3.4.4 Genetic diversity and adaptation

Different versions of a single (particular) gene

The number of different alleles of genes in a population

Group of organisms of one species living in a particular habitat

Gene mutations involve a change in the base sequence of chromosomes Chromosomal mutations involve a change in the number of chromosomes

Bodily structure

processes that occur in the body

observable actions or reactions of an organism in response to stimuli, which can be internal / external

Changes in allele frequencies over generations

Individuals with advantageous inherited alleles are more likely to survive and reproduce, passing those alleles to their offspring. This leads to a change in the frequency of those alleles within a population over generations, driving evolutionary change

The complete range of alleles in a population

• mutations in the DNA, forming new alleles • Different alleles being introduced into a population when individuals from another population migrated into them and reproduce. This is known as gene flow.

It allows natural selection to occur.

• Genetic diversity in a population due to random mutations (gene pool) • The ability to reproduce and pass on alleles • Presence of limited resources leads to competition for these resources • Those that are better adapted (fittest) are more likely to survive and reproduce (produce the most offspring) passing on advantageous alleles • Over many generations the desired allele will increase in frequency • Differential survival and reproduction: some members of a population will survive and others will die without reproducing

Genetic variation: - mutation during S phase of interphase - Independent assortment during anaphase I of meiosis - crossing over during prophase I of meiosis - Sexual reproduction - random fertilisation of gametes Environment: - food availability - prevailing wind can affect direction of tree growth Epigenetics (labelling of genes to switch them on and off)

Labelling of genes (addition of chemical tags) to switch them on and off. Way of influencing how our genome is regulated without changing the DNA code itself.

Environmental force altering the frequency of alleles in a population

• Random mutation can result in new alleles of a gene • Many mutations are harmful, but in certain environments (due to selective pressures), the new allele of a gene might benefit its possessor • Individuals with the advantageous allele that increases their chance of survival are more likely to survive and therefore reproduce • passing on their advantageous allele to their offspring • over many generations the allele frequency changes, with the frequency of the advantageous allele increasing

• Anatomical adaptations • Physiological adaptations • Behavioural adaptations

It results in species that are better adapted to their environment.

• structural features of an organism’s body that increase its chance of survival e.g. whales having a thick layer of blubber to keep them warm in the cold sea

Processes inside an organism’s body that increase its chance of survival e.g. hibernation of brown bears in winter to lower metabolism and conserve energy so no need to look for food when it’s scarce

Ways an organism acts that increases its chance of survival and reproduction e.g. possums play dead if threatened by a predator / escape attack.

• directional selection • stabilising selection • disruptive selection

where phenotypes at the extreme end are selected for i.e. where individuals with alleles (phenotypes) for characteristics of an extreme type are more likely to survive and reproduce