• Selective breeding is where two of the best animals or plants are bred together. Their resulting offspring is then bred together until the optimum plant or animal is produced.
• Selective breeding is financially worthwhile however it leads to a loss of alleles which causes the gene pool to shrink.
• Genetic drift is a change in frequency of a gene in a gene pool.
• The Founder Effect is where there’s no diversity left in a gene pool.
• A genetic bottleneck is where the numbers in a population crash thereby decreasing the amount of genetic variation within that population.

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TEST IT!

1.

In the late 1900s northern elephant seals numbered approximately 150,000 and lived in different colonies in different areas. People began to hunt them and by 1910 there numbers had dropped to less than 100, all of them living now in one single colony together. The hunting stopped and today their numbers have risen back to 150,000 and the seals again live in different colonies.
a. What’s a genetic bottleneck? Explain using the elephant seals as an example.
b. After 1910, how do you think the Founder Effect would have had an influence on the seals’ genetic diversity?

2.

Selective breeding is popular within farming.
a. What is an advantage of selective breeding?
b. Explain how selective breeding can lead to genetic drift.

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ANSWERS

1.

a. A genetic bottleneck is linked to a smaller gene pool. This would have occurred due to the heavy hunting of the seals which brought their population down to less than 100.
b. New colonies were created by a smaller number of seals. This means that there were less alleles to create these new colonies due to the smaller gene pool.

2.

a. Answers include:
i. Saves money
ii. The optimum animal or plant can be produced
b. If only certain traits are bred then alleles are lost and the gene pool shrinks which has a negative effect on biodiversity. A change in the frequency of a gene is known as genetic drift.