Question

10. Explain how eukaryotic cells are thought to have evolved from prokaryotic cells. You must use these words in your essay, but are not limited to them: endosymbiotic, enfolding, phagocytosis, mitochondrion, chloroplasts, eukaryotic, bacterial endosymbiont.

Answer 1

Evolution of eukaryotic cells has occurred due to development of internal membranes by the prokaryotic cells and this was started some 2 billion years ago. The eukaryotic organelles such as mitochondria and chloroplast resemble the prokaryotic cells. This has happened due to establishment of symbiotic relationship between prokaryotes that entered the eukaryotic cells. Thus, endosymbiotic theory states that the eukaryotic cells are produced from living communities formed by prokaryotic organisms.

The endosymbiotic hypothesis emphasizes that the mitochondria arose from the stable incorporation of aerobic bacterium in to other cells and the chloroplasts arose from incorporation of a cyanobacterium like organism performing the oxygenic photosynthesis by phagocytosis.

Thus, the physiology and metabolism of mitochondria and chloroplast along with their structure and sequence of genomes support the endosymbiotic hypothesis. Endosymbiotic evolution of eukaryotic organelles is evident by similarities of the prokaryotic organisms, the mitochondria and the chloroplast containing 70S type of ribosomes and their 16S ribosomal RNA sequence is similar and characteristic to bacteria.