Drift and Selection

Question 1

What is evolution?

Answer 1

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

Question 2

During evolution, how does changes in allele frequency occur?

Answer 2

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

Question 3

Natural selection acts on…

Answer 3

…genetic variation in a population

Question 4

Populations produce more offspring than…

Answer 4

…the environment can support

Question 5

Individuals with variations that are better suited to their environment tend to survive longer and…

Answer 5

…produce more offspring, breeding to pass on those alleles that conferred an advantage
to the next generation

Question 6

What is sexual selection?

Answer 6

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

Question 7

What may sexual selection lead to?

Answer 7

Sexual dimorphism

Question 8

What can sexual selection be due to?

Answer 8

Male-male rivalry and female choice

Question 9

When does genetic drift occur?

Answer 9

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

Question 10

Why is genetic drift more important in small populations?

Answer 10

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

Question 11

The Hardy-Weinberg (HW) principle states that…

Answer 11

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

Question 12

Where selection pressures are strong…

Answer 12

…the rate of evolution can be rapid

Question 13

What can the HW principle be used to determine?

Answer 13

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

Question 14

Changes suggest…

Answer 14

…evolution is occurning.

Question 15

Variation in traits arises as a result of…

Answer 15

…mutation

Question 16

Mutation is the original source of…

Answer 16

…new sequences of DNA (These new
sequences can be novel alleles)

Question 17

Most mutations are…

Answer 17

…harmful or neutral, but in rare cases they may be beneficial to the fitness of an individual

Question 18

What does selection result in?

Answer 18

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 19

What is male-male rivalry?

Answer 19

Male-male rivalry: large size or weaponry
increases access to females through conflict

Question 20

Female choice involves…

Answer 20

…females assessing
the fitness of males

Question 21

When do population bottlenecks occur?

Answer 21

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

Question 22

When do founder effects occur?

Answer 22

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 23

What are selection pressures?

Answer 23

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

Question 24

What are some biotic selection pressures?

Answer 24

Competition, predation, disease, parasitism

Question 25

What are some abiotic selection pressures?

Answer 25

Changes in
temperature, light, humidity, pH, salinity

Question 26

The conditions for maintaining the HW
equilibrium are…

Answer 26

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