UNIT 3 - Natural Selection, Adaption & Behaviour

A random change to genetic material. Mutations are spontaneous and are the only sources of new alleles

-Neutral, -Advantageous, -Disadvantageous,

-radiation (X-rays, UV) -some chemicals (e.g. those found in cigarettes)

It is an inherited characteristic that makes an organism well suited to survive in its environment

It makes it possible for a population to evolve over time in response to changing environmental conditions

Natural selection is a process where organisms which are better adapted to their environment survive and reproduce, passing on their favourable alleles. Those organisms which are less well adapted die before they reproduce

When there are selection presssures

-Temperature: some organisms may be better adapted to colder temperatures. -Predators: some organisms might be better adapted to camouflage and avoid predators.

1) Species produce more offspring than the environment can sustain. 2)Variation exists between members of a species. 3)The best adapted survive. 4)Those who survive reproduce, passing on their favourable alleles that give a selective advantage. 5)This happens over many generations and these alleles increase in frequency within the population.

Speciation is the evolution of new species from pre-existing ones.

When populations become isolated from each other by a barrier and interbreeding is prevented

-Geographical -Ecological -Behavioural

Split the population into sub-populations

Mutations occur in each sub-population causing new variation within each sub-population

-Isolating barriers -Mutations occurs in sub-populations -Natural selection happens in each sub-population due to different selection pressures. -Speciation