Evolution of Populations

Question 1

Natural selection acts on

Answer 1

individuals

Question 2

only ____ evolve by natural selection

Answer 2

populations

Question 3

The smallest unit of evolutionary change

Answer 3

population

Question 4

Microevolution

Answer 4

a change in allele frequencies in populations over generations

Question 5

Alleles

Answer 5

different forms of a gene, corresponding to different DNA sequences in each form (one allele per chromosome)

Question 6

Population

Answer 6

a localized group of individuals of a single species that interbreed (share alleles) and produce fertile offspring

Question 7

Gene pool

Answer 7

all the alleles present in all individuals in the population

Question 8

Gene variation is advantageous to a population because:

Answer 8

enables adaptation of the population to the environment via natural selection

Question 9

Phenotype is a product of

Answer 9

genotype and environmental influences

Question 10

New genes and alleles arise by

Answer 10

mutation and gene duplication

Question 11

Mutations

Answer 11

changes in an individuals DNA sequence

Question 12

Mutations can be caused by

Answer 12

i) small-scale (e.g. point mutation) or chromosomal (e.g. insertion/deletion) errors in DNA
replication
ii) structural damage to DNA (e.g. radiation)

Question 13

Sources of genetic variation

Answer 13

mutations, sexual preproduction

Question 14

Sexual reproduction

Answer 14

can shuffle existing alleles into new combinations

Question 15

Adaptation

Answer 15

feature or trait (created through natural selection) that provides an advantage (higher relative fitness) to an individual possessing it.

Question 16

relative fitness

Answer 16

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

Question 17

Three modes of natural selection

Answer 17

directional selection, disruptive selection, stabilizing selection

Question 18

Directional selection

Answer 18

favors individuals at one end of the phenotypic range and occurs in response to consistent selective pressure

Question 19

Disruptive selection

Answer 19

favors individuals at both extremes of the phenotypic range (results in 2 or more divergent phenotypes)

Question 20

Stabilizing Selection

Answer 20

favors intermediate or common variants (mean of the population stays the same and variation of the population decreases)

Question 21

Factor that alter allele frequencies in populations

Answer 21

natural selection, genetic drift, gene flow

Question 22

Genetic drift

Answer 22

random changes in allele frequency in a population and is more likely in small populations

Question 23

Genetic drift does not create

Answer 23

evolutionary adaptations

Question 24

Examples of genetic drift

Answer 24

bottleneck effect, founder effect

Question 25

Rare alleles are more likely lost due to

Answer 25

genetic drift

Question 26

Bottleneck effect

Answer 26

a sudden reduction in population size due to a change in the environment and allele frequency in the next generation is different than the previous generation

Question 27

Founder effect

Answer 27

occurs when a few individuals become isolated from a larger population which has a small fraction of the total gene pool present in the original population

Question 28

Key points of genetic drift

Answer 28

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

Question 29

Gene flow

Answer 29

gene flow is the movement of alleles between populations of the same species (by fertile individuals or games like pollen)

Question 30

Gene flow reduces ___ between populations over time

Answer 30

reduces variation

Question 31

Gene flow can ____ the fitness of a population

Answer 31

increase/decrease

Question 32

Neutral variation

Answer 32

genetic variation that does not confer a selective advantage or disadvantage

Question 33

Genetic variation in populations is maintained by

Answer 33

Mutation.
− Recombination (crossing-over of chromosomes during meiosis).
− Independent assortment (of alleles) during meiosis.
− Random mating between organisms (sexual reproduction).
− Random fertilization (sexual reproduction).
− Recessive alleles are hidden from selection in heterozygote individuals.
− Disruptive selection (natural selection).
− Gene flow (between populations).
− Balancing selection.

Question 34

Balancing selection

Answer 34

occurs when natural selection maintains stable frequencies of two or more alleles in a population

Question 35

Mechanisms of balancing selection

Answer 35

− Heterozygote advantage

− Frequency-dependent selection

Question 36

Heterozygote advantage

Answer 36

occurs when heterozygotes have higher fitness than do bot homozygotes

Question 37

example of Heterozygote advantage

Answer 37

sickle cell disease

Question 38

Frequency dependent selection

Answer 38

the fitness of a phenotype declines if it becomes too abundant in the population where the rare genotype has a selective advantage