Biology Midterm 1

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atom

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fundamental building block of all matter

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biology

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systematic study of life

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biosphere

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all regions of Earth where organisms live

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cell

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smallest unit of life

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community

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all populations of all species in a given area

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ecosystem

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a community interacting with its environment

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emergent property

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a characteristic of a system that does not appear in any of a system's component parts

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molecule

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an association of two or more atoms

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nature

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everything in the universe except what humans have manufactured

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organism

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individual that consists of one or more cells

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population

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group of individuals of the same species that live in a given area

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levels of organization in nature, from singular to more complex:

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atoms
molecules
cells
organisms
populations
communities
ecosystems
the biosphere

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consumer

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organism that gets energy and carbon by feeding on tissues, wastes, or remains of other organisms

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development

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multistep process by which the first cell of a new individual becomes a multicelled adult

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DNA

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deoxyribonucleic acid; molecule that carries hereditary information about traits

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energy

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the capacity to do work

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growth

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increases in the number, size, and volume of cells in multicelled species

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homeostasis

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set of processes by which an organism keeps its internal conditions within tolerable ranges

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inheritance

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transmission of DNA from parents to offspring

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nutrient

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substance that an organism needs for growth and survival, but cannot make for itself

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receptor

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molecule or structure that responds to a specific form of stimulation

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reproduction

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process by which parents produce offspring

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animal

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multicelled consumer that develops through a series of embryonic stages and moves about during part or all of the life cycle

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archaean

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a member of the prokaryotic domain Archaea

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bacterium

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a member of the prokaryotic domain Bacteria

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critical thinking

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mental process of judging information before accepting it

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eukaryote

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organism whose cells characteristically have a nucleus

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fungus

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type of eukaryotic consumer that obtains nutrients by digestion and absorption outside the body

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genus

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a group of species that share a unique set of traits

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plant

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a mutlicelled, typically photosynthetic producer

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prokaryote

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single-celled organism in which the DNA is not contained by a nucleus

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protist

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diverse group of simple eukaryotes

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science

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systematic study of nature

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species

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a type of organism

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hypothesis

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testable explanation of a natural phenomenon

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law of nature

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generalization that describes a consistent natural phenomenon for which there is incomplete scientific explanation

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model

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system similar to an object or event that cannot itself be tested directly

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prediction

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a statement, based on a hypothesis, about a condition that should exist if the hypothesis is not wrong

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scientific theory

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hypothesis that has not been disproven after many years of rigorous testing, and is useful for making predictions about other phenomena

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control group

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a group of objects or individuals that is identical to an experimental group except for one variable

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experiment

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a test designed to support or falsify a prediction

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experimental group

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a group of objects or individuals that display or are exposed to a variable under investigation

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variable

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a characteristic or event that differs among individuals

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sampling error

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difference between results derived from testing an entire group of events or individuals, and results derived from testing a subset of the group

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statistically significant

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refers to a result that is statistically unlikely to have occurred by chance

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taxon (taxa)

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a grouping of organisms

*Linnaean classification in which each species is assigned to ever more inclusive groups, or taxa,
domain
kingdom
phylum
class
order
family
genus
species
common name

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taxonomy

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science of naming and classifying species

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character

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quantifiable, heritable characteristic or trait

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clade

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a group of species that share a set of characters

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cladistics

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method of determining evolutionary relationships by grouping species into clades

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cladogram

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evolutionary tree diagram that shows a network of evolutionary relationships among clades

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evolutionary tree

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type of diagram that summarizes evolutionary relationships among a group of species

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monophyletic group

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an ancestor and all of its descendants

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phylogeny

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evolutionary history of a species or groups of species

the central question is, who is related to whom?

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sister groups

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the two lineages that emerge from a node on a cladogram
the same age

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hydrothermal vent

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submerged opening where hot, mineral-rich water streams out

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protocells

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membranous sacs that contain interacting organic molecules

grow and divide and may have been the ancestors of the first cells

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RNA world

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hypothetical early interval when RNA served as the material of inheritance

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endosymbiosis

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one species lives inside another

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eukaryote

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organism that encloses its DNA in a nucleus; a protist, plant, fungus, or animal

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ozone layer

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atmospheric layer with a high concentration of ozone that prevents much UV radiation from reaching the Earth's surface

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prokaryote

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single-celled organism in which the DNA resides in the cytoplasm; a bacterium or archaean

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stromatolites

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dome-shaped structures composed of layers of prokaryotic cells and sediments; form in shallow seas

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plasmid

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of a prokaryote, a small ring of nonchromosomal DNA with a few genes

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prokaryotic conjugation

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one prokaryotic cell transfers a plasmid to another

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prokaryotic fission

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method of asexual reproduction in which one prokaryotic cell divides and forms two identical descendant cells

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strain

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a subgroup within a species that has a characteristic trait or traits

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archaea

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prokaryotic domain most closely related to eukaryotes; many members live in extreme environments

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bacteria

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most diverse prokaryotic domain

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decomposer

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organism that breaks organic material down into its inorganic subunits

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extreme halophile

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organism that lives where the salt concentration is high

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extreme thermophile

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organism that lives where the temperature is very high

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methanogen

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organism that produces methane gas as a metabolic by-product

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nitrogen fixation

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process of combining nitrogen gas with hydrogen to form ammonia

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normal flora

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collection of microorganisms that normally live in or on a healthy animal or person

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pathogen

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organism that infects another that causes disease

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vector

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animal that transmits a pathogen between its hosts

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flagellated protozoan

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member of a heterotrophic lineage of protists that have one or more flagella

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pellicle

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layer of proteins that gives shape to many unwalled, single-celled protists

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protist

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a eukaryote that is not a fungus, plant, or animal

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catastrophism

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now-abandoned hypothesis that catastrophic geologic forces unlike those of the present day shaped Earth's surface

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evolution

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change in a line of descent

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theory of uniformity

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idea that gradual, repetitive processes occurring over long time spans shaped Earth's surface

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adaption (adaptive trait)

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a heritable trait that enhances an individual's fitness

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fitness

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the degree of adaption to an environment, as measured by an individual's relative genetic contribution to future generations

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natural selection

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a process of evolution in which individuals of a population who vary in the details of heritable traits survive and reproduce with differing success

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genetic drift

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change in allele frequencies in a population due to chance alone

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fixed

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refers to an allele for which all members of a population are homozygous

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bottleneck

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reduction in population size so severe that it reduces genetic diversity

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founder effect

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change in allele frequencies that occurs after a small number of individuals establish a population

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inbreeding

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nonrandom mating among close relatives, which share a large number of alleles

lowers the genetic diversity in a populationT

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gene flow

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the movement of alleles into and out of a population, as by individuals that immigrate or emigrate

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homozygous

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having identical alleles of a gene

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hybrid

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the offspring of a cross between two individuals that breed true for different forms of a trait

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phenotype

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an individual's observable traits

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genotype

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the particular alleles carried by an individual

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dominant

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refers to an allele that masks the effect of a recessive allele paired with it

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recessive

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refers to an allele with an effect that is masked by a dominant allele on the homologous chromosome

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heterozygous

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having two different alleles of a gene

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monohybrid cross

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experiment in which individuals with different alleles of a gene are crossed

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continuous variation

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a range of small differences in a shared trait

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bell curve

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Bell shaped curve; typically results from graphing frequency versus distribution for a trait that varies continuously in a population

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centromere

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constricted region in a eukaryotic chromosome where sister chromotids are attached

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chromosome

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a structure that consists of DNA and associated proteins; carries part or all of a cell's genetic information

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histone

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type of protein that structurally organizes eukaryotic chromosomes

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nucleosome

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a length of DNA wound around a spool of histone proteins

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sister chromatid

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one of two attached members of a duplicated eukaryotic chromosome

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autosome

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any chromosome other than a sex chromosome

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chromosome number

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the sum of all chromosomes in a cell of a given type

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diploid

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having two of each type of chromosome characteristic of the species (2n)

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karytope

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image of an individual's complement of chromosomes arranged by size, length, shape, and centromere location

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sex chromosome

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member of a pair of chromosomes that differs between males and females

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DNA sequence

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The order of nucleotide bases in a strand of DNA

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genitically modified organisms (GMOs)

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An organism whose genome has been deliberately modified

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transgenic

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refers to an organism that has been genetically modified to carry a gene from a different species

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xenotransplantation

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transplant of an organ from one species into another

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eugenics

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idea of deliberately improving the genetic qualities of the human race

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gene therapy

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the transfer of a normal or modified gene into an individual with the goal of treating a genetic defect or disorder

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gene

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part of a DNA base sequence; specifies an RNA or protein product

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transcription

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process by which an RNA is assembled from nucleotides using the base sequence of a gene as a template

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messenger RNA (mRNA)

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type of RNA that has a protein building message

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translation

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process by which a polypeptide chain is assembled from amino acids in the order specified by an nRNA

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gene expression

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process by which the information in a gene becomes converted to an RNA or protein product

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RNA polymerase

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enzyme that carries out transcription

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stabilizing selection

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mode of natural selection in which intermediate phenotypes are favored over extremes

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disruptive selection

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mode of natural selection that favors two forms in a range of variation; intermediate forms are selected against

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fossil

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physical evidence of an organism that lived in the ancient past

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half-life

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characteristic time it takes for half of a quantity of radioisotope to decay

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lineage

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line of descent

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radiometric dating

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method of estimating the age of a rock or fossil by measuring the content and proportions of a radiosotope and its daughter elements

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geologic time scale

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chronology of Earth history

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gondwana

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supercontinent that formed more than 500 million years ago

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pangea

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supercontinent that formed about 237 million years ago and broke up about 152 million years ago

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plate tectonics

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theory that Earth's outer layer of rock is cracked into plates, the slow movement of which rafts continents to new locations over geologic time

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analogous structures

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similar structures that evolved separately in different lineages

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homologous structures

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similar body parts that reflect shared ancestry among lineages

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morphological structures

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evolutionary pattern in which similar body parts evolve separately in different lineages

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morphological divergence

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evolutionary pattern in which a body part of an ancestor changes in its descendants

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speciation

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process by which new species arise from existing species

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reproductive isolation

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absence of gene flow between populations; part of speciation

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allopatric speciation

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speciation pattern in which a physical barrier that separates members of a population ends gene flow between them

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sympatric speciation

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pattern in which speciation occurs in the absence of a physical barrier