Question 15 • PA Human Anatomy & Physiology A 2026-2027 SMITH IC
Which definition describes endosymbiosis best?a symbiotic relationship in which one organism lives on the other organism and both organisms benefita symbiotic relationship in which one organism lives inside the other and both organisms benefita symbiotic relationship in which one organism benefits, while the other organism is harmed
Answer
A
a symbiotic relationship in which one organism lives on the other organism and both organisms benefit
B
a symbiotic relationship in which one organism lives inside the other and both organisms benefit
C
a symbiotic relationship in which one organism benefits, while the other organism is harmed
Explanation
Endosymbiosis describes a relationship in which one organism lives inside another organism. The organisms typically both benefit, so the best definition is “a symbiotic relationship in which one organism lives inside the other and both organisms benefit.” Choice A describes living on another organism, not inside it; choice C describes parasitism.
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