evolution chapter 9 terms

Question 1

gene flow

Answer 1

net movement of alleles from one population to another

Question 2

non-random mating

Answer 2

occurs when individuals select mates based on particular phenotypes or due to interbreeding

Question 3

genetic drift

Answer 3

changes in allele frequency due to chance events

Question 4

founder effect

Answer 4

few individuals start and establish a new, isolated population
ex: galapagos islands

Question 5

bottleneck effect

Answer 5

change in gene pool resulting from rapid decrease in population size
ex: elephant seals (due to overhunting)

Question 6

stabilizing selection

Answer 6

favours intermediate phenotypes and acts against extreme phenotypes
- results in narrower phenotype range
ex: babies birth weight

Question 7

directional selection

Answer 7

favours phenotypes at one extreme over another
- results in shifted range
ex: peppered moths

Question 8

disruptive selection

Answer 8

favours both extremes rather than intermediate phenotypes
- results in split gene pool
ex: salmon size differences

Question 9

sexual selection

Answer 9

competition between males and choices made by females

Question 10

sexual dimorphism

Answer 10

difference in phenotypes of male and female
ex: colours (bright vs. dull)

Question 11

balanced polymorphism

Answer 11

selection can favour 2 or more alleles for same trait in steady proportions
ex: sickle cell anemia

Question 12

speciation

Answer 12

formation of new species from existing species; a continuous process

Question 13

pre-zygotic

Answer 13

pre-fertilization barriers
- prevents fertilization of eggs

Question 14

post-zygotic

Answer 14

barriers after fertilization
- prevent hybrid zygotes from developing into fertile, viable offspring

Question 15

sympatric speciation

Answer 15

populations within same geographical area diverge genetically
ex: polyploidy- results in extra chromosomes due to error in cell division

Question 16

allopatric speciation

Answer 16

populations separated by a geographical barrier and diverge genetically
ex: lava flow, water

Question 17

adaptive radiation

Answer 17

diversification of a common ancestral species into a variety of differently adapted species
ex: galapagos islands

Question 18

ecological niche

Answer 18

increase in number of species, sharp declines in number of species

Question 19

divergent evolution

Answer 19

occurs when populations adapt to different environmental conditions, diverge and become distinct
- common ancestor
ex: adaptive radiation

Question 20

convergent evolution

Answer 20

occurs when unrelated species occupy similar environments in different parts of the world
- no common ancestor
ex: birds and bats have wings

Question 21

gradualism

Answer 21

small, adaptive changes gradually accumulate over time
- fossils rarely reveal gradual transition

Question 22

punctuated equilibrium

Answer 22

interrupted by periods of divergence
- supported by fossil evidence