17 SELECTION & EVOLUTION

Question 1

What are variations?

Answer 1

Differences between individuals of the same species

Question 2

What are phenotypic variations?

Answer 2

Differences in the observable characteristics of individuals within a species

Question 3

What are genetic differences?

Answer 3

Differences between the DNA base sequences of individuals of the same species

Question 4

List the causes of genetic variation.

Answer 4

• Independent assortment
• Crossing over
• Random fusion of gametes
• Mutation

Question 5

How do independent assortment, crossing over, and random fusion of gametes contribute to genetic variation?

Answer 5

They cause a reshuffle of the existing alleles resulting in combinations that differ from parents and their offspring

Question 6

What is the effect of mutation on alleles?

Answer 6

Produces completely new alleles

Question 7

What happens if a mutation occurs in body cells?

Answer 7

Usually has no effect on the organisms

Question 8

What is the consequence of a mutation occurring in cells used to produce gametes?

Answer 8

The mutation will be inherited

Question 9

What factors cause phenotypic variations?

Answer 9

• Genetic factors (e.g., human blood group)
• Environmental factors (e.g., fur colour of the Siamese cat)
• Combination of genetic and environmental factors

Question 10

What is continuous variation?

Answer 10

Differences between individuals of a species that can lie at any point in the range between the highest and lowest values

Question 11

What are the characteristics of continuous variation?

Answer 11

• Gives quantitative differences
• Results in a continuous distribution of values
• Determined by both genes and environmental factors

Question 12

What is discontinuous variation?

Answer 12

Differences between individuals of a species that belong to distinct categories with no intermediates

Question 13

What are the characteristics of discontinuous variation?

Answer 13

• Gives qualitative differences
• Clear cut/distinct with no intermediates

Question 14

How is discontinuous variation caused?

Answer 14

Entirely by genes, not by the environment

Question 15

What is genetic drift?

Answer 15

Change in allele frequency that occurs by chance, not as a result of natural selection

Question 16

What is the founder effect?

Answer 16

Reduction in a gene pool due to only a few individuals starting a new population

Question 17

What is the bottleneck effect?

Answer 17

A sudden reduction in population size that leads to loss of alleles and reduced genetic variation

Question 18

What is natural selection?

Answer 18

Process by which individuals with advantageous alleles are more likely to survive and reproduce

Question 19

What is fitness in the context of natural selection?

Answer 19

The ability of an organism to survive and reproduce

Question 20

What are selection pressures?

Answer 20

Environmental factors that affect the chance of survival of an organism

Question 21

What is stabilising selection?

Answer 21

Type of natural selection that maintains allele frequencies relatively constant over generations

Question 22

What is directional selection?

Answer 22

Occurs when a new environmental factor causes allele frequencies to change in a particular direction

Question 23

What is disruptive selection?

Answer 23

Occurs when conditions favor both extremes of a population, leading to the maintenance of different phenotypes

Question 24

What is an example of directional selection?

Answer 24

Development of antibiotic resistance in bacteria

Question 25

What is the Hardy-Weinberg principle?

Answer 25

A principle used to calculate allele and genotype frequencies and indicates if a population is evolving

Question 26

What does the Hardy-Weinberg equation consist of?

Answer 26

p + q = 1 and p² + 2pq + q² = 1

Question 27

What does 'p' represent in the Hardy-Weinberg equation?

Answer 27

Frequency of the dominant allele

Question 28

What does 'q' represent in the Hardy-Weinberg equation?

Answer 28

Frequency of the recessive allele

Question 29

When do Hardy-Weinberg calculations not apply?

Answer 29

When the population is small, there is significant selective pressure, migration, or non-random mating

Question 30

What is allele frequency?

Answer 30

The number of times an allele occurs in a gene pool relative to other alleles

Question 31

What is a gene pool?

Answer 31

Total number of alleles of all genes of all individuals in a population at a given time

Question 32

What does the Hardy-Weinberg principle predict about gene pools in a population?

Answer 32

The gene pool does not change in succeeding generations; allele and genotype frequencies remain constant.

Question 33

What is a condition for the Hardy-Weinberg principle to be applicable?

Answer 33

Random mating must occur in the population.

Question 34

Fill in the blank: The Hardy-Weinberg principle assumes there is no _______ of new alleles or removal of alleles by migration.

Answer 34

introduction

Question 35

What effect does mutation have in the context of the Hardy-Weinberg principle?

Answer 35

There is no mutation; no creation of new alleles.

Question 36

Why is a large population necessary according to the Hardy-Weinberg principle?

Answer 36

To prevent fluctuations of allele frequency due to chance, known as genetic drift.

Question 37

What type of selection pressure does the Hardy-Weinberg principle assume is absent?

Answer 37

There is no selection or selection pressure.

Question 38

What can be compared once the ratios of different genotypes in a population have been determined?

Answer 38

Predicted ratios in the next generation can be compared with observed values.

Question 39

What statistical test can be used to test the significance of differences between predicted and observed genotype ratios?

Answer 39

χ2 test (chi-squared test).

Question 40

True or False: The Hardy-Weinberg principle allows for significant differences in genotype ratios if migration and non-random mating can be discounted.

Answer 40

True

Question 41

What does significant difference in genotype ratios suggest about a population?

Answer 41

It suggests that directional selection is occurring.

Question 42

Fill in the blank: The Hardy-Weinberg principle assumes that the probability of one individual mating with another is _______.

Answer 42

equal

Question 43

What does 'genetic drift' refer to in the context of population genetics?

Answer 43

Fluctuations of allele frequency due to chance.

Question 44

What is the main focus of artificial selection or selective breeding?

Answer 44

To favor specific traits in a population.