Which of the following is not a physiological adaptation :-

Options

A. Blubber in whale, seal in antarctica region
B. Antifreezing protein
C. Increase number of RBC in blood at high alfitude
D. In Cactus leaves modified into spines

Answer

To determine which of the following is not a physiological adaptation, we will analyze each option provided:

1. **Blubber in whale and seal in Antarctic region**:
- Blubber is a thick layer of fat that helps these marine mammals insulate against the cold temperatures of their environment. This adaptation allows them to maintain their body temperature in frigid waters. Therefore, this is a physiological adaptation.

2. **Antifreezing protein**:
- Certain fish in cold climates, such as those found in the Arctic and Antarctic regions, produce antifreezing proteins. These proteins prevent their bodily fluids from freezing, allowing them to survive in extremely cold waters. This is also a physiological adaptation.

3. **Increase in number of RBC in blood at high altitude**:
- At high altitudes, the oxygen levels are lower, and the body compensates by increasing the number of red blood cells (RBCs) to enhance oxygen transport. This is indeed a physiological response to hypoxia (low oxygen levels) and is considered a physiological adaptation.

4. **In cactus, leaves are modified into spines**:
- In desert environments, cacti have adapted by modifying their leaves into spines. This adaptation helps reduce water loss through transpiration and provides some protection from herbivores. However, this is a structural adaptation rather than a physiological one.

Based on the analysis above, the option that is **not** a physiological adaptation is:

**In cactus, leaves are modified into spines.**

### Step-by-Step Solution:
1. Identify the options provided in the question.
2. Analyze each option to determine if it is a physiological adaptation.
3. Conclude that the modification of cactus leaves into spines is a structural adaptation, not a physiological one.