2.2a Drift and selection

Question 1

Evolution

Answer 1

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

During evolution, changes in allele frequency occur the non-random processes of natural selection and sexual selection, and the random process of genetic drift.

Question 2

Natural Selection

Answer 2

Natural selection acts on genetic variation in populations.

Variation in traits arises as a result of mutation.

Question 3

Mutations

Answer 3

Mutation is the original source of new sequences of DNA. These new sequences can be novel alleles. Most mutations are harmful or neutral, but in rare cases they may be beneficial to the fitness of an individual.

Question 4

Population

Answer 4

Populations produce more offspring than the environment can support.

Question 5

Individuals with variation

Answer 5

Individuals with variations that are better suited to their environment tend to survive longer and produce more offspring, breeding to pass on those alleles that conferred an advantage to the next generation.

Question 6

What does selection result in?

Answer 6

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

Question 7

Sexual Selection

Answer 7

Sexual Selection is the non random process involving the selection of alleles that increase the individuals chances of mating and producing offspring.

Sexual selection may lead to sexual dimorphism.
Sexual selection can be due to male - male rivalry and female choice.

Question 8

Male-Male rivalry

Answer 8

Large size or weaponry increases access to females through conflict.

Question 9

Female choice

Answer 9

Female choice involves females assessing the fitness of males.

Question 10

Genetic Drift

Answer 10

Genetic Drift occurs when chance events cause unpredictable fluctuations in allele frequencies from one generation to the next.

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

Population bottlenecks and founders effect are important on genetic drift.

Question 11

Population bottlenecks

Answer 11

Population Bottlenecks occur when a population size is reduced for at least one generation.

Question 12

Founder effects

Answer 12

Founder effects occur through the isolation of a 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 13

What alters the gene pool?

Answer 13

A gene pool is altered by genetic drift because certain alleles may be under represented or over represented and allele frequencies change.

Question 14

Rate of evolution

Answer 14

Where selection pressures are strong, the rate of evolution can be rapid.

Question 15

Selection pressures

Answer 15

Selection pressures are then environment factors that influence which individuals in a population pass on their alleles.

They can be biotic: competition, predation, disease, parasitism
Or they can be abiotic: changes in temperature, light, humidity, pH, salinity.

Question 16

Hardy-Weinberg principle

Answer 16

The Hardy Weinberg principles states that, in the absence of evolutionary influences, allele and genotype frequencies in a population will remain constant over the generations.

Question 17

Conditions for maintaining HW equilibrium:

Answer 17

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

Question 18

HW principle

Answer 18

The HW principle can be used to determine whether a change in allele frequency is occurring in a population over time.
Changes suggest evolution is occurring.

Question 19

HW principle letters meaning

Answer 19

p^2 + 2pq + q^2 = 1 p+q=1
p= frequency of dominant allele
q= frequency of recessive allele
p^2= frequency of homozygous dominant genotype
2pq= frequency of heterozygous genotype
q^2= frequency of homozygous recessive genotype

Question 20

what is a novel allele?

Answer 20

If a mutation results in a base sequence which codes for a different amino acid in a polypeptide, then the mutation has produced a novel allele.