Topic 7

Question 1

What is microevolution?

Answer 1

the change in allele frequencies in populations over generations

Question 2

What is a gene?

Answer 2

consists of two alleles in diploid individuals

(more accurately, genetic locus)

Question 3

What are alleles?

Answer 3

different forms of a gene corresponding to different DNA sequences in each form

• one allele per chromosome, and one chromosome from each parent

Question 4

What is a phenotype?

Answer 4

a product of inherited genotype and environmental influences

Question 5

What is a mutation?

Answer 5

changes in an individual’s DNA sequence

• mutations occur randomly and create new alleles
• mutations can have no effect (no change in phenotype) or can have a large effect (lethal)

Question 6

What are mutations caused by?

Answer 6

1. errors in DNA replication (small-scale or chromosomal)
2. structural damage to DNA

Question 7

What is whole-genome duplication?

Answer 7

it’s an important driver of evolution by supplying genetic material and increasing genome complexity

Question 8

What are the two sources of genetic variation?

Answer 8

1. Mutations
2. sexual reproduction

Question 9

What three factors alter allele frequencies in populations?

Answer 9

Natural selection, genetic drift, and gene flow

Question 10

What causes adaptive evolution?

Answer 10

natural selection.

non adaptive evolution: any change in allele frequency that does not lead to a population to become more adapted to its environment.

Question 11

What causes non-adaptive gene flow?

Answer 11

Genetic drift & gene flow.

• their effect on allele frequencies is primarily random.

Question 12

What is directional selection?

Answer 12

favors individuals differ from the current mean phenotype of a population in one direction.

• a population’s genetic variance shifts toward a new phenotype with higher relative fitness

Question 13

What is relative fitness?

Answer 13

the contribution an individual makes to the gene pool of the next generation, relative to the contributions of others

Question 14

What is disruptive selection?

Answer 14

favours individuals at both extremes of the phenotypic range

• average phenotypes are less fit than either extreme phenotype, and maintains genetic variation in the population

Question 15

what is stabilizing selection?

Answer 15

favours intermediate or common traits by selecting against extreme phenotypes.

• the mean of the population stays the same, but the genetic variation in the population decreases.
• very common, removes individuals with lower fitness

Question 16

What is genetic drift?

Answer 16

• random changes in allele frequency in a population
• genetic drift is more likely in small populations
• rare alleles are more likely to be lost due to genetic drift
• reduces genetic variation in a population through loss of alleles
• creates evolutionary change, but is non-adaptive

Question 17

What is the bottleneck effect?

Answer 17

a sudden reduction in population size due to a change in the environment (within its natural range)

• allele frequency in the next generation is different than the previous generation. If the population is small, it may be further affected by genetic drift

Question 18

What is the founder effect?

Answer 18

occurs when a few individuals become isolated from a larger population

• the founding population has a small fraction of the total gene pool in the original population.

Question 19

What are the effects of genetic drift?

Answer 19

1. has the largest impact on small populations
2. causes allele frequencies to change at random
3. can lead to loss of genetic variation within populations
4. can cause harmful alleles to become fixed in small populations

Question 20

What is gene flow?

Answer 20

the movement of alleles between populations of a species

• different from the founder effect, it can introduce new variation into the receiving population
• gene flow reduces variation between populations over time

Question 21

What are the three factors that alter allele frequencies in populations and bring about most evolutionary change?

Answer 21

1. natural selection (adaptive)
2. genetic drift (non-adaptive)
3. gene flow (non-adaptive)

Question 22

What is neutral variation?

Answer 22

genetic variation that does not confer a selective advantage or disadvantage

• natural selection does not affect the frequency of neutral mutations

Question 23

what is balancing selection?

Answer 23

occurs when natural selection maintains stable frequencies of multiple alleles in the gene pool of the population

Question 24

What is heterozygote advantage?

Answer 24

occurs when an organism in two different alleles of a particular gene (heterozygote) has greater fitness than an organism with two identical copies of either allele (homozygote)