Ch.23: Evolutionary Processes

Question 1

Processes that drive evolution

Answer 1

natural selection, genetic drift, gene flow, and mutations

Question 2

Gene Pool

Answer 2

population made up of individuals of the same species and includes all genes and combinations of genes in the population

Question 3

Assumptions of Hardy-Weinberg Model

Answer 3

no natural selection, no genetic drift, no gene flow, no mutations, and random mating

Question 4

What is HWP used to test?

Answer 4

It is used to test the hypothesis that no evolution is occurring at a particular gene and that in the previous generation, mating was random with respect to the gene in question
used to test microevolution

Question 5

How would you know if a population is evolving?

Answer 5

look for changes in the gene pool and follow the population’s gene frequencies over time and look for changes

Question 6

Hardy-Weinberg Theorem

Answer 6

frequencies of alleles and genotypes in a population’s gene pool remain constant over generations unless acted upon by another agent other than sexual recombination

Question 7

Microevolution

Answer 7

generation to generation change in a population’s genetic structure
small scale evolutionary change

Question 8

Modes/patterns of natural selection

Answer 8

directional, stabilizing, disruptive, and balancing selection

Question 9

Directional Selection

Answer 9

• tends to reduces genetic variation
• favours one extreme phenotype and causes the average phenotype of the trait to change
• ex. during cold weather -> cliff swallows

Question 10

Stabilizing Selection

Answer 10

• tends to reduce genetic variation
• favours the average phenotype
• there is no change in average value of a trait over time
• ex. birth weight in babies

Question 11

Disruptive Selection

Answer 11

• tends to increase genetic variation
• favours the most extreme phenotypes and eliminates phenotypes near the average value
• ex. birds that eat large and small seeds

Question 12

Balancing Selection

Answer 12

• no allele has a distinct advantage
• there is balance in terms of fitness and frequency
• occurs due to heterozygote advantage and frequency-dependent selection

Question 13

Heterozygote advantage

Answer 13

heterozygous individuals have higher fitness than homozygous individuals

Question 14

Frequency-dependent selection

Answer 14

certain alleles are favoured when they are rare, but not when they are common

Question 15

Genetic Drift

Answer 15

any change in allele frequencies in a population due to chance
undirectional and random
caused by founder effects and genetic bottlenecks

Question 16

Founder effect

Answer 16

change in allele frequencies that occurs when a new population is established

Question 17

Genetic bottleneck

Answer 17

sudden reduction in the number of alleles in a population

Question 18

Which of the modes of selection may lead to speciation?

Answer 18

disruptive selection

Question 19

Gene flow

Answer 19

movement of alleles between populations when an individual leaves one population, joins another and breeds
movement of alleles between populations tends to reduce their genetic differences

Question 20

Sampling Error

Answer 20

the idea that allele frequencies change due to blind luck when drift occurs

Question 21

How are new alleles formed?

Answer 21

mutations

Question 22

three ways in which mutations can occur as

Answer 22

point mutations, chromosome-level mutations, and lateral gene transfer

Question 23

Evolution cannot occur without __________.

Answer 23

mutations

Question 24

Deleterious alleles

Answer 24

alleles that lower fitness and tend to be eliminated by purifying selection

Question 25

Beneficial alleles

Answer 25

alleles that allow individuals to produce more offspring | very rare

Question 26

Neutral alleles

Answer 26

- allele with not effect on fitness | - occurs when point mutation is silent

Question 27

three mechanisms that violate HW assumption of random mating

Answer 27

inbreeding, assortative mating, and sexual selection

Question 28

Inbreeding

Answer 28

- mating between relatives - increases homozygosity and decreases heterozygosity - can speed the rate of evolutionary change (i.e. increases rate at which natural selection can eliminate the recessive deleterious alleles from population)

Question 29

What is the most extreme form of inbreeding?

Answer 29

self-fertilization

Question 30

Inbreeding depression

Answer 30

decline in average fitness that takes place when homozygosity increases and heterozygosity decreases

Question 31

Assortative Mating

Answer 31

takes place when mating is nonrandom with respect to specific traits

Question 32

Positive assortment

Answer 32

individuals tend to choose mates that share a particular phenotype with them

Question 33

Negative assortment

Answer 33

individuals tend to choose mates that differ in specific phenotypic trait

Question 34

Sexual selection

Answer 34

occurs when individuals within a population differ in their ability to attract mates

Question 35

Intersexual selection

Answer 35

selection of an individual of one gender for mating by an individual for another

Question 36

Intrasexual selection

Answer 36

form of selection within a gender in which individuals sometimes compete with one another to obtain mates

Question 37

Fundamental Asymmetry of Sex

Answer 37

females invest much more in offspring than males

Question 38

Why should sexual selection act more strongly on males than females? Use Bateman-Trivers theory predictions to explain.

Answer 38

Females fitness is limited by its ability to gain resources for its offspring while males fitness is limited by the number of females he can mate with. Females can be choosy in terms of who they want to mate with and as a result males need to compete with each other to gain females to mate with.

Question 39

three factors that females may choose mates based on

Answer 39

1. physical characteristics that indicate male genetic quality 2. behavioural characteristics that indicate their ability to provide parental care 3. both

Question 40

Sexual dimorphism

Answer 40

any trait that differs between males and females