6

Set 5: Central Ideas (Advanced)

Explanation

Answer: C

PASSAGE

The following text discusses 'Symbiosis'. Symbiosis defines any close and long-term biological interaction between two different biological organisms. It includes mutualism (where both benefit), commensalism (where one benefits and the other is unaffected), and parasitism (where one benefits at the expense of the other). The endosymbiotic theory suggests that key organelles in eukaryotic cells, such as mitochondria and chloroplasts, originated as separate prokaryotic organisms that were taken inside a host cell in a symbiotic relationship.

What does the endosymbiotic theory propose about mitochondria?

A. They are parasites that destroy the cell
B. They originated as separate prokaryotic organisms
C. They are created by the cell's nucleus✓ Correct
D. They have no function in the cell

Detailed Explanation

Choice B is correct. The text states the theory suggests they 'originated as separate prokaryotic organisms that were taken inside a host cell.'

Key Evidence:

• "originated as separate prokaryotic organisms"

Why others are wrong: A (Inaccurate (Text mentions mutualism/symbiosis generally, but explains origin explicitly)), C (Opposite (Originated externally)), D (Inaccurate).

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