2.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 the allele frequency occur?

Answer 2

• the non-random processes of natural selection and sexual selection
• the random processes of genetic drift

Question 3

How does varaition arise?

Answer 3

As a result of mutation

Question 4

What are most mutations?

Answer 4

Mutations are harmful or neutral and in some rare cases may be beneficial to the fitness of an organism.

Question 5

What does natural selection act on

Answer 5

Genetic variation in populations

Question 6

What is Natural selection?

Answer 6

A non-random increase in frequency of DNA sequences that increase survival.

Question 7

What are the characteristics of natural selection?

Answer 7

• Population produces more offspring than environment can support
• There is variation amongst offspring
• There are selection pressures
• Individuals with a selective advantage survive to reproduce and pass of favourable alleles to their offspring.
• Those favoured alleles confer advantage to the next generation and become more frequent

Question 8

What does selection result in?

Answer 8

The non-random increase in the frequency of advantageous alleles and the non-random decrease in the frequency in disadvantageous alleles.

Question 9

What are selection pressures?

Answer 9

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

Question 10

What are examples of biotic selection pressures?

Answer 10

Competition (for food, a mate), predation, disease, parasitism

Question 11

What are examples of abiotic selection pressures?

Answer 11

Change in temperature, light, humidity, pH and salinity

Question 12

What does it mean if selection pressures are strong?

Answer 12

The rate of evolution can be rapid.

Question 13

What is sexual selection?

Answer 13

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

Question 14

What is sexual dimorphism?

Answer 14

Occurs in animals where there is a physical difference between males and females of the same species (other than in the sex organs)

Question 15

What can sexual selection be due to?

Answer 15

Male-male rivalry and female choice

Question 16

Why do males that have that increase access to females through conflict?

Answer 16

Large size or weaponry

Question 17

What do females look for in assessing a suitable mate?

Answer 17

Fitness in terms of honest signals. Honest signals can indicate favourable alleles that increase the chances of survival of offspring (fitness) or a low parasite burden suggesting a healthy individual.

Question 18

What is genetic drift?

Answer 18

Genetic drift occurs when chance events cause unpredictable fluctuations in alleles frquencies from one generaton to the next

Question 19

When is genetic drift more important?

Answer 19

More important in a small population as alleles are more likely to be lost from the gene pool.

Question 20

How is gene pool altered by genetic drift?

Answer 20

Certain alleles may be under-represented or overrepresented and allele frequencies change.

Question 21

What is the founder effect?

Answer 21

An example of genetic drift that occurs when a small subpopulation randomly breaks away from a large population.

Question 22

What is the bottleneck effect?

Answer 22

An example of genetic drift that occurs when a small subpopulation randomly survives when a large population reduces greatly.

Question 23

What does Hardy-Weinberg principle state?

Answer 23

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

Question 24

What are the conditions for maintaining Hardy-Weinberg?

Answer 24

• No natural selection
• Random mating
• No mutation
• Large population size
• No gene flow (through migration, in or out)

Question 25

What does p represent?

Answer 25

The frequency of the dominant allele

Question 26

What does q represent?

Answer 26

The frequency of the recessive allele

Question 27

What does p^2 represent?

Answer 27

Frequency of the homozygous dominant genotype

Question 28

What does q^2 represent?

Answer 28

Frequency of homozygous recessive genotype

Question 29

What does 2pq represent?

Answer 29

Frequency of heterozygous genotype

Question 30

What does it mean if there is a change in the Hardy-Weinberg value?

Answer 30

That evolution is occurring