Midterm 2 Key terms

Question 1

species

Answer 1

a group of individuals that can exchange genetic material through interbreeding to produce fertile offspring

Question 2

gene pool

Answer 2

all alleles present in all individuals in a population or species

Question 3

population

Answer 3

all the individuals of a given species that live and reproduce in a particular place; one of the several interbreeding groups of organisms of the same species living in the same geographical area

Question 4

somatic mutation

Answer 4

mutation that occurs in the somatic cells (in the body’s tissues)

Question 5

germ-line mutation

Answer 5

mutation that occurs in eggs & sperm, or in the cells that give rise to these reproductive cells

passed on to the next generation

Question 6

neutral mutations

Answer 6

genetic changes that have no effect or negligible effects on the organism, or whose effects are not associated with differences in survival or reproduction

Question 7

deleterious mutations

Answer 7

genetic changes that are harmful to an organism

Question 8

advantageous mutations

Answer 8

genetic changes that improve their carriers’ chance of survival or reproduction

Question 9

allele frequencies

Answer 9

among all the alleles of a gene in a population, the proportion that are a specified allele

Question 10

fitness

Answer 10

a measure of the extent to which an individual’s genotype is represented in the next generation

Question 11

positive selection

Answer 11

natural selection that increases the frequency of a favorable allele

Question 12

negative selection

Answer 12

natural selection that reduces the frequency of a deleterious allele

Question 13

balancing selection

Answer 13

natural selection that acts to maintain two or more alleles of a given gene in a population

Question 14

heterozygote advantage

Answer 14

a balancing form of selection in which the heterozygote’s fitness is higher than that of either the homozygotes, resulting in selection that ensures that both alleles remain in the population at intermediate frequencies

Question 15

stabilizing selection

Answer 15

a form of selection that selects against extremes and so maintains the status quo.

Question 16

directional selection

Answer 16

a form of selection that selects against one of two extremes and leads over time to change in a trait

Question 17

artificial selection

Answer 17

a form of directional selection analogous to natural selection, but without the competitive element; successful genotypes are selected by the breeder, not by competition

Question 18

disruptive selection

Answer 18

form of selection that operates in favor of extremes and against intermediate forms, selecting against the mean

Question 19

sexual selection

Answer 19

a form of selection that promotes traits that increase an individual’s access to reproductive opportunities

Question 20

intrasexual selection

Answer 20

a form of sexual selection involving interactions between individuals of one sex, as when members of one sex compete with one another for access to the other sex

Question 21

intersexual selection

Answer 21

form of sexual selection involving interaction between males and females, as when females choose from among males

Question 22

migration

Answer 22

movement of individuals from one population to another

resulting in gene flow

Question 23

gene flow

Answer 23

movement of alleles from one population to another thorugh interbreeding of their respective members

Question 24

bottleneck effect

Answer 24

an extreme, usually temporary, reduction in population size that often results in marked genetic drift

Question 25

founder event

Answer 25

a type of bottleneck that occurs when only a few individuals establish a new population

Question 26

inbreeding depression

Answer 26

a _reduction in fitness_ resulting from _breeding among relatives_ causing homozygosity of deleterious recessive mutations

Question 27

altruistic

Answer 27

self-sacrificing behavior in which an individual's actions decrease its own fitness while increasing that of another individual

Question 28

group selection

Answer 28

selection caused by the differential success of groups rather than individuals

Question 29

evolutionarily stable strategy

Answer 29

a type of behavior that cannot readily be driven to extinction by an alternative strategy

Question 30

reciprocal altruism

Answer 30

the exchange of favors between individuals

Question 31

kin selection

Answer 31

a form of natural selection that favors the spread of alleles promoting behaviors that help close relatives

Question 32

Hardy-Weinberg Equilibrium (& the conditions that must be met)

Answer 32

a state in which particular allele and genotype frequencies _do not change over time_, implying the absence of evolutionary forces. it also specifies a mathematical relationship between **allele frequencies** and **genotype frequencies** Meets the following conditions: 1. there can be _no differences_ in the survival and reproductive success of individuals 2. populations must not be added to or subtrated from by migration 3. there can be _no mutation_ 4. the population must be sufficiently _large_ to prevent sampling errors 5. individuals must _mate at random_

Question 33

genetic drift

Answer 33

a change in the frequency of an allele due to the random effects of finite population size

Question 34

non-random mating

Answer 34

mate selection biased by genotype or relatedness

Question 35

symbiont

Answer 35

an organism that lives in closely evolved association with another species

Question 36

symbiosis

Answer 36

close interaction between species that live together, often interdependently

Question 37

endosymbiosis

Answer 37

a symbiosis in which one partner lives within the other