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Flashcards in Chapter 4: From Variant to Species Deck (52)
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1

founder effect

the potentially biased sampling of the genetic variation in a species due to the isolation of a small number of its members

2

variants

individuals within populations having different expressions of a trait

3

variability

the tendency for members of a population to exhibit different versions of a particular trait

4

variation

the expression of differences for a characteristic among members of a population

5

population genetics

a science concerned with variation in gene frequencies within the populations and the forces that modify them over time

6

Hardy-Weinberg (H-W) Equilibrium

a model specifying the conditions under which the frequency of alleles or phenotypes in a natural population remain in equilibrium unless acted on by one or more evolutionary forces

7

heterosis

also known as heterozygote advantage; the tendency for offspring of genetically distinct individuals to have increased vigour as they are less likely to express deleterious recessive alleles, which increase in frequency when males and females with similar genetic background mate

8

epigenetic

mechanisms acting during mitosis (development) to modify gene expression without modifying the actual DNA sequence; may result in heritable variation

9

speciation

the formation of new species from pre-existing forms

10

evo-devo

evolutionary developmental biology; a branch of evolutionary theory that invokes a prominent role for embryonic development and epigenetic mechanisms in the ontogeny and phylogeny of phenotypes

11

phenotypic plasticity

a potential for individuals to modify their phenotype in response to variation in external conditions in order to maintain homeostasis and function

12

transgenerational epigenetic inheritance

the transmission of novel phenotypic features from parent to offspring acquired without recourse to modification in DNA base sequences

13

demes

local breeding populations; a deme is a subset of a species within which most members find a mate

14

biogeography

the study of the geographic distribution of organisms, habitats, and evolutionary history as it relates to landscape and ecology

15

sympatric

refers to species that coexist in the same geographic region

16

allopatric

refers to species that "live apart" and do not occupy the same geographic locale; allopatric species are presumed to exist in genetic isolation

17

parapatric

refers to species whose ranges are contiguous but not overlapping; gene flow is possible

18

hybrid zones

ecological regions in which closely related species overlap in occurrence, allowing for interbreeding to occur, producing hybrid offspring

19

recognition species concept (RSC)

a concept of the species as a group whose members, according to particular cues, identify potential mates with whom they might successfully interbreed (in contract, the BSC emphasizes an absence of breeding potential)

20

conspecific

belonging to the same species

21

morphospecies

designation of species in the fossil record according to similarity in form irrespective of time

22

chronospecies

designation of species identity by virtue of the passage of time; two fossils may be deemed species if separated by sufficient time

23

tempo and mode of evolution

refers to the pace and manner of evolutionary change

24

anagenesis

a pattern of slow, linear evolutionary change, also known as Darwinian gradualism

25

phyletic evolution

an alternative term for anagenesis, with "phyletic" denoting a line of direct ancestor-descendant relationship

26

cladogenesis

a pattern of evolution characterized by branching, in which a single species may give rise to one (or more) "daughter" species that subsequently diverge; also known as horizontal speciation

27

clades

groups of species sharing a closer ancestry among themselves than any of them do with species of other clades

28

punctuated equilibrium

a pattern of evolution characterized by periods of stasis interrupted by rapid evolutionary change; more commonly found in small, peripheral populations on the edge of a species range

29

gene flow

the movement of genes with or without the movement of individuals over geographic space

30

genetic drift

random changes in allele frequencies in small populations, independent of selection