KA7 - evolution :)

Question 1

What is the definition of evolution?

Answer 1

Changes in organisms over generations as a result of genomic variation

Question 2

What is vertical gene transfer?

Answer 2

• genes transferred from parent to offspring

- sexual or asexual reproduction

Question 3

What is horizontal gene transfer?

Answer 3

• Where genes are transferred in the same generation

Question 4

What is an example of horizontal gene transfer and how is it beneficial?

Answer 4

Prokaryotes

- faster evolutionary change than vertical gene transfer

Question 5

What is natural selection?

Answer 5

The non-random increase in the frequency of DNA sequences that increase survival

The non-random reduction in frequency of deleterious sequences

Question 6

What is stabilising selection? How does it look on a graph?

Answer 6

One high point

• An average phenotype is selected for
• Extremes of phenotype range are selected against

Question 7

What is directional selection? How does it look like on a graph?

Answer 7

Over to the right - one extreme of a phenotype is selected for

Question 8

What is disruptive selection? How does it look on a graph?

Answer 8

Two bumps - 2 or more phenotypes are selected for

Question 9

What is the definition of a species?

Answer 9

A group of organisms capable of interbreeding to produce fertile offspring which would usually not interbreed with other groups

Question 10

What is speciation?

Answer 10

The generation of new biological species by evolution as a result of

• Isolation
• Mutation
• Selection

Question 11

What do isolation barriers do?

Answer 11

They prevent gene flow between sub-populations during speciation

Question 12

Allopatric is?

Answer 12

geographical.

Question 13

What are the steps of allopatric speciation?

Answer 13

1. One large interbreeding population
2. A barrier separates the two (geographical), and they are isolated. No interbreeding or gene exchange can occur the two sup populations
3. Different mutations occur randomly in each population and natural selection over time may favour the mutants
4. Natural selection increases the frequency of new alleles
5. Speciation has occurred as the two sub-populations cannot interbreed to produce fertile offspring even if the barrier is removed.

Question 14

Sympatric is?

Answer 14

ecological or behavioural.

Question 15

What are the steps of sympatric speciation?

Answer 15

1. One large interbreeding population share the same ecological niche
2. An alternative ecological niche appears. Some members start to exploit the new niche
3. The 2 sub-populations exploit different resources (such as food source) and no longer interbreed. Behaviour has become an isolating barrier
4. Mutants have better adapted to exploit the new resources that appear and successfully breed with one another.
5. Natural selection may favour the mutants and overtime two genetically distinct species are formed, as they can no longer interbreed - ie speciation has occured.