Question

A few years ago, a very small population of zebrafish became isolated by a newly built dam. As a result, which statement is most likely to be true about this population of zebrafish now?

• A. Genetic variability is low.
• B. Fixation of genotypes due to drift is low.
• C. Inbreeding is low.
• D. Mutation rate is high.

Hint:

For isolated small populations:
1. Expect reduced genetic variability due to limited gene flow.
2. Genetic drift has a greater effect, potentially fixing certain alleles.
3. Inbreeding increases, leading to reduced fitness in some cases.

Answer 1

The Correct Option is A

Step 1: Understand the implications of a small, isolated population. When a population becomes isolated and is small in size, several genetic and evolutionary effects occur: 1. Reduced genetic variability: Small populations have less genetic diversity due to the limited number of individuals contributing alleles to the gene pool. 2. Increased genetic drift: Random changes in allele frequencies become more pronounced in small populations, potentially leading to the fixation of certain alleles and the loss of others. 3. Inbreeding: In small populations, individuals are more likely to mate with close relatives, increasing inbreeding and the potential for inbreeding depression. Step 2: Evaluate the options. Option (A): Genetic variability is low. This is true because small population size and isolation lead to reduced genetic diversity due to genetic drift and lack of gene flow. Option (B): Fixation of genotypes due to drift is low. This is incorrect because genetic drift has a more significant impact in small populations, making the fixation of alleles more likely. Option (C): Inbreeding is low. This is incorrect because inbreeding is higher in small, isolated populations due to limited mating options. Option (D): Mutation rate is high. This is incorrect because mutation rates are not affected by population size or isolation. Mutation rates remain constant regardless of the population's genetic diversity.