Final answer:
The theory of endosymbiosis suggests that certain organelles in eukaryotic cells originated from free-living prokaryotes. Examples include mitochondria and chloroplasts, which were engulfed by ancestral host cells and developed a symbiotic relationship.
Step-by-step explanation:
The theory of endosymbiosis proposes that certain organelles in eukaryotic cells, such as mitochondria and chloroplasts, were once free-living prokaryotes that were engulfed by ancestral host cells. Over time, a symbiotic relationship developed, with the host cell providing protection and nutrients, while the organelles provided energy through processes like respiration or photosynthesis. This theory is supported by evidence such as the presence of double membranes, circular DNA, and the ability of organelles to divide independently.
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