The main function of loop of henle is the reabsorption of water from the contents of renal tubules. In which of the following will the loop of Henle be poorly developed or even absent?

Options

A. (I) desert mouse
B. (2) carnivorous bird
C. (3) fresh water fish
D. (4) garden lizard

Answer

To determine in which organism the loop of Henle is poorly developed or even absent, we need to analyze the options provided based on the function and adaptation of the loop of Henle.

### Step-by-Step Solution:

1. **Understand the Function of the Loop of Henle**:
The loop of Henle is a U-shaped portion of the nephron in the kidney that plays a crucial role in concentrating urine by reabsorbing water and sodium chloride. This adaptation is particularly important for animals that live in arid environments, as it helps them conserve water.

**Hint**: Recall that the loop of Henle is essential for water reabsorption and urine concentration.

2. **Identify the Organisms**:
The options given are:
- Desert mouse
- Carnivorous bird
- Freshwater fish
- Garden lizard

**Hint**: List the adaptations of each organism in relation to their habitat.

3. **Analyze Each Option**:
- **Desert Mouse**: Lives in arid environments and has a well-developed loop of Henle to conserve water.
- **Carnivorous Bird**: Also has a developed loop of Henle to concentrate urine and retain water.
- **Freshwater Fish**: Lives in an environment where water is abundant. They do not need to conserve water, so they produce large volumes of dilute urine and have a poorly developed or absent loop of Henle.
- **Garden Lizard**: Typically has a developed loop of Henle for water reabsorption.

**Hint**: Consider the environmental conditions each organism faces and how that influences their kidney structure.

4. **Conclusion**:
Based on the analysis, the organism in which the loop of Henle is poorly developed or absent is the **Freshwater Fish**. This is because they need to excrete excess water rather than conserve it.

**Final Answer**: The correct answer is **Freshwater Fish (Option 3)**.