The endosymbiotic theory is concerned with

Options

A. orgin of lichens
B. origin of eukaryotes
C. origin of chloroplast and mitochondria
D. origin of viruses

Answer

**Step-by-Step Solution:**

1. **Understanding the Endosymbiotic Theory**: The endosymbiotic theory is an evolutionary concept that explains how eukaryotic cells (cells with a nucleus) originated from prokaryotic cells (simple cells without a nucleus).

2. **Formation of Eukaryotes**: According to this theory, eukaryotes were formed when one prokaryotic cell engulfed another prokaryotic cell. This engulfing process led to a symbiotic relationship where the engulfed cell became an integral part of the host cell.

3. **Examples of Organelles**: The theory particularly focuses on the origins of certain organelles within eukaryotic cells, such as mitochondria and chloroplasts. These organelles are believed to have originated from free-living prokaryotes.

4. **Phylogenetic Similarity**: Mitochondria and chloroplasts are phylogenetically similar to prokaryotes. This is evidenced by the fact that both organelles contain their own circular DNA, similar to that of prokaryotic bacteria.

5. **Ribosomal Evidence**: The ribosomes found in mitochondria and chloroplasts are of the 70s type, which is also characteristic of prokaryotic cells. This further supports the idea that these organelles share a common ancestry with prokaryotes.

6. **Conclusion**: The endosymbiotic theory thus explains the origin of eukaryotic cells and their organelles, highlighting the evolutionary relationship between prokaryotes and eukaryotes.

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