[Campbell Biology P.666] Biologists think that endosymbiosis gave rise to mitochondria befor... | Practice Question

Biologists think that endosymbiosis gave rise to mitochondria before plastids partly because:

  • A: the products of photosynthesis could not be metabolized without mitochondrial enzymes.
  • B: all eukaryotes have mitochondria (or their remnants), whereas many eukaryotes do not have plastids.
  • C: mitochondrial DNA is less similar to prokaryotic DNA than is plastid DNA.
  • D: without mitochondrial CO2 production, photosynthesis could not occur.

Explanation

The prevalence of mitochondria or their remnants in virtually all eukaryotic lineages, coupled with the more restricted distribution of plastids only in Archaeplastida and groups that acquired them via secondary endosymbiosis , strongly suggests that the endosymbiotic event leading to mitochondria occurred earlier and was foundational to eukaryotic evolution. Plastids were acquired later by a subset of these early eukaryotes.