2.4 VARIATION AND EVOLUTION

Question 1

WHAT IS VARIATION?

Answer 1

The differences between individuals of the same species

Question 2

WHAT CAUSES VARIATION?

Answer 2

• genetics
• environment

Question 3

WHAT IS CONTINUOUS VARIATION?

Answer 3

When a feature changes gradually over a period of time. e.g. height, weight and hand span

Question 4

WHAT IS DISCONTINUOUS VARIATION?

Answer 4

When a feature has a limited number of possible values. e.g. eye colour, blood group and biological sex

Question 5

WHAT HAPPENS DURING SEXUAL REPRODUCTION?

Answer 5

The nuclei of the male and female gametes join together. This process is called fertilisation

Question 6

WHAT HAPPENS DURING ASEXUAL REPRODUCTION?

Answer 6

Produces offspring from one single parent. There are no gametes involved

Question 7

WHAT IS A GENOME?

Answer 7

An organism’s entire genetic material

Question 8

WHAT IS A MUTATION?

Answer 8

A change in a gene. New genes can result from these changes.
Mutations can be harmless, beneficial or harmful, and may be passed from parent to offspring.

Question 9

WHAT DOES CYSTIC FIBROSIS CAUSE?

Answer 9

A thick mucus to build up in the lungs, leading to the blocking of the bronchioles

Question 10

WHAT CAUSES CYSTIC FIBROSIS?

Answer 10

A mutation

Question 11

WHAT IS GENE THERAPY?

Answer 11

It involves inserting copies of a normal allele into the DNA of a person who carries the faulty cystic fibrosis allele

Question 12

WHAT ARE THE POTENTIAL PROBLEMS WITH CYSTIC FIBROSIS?

Answer 12

• The alleles may join with DNA in incorrect places.
• The alleles may not enter every target cell.
• Treated cells (with the normal allele) will eventually be worn away and replaced by the patient’s own untreated cells (with the faulty allele).

Question 13

DESCRIBE CHARLES DARWINS THEORY OF NATURAL SELECTION

Answer 13

1. Individuals with features that make them better adapted to the environment will survive and breed. This is ‘survival of the fittest’.
2. Genes are passed to offspring. This means that offspring inherit the features that make them better adapted to the environment.
3. As a result of this, over many years, a species may evolve and change.