Page 54 - CB1.3 Genetic Varation sciPAD

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54 CB 1.3 GENETIC VARIATION
GENETICS OF POPULATIONS
Natural Selection and the Importance of Genetic Variation
‘Natural selection’ is the name for the process by which beneficial traits in a population tend to be
preserved while unfavourable traits are likely to be eliminated.
The stability of a population is influenced by its level of genetic variation. In populations with high
genetic variation, alleles that give a survival advantage are more likely to be present. Therefore,
when environmental conditions change - be it through the introduction of new predators, diseases,
or climate shifts - individuals possessing favourable allele combinations have a better chance of
survival, thus ensuring the continued existence of the species.
On the other hand, populations with low genetic variation are less likely to possess the necessary
alleles to adapt to environmental changes, making them more vulnerable to extinction.
Natural selection acts on the genetic variation present in a population to:
•
remove individuals (and their alleles) that fail to produce offspring in a particular situation.
•
increase the number of individuals (and their alleles) that are particularly good at producing
offspring in the same situation.
1. Use the word list provided to complete the paragraph below.
favourable - suited - variation - selects - survive
populations - reproduce - die - evolution
In nature, no two organisms of the same species are exactly the same, they all show some
kind of . As a result, some individuals are better
to their environment than others. of organisms tend to produce more
offspring than their environment can sustain. Therefore, those individuals that are best
suited to their environment and . Those that
are not well suited tend to off. In this way, the environment ‘ ’
the best individuals. The reproduction of those better suited to their environment mean
that their alleles will increase in frequency within the gene
pool. When the frequency of alleles within a population changes,
is occurring.
2. Identify whether the following statements refer to a population with high genetic variation
or low genetic variation.
(a) In this population, there is likely to be little or no evolution because they cannot
respond to environmental or situational changes. 
(b) In this population, there is likely to be evolution because they can respond to
environmental or situational changes. 
Low population and limited genetic variation heightens New Zealand’s endangered birds’ risk of extinction. It
makes these birds highly vulnerable to disease outbreaks, environmental changes, and predation. The lack of
genetic variation reduces adaptability, making recovery and long-term survival increasingly difficult.
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