2.2.1 evolution: drift and selection

Question 1

what is evolution

Answer 1

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

Question 2

what happens during evolution

Answer 2

changes in allele frequency occur through the non random processes of natural selection and sexual selection, and the random processes of genetic drift

Question 3

what does natural selection act on

Answer 3

the genetic variation in populations

Question 4

how does variation in traits arise

Answer 4

mutation

Question 5

what is mutation

Answer 5

the original source of new sequences of DNA. they can be novel alleles. most mutations are harmful or neutral

Question 6

can mutations be beneficial to the fitness of an individual

Answer 6

yes

Question 7

how much offspring do populations produce

Answer 7

more than the environment can support

Question 8

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

Answer 8

individuals with variations that are better suited to their environment

Question 9

what does selection result in

Answer 9

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

Question 10

what is sexual selection

Answer 10

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

Question 11

what may sexual selection lead to

Answer 11

sexual dimorphism, which is when the different sexes of a species have distinct differences in size or appearance

Question 12

what can cause sexual selection

Answer 12

male-male rivalry and female choice

Question 13

what is male male rivalry

Answer 13

large size or weaponry which increases access to females through conflict

Question 14

what does female choice involve

Answer 14

females assessing the fitness of males

Question 15

when does genetic drift occur

Answer 15

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

Question 16

why is genetic drift more important in small populations

Answer 16

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

Question 17

when do population bottlenecks occur

Answer 17

when a population size is reduced for at least one generation

Question 18

what is the founder effect

Answer 18

this occurs through the isoltion of a few members of a population from a larger population. the gene pool of the new population is not as representative of that in the original gene pool

Question 19

what are gene pools altered by

Answer 19

genetic drift

Question 20

how are gene pools altered by genetic drift

Answer 20

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

Question 21

when can the rate of evolution be rapid

Answer 21

when selection pressures are strong

Question 22

what are selection pressures

Answer 22

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

Question 23

what are examples of biotic selection pressures

Answer 23

competition
predation
disease
parasitism

Question 24

what are examples of abiotic selection pressures

Answer 24

changes in temperature
light
humidity
pH
salinity

Question 25

what does the HW principle state

Answer 25

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

Question 26

what are the conditions for maintaining the HW equilibrium

Answer 26

no natural selection random mating no mutation large population size no gene flow

Question 27

what can the HW principle be used to determine

Answer 27

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

Question 28

what is the HW principle

Answer 28

p2 + 2pq + q2 = 1

Question 29

what does p mean in the HW principle

Answer 29

the frequency of the dominant allele

Question 30

what does q mean in the HW principle

Answer 30

the frequency of the recessive allele

Question 31

what does p2 mean in the HW principle

Answer 31

the frequency of the homozygous dominant genotype

Question 32

what does 2pq mean in the HW principle

Answer 32

the frequnecy of the heterozygous genotype

Question 33

what does q2 mean in the HW principle

Answer 33

the frequency of the homozygous recessive genotype

Question 34

what do changes in allele frequency in a population over time suggest

Answer 34

that evolution is occuring