Question

A population of bears has genetic diversity. Some of the bears have an allele that gives them
thicker fur. Due to climate change, the winters have gotten colder in their habitat. Now the bears with
thicker fur are becoming more common in the population.

a.) which type of bear is selected for in the coldest ecosystem?
b.) what must be the other allele for the type of fur, and what term would you use to describe the fact that the allele is becoming less common in the colder climate?
c.) describe the change in the bear population in terms of changing allele frequencies and phenotypes
d.) is this an example of natural selection

Answer 1

a) The type of bear that would be selected for the coldest ecosystem would be the one with the thickest fur. Since the climate is changing in this scenario and it is becoming colder, the bears that have the allele for thicker fur would be the ones that would become more dominant through natural selection. The reason for that is that those bears will have an advantageous trait that will have them survive int he changing climate and environment.

b) Apart from the allele for thicker fur, the other allele that will accompany it would be the allele doe longer fur. In this way, by having both longer and thicker fur, the bears would have much better isolation from the cold weather, thus being able to function normally and not die out because of the severe cold. The alleles that would be becoming less common in the colder climate would be the ones for shorter and thinner fur, as they will not be suitable for the living conditions in which the bears have found themselves. These alleles would gradually decline, and that process is called natural selection.

c) As the climate will be getting colder and colder, the bear population will also change. The bears that will have the advantageous alleles will have an advantage over the other bears when it comes to survival. Because of this, they will be the ones that would be preferred for matting, as they will guarantee that the offspring will have those alleles too. The bear population will gradually start to become dominated by the bears with the alleles for longer and thicker fur, while the other bears will be in constant decline.

d) This scenario is an excellent example of natural selection. With the changing climate conditions, not all bears will be able to survive, but mostly it will be the ones with the alleles for thicker and longer fur. Apart from being able to survive without any particular problem, the bears with these alleles will be the ones that will be the preferable mating partners, thus the bears will start to select each other by advantageous traits, and push aside the ones that do not posses them. This is a prime example of how the natural selection works, as by selecting the mating partners, the bears are selecting who survives and who doesn't, gradually changing the population in the advantage of some of them, and disadvantage of the others.