7B Variation and Selection

Question 1

Define variation

Answer 1

The differences between individuals

Question 2

What is the main source of variation?

Answer 2

Mutations but it can also be due to independent segregation, crossing over and random fertilisation of gametes

Question 3

What is the most variation caused by?

Answer 3

Combination of genetic and environmental factors

Question 4

Natural selection process

Answer 4

Individuals of the same species vary as they have different alleles
Predation disease and competition create a struggle for survival
Some are better adapted than others
Individual with the a phenotype that increases the chance of survival are more likely to survive reproduce and pass on their alleles
A greater proportion of the next generation inherit beneficial alleles
They reproduce and pass on their alleles
The frequency of the beneficial allele in the gene pool increases friction generation to generation

Question 5

Describe stabilising selection

Answer 5

Where individuals with alleles four characteristics towards the middle of the range are more likely to survive and reproduce
It occurs when the environment is not changing

Question 6

Describe directional selection

Answer 6

Where individuals with alleles for a single extreme phenotype are more likely , to survive and reproduce
This is in response to an environmental change

Question 7

Describe disruptive selection

Answer 7

Where individuals with alleles for extreme phenotypes at either end of the range are more likely to survive and reproduce