Chapter 18: Polulations And Evolution

Question 1

2pq

Answer 1

Heterozygous

Question 2

Hardy Weinberg equation?

Answer 2

P^2 + 2pq + q^2 = 1.0

P + q = 1.0

Question 3

What is the hardy Weinberg principle?

Answer 3

Mathematical equation that can be used to calculate the frequencies of the alleles of a particular gene in a population.

Question 4

What does the hardy Weinberg principle assume that?

Answer 4

• No mutations arrive.
• Large population.
• Mating within the population is random.
• There is no selection.
• Population is isolated.

Question 5

What does genetic variation arise as a result of?

Answer 5

Mutations
Meiosis
Random fertilisation of gametes

Question 6

What does natural selection depend upon?

Answer 6

• Genetic variety within the population.
• A variety of phenotype that selection operates against.
• Organisms produce more offspring than can be supported by the available resources.

Question 7

Gene pool

Answer 7

Total number of all the alleles of all genes of all individuals within a particular population at a given time.

Question 8

When does disruptive selection occur?

Answer 8

When an environmental factor takes two or more distinct forms.

Question 9

What does disruptive selection favour?

Answer 9

Favours those with extreme phenotype.

Question 10

What does stabilising section favour?

Answer 10

The average phenotypes.

Question 11

What does directional stabilising selection favour?

Answer 11

Favours phenotypes that vary in one direction from the mean of the population.

Question 12

Speciation

Answer 12

Evolution of a new species from an existing one.

Question 13

Adaptive radiation

Answer 13

Each phenotypes present will be subject to selective pressures that will lead to populations becoming adapted to its local environment.

Question 14

What type of population does genetic drift occur in?

Answer 14

Small

Question 15

Why does genetic drift occur in small populations?

Answer 15

Less genetic diversity. Genetic diversity is restricted to few alleles. As small number, not an equal chance of them all being passed on. Those passed on will quickly affect whole population as the frequency is high. Any mutation to one of these alleles that is selectively favoured will also quickly affect the population as the frequency is high.

Question 16

Two types of speciation.

Answer 16

Allopatric

Sympatric

Question 17

Describe the process of allopatric speciation.

Answer 17

• Two populations become geographically separated.
• Environmental conditions may differ on either side of the barrier. Therefore, natural selection will affect both populations differently.
• Over many generations this may lead to reproductive separation and the formation of separate species.

Question 18

Describe the process of sympatric speciation.

Answer 18

• Occurs between populations of species within the same area.
• Occurs when random mutations within a population prevent individuals that carry the mutation from breeding with other members of the population that don’t carry the mutation.

Question 19

What are the changes that results in reproductive isolation?

Answer 19

• Seasonal change. (Different flowering or mating patterns).
• Mechanical change. (Changes in size and shape).
• Behavioural changes. (Group of individuals may develop courtship rituals that aren’t attractive to the rest of species).

Question 20

What is the advantage of presenting results as a ratio?

Answer 20

Comparisons can be made.

Number/ sample size may vary.