3.4.4 genetic diversity and adaptation

Question 1

What is genetic diversity

Answer 1

Number of different alleles of a gene in a population

Population - group of interbreeding individuals of the same species

Question 2

Principles of natural selection in the evolution of populations

Answer 2

Variation of alleles exists in populations due to random DNA mutations

Selection pressure/Change in environment

Those with advantageous allele have increased chance of survival and reproduction - differential survival/reproductive success

Those surviving / reproducing pass advantageous allele to offspring

Frequency of advantageous allele and (named) characteristic increases in the population

Over many generations / long period of time

Question 3

Directional selection e.g. antibiotic resistance in bacteria

Answer 3

Change to the environment

Selection pressure acts on side of the mean

One extreme phenotype more likely to survive and produce
- bacteria with gene for antibiotic resistance

Mean phenotype changes

Question 4

Stabilising selection e.g. human birth weights

Answer 4

Stable environment

Selection pressure acts either side of the mean

Both extremes of phenotype less likely to survive and reproduce
- very small or very large babies

Mean phenotype remains the same

Question 5

Natural selection results in better adapted species

Answer 5

Adaptations increase an organism’s chance of survival

Anatomical
- structural features of organisms body
E.g. whales thick layer of blubber keeps it warm in cold sea

Physiological
- processes inside the body
E.g. brown bears hibernate in the winter, lower metabolism to conserve energy so they don’t need to look for food when its scarce

Behavioural
- ways an organism acts
E.g. possum plays dead if they’re being threatened by a predator, to escape attack