Question

Background Information: A large population of squirrels is split into two equal sized subpopulations (A and B) by the formation of a deep, rushing river that goes between them. This prevents gene flow since the squirrels can neither swim nor fly. A powerful magician living near population A loves these squirrels and the traits they exhibit very much, and performs a spell that prevents any mutations from occurring in that group. This magician is practically immortal, so the spell continues to operate for thousands of years. Statement: The mutations that continue to occur make Population B more likely to go extinct than Population A, in which mutations do not occur. After reviewing the background information, do you agree or disagree with the statement above? Thoroughly explain your reasoning.

Answer 1

Evolution is how species experience heritable (passed from one generation to the next) changes in their traits over time. There are four mechanisms of evolution (how evolution happens):

1. Natural selection,
2. Mutations,
3. Genetic drift, and
4. Gene flow.

Mutations are changes to an organism’s DNA. Mutations are one of the fundamental forces of evolution because they fuel the variability in populations and enable evolutionary change. Species evolve because of the accumulation of such mutations that occur over time.

Based on their effects on fitness, mutations can be divided into three broad categories:

1. the ‘good’ or advantageous, that increase an organism’s ability to survive and reproduce,
2. the ‘bad’ or deleterious, that decrease its fitness (such as a malformed oxygen-carrying protein),and
3. the ‘indifferent’ or neutral that are not affected by selection because their effects are too small.

Thus all mutations may not be deleterious. The unfavorable or harmful mutatioins are quickly eliminated from the population by natural selection. Others that are beneficial will spread through the population.

Mutation is context-dependent. Whether or not a mutation is beneficial or harmful is determined by whether it helps an organism survive to sexual maturity and reproduce. The effects of mutations often depend on

(i) the presence or absence of other mutations,

(ii) the environment,

(iii) the size and structure of the population, and

(iv) the fate of other individuals (both, those that have more pronounced effects and those that are in close proximity to the old chromosome.)

Hence, genetic variation is advantageous because it enables some individuals and, therefore, a population, to survive a changing environment. Therefore, I disagree with the statement, and think mutations that continue to occur in Population B make it more likely to adapt to changing environment and survive than Population A, in which mutations do not occur.