ap biology midterm

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756 terms · units 1-7

natural selection

differential success in the reproduction of different phenotypes resulting from the interaction of organisms with their environment; population can change over generations if individuals that possess certain heritable traits leave more offspring than other individuals

evolutionary adaptation

an accumulation of inherited characteristics that enhance organisms' ability to survive and reproduce in specific environments


a change over time in the genetic composition of a population


the branch of biology concerned with naming and classifying organisms


remains or traces of organisms from the past

sedimentary rocks

rock formed from sand and mud that once settled in layers on the bottom of seas, lakes, and marshes- often rich in fossils


the study of fossils


the hypothesis by Georges Cuvier that each boundary between strata corresponded in time to a catastrophe, such as a flood or drought, that had destroyed many of the species living there at that time


the idea that profound change can take place through the cumulative effect of slow but continuous processes


Charles Lyell's idea that geologic processes have not changed throughout Earth's history

descent with modification

Darwin's initial phrase for the general process of evolution

artificial selection

the selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits


similarity in characteristics resulting from a shared ancestry

homologous structures

structures in different species that are similar because of common ancestry

vestigial organs

a structure of marginal, if any, importance to an organism; historical remnants of structures that had important functions in ancestors


the study of the past and present distribution of species


species that are confined to a specific, relatively small geographic area


evolutionary change below the species level; change in the genetic makeup of a population from generation to generation

population genetics

the study of how populations change genetically over time

modern synthesis

a comprehensive theory of evolution emphasizing populations as units of evolution and integrating ideas from many fields, including genetics, statistics, paleontology, taxonomy, and biogeography


a localized group of individuals that are capable of interbreeding and producing fertile offspring

gene pool

the total aggregate of genes in a population at any one time

Hardy-Weinberg theorem

the principle that frequencies of alleles and genotypes in a population remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work

Hardy-Weinberg equilibrium

a state in which a population has the same allele frequencies from one generation to the next; conditions- 1) extremely large population size 2) no gene flow 3) no mutations 4) random mating 5) no natural selection


changes in the nucleotide sequence of DNA


an aberration in chromosome structure due to fusion with a fragment from a homologous chromosome, such that a portion of a chromosome is duplicated

genetic drift

unpredictable fluctuations in allele frequencies from one generation to the next because of a population's finite size

bottleneck effect

genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population

founder effect

genetic drift that occurs when a few individuals become isolated from a larger population, with the result that the new population's gene pool is not reflective of the original population

gene flow

genetic additions to and/or subtractions from a population resulting from the movement of fertile individuals or gametes

phenotypic polymorphism

the existence of two or more distinct morphs, each represented in a population in high enough frequencies to be readily noticeable


different forms of a discrete character

genetic polymorphism

the existence of two or more distinct alleles at a given locus in a population's gene pool

average heterozygosity

the percent, on average, of a population's loci that are heterozygous in members of the population

geographic variation

differences between the gene pools of separate populations or population subgroups


a graded change in a trait along a geographic axis


the contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals

relative fitness

the contribution of a genotype to the next generation compared to the contributions of alternative genotypes for the same locus

directional selection

natural selection that favors individuals at one end of the phenotypic range

disruptive selection

natural selection that favors individuals on both extremes of a phenotypic range over intermediate phenotypes

stabilizing selection

natural selection that favors intermediate variants by acting against extreme phenotypes

balancing selection

natural selection that maintains stable frequencies of two or more phenotypic forms in a population

balanced polymorphism

the ability of natural selection to maintain diversity in a population

heterozygote advantage

greater reproductive success of heterozygous individuals compared to homozygotes; tends to preserve variation in gene pools

frequency-dependent selection

a decline in the reproductive success of a morph resulting from the morph's phenotype becoming too common in a population; a cause of balanced polymorphism in populations

neutral variation

genetic diversity that confers no apparent selective advantage


genes that have become inactivated by mutations

sexual selection

natural selection for mating success

sexual dimorphism

marked differences between the sexes in secondary sexual characteristics, which are not directly associated with reproduction

intrasexual selection

a direct competition among individuals of one sex (usually the males in vertebrates) for mates of the opposite sex

intersexual selectoin

selection whereby individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex; also called mate choice


the origin of a new species in evolution


evolutionary change above the species level, including the appearance of major evolutionary developments, such as flight, that we use to define higher taxa


a group whose members possess similar anatomical characteristics and have the ability to interbreed

biological species concept

definition of a species as a population or group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but are not able to produce viable, fertile offspring with members of other populations

reproductive isolation

the existence of biological factors (barriers) that impede members of two species from producing viable, fertile hybrids

prezygotic barrier

a reproductive barrier that impedes mating between species or hinders fertilization of ova if interspecific mating is attempted

postzygotic barriers

any of several species-isolating mechanisms that prevent hybrids produced by two different species from developing into viable, fertile adults

morphological species concept

characterizes a species by its body shape, size, and other structural features

paleontological species concept

definition of species based on morphological differences known only from the fossil record

ecological species concept

defining species in terms of ecological roles (niches)

phylogenetic species concept

defines a species as a set of organisms with a unique genetic history- as one branch on the tree of life

sibling species

species that appear so similar that they cannot be distinguished on morphological grounds

allopatric speciation

a mode of speciation induced when an ancestral population becomes segregated by a geographic barrier or is itself divided into two or more geographically isolated subpopulations

sympatric speciation

a mode of speciation occurring as a result of a radical change in the genome of a subpopulation, reproductively isolating the subpopulation from the parent population


a chromosomal alteration in which the organism possesses more than two complete chromosome sets


a common type of polyploid species resulting from two different species interbreeding and combining their chromosomes

adaptive radiation

the emergence of numerous species from a common ancestor introduced into an environment that presents a diversity of new opportunities and problems

punctuated equilibrium

in evolutionary theory, long periods of apparent stasis (no change) interrupted by relatively brief periods of sudden change


evolutionary change in the timing or rate of an organism's development

allometric growth

the variation in the relative rates of growth of various parts of the body, which helps shape the organism


the retention in an adult organism of the juvenile features of its evolutionary ancestors

homeotic genes

any of the genes that control the overall body plan of animals and plants by controlling the developmental fate of groups of cells

species selection

a theory maintaining that species living the longest and generating the greatest number of species determine the direction of major evolutionary trends


the evolutionary history of a species or group of related species


the analytical study of the diversity and relationships of organisms, both present day and extinct

molecular systematics

the comparison of nucleic acids or other molecules in different species to infer relatedness

fossil record

the chronicle of evolution over millions of years of geologic time engraved in the order in which fossils appear in rock strata


similarity between two species that is due to convergent evolution rather than to descent from a common ancestor with same trait


similar structure or molecular sequence that has evolved independently in two species


the two-part format of the scientific name


first part of the binomial

specific epithet

second part of the binomial

domain kingdom phylum class order family genus species

order of organism classification


the named taxonomic unit at any level

phylogenetic trees

a branching diagram that represents a hypothesis about evolutionary relationships


a diagram depicting patterns of shared characteristics among species


a group of species that includes an ancestral species and all its descendants


the analysis of how species may be grouped into clades


pertaining to a grouping of species consisting of an ancestral species and all its descendants; a valid clade


pertaining to a grouping of species that consists of an ancestral species and some, but not all, of its descendants; lacking information about some members of a clade


pertaining to a grouping of species derived from two or more different ancestral forms

shared primitive character

a character displayed in species outside a particular taxon

shared derived character

an evolutionary novelty that evolved within a particular clade


a species or group of species that is closely related to a group of species being studied, but clearly not as closely related as any study-group members are to each other


in a cladistic study of evolutionary relationships among taxa of organisms, the group of taxa that is actually being analyzed


a phylogenetic tree in which the lengths of the branches reflect the number of genetic changes that have taken place in a particular DNA or RNA sequence in the various lineages

ultrametric tree

a phylogenetic tree in which the lengths of the branches reflect measurements of geologic time

maximum parsimony

a principle that states that when considering multiple explanations for an observation, one should first investigate the simplest explanation that is consistent with the facts

maximum likelihood

a principle that states that when considering multiple phylogenetic hypotheses, one should take into account the one that reflects the most likely sequence of evolutionary events, given certain rules about how DNA changes over time

orthologous genes

homologous genes that are passed in a straight line from one generation to the next but have ended up in different gene pools because of speciation

paralogous genes

homologous genes that are found in the same genome due to gene duplication

molecular clock

an evolutionary timing method based on the observation that at least some regions of genomes evolve at constant rates

neutral theory

the hypothesis that much evolutionary change in genes and proteins has no effect on fitness and therefore is not influenced by Darwinian natural selection

horizontal gene transfer

genes are transferred from one genome to another through mechanisms such as transposable elements, and perhaps through fusions of different organisms


aggregates of abiotically produced molecules surrounded by a membrane or membrane-like structure


enzyme-like RNA molecules that catalyze reactions during RNA splicing

radiometric dating

a method paleontologists use for determining the ages of rocks and fossils on a scale of absolute time, based on the half-life of radioactive isotopes

half life

the number of years it takes for half of the original sample to decay

geologic record

the division of Earth's history into time periods, grouped into three eras: Archaean, Proterozoic, and Phanerozoic, and further subdivided into eras and epochs


rocklike structures composed of many layers of bacteria and sediment

serial endosymbiosis

a model of the origin of eukaryotes consisting of a sequence of endosymbiotic events in which mitochondria, chloroplasts, and perhaps other cellular structures were derived from small prokaryotes that had been engulfed by larger cells

genetic annealing

the production of a new genome through the transfer of part of the genome of one organism to another organism

snowball Earth hypothesis

the hypothesis that glaciers covered the planet's landmasses from pole to pole 750-570 million years ago, confining life to very limited areas


collections of autonomously replicating cells


the supercontinent formed near the end of the Paleozoic era when plate movements brought all the landmasses of Earth together

three domain system

a system of taxonomic classification based on three "superkingdoms": Bacteria, Archaea, and Eukarya


catabolic process; a partial degradation of sugars that occurs without the use of oxygen

cellular respiration

catabolic pathway; oxygen is consumed as a reactant along with the organic fuel to produce ATP

redox reaction

a chemical reaction involving the transfer of one or more electrons from one reactant to another


addition of electrons to another substance


the loss of electrons from one substance

reducing agent

the electron donor in a redox reaction

oxidizing agent

the electron acceptor in a redox reaction


a coenzyme present in all cells that helps enzymes transfer electrons during the redox reactions of metabolism

electron transport chain

a sequence of electron carrier molecules that shuttle electrons during the redox reactions that release energy used to make ATP


the splitting of glucose into pyruvate

citric acid cycle

a chemical cycle involving 8 steps that completes the metabolic breakdown of glucose molecules to carbon dioxide; occurs within the mitochondrion; the second major stage in cellular respiration

oxidative phosphorylation

the production of ATP using energy derived from the redox reactions of an electron transport chain

substrate-level phosphorylation

the formation of ATP by directly transferring a phosphate group to ADP from an intermediate substrate in catabolism

acetyl coA

the entry compound for the citric acid cycle in cellular respiration, formed from a fragment of pyruvate attached to a coenzyme


iron-containing proteins; components of the electron transport chains in mitochondria and chloroplasts

ATP synthase

protein complex/enzyme that makes ATP from ADP and inorganic phosphate


an energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP

proton-motive force

the potential energy stored in the form of an electrochemical gradient, generated by the pumping of hydrogen ions across biological membranes during chemiosmosis


referring to an organism, environment, or cellular process that requires oxygen


referring to an organism, environment, or cellular process that lacks oxygen

alcohol fermentation

the conversion to pyruvate to carbon dioxide and ethyl alchohol

lactic acid fermentation

the conversion of pyruvate to lactate with no release of carbon dioxide

facultative anaerobe

an organism that makes ATP by aerobic respiration if oxygen is present but that switches to fermentation under anaerobic conditions

beta oxidation

a metabolic sequence that breaks fatty acids down to two-carbon fragments that enter the citric acid cycle as acetyl coA


the conversion of light energy to chemical energy that is stored in glucose or other organic compounds; occurs in plants, algae, and certain prokaryotes


an organism that obtains organic food molecules without eating other organisms or substances derived from other organisms; use energy from the sun or from the oxidation of inorganic substances to make organic molecules from inorganic ones; "self feeders"


an organism that obtains organic food molecules by eating other organisms or their by-products


the green pigment located within the chloroplasts of plants


the tissue in the interior of a leaf


microscopic pores in the epidermis of leaves and stems that allow gas exchange between the environment and the interior of the plant; carbon dioxide in, oxygen out


the fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water


a flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy

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