Genetic Drift

Genetic Drift - The Bottleneck Effect

The population starts off normally.


Then a catastrophic event happens, a chasm opens up in the cats' habitat and swallows up a good chunk of the population.

This chasm, as a result, erases all of the orange cat population. The orange cat population did not go extinct because they were not "fit" enough or "good" enough to survive, this was simply due to random chance. The grey or calico cats are not better adapted, they just got lucky they were not in the area where the chasm opened up in. By luck, the grey and calico cats survived. The not-so-lucky orange cats go extinct, which will change the allelic frequency of the population due to this random catastrophic event. This illustrates the bottleneck effect.

Genetic Drift - The Founder Effect

The population starts off normally. There is a dry river in between the high land, and the lowland. Some of the cats get curious and decide to wander off to the lowland to see what is over there.

Some of the curious cats make it over to the lowland and decide they like it there. Some of the other cats stay on the highland because they don't want to explore the lowland. One night, a terrible storm passes through and replenishes the river.

Once the river is replenished, none of the cats can return to the highland, nor can the other cats explore the lowland. Thus, creating two separate populations. The new population on the lowland does not represent the original population that they originated from as no grey cats made it to the lowland. The orange and calico cats founding the lowland habitat is due to random chance. This illustrates the founder effect.

Genetic drift is due to random chance and is not to be confused with natural selection which deals with fitness, and who is "good enough" to survive to reproduce. 

Comments

  1. Marie KamaraNovember 20, 2022 at 8:54 PM

    Hi Kara I like your ca examples. How do you understand the differences between the founder effect and the bottleneck effect since they both happen due to random chance?

    ReplyDelete

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