AP BIOLOGY

Detailed explanation-1: -The endosymbiotic theory posits that some eukaryotic cell organelles, such as mitochondria and plastids, evolved from free-living prokaryotes. Available data indicate that the mitochondrial endosymbiosis initiated the evolution of the eukaryotic cell, as suggested by Margulis.

Detailed explanation-2: -The endosymbiotic theory states that some of the organelles in eukaryotic cells were once prokaryotic microbes. Mitochondria and chloroplasts are the same size as prokaryotic cells and divide by binary fission.

Detailed explanation-3: -Mitochondria and chloroplasts likely evolved from engulfed prokaryotes that once lived as independent organisms. At some point, a eukaryotic cell engulfed an aerobic prokaryote, which then formed an endosymbiotic relationship with the host eukaryote, gradually developing into a mitochondrion.

Detailed explanation-4: -The endosymbiotic hypothesis for the origin of mitochondria (and chloroplasts) suggests that mitochondria are descended from specialized bacteria (probably purple nonsulfur bacteria) that somehow survived endocytosis by another species of prokaryote or some other cell type, and became incorporated into the cytoplasm.

Detailed explanation-5: -The Theory Endosymbiotic Theory proposes that mitochondria developed from proteobacteria, or Rickettsia, (respiring Bacteria) and that chloroplasts were originally from cyanobacteria. Anaerobic bacteria engulfed the aerobic bacteria, which was not completely digested.