Intracellular endosymbionts that originally descended from free-living prokaryotes have been important in the evolution of eukaryotes by giving rise to two cytoplasmic organelles. Mitochondria ...

To help you explore this tree and understand the amazing mechanism behind it, we’ve created the NOVA Evolution Lab. Play this Lab and you’ll be on your way to becoming an expert in ...

(Darwin 131–132) In the years following Darwin's work, biologists formally rejected the ladder of life in favor of the tree concept. Nonetheless, many current discussions of evolution ...