Chpt 23: Evolutionary Processes

Question 1

Speciation

Answer 1

When a new species branches off from an existing one;

can be caused by disruptive natural selection

Question 2

stabilizing natural selection

Answer 2

1 of 4 patterns of natural selection

when natural selection causes variation to DECREASE by favoring moderate (not extreme) traits (but the overall average trait remains the same bc)

Question 3

“Purifying” directional selection

Answer 3

Extreme version of directional natural selection where some alleles propagate and become FIXED (approach 100% frequency) as unfavored alleles are LOST (approach 0% frequency)

Question 4

balancing natural selection

Answer 4

1 of 4 patterns of natural selection

when natural selection favors multiple alleles equally; balances the effect of heterozygote advantage, fluid environment, & frequency dependent selection

Question 5

Frequency dependent selection

Answer 5

When an allele is favored when/because it’s rare but NOT when it’s common

Question 6

Heterozygote advantage

Answer 6

when variety confers fitness

when heterozygous genotypes/diversity are favored

Question 7

inbreeding depression

Answer 7

when average fitness goes down because homozygosity goes up

less variety = less fitness

Question 8

4 patterns of natural selection

Answer 8

disruptive
directional
balancing
Stabilizing

Question 9

Disruptive natural selection

Answer 9

1 of 4 patterns of natural selection

selection against the mean phenotype

when natural selection causes variation to INCREASE by favoring extremes/outlier traits; moderate traits decrease as a result

Question 10

Directional natural selection

Answer 10

1 of 4 patterns of natural selection

when natural selection causes the average phenotype to change in one direction (up or down)

Question 11

Natural selection

Answer 11

when heritable variation results in different success rates in survival and reproduction

Question 12

5 requirements for EVOLUTION by natural selection

Answer 12

1. Phenotype variation
2. Phenotype heritability
3. Selective pressure
4. Differential survival/reproduction
5. Increase in alleles for adaptive phenotype in the next generation

Question 13

Inbreeding

Answer 13

mating between relatives that can speed up the rate at which natural selection removes unfavorable traits

Question 14

genetic variation

Answer 14

number and relative frequency of alleles in a population

Question 15

founder effect

Answer 15

1 of 2 special types of genetic drift

when a few individuals from an original population disperse and inhabit/found a new area

Question 16

Population bottleneck

Answer 16

1 of 2 special types of genetic drift

when a population is greatly reduced, but then recovers.