AP Biology Chapters 22-24

AP Biology units on Darwinism, natural Selection, Evolution, and mroe

Speciation

The origin of new species in evolution.

Macroevolution

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

Microevolution

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

Anagenesis

Phyletic evolution, is the accumulation of changes that gradually transform a given species into a species with different characteristics.

Cladogenesis

Branching evolution, is the splitting of a gene pool into two or more separate pools, which each give rise to one or more new species. Can promote biological diversity by increasing the number of species.

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 Barrier

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. It can be applied to asexual and sexual organisms, and it can be useful even without information on the extent of gene flow.

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

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.

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.

Heterochrony

Evolutionary change in the timing or rate of an organism′s development.

Allometric Growth

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

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.

Paedomorphosis

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

average heterozygosity

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

balanced polymorphism

The ability of natural selection to maintain diversity in a population.

balancing selection

Natural selection that maintains stable frequencies of two or more phenotypic forms in a population (balanced polymorphism).

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.

cline

A graded variation in a trait that parallels a gradient in the environment.

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.

fitness

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

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.

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.

gene flow

Genetic additions to or substractions from a population resulting from the movement of fertile individuals or gametes.

gene pool

The total aggregate of genes in a population at any one time.

genetic drift

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

genetic polymorphism

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

geographic variation

Differences between the gene pools of separate populations or population subgroups.

Hardy-Weinberg equilibrium

The condition describing a non-evolving population (one that is in genetic equilibrium).

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.

heterozygote advantage

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

intersexual selection

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

intrasexual selection

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

microevolution

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

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.

mutation

A rare change in the DNA of a gene, ultimately creating genetic diversity.

neutral variation

Genetic diversity that confers no apparent selective advantage.

phenotypic polymorphism

The existence of two or more distinct morphs (discrete forms), each represented in a population in high enough frequencies to be readily noticeable.

polymorphism

The coexistence of two or more distinct forms in the same population.

population

A localized group of individuals that belong to the same biological species (that are capable of interbreeding and producing fertile offspring).

population genetics

The study of how populations change genetically over time.

relative fitness

The contribution of one genotype to the next generation compared to that of alternative genotypes for the same locus.

sexual dimorphism

A special case of polymorphism based on the distinction between the secondary sex characteristics of males and females.

stabilizing selection

Natural selection that favors intermediate variants by acting against extreme phenotypes.

Darwin

English natural scientist who formulated a theory of evolution by natural selection (1809-1882)

natural selection

the process by which forms of life having traits that better enable them to adapt to specific environmental pressures will tend to survive and reproduce in greater numbers than others of their kind, thus ensuring the perpetuation of those favorable traits in succeeding generations.

adaptations

the behaviors and physical characteristics that allow organisms to live successfully in their environments

evolution

change in the genetics of a population of organisms over time; process by which modern organisms have descended from ancient organisms

artificial selection

selection by humans for breeding of useful traits from the natural variation among different organisms

biogeography

evidence for evolution dealing with the geographical distribution of animals and plants

homologous structures

Structures in different species that are similar because of common ancestry.

analogous structures

similarities among unrelated species that result from convergent evolution

catastrophism

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.

descent with modification

Darwin's initial phrase for the general process of evolution.

fossil

A preserved remnant or impression of an organism that lived in the past.

gradualism

A view of Earth's history that attributes profound change to the cumulative product of slow but continuous processes.

homology

Similarity in characteristics resulting from a shared ancestry.

taxonomy

A set of characteristics used to assess the similarities and differences between various species, leading to a classification scheme; the branch of biology concerned with naming and classifying the diverse forms of life.

uniformitarianism

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

vestigial organ

A structure of marginal, if any, importance to an organism. Vestigial organs are historical remnants of structures that had important functions in ancestors.