KA 2: evolution: drift and selection

Question 1

what is 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, when do changes in allele frequency occur?

Answer 2

-non-random processes of natural selection and sexual selection

-random process of genetic drift

Question 3

what does natural selection act on in populations?

Answer 3

genetic variation

Question 4

variation in traits arises as a result of…

Answer 4

mutation

Question 5

what is mutation?

Answer 5

the original source of new sequences of DNA

Question 6

what can the new sequences from a mutation be?

Answer 6

novel alleles

Question 7

what are most mutations?

Answer 7

harmful or neutral

in rare cases they may be beneficial to the fitness of an individual

Question 8

populations produce…

Answer 8

more offspring than the environment can support

Question 9

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

Answer 9

they tend to survive longer and produce more offspring, breeding to pass on those alleles that conferred an advantage to the next generation

Question 10

what does the selection result in?

Answer 10

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

Question 11

what is sexual selection?

Answer 11

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

Question 12

what does sexual selection lead to?

Answer 12

dimorphism

Question 13

what can sexual selection be due to?

Answer 13

• male-male rivalry
• female choice

Question 14

what is male-male rivalry?

Answer 14

large size or weaponry increases access to females through conflict

Question 15

what is female choice?

Answer 15

involves females assessing the fitness of males

Question 16

when does genetic drift occur?

Answer 16

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

Question 17

why is genetic drift more important in small populations?

Answer 17

as alleles are more likely to be lost from the gene pool

Question 18

when do population bottlenecks occur?

Answer 18

when a population size is reduced for at least one generation

Question 19

when does the founder effect occur?

Answer 19

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

the gene pool of the new population is not representative of that in the original gene pool

Question 20

why is a gene pool altered by genetic drift?

Answer 20

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

Question 21

where selection pressures are strong…

Answer 21

the rate of evolution can be rapid

Question 22

what are selection pressures?

Answer 22

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

Question 23

selection pressures can be: (give examples)

Answer 23

-biotic (competition, predation, disease, parasitism)

-abiotic (changes in temp, light, humidity, pH, salinity)

Question 24

State The Hardy-Weinberg (HW) principle

Answer 24

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

Question 25

what are the conditions for maintaining the HW equilibrium?

Answer 25

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

Question 26

what can the HW principle be used to determine?

Answer 26

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

Question 27

what is the HW formula?

Answer 27

p2 + 2pq + q2 = 1

Question 28

what does each letter in the Hardy-Weinberg (HW) formula mean?

Answer 28

p=frequency of dominant allele
q=frequency of recessive allele
p^2=frequency of homoxygous dominant genotype
2pq= frequency of heterozygous genotype
q^2=frequency of homozygous recessive genotype

Question 29

changes suggest…

Answer 29

evolution is occuring