4.4 Variation And Evolution

Question 1

Discontinuous variation

Answer 1

Discontinuous variation: normally controlled by a single gene.
This gene may have two or more alleles. There are no intermediate forms, e.g. light and dark forms in some moth species.

Question 2

Continuous variation

Answer 2

influenced by the combined effect of a number of genes (polygenes). The effect of an individual gene may be small, but their combined effect is large.

Question 3

How would you compare discontinuous variation

Answer 3

numbers or percentages in each group
the ratio of the numbers in one group compared to another.

Question 4

How is continuous variation compared

Answer 4

you compare the mean of each group and the variance from the mean.

Question 5

Non heritable variation

Answer 5

Variations due to the environment have little evolutionary significance, as they are not passed from one generation to the next.

Question 6

Intra specific competition

Answer 6

Competition between individuals of the same species
Eg natural selection

Question 7

Interspecific competition

Answer 7

Competition between individuals of different species
Eg predator and prey relationships

Question 8

Selection pressure

Answer 8

An environmental factor that can alter the frequency of allies in a population when it is limiting.

Question 9

Natural selection

Answer 9

The increased chance of survival and reproduction of organisms with phenotypes suited to their environments
Enhancing the transfer of favourable alleles from one generation to the next.

Question 10

Gene pool

Answer 10

The total of all alleles of all the genes in a population at a given time.

Question 11

How do selection pressures change the frequency of alleles in a population?

Answer 11

Selection pressures can change the allele frequencies of the alleles present at a particular gene locus in a population and that allele frequency can be expressed either as a proportion or a percentage of the total number of copies for that gene.