Populations and evolution

Question 1

What does the Hardy-Weinburg principle predict?

Answer 1

The proportion of dominant and recessive alleles will remain the same from one generation to the next.

Question 2

What are the 5 conditions required for the Hardy-Weinberg theory to work?

Answer 2

1. No mutations occur
2. The population is isolated
3. No selection occurs
4. There is a large population
5. mating between individuals is random

Question 3

Define a gene pool

Answer 3

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

Question 4

What is meant by allelic frequency?

Answer 4

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

Question 5

What are the two equations in the Hardy-Weinberg principle?

Answer 5

p+q=1

p^2+2pq+q^2=1

Question 6

What does p represent?

Answer 6

The dominant allele

Question 7

What does q represent?

Answer 7

The recessive allele.

Question 8

What genetic factors can cause variation in phenotypes?

Answer 8

mutations, meiosis and random fertilisation of gametes.

Question 9

What is a selection pressure?

Answer 9

An environmental factor which can limit the population of a species.

Question 10

Why must organisms produce more offspring than can be supported by the environment?

Answer 10

Over production ensures that there is competition between organisms resulting in differential reproduction.

Question 11

What is the advantage of genetic variation?

Answer 11

Some individuals will have the combination of genes needed to survive.

Question 12

What is stabalising selection?

Answer 12

Selection which preserves the average phenotype by favouring average individuals and selecting against the extreme phenotypes.

Question 13

What is directional selection?

Answer 13

Selection which changes the phenotypes of a population by faviouring the phenotypes that vary in one direction from the mean. Selecting for the extreme phenotypes.

Question 14

What is disruptive selection?

Answer 14

Selection that favours individuals with extreme phenotypes when an environmental factor takes on two or more distinct forms. Most important in evolutionary change.

Question 15

What is speciation?

Answer 15

The evolution of new species from existing ones.

Question 16

What is a species?

Answer 16

A group of individuals that have a common ancestry and are capable of breeding to produce fertile offspring. They are reproductively separated from other species.

Question 17

What is allopatric speciation?

Answer 17

When 2 populations are geographically isolated and the environmental conditions are different in each isolated area.

Question 18

What is sympatric speciation?

Answer 18

when 2 populations are reproductively separated in the same area.

Question 19

Where can genetic drift take place?

Answer 19

In small populations

Question 20

What is genetic drift?

Answer 20

In a small population, those alleles that are passed on will quickly affect the population as their frequency is high. The effect will be more rapid and they are more likely to develop into a new species.

Question 21

Within each subspecies there is a range of phenotypes. Explain the factors that give rise to this variation.

Answer 21

Mutation produces new alleles

Phenotype depends on the environment/selection pressures.

Question 22

Why may the frequency of a species remain the same for many generations?

Answer 22

If there is no migration and the selection pressures stay the same.

Question 23

Explain why correlation does not mean causation?

Answer 23

There may be another factor.

Question 24

Give two possible causes f variation that result from mitosis during gamete formation?

Answer 24

Crossing over and continuous variation

Question 25

Other than DNA base sequence, give two types of evidence that can be used to determine evolutionary relationships

Answer 25

Anatomy/physical differences and biochemistry