🧬ap biology review

Endosymbiosis

Written by the Fiveable Content Team • Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 examWritten by the Fiveable Content Team • Last updated September 2025

Definition

Endosymbiosis is a mutually beneficial relationship where one organism lives inside another. This theory explains how complex cells (eukaryotes) evolved from simple cells (prokaryotes).

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