Question

the endosymbiont theory states that mitochondria and chloroplast are usually bacteria. what are 4 pecies of evidence that support this theory and what you think about this theory?

Answer 1

The endosymbiotic theory states that the eukaryotic cells ( cells with clearly defined nucleus enclosed within membranes) evolved from a symbiotic relation with different prokaryotic cells ( having no membrane bound organelles). Certain prokaryotes that lived inside the eukaryotes are formed as the mitochondria and chloroplasts. In this symbiotic relation, the prokaryotes gets shelter and the eukaryotes gets food in the form of ATP.

The evidence which supports this theory includes

• The mitochondria and chloroplasts contains small DNA molecules. The mitochondrial DNA as well as the DNA present inside the chloroplasts are similar to that of the bacterial DNA.
• The size and structure of ribosomes present in the mitochondria and the chloroplasts are closely resemble that of the bacterial DNA.
• Bacterias reproduce by the process of binary fission. Same as that of bacteria, the mitochondria and the chloroplasts divide by binary fission while the cells that containing mitochondria and chloroplasts divide by mitosis.
• Mitochondria has certain similar characteristics with the purple - aerobic bacteria. Both the mitochondria and purple-aerobic bacteria uses oxygen for the production of energy (ATP) using the process of Kreb's cycle and oxidative phosphorylation.

Chloroplasts have similar characteristics with the photosynthetic bacteria. Both the chloroplasts and the photosynthetic bacteria uses light energy and convert into chemical energy.

Both mitochondria and chloroplasts provides advantages to the host cells as they produced chemical energy for the host. The cells itself has an internal energy source.They gets protection and also nutrients from the host cells. But the organelles became completely dependent of their host cell and required the host cells to import nutrition inorder for them to function correctly. This is the main drawback.