Which of the following statements about Spongilla, leech, dolphin and penguin is correct?

Options

A. Penguin is homoiothermic while the remaining three are poikilothermic.
B. Leech is found in freshwater while all others are marine.
C. Spongilla has special collar cells called choanocytes, not found in the remaining three.
D. All are bilaterally symmetrical.

Answer

To determine which statement about Spongilla, leech, dolphin, and penguin is correct, we need to analyze the characteristics of each organism. Here’s a step-by-step breakdown:

### Step 1: Identify the Classification of Each Organism
- **Spongilla**: This organism belongs to the phylum **Porifera**, which includes sponges. They are simple, multicellular organisms that are primarily aquatic.
- **Leech**: Leeches belong to the phylum **Annelida**. They are segmented worms and can be found in freshwater environments.
- **Dolphin**: Dolphins are mammals, classified under the class **Mammalia**. They are warm-blooded and live in marine environments.
- **Penguin**: Penguins are birds, classified under the class **Aves**. They are also warm-blooded and primarily found in marine environments.

### Step 2: Analyze the Statements
1. **Penguin is homeothermic, while the remaining are poikilothermic**:
- Penguins and dolphins are both homeothermic (warm-blooded), while Spongilla and leeches are poikilothermic (cold-blooded).
- This statement is **incorrect**.

2. **Leech is found in freshwater, while others are marine**:
- Leeches are indeed found in freshwater, but Spongilla is also found in freshwater. Dolphins and penguins are marine.
- This statement is **incorrect**.

3. **Spongilla has special color cells called choanocytes, not found in the remaining three**:
- Choanocytes are unique to sponges (like Spongilla) and are responsible for water flow and feeding. The other organisms do not have these cells.
- This statement is **correct**.

4. **All are bilaterally symmetrical**:
- Spongilla (Porifera) is asymmetrical, while leeches, dolphins, and penguins exhibit bilateral symmetry.
- This statement is **incorrect**.

### Conclusion
The correct statement is that **Spongilla has special color cells called choanocytes, not found in the remaining three**.