18 - Population and evolution

Question 1

Define a gene pool.

Answer 1

All alleles of all genes of all individuals in a population at a given time.

Question 2

Define allele frequency.

Answer 2

The number of times an allele occurs within a gene pool.

Question 3

Define a population.

Answer 3

A group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed.

Question 4

GIve 5 conditions for using the Hardy Weinberg principle.

Answer 4

• no mutations arise
• population is isolated, so there is no allele flow in or out
• there is no selection
• the population is large
• mating within the population is random

Question 5

What does the Hardy Weinberg principle assume?

Answer 5

The proportion of dominant and recessive alleles of any gene in a population remain the same from one generation to the next.

Question 6

Give three types of selection.

Answer 6

• Disruptive
• Stabilising
• Directional

Question 7

How should allele frequency be expressed?

Answer 7

Decimal

Question 8

Describe sympatric separation in plant species with different flowering times. (6)

Answer 8

1. Not geographical isolation
2. Mutations cause different flowering times
3. Reproductive separation
4. Change in allele frequencies
5. Disruptive selection
6. Different sorted cannot breed to produce fertile offspring

Question 9

Describe why there may be a time lag from the introduction of an allele to the appearance of a species (3)

Answer 9

1. Initially only a few individuals with favourable allele
2. Individuals with favourable allele have more offspring
3. Takes many generations for allele to become most common allele

Question 10

How can mitochondrial DNA be used to define species? (2)

Answer 10

Compare base sequence
Different in different species, similar in subspecies.