Which one of the following living organisms completely lacks a cell wall
(a) Cyanobacteria
(b) Sea-fan (Gorgonia )
(c) Saccharomyces
(d) Blue-green alga

Options

A. Cyanobacteria
B. Sea-fan (Gorgonia )
C. Saccharomyces
D. Blue-green alga

Answer

To determine which of the following organisms completely lacks a cell wall, let's analyze each option step by step:

1. **Cyanobacteria (Option a)**:
- Cyanobacteria are a type of bacteria that belong to the kingdom Monera.
- They possess a cell wall made of peptidoglycan, which is a characteristic feature of bacterial cell walls.
- **Conclusion**: Cyanobacteria have a cell wall.

2. **Sea-fan (Gorgonia) (Option b)**:
- Gorgonia, commonly known as sea-fans, belong to the phylum Cnidaria and are classified under the order Gorgonacea.
- Organisms in the kingdom Animalia (which includes Gorgonia) do not have cell walls.
- **Conclusion**: Gorgonia does not have a cell wall.

3. **Saccharomyces (Option c)**:
- Saccharomyces is a genus of yeast that belongs to the kingdom Fungi.
- Fungi have cell walls that are primarily composed of chitin.
- **Conclusion**: Saccharomyces has a cell wall.

4. **Blue-green alga (Option d)**:
- Blue-green algae are essentially another name for cyanobacteria and thus also belong to the kingdom Monera.
- As with cyanobacteria, they have a cell wall made of peptidoglycan.
- **Conclusion**: Blue-green algae have a cell wall.

After analyzing all the options, the only organism that completely lacks a cell wall is:

**Correct Answer: (b) Sea-fan (Gorgonia)**