4.4 - Genetic diversity and adaptation

Define population.

All the organisms of a particular species

that live in the same place.

What is an allele?

Different forms of a particular gene,

found at the same locus (position) on a

chromosome. A single gene could have

many alleles.

Define genetic diversity.

The total number of different alleles in a

population

What advantage does a high genetic

diversity provide?

Ability to adapt to a change in

environment; allows natural selection to

occur.

Explain how natural selection results in

development of new characteristics.

● Random mutations result in new alleles.

● Some alleles provide an advantage, making an

individual more likely to survive and reproduce.

● Their offspring receive the new allele, and

frequency continues to increase over many

generations.

What is directional selection?

Occurs when environmental conditions

change. Individuals with phenotypes suited to

the new conditions will survive and pass on

their genes. Over time the mean of the

population will move towards these

characteristics.

Give an example of directional selection.

Antibiotic resistance. Bacteria with a mutation

allowing them to survive in the presence of

antibiotics will reproduce. Therefore frequency

of this allele will increase and the population

will shift to have greater antibiotic resistance.

What is stabilising selection?

Occurs when environmental conditions

stay the same. Individuals closest to the

mean are favoured, and any new

characteristics are selected against.

Results in low diversity.

Give an example of stabilising selection.

Birth weight; babies that weigh around

3kg are more likely to survive than those

at lower or higher weights.

Define a niche.

The role of a species within its

environment. Species sharing the same

niche will compete with each other.

What are the three types of adaptation?

Give examples of each.

● Anatomical (changes to body structure) e.g. oily

fur.

● Physiological (changes to bodily processes) e.g.

venom production.

● Behavioural (changes to actions) e.g. hibernation.