3.6 Evolution of a species

Question 1

What is a mutation?

Answer 1

A random change to the genetic material of an organism
The only source of new alleles
Can be advantageous, disadvantageous, or neutral

Question 2

What can affect the rate of mutation (mutagenic agents)?

Answer 2

Radiation and some chemicals

Question 3

What is an adaptation?

Answer 3

An inherited characteristic that makes an organism more suited to it’s environment
Either structural or behavioural

Question 4

What are 5 selection pressures?

Answer 4

Competition
Lack of food
Overcrowding
Inability to escape predators
Lack of resistance to a disease

Question 5

What is the theory of natural selection?

Answer 5

1. There is more offspring than the environment can support
2. Offspring show variation due to different combinations of alleles
3. They struggle to survive due to selection pressures
4. The best adapted survive to reproduce and pass on their favourable alleles
5. These alleles increase in frequency across the species

Question 6

When does speciation occur?

Answer 6

After a part of the population becomes separated from the rest of its species by an isolation barrier

Question 7

What are the 3 types of isolation barriers?

Answer 7

Geographical - river, mountain range, desert, sea
Ecological - caused by changes in temperature, pH, humidity
Behavioural - flowering at different times, different mating rituals

Question 8

What is the process of speciation?

Answer 8

1. Members of a species interbreed freely
2. A population becomes seperated by an isolation barrier
3. Mutations occur in each sub-population
4. Natural selection will select for different mutations in each group due to different selection pressures
5. The sub populations become genetically different
6. If the barrier is removed, the two populations will no longer be able to interbreed to produce fertile offspring - 2 new species have been formed