EVOLUTION U1

Question 1

State the definition of evolution

Answer 1

Evolution is defined as the changes in organisms over generations as a result of genomic variations.

Question 2

State the definition of natural selection

Answer 2

Natural selection is the non-random increase in frequency of DNA sequences that increase survival and the non-random reduction in the frequency of deleterious alleles.

Question 3

There are 3 types of selection caused by a change in phenotype frequency?

Answer 3

Stabilising selection , Directional selection , Disruptive selection, two or more phenotypes are selected for.

Question 4

Stabilising selection

Answer 4

An average phenotype is selected for and extremes of phenotype are selected against.

Example: Clutch size in birds – a large number of eggs may result in some young starving, whereas too few could to increases mortality and failure to breed and pass on genes.

Question 5

Directional selection

Answer 5

One extreme of the phenotype is selected for.

Example: Giraffe neck length. The environment favoured giraffes with longer necks as they could reach more vegetation on the trees.

Question 6

Disruptive selection, two or more phenotypes are selected for.

Answer 6

Example: Male Coho salmon – large and small males are selected for when breeding. The small males are small enough to sneak in amongst the females and breed. The larger males have the size to fight off the competition and so breed with the females. The medium (middle) males are disadvantaged

Question 7

Describe the difference between horizontal and vertical gene transfer

Answer 7

Horizontal gene transfer is where genes are transferred between individuals of the same generation.
(imagine you could hand over some of your genes to one of your friends – this would be horizontal gene transfer).

Vertical gene transfer is where genes are transferred from parent to offspring as a result of sexual or asexual reproduction.
(Any type of reproduction involving one parent, or two parents will be an example of vertical gene transfer).

Question 8

Describe natural selection in prokaryotes

Answer 8

Natural selection is more rapid in prokaryotes. Prokaryotes can exchange material horizontally, resulting in a faster evolutionary change than in organisms that only use vertical transfer.

Question 9

State the definition of a species and speciation

Answer 9

A species is a group of organisms capable of interbreeding and producing fertile offspring, which does not normally breed with other groups.

Speciation is the generation of new biological species by evolution as a result of isolation, mutation and selection.

Question 10

Name the type of speciation that occurs as a result of geographical, ecological and behavioural barriers

Answer 10

Geographical barriers lead to allopatric speciation.

Example:

Lakes drying out and volcanic eruptions.
Behavioural and ecological barriers lead to sympatric speciation.

Examples:

Behavioural – slight change in mating call such as pitch or tone. Which would prevent breeding.
Ecological – Difference in flowering time of plants.