Biology / Unit 9 Bio 1983 short lesson, about 20 seconds
Eukaryotic Characteristics of the Last Common Ancestor
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The idea
Comparing living eukaryotic lineages shows their last common ancestor had a nucleus, mitochondria, a cytoskeleton, and histone-organized chromosomes.
In practice
Even eukaryotes that later lost typical mitochondria, such as some anaerobic protists, carry reduced mitochondrial remnants inherited from that shared ancestor.
Where people slip
A trait's absence in one living lineage does not mean the last common ancestor lacked it— losses happen after divergence, not before.
Your place on the trail
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