Page 56 - CB1.3 Genetic Varation sciPAD

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56 CB 1.3 GENETIC VARIATION
GENETICS OF POPULATIONS
Population Bottlenecks
A population bottleneck occurs when a species undergoes a significant reduction in numbers,
due to a catastrophic event such as an adverse environmental event, a natural disaster, or
human activity. This sudden drop in population size leads to reduced genetic variation, making
the species more vulnerable to diseases and reduces its ability to adapt to future changes.
The original population had high
genetic variation.
Hunting white and dark phenotypes
reduces the population size.
The population has different allele
frequency and less genetic variation.
The population recovers but with a
lower level of genetic variation.
1. Define a ‘population bottleneck’. 


2. Explain why genetic variation is important for the long-term survival of a species. 



3. Explain how a population bottleneck can lead to reduced genetic variation. 




4. Describe the cause and consequences of 'inbreeding depression'. 




5. Outline how the actions of humans can contribute to population bottlenecks. 



A major issue that can arise in populations that have been through a bottleneck event is 'inbreeding
depression'. This occurs when closely related individuals mate. When relatives breed, both parents
are more likely to carry the same harmful alleles. As a result, their offspring have a higher chance
of inheriting these harmful alleles from both parents. This can lead to undesirable traits and genetic
disorders. Inbreeding depression typically makes a population more vulnerable. It often results in
lower fertility rates, higher susceptibility to diseases, reduced growth rates and increased mortality.
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