32. The theory of endosymbiosis states that today's eukaryotic
cells evolved via a symbiosis (living together) of prokaryotic bacteria. In
other words, one species of prokaryote was engulfed by and lived inside of another
species of prokaryotic cell. This is supported by the fact that both chloroplasts
and mitochondria are very prokaryotic in nature, and both organelles can actually
exist and reproduce on their own.
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Long & Slichter