Biology Unit 5 Terms

Front 1

balanced polymorphism

Back 1

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

Front 2

bottleneck effect

Back 2

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.

Front 3

cline

Back 3

cline

Graded variation in some traits of individuals that parallels a gradient in the environment.

Front 4

Darwinian fitness

Back 4

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

Front 5

founder effect

Back 5

founder effect

Genetic drift attributable to colonization by a limited number of individuals from a parent population.

Front 6

frequency-dependant selection

Back 6

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.

Front 7

gene flow

Back 7

The loss or gain of alleles in a population due to the migration of fertile individuals or gametes between populations.

Front 8

gene pool

Back 8

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

Front 9

genetic drift

Back 9

Changes in the gene pool of a small population due to chance.

Front 10

geographic variation

Back 10

Differences in genetic structure between populations.

Front 11

Hardy-Weinberg formula

Back 11

A formula for calculating the frequencies of genotypes in a gene pool from the frequencies of alleles, and vice versa.

Front 12

Hardy-Weinberg equilibrium

Back 12

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

Front 13

Hardy-Weinberg theorem

Back 13

An axiom maintaining that the sexual shuffling of genes alone cannot alter the overall genetic makeup of a population.

Front 14

heterozygote advantage

Back 14

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

Front 15

intersexual selection

Back 15

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

Front 16

intrasexual selection

Back 16

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

Front 17

microevolution

Back 17

A change in the gene pool of a population from generation to generation.

Front 18

modern synthesis

Back 18

A comprehensive theory of evolution emphasizing natural selection, gradualism, and populations as the fundamental units of evolutionary change; also called neo-Darwinism.

Front 19

mutation

Back 19

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

Front 20

natural selection

Back 20

Differential success in the reproduction of different phenotypes resulting from the interaction of organisms with their environment. Evolution occurs when natural selection causes changes in relative frequencies of alleles in the gene pool.

Front 21

neutral variation

Back 21

Genetic diversity that confers no apparent selective advantage.

Front 22

polymorphism

Back 22

The coexistence of two or more distinct forms of individuals (polymorphic characters) in the same population.

Front 23

population genetics

Back 23

population genetics

The study of genetic changes in populations; the science of microevolutionary changes in populations.

Front 24

population

Back 24

A group of individuals of one species that live in a particular geographic area.

Front 25

relative fitness

Back 25

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

Front 26

sexual dimorphism

Back 26

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

Front 27

species

Back 27

species

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

Front 28

adaptive radiation

Back 28

adaptive radiation

The emergence of numerous species from a common ancestor introduced into an environment, presenting a diversity of new opportunities and problems.

Front 29

allometric growth

Back 29

allometric growth

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

Front 30

allopatric speciation

Back 30

A mode of speciation induced when the ancestral population becomes segregated by a geographic barrier.

Front 31

allopolyploid

Back 31

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

Front 32

anagenesis

Back 32

A pattern of evolutionary change involving the transformation of an entire population, sometimes to a state different enough from the ancestral population to justify renaming it as a separate species; also called phyletic evolution.

Front 33

autopolyploid

Back 33

autopolyploid

A type of polyploid species resulting from one species doubling its chromosome number to become tetraploid, which may self-fertilize or mate with other tetraploids.

Front 34

biological species concept

Back 34

biological species concept

The definition of a species as a population or group of populations whose members have the potential in nature to interbreed and produce fertile offspring; a biological species is also called a sexual species.

Front 35

cladogenesis

Back 35

A pattern of evolutionary change that produces biological diversity by budding one or more new species from a parent species that continues to exist; also called branching evolution.

Front 36

exological species concept

Back 36

The idea that ecological roles (niches) define species.

Front 37

heterochrony

Back 37

Evolutionary change in the timing or rate of development.

Front 38

macroevolution

Back 38

macroevolution

Evolutionary change on a grand scale, encompassing the origin of new taxonomic groups, evolutionary trends, adaptive radiation, and mass extinction.

Front 39

morphological species concept

Back 39

The idea that species are defined by measurable anatomical criteria.

Front 40

paedomorphosis

Back 40

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

Front 41

pluralistic species concept

Back 41

pluralistic species concept

The idea that there is no universal explanation for the cohesion of individuals that make up species.

Front 42

polyploidy

Back 42

polyploidy

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

Front 43

postzygotic barrier

Back 43

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

Front 44

punctuated equilibrium

Back 44

punctuated equilibrium

A theory of evolution advocating spurts of relatively rapid change followed by long periods of stasis.

Front 45

speciation

Back 45

The origin of new species in evolution.

Front 46

species selction

Back 46

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

Front 47

sympatric speciation

Back 47

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.