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 the same gene, found at the same locus on a chromosome. a single gene can 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 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 increases and population shifts 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 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