Topic 1 - Variation: Species and genes

Question 1

Two populations of the same species have become separated and over time have developed new characteristics. How can you tell if speciation has occurred?

Answer 1

Speciation has occurred if the two populations have become so different that they can’t breed with one another to produce fertile offspring.

Question 2

Describe the relationship between the nucleus, chromosomes and genes in a cell.

Answer 2

The nucleus contains chromosomes. A gene is a short length of a chromosome.

Question 3

How can alleles explain why humans have different eye colours?

Answer 3

You can get different versions of the same gene, which give different versions of a particular inherited characteristic. These are called alleles. The alleles that you have will determine your eye colour.

Question 4

In terms of populations, what do we mean by the term isolation?

Answer 4

Where populations of a species become separated, due to a physical barrier, e.g. caused by a natural event such as an earthquake or a flood.

Question 5

How might speciation occur if two populations of the same species are isolated from one another by a flood?

Answer 5

Each population has a range of alleles that control their characteristics.
As the conditions on either side of the flood may vary, different characteristics will become more common in each population due to natural selection.
Eventually individuals from each population will have become so different that they can’t breed with one another to produce fertile offspring.