A farmer in Guyana noticed that after several years of using the same herbicide on his rice fields, more weeds survived each season. Which factor is ESSENTIAL for natural selection to occur in this weed population?

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Question

A farmer in Guyana noticed that after several years of using the same herbicide on his rice fields, more weeds survived each season. Which factor is ESSENTIAL for natural selection to occur in this weed population?

Accepted Answer

Variation must exist within the weed population — Award 1 mark for identifying genetic variation as essential for natural selection. A is incorrect — identical genes would mean no differential survival. C is incorrect — this describes artificial selection, not natural selection. D is incorrect — natural selection acts on existing variation, not new species.

Answer

Variation must exist within the weed population

Answer

All weeds must have identical genes

Answer

The farmer must select which weeds survive

Answer

New species of weeds must be introduced

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