unit 4 exam

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What's the best way to describe natural selection (3 Marks) given a scenario?

Population was spilt by some means. (e.g Physical barrier)
Due to being in distinct areas each of these populations have different selection pressures. As a result different adaptations from natural selection ensue leading to distinct changes in gene pool.
Gradually over a long period of time speciation occurs so when brought back together the two populations cannot interbreed to produce  viable fertile offspring.

any ways to make the answer stonger?

[zarrin101]

it seems like you've got allopatric sepciation and natural selection mixed up. you wrote the answer for allopatric speciation.
for Natural Selection:
Variation already exists within the population and is inherited. There is a change in the environment - Selection pressure selects for and against particular traits. Over generations, the allelic frequency of the desired trait increases in the population.