960

Plant hormone that causes ripening of fruit and is also involved in abscission

Back 960

ethylene

Front 961

Beginning of growth of a seed, spore, or zygote, especially after a period of dormancy.

Back 961

germination

Front 962

Plant hormone promoting increased stem growth; also involved in flowering and seed germination.

Back 962

gibberellin

Front 963

Growth response of roots and stems of plants to the Earth's gravity; roots demonstrate positive gravitropism, and stems demonstrate negative gravitropism.

Back 963

gravitropism

Front 964

Chemical messenger produced in one part of the body that controls the activity of other parts.

Back 964

hormone

Front 965

Plant that flowers when day length is longer than a critical length; e.g., wheat, barley, clover, and spinach

Back 965

long-day plant

Front 966

Relative lengths of daylight and darknessa that affect the physiology and behavior of an organism.

Back 966

photoperiodism

Front 967

Growth response of plant stems to light; stems demonstrate positive phototropism.

Back 967

phototropism

Front 968

Photoreversible plant pigment that is involved in photoperiodism and other responses of plants, such as etiolation.

Back 968

phytochrome

Front 969

Sum of the processes involving aging, decline, and eventual death of a plant or plant part.

Back 969

senescence

Front 970

Plant that flowers when day length is shorter than a critical length -- e.g., cocklebur, poinsettia, and chrysanthemum

Back 970

short-day plant

Front 971

Sensors found in root cap cells that cause a plant to demonstrate gravitropism.

Back 971

statolith

Front 972

In plants, unequal growth due to contact with solid objects, as the coiling of tendrils around a pole.

Back 972

thigmotropism

Front 973

In plants, a growth response toward or away from a directional stimulus.

Back 973

tropism

Front 974

In flowering plants, pollenbearing portion of stamen

Back 974

anther

Front 975

Ovule-bearing unit that is a part of a pistil

Back 975

carpel

Front 976

Joint evolution in which one species exerts selective pressure on the other species.

Back 976

coevolution

Front 977

Seed leaf for embryo of a flowering plant; provides nutrient molecules for the developing plant before photosynthesis begins

Back 977

cotyledon

Front 978

In flowering plants, one sperm nucleus unites with the egg nucleus, and a second sperm nucleus unites with the polar nuclei of an embryo sac.

Back 978

double fertilization

Front 979

Stage of a multicellular organism that develops from a zygote before it becomes free-living; in seed plants, the embryo is part of the seed.

Back 979

embryo

Front 980

Female gametophyte (megagametophyte) of flowering plants

Back 980

embryo sac

Front 981

In flowering plants, nutritive storage tissue that is derived from the union of a sperm nucleus and polar nuclei in the embryo sac.

Back 981

endosperm

Front 982

In seed plants, the gametophyte that produces an egg; in flowering plants, an embry sac. Sometimes called a megagametophyte

Back 982

female gametophyte

Front 983

End-to-end chains of cells that form as cell division occurs in only one plane; in plants, the elongated stalk of a stamen.

Back 983

filament

Front 984

Reproductive organ of a flowering plant, consisting of several kinds of modified leaves arranged in concentric rings and attached to a modified stem called the receptacle.

Back 984

flower

Front 985

Flowering plant structure consisting of one or more ripened ovaries that usually contain seeds.

Back 985

fruit

Front 986

Haploid generation of the alternation of generations life cycle of a plant; produces gametes that unite to form diploid zygote.

Back 986

gametophyte

Front 987

Crossing of different species.

Back 987

hybridization

Front 988

In seed plants, the gametophyte that produces sperm; a pollen grain. Sometimes called a microgametophyte.

Back 988

male gametophyte

Front 989

One of the two types of spores produced by seed plants; develops into a female gametophyte (embryo sac)

Back 989

megaspore

Front 990

Megaspore mother cell; produces megaspores by meiosis; only one megaspore persists.

Back 990

megasporocyte

Front 991

One of the two types of spores produced by seed plants; develops into a male gametophyte (pollen grain)

Back 991

microspore

Front 992

Microspore mother cell; produces microspores by meiosis.

Back 992

microsporocyte

Front 993

In flowering plants, the enlarged, ovulebearing portion of the carpel that develops into a fruit; female gonad in animals that produces an egg and female sex hormones.

Back 993

ovary

Front 994

In seed plants, a structure that contains the female gametophyte and has the potential to develop into a seed.

Back 994

ovule

Front 995

A flower part that occurs just inside the sepals; often conspicuously colored to attract pollinators.

Back 995

petal

Front 996

In flowering plants, the embryonic plant shoot that bears young leaves.

Back 996

plumule

Front 997

In seed plants, structure that is derived from a microspore and develops into a male gametophyte.

Back 997

pollen grain

Front 998

In gymnosperms, the transfer of pollen from pollen cone to seed cone; in angiosperms, the transfer of pollen from anther to stigma.

Back 998

pollination

Front 999

Plant cell from which the cell wall has been removed.

Back 999

protoplast

Front 1000

Mature ovule that contains an embryo, with stored food enclosed in a protective coat.

Back 1000

seed

Front 1001

Beginning of plant growth.

Back 1001

seed germination

Front 1002

Outermost, sterile, leaflike covering of the flower; usually green in color.

Back 1002

sepal

Front 1003

Plant cell embryo that is asexually produced through tissue culture techniques.

Back 1003

somatic embryo

Front 1004

Diploid generation of the alternation of generations life cycle of a plant; produces haploid spores that develop into the haploid generation.

Back 1004

sporophyte

Front 1005

In flowering plants, the portion of the flower that consists of a filament and an anther containing pollen sacs where pollen is produced.

Back 1005

stamen

Front 1006

In flowering plants, portion of the carpel where pollen grains adhere and germinate before fertilization can occur.

Back 1006

stigma

Front 1007

Elongated, central portion of the carpel between the ovary and stigma.

Back 1007

style

Front 1008

Process of growing tissue artificially, usually in a liquid medium in laboratory glassware.

Back 1008

tissue culture

Front 1009

Cell that has the full genetic potential of the organism, including the potential to develop into a complete organism.

Back 1009

totipotent

Front 1010

Plant that carries genes of another organism as a result of DNA technology; also genetically modified plant.

Back 1010

transgenic plant

Front 1011

Animal that has no body cavity (i.e., tapeworm)

Back 1011

acoelomate

Front 1012

Kingdom of animals

Back 1012

Animalia

Front 1013

Dissimilar in corresponding parts of organs on opposite sides of the body that are normally alike in symmetrical animals

Back 1013

asymmetrical

Front 1014

Body plan having two corresponding or complementary halves

Back 1014

bilateral symmetry

Front 1015

Having a well-recognized anterior head with a brain and sensory receptors

Back 1015

cephalization

Front 1016

Member of the phylum Platyhelminthes (flatworm); tapeworms that are intestinal parasites of vertebrate hosts

Back 1016

cestode

Front 1017

Invertebrate in the phylum Cnidaria existing as either a polyp or medusa with two tissue layers and radial symmetry

Back 1017

cnidarian

Front 1018

Body cavity lying between the digestive tract and body wall that is completely lined by mesoderm

Back 1018

coelom

Front 1019

Animal possessing a coelom (body cavity) completely lined by mesoderm (e.g., protostomes and deuterostomes).

Back 1019

coelomate

Front 1020

Member of the phylum Ctenophora; free-swimming marine invertebrates

Back 1020

comb jelly

Front 1021

In protists and invetebrates, resting stage that contains reproductive bodies or embryos

Back 1021

cyst

Front 1022

Group of coelomate animals in which the second embryonic opening is associated with the mouth; the first embryonic opening, the blasopore, is associated with the anus.

Back 1022

deutorostome

Front 1023

In cnidarians, when both body forms (polyp and medusa) are present

Back 1023

dimorphic

Front 1024

A swelling of the limbs due to blockage of lymphatic vessles by parasitic filarial roundworms

Back 1024

elephantiasis

Front 1025

Member of the phylum Platyhelminthes (e.g., tapeworms, planarians)

Back 1025

flatworm

Front 1026

Blind digestive cavity in animals that have a sac body plan

Back 1026

gastrovascular cavity

Front 1027

Disease in dogs caused by the filarial worm, a roundworm; worms live in the heart and arteries that serve the lungs

Back 1027

heartworm disease

Front 1028

Type of animal that has both male and female sex organs

Back 1028

hermaphroditic

Front 1029

Freshwater member of phylum Cnidaria

Back 1029

hydra

Front 1030

Animal without endoskeleton of bone or cartilage

Back 1030

invertebrate

Front 1031

Among snicarians, bell-shaped body form that is directed downward and contains much mesoglea.

Back 1031

medusa

Front 1032

Jellylike layer between the epideermis and the gastrodermis of a cnidarian

Back 1032

mesoglea

Front 1033

In cnidarians, a capsule that contains a threadlike fiber, the release of which aids in the capture of prey.

Back 1033

nematocyst

Front 1034

Member of phylum Cnidaria; common colonial hydrozoan found in brackish water or the ocean.

Back 1034

Obelia

Front 1035

Among cnidarians, body form that is directed upward and contains much mesoglea; in anatomy, small, abnormal growth that arises from the epithelial lining.

Back 1035

polyp

Front 1036

Segment of a tapeworm that contains both male and female sex organs and becomes a bag of eggs

Back 1036

proglottid

Front 1037

Group of coelomate animals in which the first embryonic opening (the blasopore) is associated with the mouth

Back 1037

protostome

Front 1038

Animal possessing a coelom (body cavity) incompletely lined by mesoderm (i.e., roundworms)

Back 1038

pseudocoelomate

Front 1039

Body plan in which similar parts are arranged around a central axis, like spokes of a wheel.

Back 1039

radial symmetry

Front 1040

Marine invertebrate of the phylum Nemertea having a distinctive proboscis apparatus

Back 1040

ribbon worm

Front 1041

Member of phylum Rotiferea; rotifers are primarily freshwater organisms

Back 1041

rotifer

Front 1042

Member of the phylum Nematoda with a cylindrical body that has a complete digestive tract and a pseudocoelom; some forms are free-living in water and soil, and many are parasitic

Back 1042

roundworm

Front 1043

Disease caused by the blood flke, a parasitic flatworm of the phylum Platyhelminthes

Back 1043

schistosomiasis

Front 1044

Tapeworm head region; contains hooks and suckers for attachment to host.

Back 1044

scolex

Front 1045

Repetition of body units as seen in the earthworm

Back 1045

segmentation

Front 1046

Tending to stay in one place

Back 1046

sessile

Front 1047

Animal that stays in one place and filters small food particles from the water (e.g., sponge)

Back 1047

sessile filter feeder

Front 1048

Skeletal structure of sponges composed of calcium carbonate or silicate

Back 1048

spicule

Front 1049

Invertebrate animal of the phylum Porifera; pore-bearing filter feeder whose inner body wall is lined by collar cells

Back 1049

sponge

Front 1050

Collabenous fibers found in the body wall of sponges

Back 1050

spongin

Front 1051

Member of the phylum Platyhelminthes (flatworm); ectoparasitic or endoparasitic flukes

Back 1051

trematode

Front 1052

Serious infection caused by parasitic roundworm of the phylum Nematoda whose larvae encyst in muscles

Back 1052

trichinosis

Front 1053

Member of the phylum Platyhelminthes (flatworm); free-living aquatic planarians and their relatives

Back 1053

tubellarian

Front 1054

Chordate in which the notochord is replaced by a vertebral column.

Back 1054

vertebrate

Front 1055

Member of a phylum of invertebrates (phylum Annelida) that contains segmented worms, such as the earthworm and the clam worm

Back 1055

annelid

Front 1056

Member of a phylum of invertebrates (phylum Arthropoda) that contains, among other groups, crustaceans and insects, which have an exoskeleton and jointed appendages

Back 1056

arthropod

Front 1057

Type of mollusc with a shell composed of two valves; includes clams, oysters, and scallops

Back 1057

bivalve

Front 1058

Elongated arthropod characterized by having one pair of legs to each body segment; they may have 15 to 173 pairs of legs

Back 1058

centipede

Front 1059

Type of mollusc in which a modified foot develops into the head region; includes squids, cuttlefish, octopuses, and nautiluses

Back 1059

cephalapod

Front 1060

Fused head and thorax found in decapods (shrimps, lobsters, crayfish, and crabs)

Back 1060

cephalothorax

Front 1061

Group of arthropods (e.g., horseshoe crabs, sea spiders, arachnids), which have a pair of appendages in the form of pinchers or fangs

Back 1061

chelicerate

Front 1062

Strong but flexible nitrogenous polysaccharide found in the exoskeleton of arthropods

Back 1062

chitin

Front 1063

Body cavity lying between the digestive tract and body wall that is completely lined by mesoderm

Back 1063

coelom

Front 1064

Member of a group of marine arthropods that contains, among others, shrimps, crabs, crayfish, and lobsters

Back 1064

crustacean

Front 1065

Type of crustacean in which the thorax bears five pairs of walking legs; includes shrimps, lobsters, crayfish, and crabs

Back 1065

decapod

Front 1066

Group of coelomate animals in which the second embryonic opening is associated with the mouth; the first embryonic opening, the blastopore, is associated with the anus

Back 1066

deuterostome

Front 1067

Phylum of marine animals that includes sea stars, sea urchins, and sand dollars; characterized by radial symmetry and a water vascular system

Back 1067

echnioderm

Front 1068

Body cavity that forms by the fusion of a pair of mesodermal pouches from the wall of the primitive gut

Back 1068

enterocoelom

Front 1069

Protective external skeleton, as in arthropods

Back 1069

exoskeleton

Front 1070

Mollusc with a broad, flat foot for crawling (e.g., snails and slugs)

Back 1070

gastropod

Front 1071

Residual coelom found in arthropods, which is filled with hemolymph

Back 1071

hemocoel

Front 1072

Type of arthropod. The head has antennae, compound eyes, and simple eyes; the thorax has three pairs of legs and often wings; and the abdomen has internal organs

Back 1072

insect

Front 1073

Blood-sucking annelid, usually found in fresh water, with a sucker at each end of a segmented body

Back 1073

leech

Front 1074

Blind, threadlike excretory tubule near the anterior end of an insect's hindgut

Back 1074

Malpighian tubule

Front 1075

In molluscs, an extension of the body wall that may secrete a shell

Back 1075

mantle

Front 1076

Change in shape and form that some animals, such as insects, undergo during development

Back 1076

metamorphosis

Front 1077

More or less cylindrical arthropod characterized by having two pairs of short legs on most of its body segments; may have 13 to almost 200 pairs of legs

Back 1077

millipede

Front 1078

Member of the phylum Mollusca, which includes squids, clams, snails, and chitons; characterized by a visceral mass, a mantle, and a foot

Back 1078

mollusc

Front 1079

Periodic shedding of the exoskeleton in arthropods

Back 1079

molt

Front 1080

Segmentally arranged, paired excretory tubules of many invertebrates, as in the earthworm

Back 1080

nephridium (pl., nephridia)

Front 1081

Inveretebrate member of the phylum Annelida; characterized by body segmentationand the presence of setae (e.g., earthworms)

Back 1081

oligochaete

Front 1082

Invertebrate member of the phylum Annelida; marine organisms characterized by the presence of many setae (e.g., tube worms and clam worms)

Back 1082

polychaete

Front 1083

Group of coelomate animals in which the first embryonic opening (the blastopore) is associated with the mouth

Back 1083

protostome

Front 1084

Tonguelike organ found in molluscs that bears rows of tiny teeth, which point backward; used to obtain food

Back 1084

radula

Front 1085

In protostomes, coelom formed by splitting of the embryonic mesoderm

Back 1085

schizocoelom

Front 1086

Invertebrate member of the phylum Echinodermata; characterized by water vascular system and tube feet (also called starfish)

Back 1086

sea star

Front 1087

A needlelike, chitinous bristle in annelids, arthropods, and others

Back 1087

seta (pl., setae)

Front 1088

In insecs, air tubes located between the spiracles and the tracheoles. In tetrapod vertebrates, air tube (windpipe) that runs between the larynx and the bronchi

Back 1088

trachea (pl., tracheae)

Front 1089

Part of the water vascular system in sea stars, located on the oral surface of each arm, functions in locomotion

Back 1089

tube foot

Front 1090

Expanded dorsal surface of long intestine of earthworms, allowing additional surface for absorption

Back 1090

typhlosole

Front 1091

Members of animal phylum Arthropoda that includes centipedes, millipeds, and insects

Back 1091

uniramians

Front 1092

Series of canals that takes water to the tube feet of an echinoderm, allowing them to expand

Back 1092

water vascular system

Front 1093

Vertebrate that lacks jaws; supereclass Agnatha includes only the jawless fishes -- ie the lampreys and hagfishes

Back 1093

agnathan

Front 1094

Egg that has an amnion, as seen during the development of reptiles, birds, and mammals

Back 1094

amniotic egg

Front 1095

Member of a class of vertebrates that includes frogs, toads, and salamanders; they are still tied to a watery environment for reproduction

Back 1095

amphibian

Front 1096

Endothermic vertebrate that has feathers and wings, is often adapted for flight, and lays hard-shelled eggs.

Back 1096

bird

Front 1097

Members of a class of vertebrates (class Osteichithyes) containing numerous diverse fishes, with a bony rather than cartilaginous skeleton.

Back 1097

bony fishes

Front 1098

Members of a class of vertebrates (class Chondrichthyes) with a cartilaginous rather than bony skeleton; includes sharks, rays, and skates.

Back 1098

cartilaginous fishes

Front 1099

Animals in the phylum Chordata that have a dorsal tubular nerve cord, a notochord, pharyngeal gill pouches, and postanal tail at some point in their life cycle.

Back 1099

chordate

Front 1100

Posterior portion of the digestive tract in certain vertebrates that receives feces and urogenital products.

Back 1100

cloaca

Front 1101

Organism having a body temperature that varies according to the environmental temperature.

Back 1101

ectotherm

Front 1102

Innermost primary tissue layer of an animal embryo that gives rise to the linings of the digestive tract and associated structures

Back 1102

endotherm

Front 1103

One of the light, horny, epidermal outgrowths that form the external covering of the bodies of birds and the greater part of the surface of their wings.

Back 1103

feather

Front 1104

In fish and other aquatic animals, membranous, winglike, or paddlelike process used to propel, balance, or guide the body.

Back 1104

fin

Front 1105

Aquatic, gill-breathing vertebrate that usually has fins and skin covered with scales; fishes were among the earliest vertebrates that evolved.

Back 1105

fishes

Front 1106

Respiratory organ in most aquatic animals; in fish, an outward extension of the pharynx.

Back 1106

gills

Front 1107

Tooth-bearing bone of the head.

Back 1107

jaw

Front 1108

Type of fish that has no jaws; includes today's hagfishes and lampreys.

Back 1108

jawless fishes

Front 1109

Type of fishes with limblike fins.

Back 1109

lobe-finned fishes

Front 1110

Internal respiratory organ containing moist surfaces for gas exchange.

Back 1110

lungs

Front 1111

Endothermic vertebrate characterized especially by the presence of hair and mammary glands.

Back 1111

mammal

Front 1112

Member of a group of mammals bearing immature young nursed in a marsupium, or pouch -- for example, kangaroo and opossum.

Back 1112

marsupial

Front 1113

Change in shape and form that some animals, such as insects, undergo during development.

Back 1113

metamorphosis

Front 1114

Egg-laying mammal -- e.g., duckbill platypus and spiny anteater.

Back 1114

monotreme

Front 1115

In many complex animals, a centrally placed cord of nervous tissue that receives sensory information and exercises motor control.

Back 1115

nerve cord

Front 1116

Cartilaginous-like supportive dorsal rod in all chordates sometime in their life cycle; replaced by veretebrae in vertebrates.

Back 1116

notochord

Front 1117

Earliest vertebrate fossils of the Cambrian and Devonian periods; these fishes were small, jawless, and finless.

Back 1117

ostracoderm

Front 1118

Organ formed during the development of placental mammals from the chorion and the uterine wall; allows the embryo, and then the fetus, to acquire nutrients and rid itself of wastes; produces hormones that regulate pregnancy.

Back 1118

placenta

Front 1119

First jawed vertebrates; heavily armored fishes of the Devonian period.

Back 1119

placoderm

Front 1120

Group of bony fishes with fins supported by parallel bony rays connected by webs of thin tissue.

Back 1120

ray-finned bony fishes

Front 1121

Member of a class of terrestrial invertebrates with internal fertilization, scaly skin, and an egg with a leathery shell; includes snakes, lizards, turtles, and crocodiles.

Back 1121

reptile

Front 1122

In fishes and reptiles, a thin flake; scales cover the body and offer protection.

Back 1122

scale

Front 1123

In fishes, a gas-filled sac whose pressure can be altered to change buoyancy.

Back 1123

swim bladder

Front 1124

Four-footed vertebrate; includes amphibians, reptiles, birds, and mammals.

Back 1124

tetrapod

Front 1125

Mammal-like reptiles appearing in the middle Permian period; ancestral to mammals.

Back 1125

therapsid

Front 1126

Chordate in which the notochord is replaced by a vertebral column.

Back 1126

vertebrate