Page 50 - CB1.3 Genetic Varation sciPAD

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50 CB 1.3 GENETIC VARIATION
GENETICS OF POPULATIONS
Genetic Variation
Genetic variation refers to the variety of genes within a population. It includes the various alleles
(different versions of a gene) that exist for a particular trait, and the frequency with which they
occur. High genetic variation is important. For example, when faced with a significant change
in climate, populations with a wide range of genetic variation are more likely to have individuals
that can adapt to survive in the new conditions. This adaptability is essential for the long-term
survival of species and ecosystems.
Conversely, low genetic variation can make a population more vulnerable to diseases and
environmental changes, as it limits the range of possible adaptive responses. This is a particular
concern in conservation biology, where low genetic variation can indicate a higher risk of
extinction for endangered species.
1. Define the term ‘genetic variation’. 


2. Outline why it is important that ecosystems are genetically diverse. 




3. Identify which of the two populations shown above is likely to survive the following
environmental changes:
(a) A predator is introduced which targets fish with a allele.

(b) Water temperatures increase and fish with a allele can tolerate this change.

(c) A new disease appears but fish with a allele are resistant to it.

4. Many commercial crops (pine trees, potatoes, maize, etc) have very low genetic variation
as they are bred from a small number of parent plants. Describe the dangers of growing
crops with such low genetic variation.




Small Populations Lose Genetic Variation
2
Large Populations Retain High Genetic Variation
1
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