Question

Who was the major proponent of the endosymbiotic hypothesis
(a) Matthias Schleiden
(b) Theodore Schwann
(c) Rudolf Virchow
(d) Lynn Margulis

Answer 1

Hint: An American biologist born in Chicago in 1938 explained that mitochondria and chloroplasts of eukaryotic cells are descendants of prokaryotic organisms in the theory called symbiogenesis.

Complete answer:
After discovering the significant difference between the genetic material of mitochondria and chloroplasts from the symbiotic nuclear DNA, the endosymbiotic theory was widely accepted. This endosymbiosis hypothesis was proposed by the American biologist Lynn Margulis after being rejected by the fifteen scientific journals. The Journal of theoretical biology accepted the final journal of Lynn Margulis which led to the endosymbiotic hypothesis.

Additional information:
- Endosymbiotic theory also called symbiogenesis, which explains the theory of the origin of cell organelles of eukaryotic cells from prokaryotic organisms.
- This theory states that the organelles present in the eukaryotic cell such as mitochondria, plastids, and chloroplasts are descended from the prokaryotic organisms by endosymbiosis.
- Robert Schwartz and Margaret Dayhoff are the two scientists who made several experiments on mitochondria and chloroplasts and concluded that mitochondria descended from bacteria and chloroplasts descended from cyanobacteria.
- In the endosymbiotic hypothesis, it explains associations between the host with nucleus and prokaryotes. The host provides a suitable environment for the parasite and in return, the parasite provides energy to the host by ATP producing system.
So, the correct answer is ‘(d) Lynn Margulis’.

Note:
- Matthias Schleiden and Theodore Schwann explained cell theory which states that all living organisms are composed of cells and cell products but it fails to explain how new cells are formed.
- Rudolf Virchow explained that a new cell is produced from the pre-existing cells. He called it ‘Omnis cellula-e cellula’.