Evolution (KA7)

Key Area 7

Definition of evolution

Is the change in organism over generation as a result of genomic variations

What is natural selection

Is the non random increase in frequency of DNA sequences that increase survival and the non random reduction in frequency of deleterious sequences

What happens in stabilising selection

An average phenotype is selected for and extremes of the phenotype range are selected against

What happens in directional selection

One extreme of the phenotype range is selected for

Natural selection can cause changes in phenotype frequency.

Name the three types of selection you need to know

Stabilising, directional and disruptive

What happens in disruptive selection

Two or more phenotypes are selected for

Definition of vertical transfer

Vertical gene transfer is where transferred from parent to offspring as a result of sexual or asexual reproduction

Definition of horizontal transfer

Horizontal gene transfer is where genes are transferred between individuals in the same generation

Where does horizontal gene transfer generally occur

In prokaryotes

What is speciation

Speciation is the generation of new biological species by evolution as a result of isolation, mutation and selection

Definition of species

A species is a group of organisms capable of interbreeding and producing fertile offspring, and which does not normally breed with other groups

Why are isolation barriers important

They’re important as they prevent gene flow between subpopulation during speciation

What barriers leads to allopathic speciation

Geographical

What barriers leads to sympathetic speciation

Behavioural and ecological

Give the meaning of the term species

Is an orangish that can interbreed to produce fertile offspring

Explain why evolutionary change can occur more rapidly in prokaryotes than in organisms that only use vertical gene transfer

They can do horizontal gene transfer

Geographical barriers can lead to

Allopatric speciation

Behavioural or ecological barriers can lead to

Sympatric speciation

Explain why isolation barriers are important during speciation

They prevent gene flow between a population

State the difference between vertical gene transfer and horizontal gene transfer

Vertical gene transfer is where genetic information is passed on through generations, whereas horizontal gene transfer is where genetic information is passed on in the same generation

A bacterium acquires an antibiotic-resistance gene from another bacterium in the same generation.

Identify the type of gene transfer that has occurred.

Horizontal gene transfer