IMAT 2021 Q35 [Directional selection]

Could anybody help me with this question?

Directional selection is a form of natural selection which in itself is a mechanism of evolution. Directional selection occurs when a species is put under certain circumstances that favor the survival of one phenotype over another. A trend that can be observed when directional selection takes place is the shift of a particular phenotype of a species from one phenotype to another as the one selected had higher chances of survival. (Phenotypes are physical properties (observable characteristics) of an organism such as color, height, body shape, etc…)

All three options provided are perfectly reasonable outcomes or causes of directional selection.

  1. A low-frequency phenotype is selected: That can be the case, as the phenotype with the better chances of survival (eg. blends in better with surroundings) has no relation to how frequently it occurs in the population. That is just a result of its physical properties and how they interrelate with the environment surrounding the organism.

  2. A predator could be the cause: A predator can indeed be the cause of a particular phenotype’s demise as it could be easier for a predator to hunt down a prey with a particular color over another, for example.

  3. The frequency of a recessive allele increases: If the selected phenotype was the result of a recessive allele of a gene then obviously it’s frequency shall increase within the population.

Thank you very much!

you’re welcome. if you found an answer satisfying you can always check it as “solution”!

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