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CB 1.3 GENETIC VARIATION
GENETICS OF POPULATIONS
The Founder Effect
The founder effect occurs when a small number of individuals from a larger population establish a
new, isolated population. This new, smaller population may not have all of the alleles found in the
original population so it is not as genetically diverse.
One of the main causes of the founder effect is migration, and in animals, it is often due to a few
individuals, representing a non-random sample of genetic information, arriving on an island.
The main difference between the founder effect and a population bottleneck is the type of event
that causes them. The end result is similar in that genetic variation is reduced.
Original population Migrating population
Founding
population
Population after a
few generations
Founder population
after more generations
1. Distinguish between the types of events that cause the founder effect and the types of
events that cause a population bottleneck.
The founder effect occurs when:
A population bottleneck occurs when:
2. Describe the end result of both the founder effect and a population bottleneck.
3. Suggest how an animal such as a lizard could arrive on an island.
4. In New Zealand, endangered birds are often relocated to predator-free offshore islands
with the aim of protecting and rebuilding their populations. Explain why it would be
important to understand the genetics of the birds before they are relocated.
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