How many organelles of a eukaryotic cell are considered to have and independent existence during early events of evolution ?

Options

A. 1
B. 2
C. 3
D. 4

Answer

**Step-by-Step Solution:**

1. **Understanding Eukaryotic Cells**: Eukaryotic cells are complex cells that contain various organelles, each performing specific functions.

2. **Identifying Organelles with Independent Existence**: During the early events of evolution, two organelles in eukaryotic cells are considered to have had independent existence. These are:
- **Mitochondria**: Known as the powerhouse of the cell, mitochondria are responsible for producing energy in the form of ATP (adenosine triphosphate).
- **Chloroplasts**: These organelles are involved in photosynthesis, allowing plants to convert light energy into chemical energy.

3. **Origin of Mitochondria and Chloroplasts**: Both organelles are believed to have originated from specialized bacteria through a process called endosymbiosis. This means that ancestral eukaryotic cells engulfed these bacteria, which then became integral parts of the cells.

4. **Characteristics of Mitochondria and Chloroplasts**:
- Both organelles are double-membraned, indicating their complex structure.
- They are termed **semi-autonomous** because they possess their own DNA and ribosomes (70S ribosomes), which are similar to those found in prokaryotes.
- The DNA in mitochondria and chloroplasts is not associated with histones, which is a characteristic of prokaryotic DNA.

5. **Conclusion**: Therefore, the total number of organelles in eukaryotic cells that are considered to have had independent existence during early evolution is **2** (mitochondria and chloroplasts).

**Final Answer**: 2 organelles (mitochondria and chloroplasts).

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