Unit A-D

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biosphere

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the global ecosystem, the entire portion of Earth inhabited by life

including: soil; oceans, lakes, and other bodies of water;and the lower atmosphere

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ecosystem

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all the organisms living in a given area along with the nonliving factors with which they interact; a biological community and its physical environment.

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prokaryotic cell

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Theprokaryotic cell is much simpler and usually muchsmaller than the eukaryotic cell. The cells of bacteria areprokaryotic.

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eukaryotic cell

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In contrastto prokaryotic cells, a eukaryotic cell is subdividedby internal membranes into different functional compartmentscalled organelles.

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Darwin's observation 1

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Overproduction and competition.Any population can produce far more offspringthan the environment can possibly supportwith available resources such as foodand shelter. This overproductionleads to competition among theindividuals of a populationfor these limited resources.

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observation 2

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Individuals in a population of any species varyin many inherited traits. No two individuals in apopulation are exactly alike.

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conclusion

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Unequal reproductive success. individuals withheritable traits best suited to the local environmentare more likely to have the greatest reproductivesuccess: They will survive and leave the greatestnumber of surviving, fertile offspring. Therefore,the very traits that enhance survival and reproductivesuccess will be disproportionately represented inthe next generation.

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natural selection

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natural selection: the environment“selects” only certain heritable traits from those alreadyexisting. And the product of natural selection is adaptation,the accumulation of favorable variations in apopulation over time.

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Science

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Science is a way of knowing, an approachto understanding the natural world that is based oninquiry—a search for information, explanations, andanswers to specific questions.

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discovery science

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Verifiable observations and measurements are thedata of discovery science.discovery science enables us to describe lifeat its many levels, from ecosystems down to cells andmolecules.

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scientific method

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As a formal process of inquiry,the scientific method consists of a series of steps. These steps provide a loose guideline forscientific investigations,

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hypothesis

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A hypothesisis a tentative answer to a question—an explanation ontrial.

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Matter

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matter is anything thatoccupies space and has mass. Matter is found onEarth in three physical states: solid, liquid, and gas.

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elements

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Anelement is a substance that cannot be broken downinto other substances by chemical reactions. There are92 naturally occurring elements

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trace elements

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Trace elements are required in only very smallamounts, but you cannot live without them.

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compounds

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Elements can combine to form compounds , substances that contain two or more elements in a fixedratio.

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atoms

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An atom is the smallestunit of matter that still retains the properties of an element. Atoms are composed of subatomic particles, of whichthe three most important are protons, electrons, andneutrons.

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proton

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A proton is a subatomic particle with a singleunit of positive electrical charge

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electron

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An electron is asubatomic particle with a single negative charge

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neutron

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A neutron is electrically neutral.

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atomic number

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The number of protons in an atom, calledthe atomic number , determines which element it is.

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mass

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Mass is a measure of the amountof material in an object. A proton and a neutron havenearly identical mass. mass number is just the sum of the number of protonsand neutrons in its nucleus.

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isotopes

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isotopes of an element have thesame numbers of protons and electrons but differentnumbers of neutrons; in other words, isotopes areforms of an element that differ in mass.

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radioactive isotope

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A radioactive isotope is one in which the nucleusdecays spontaneously, giving off particles and energy.Radioactive isotopes have many uses inbiological research and medicine.

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chemical bonds

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Chemical reactions enable atoms to give upor acquire electrons, thereby completing theirouter electron shells. Atoms do this by eithertransferring or sharing their outermost electrons.

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ionic bond

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an attraction between two ions with opposite electrical charge- that holds the ions together.

ions- is an atom or molecule that has gained or lost one or more electrons, thus acquiring an electrical charge.

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covalent bond

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covalent bond forms when two atomsshare one or more pairs of outer-shell electrons. Covalentbonds are the strongest of the various bonds discussedhere; they are the ones that hold atoms togetherin a molecule .

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polar molecule

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A polar moleculeis one with an uneven distribution ofcharge.

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hydrogen bond

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is a type of weak chemical bond formed when a partially positive hydrogen atom from on polar molecule is attracted to the partially negative atom in another molecule.

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chemical reaction

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a process leading to chemical changes in matter, involving the making and or breaking of chemical bonds.

Thearrow indicates the conversion of the starting materials,the reactants, to the products.

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cohesion

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This tendency of molecules of the same kind to stick together, called cohesion

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heat

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the amount of kinetic energy contained in the movement of the atoms and molecules in a body of matter.

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Temperature

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Temperature measures the intensityof heat—that is, the averagespeed of molecules rather than the total amount of heatenergy in a body of matter.

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evaporative cooling

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Another way that water moderates temperature isby evaporative cooling

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solution

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solution is a liquid consisting of a homogeneous mixtureof two or more substances

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solvent

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The dissolving agent is calledthe solvent

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solute

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any substance that is dissolved is called asolute.

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aqueous solution

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When water is the solvent, the resulting solutionis called an aqueous solution

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acid

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A chemical compound that releases H to a solutionis called an acid

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base (or alkali)

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Abase (or alkali) is a compound that accepts H and removesthem from solution.

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pH scale

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To describe the acidity of a solution, chemists use thepH scale , a measure of the hydrogen ion (H ) concentrationin a solution. The scale ranges from 0 (most acidic) to14 (most basic). Each pH unit represents a tenfold changein the concentration of H

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organic compounds

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a chemical compound containing the element carbon and usually synthesized by cells.

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macromolecules

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a giant molecule formed by joining smaller molecules.

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polymers

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a large molecule consisting of many identical or similar molecular units. called monomers, covalently bond together.

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dehydration reaction

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dehydration reaction, a chemical reactionthat removes a molecule of water

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functional groups

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a group of atoms that form the chemically reactive part of an organic molecule. a particular functional group usually behave similarly in different chemical reactions.

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Carbohydrates

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Carbohydrates , commonly known as “carbs,” are aclass of molecules that includes sugars and polymers ofsugars.

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monosaccharides

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monosaccharides are the monomersof carbohydrates; they cannot be broken down intosmaller sugars.

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disaccharide

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A disaccharide , or double sugar, is constructed from twomonosaccharides by a dehydration reaction.

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polysaccharides

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Complex carbohydrates, or polysaccharides , are longchains of sugars—polymers of monosaccharides

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Starch

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Starch consists of long stringsof glucose monomers

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glycogen

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Animals store excess sugar in the form of a polysaccharidecalled glycogen

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Cellulose

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Cellulose forms cable-like fibrils in the tough walls thatenclose plant cells and is a major component of woodand other structural components of plants. Cellulose is also apolymer of glucose. the glucose linkagesin starch and glycogen, those in cellulose cannot bebroken by animals.

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lipids

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lipids arehydrophobic (“water-fearing”); they do not mix withwater.

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fat

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fat consists of a glycerol molecule joined withthree fatty acid molecules via dehydration reactions

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triglyceride ,

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The resulting fat is called a triglyceride ,

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hydrogen

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manufacturer can convert unsaturated fats tosaturated fats by adding hydrogen, a process calledhydrogenation . Unfortunately, hydrogenation alsocreates trans fats , a type of unsaturated fat that isparticularly bad for your health

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steroids

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a type of lipid whose carbon skeleton is in the form of four fused rings: three 6 sided rings and one 5 sided ring

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protein

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A protein is a polymer of amino acid monomers. Proteinsare the most elaborate and diverse of life’s molecules.

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amino acid

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Each amino acid consists of a central carbon atombonded to four covalent partners (carbon, remember,always forms four covalent bonds)

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peptide bond

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the covalent linkage between two amino acid unit in a polypeptide, formed by a dehydration reaction between two amino acid

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primary structure

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the first level of protein structure; the specific sequence of amino acids making up a polypeptide chain.

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denaturation

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a process in which a protein unravels, losing it specific conformation and hence its function; can be caused by changes in pH or salt concentration or by high temperature; also refers to the separation of the two strands of the DNA double helix, caused by similar factors

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Nucleic acids

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Nucleic acids are macromolecules that store informationand provide the instructions for building proteins

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DNA

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The genetic material that humans and other organismsinherit from their parents consists of giant molecules ofDNA. The DNA resides in the cell as one or more verylong fibers called chromosomes.

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gene

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A gene is a specificstretch of DNA that programs the amino acid sequenceof a polypeptide. Those programmed instructions, however,are written in a kind of chemical code that mustbe translated from “nucleic acid language” to “proteinlanguage”

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RNA

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A cell’s RNA molecules helpmake this translation

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Nucleic acids

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Nucleic acids are polymers made from monomerscalled nucleotides. Each nucleotidecontains three parts. At the center of each nucleotideis a five-carbon sugar (blue in the figure), deoxyribosein DNA and ribose in RNA

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sugar phosphate backbone

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the alternating chain of sugar and phosphate to which DNA and RNA nitrogenous bases are attached

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double helix

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A molecule of cellular DNA is double-stranded, withtwo polynucleotide strands wrapped around each otherto form a double helix