AP BIOLOGY

EVOLUTION

SOURCES OF VARIATION IN A POPULATION

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Genetic drift, or changes in allelic frequency due to chance factors, occurs in populations that are very ____
A
mobile
B
isolated
C
small in number
D
closely adapted to local environments
Explanation: 

Detailed explanation-1: -Genetic drift is a mechanism of evolution in which allele frequencies of a population change over generations due to chance (sampling error). Genetic drift occurs in all populations of non-infinite size, but its effects are strongest in small populations.

Detailed explanation-2: -Genetic drift involves changes in allele frequency due to chance events – literally, “sampling error” in selecting alleles for the next generation. Drift can occur in any population of non-infinite size, but it has a stronger effect on small populations.

Detailed explanation-3: -Small populations tend to lose genetic diversity more quickly than large populations due to stochastic sampling error (i.e., genetic drift). This is because some versions of a gene can be lost due to random chance, and this is more likely to occur when populations are small.

Detailed explanation-4: -In a population, allele frequencies are a reflection of genetic diversity. Changes in allele frequencies over time can indicate that genetic drift is occurring or that new mutations have been introduced into the population.

Detailed explanation-5: -Natural selection, genetic drift, and gene flow are the mechanisms that cause changes in allele frequencies over time. When one or more of these forces are acting in a population, the population violates the Hardy-Weinberg assumptions, and evolution occurs.

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