2.a) Evolution: Drift & Selection

Question 1

evolution

Answer 1

the change over time in the proportion of individuals in a population differing in one or more inherited traits

Question 2

during evolution, how do changes in allele frequency occur?

Answer 2

through the non-random processes of natural selection and sexual selection, and the random process of genetic drift

Question 3

what does natural selection act on?

Answer 3

genetic variation in populations

Question 4

what does variation in traits arise as a result of?

Answer 4

mutation

Question 5

what is the original source of new sequences of DNA?

Answer 5

mutation

Question 6

what can new sequences of DNA as a result of mutation be?

Answer 6

novel alleles

Question 7

most mutations are – or –

Answer 7

harmful or neutral

Question 8

can mutations be beneficial?

Answer 8

yes, in rare cases, mutations can be beneficial for the fitness of an individual

Question 9

populations produce __ offspring than the environment can support

Answer 9

populations produce more offspring than the environment can support

Question 10

what do individuals with variations that are better suited to their environment tend to do?

Answer 10

survive longer and produce more offspring, breeding to pass on alleles that confer an advantage to the next generation.

Question 11

what does selection result in?

Answer 11

the non-random increase in the frequency of advantageous alleles and the non-random decrease in the frequency of deleterious alleles

Question 12

sexual selection

Answer 12

the non-random process involving the selection of alleles that increase the individual’s chances of mating and producing offspring

Question 13

what may sexual selection lead to?

Answer 13

sexual dimorphism

Question 14

what can sexual selection be due to? (2)

Answer 14

• male-male rivalry
• female choice

Question 15

what is male-male rivalry?

Answer 15

when large size or weaponry increases access to females through conflict

Question 16

what does female choice involve?

Answer 16

assessing the fitness of males

Question 17

when does genetic drift occur?

Answer 17

when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next

Question 18

in which populations is genetic drift more important & why?

Answer 18

genetic drift is more important in small populations, as alleles are more likely to be lost from the gene pool

Question 19

when do population bottlenecks occur?

Answer 19

when a population size is reduced for at least one generation

Question 20

what do founder effects occur through?

Answer 20

the isolation of a few members of a population from a larger population

Question 21

in the founder effect, what is the gene pool not?

Answer 21

not representative of the original gene pool

Question 22

why is a gene pool altered by genetic drift?

Answer 22

because certain alleles may be under-represented or over-represented, and allele frequencies change.

Question 23

when will evolution be rapid?

Answer 23

where selection pressures are strong

Question 24

what are selection pressures?

Answer 24

the environmental factors that influence which individuals in a population pass on their alleles

Question 25

biotic selection pressures (4)

Answer 25

- competition - predation - disease - parisitism

Question 26

abiotic selection pressures (5)

Answer 26

- changes in temperature - light - humidity - pH - salinity

Question 27

what does the Hardy-Weinberg principle state?

Answer 27

in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations

Question 28

conditions for maintaining the Hardy-Weinberg equilibrium (5)

Answer 28

- no natural selection - random mating - no mutation - large population size - no gene flow (through migration in or out)

Question 29

what can the H-W principle be used to determine?

Answer 29

whether there is a change in allele frequency in a population over time

Question 30

can allele, genotype, and phenotype frequencies be calculated?

Answer 30

yes

Question 31

what do changes in allele, genotype and phenotype frequency suggest relative to the H-W principle?

Answer 31

that evolution is occuring