Prokaryotes are distinguished from eukaryotes by the

Options

A. presence of cell wall
B. absence of nucleus
C. presence of ribosomes
D. absence of chloroplasts

Answer

### Step-by-Step Solution:

1. **Understanding Prokaryotes and Eukaryotes**:
- Prokaryotes are simple, unicellular organisms without a defined nucleus. Examples include bacteria and archaea.
- Eukaryotes are more complex organisms that can be unicellular or multicellular, and they have a defined nucleus. Examples include plants, animals, fungi, and protists.

2. **Analyzing the Options**:
- **Option 1: Presence of the cell wall**:
- Both prokaryotes (like bacteria) and some eukaryotes (like plant cells) have a cell wall. Thus, this option does not distinguish between the two.
- **Option 2: Absence of the nucleus**:
- Prokaryotes do not have a well-defined nucleus, which is a key distinguishing feature. Eukaryotes have a true nucleus that contains their genetic material.
- **Option 3: Presence of ribosomes**:
- Ribosomes are present in both prokaryotes and eukaryotes, and they serve the same function of protein synthesis. Therefore, this option does not help in distinguishing them.
- **Option 4: Absence of chloroplast**:
- Chloroplasts are found in some eukaryotes (like plants) but are absent in prokaryotes. However, this is not a universal characteristic since not all eukaryotes have chloroplasts.

3. **Conclusion**:
- The most significant distinguishing feature between prokaryotes and eukaryotes is the **absence of a well-defined nucleus** in prokaryotes. Therefore, the correct answer is **Option 2: Absence of the nucleus**.