The species diversity decreases from lower to higher altitudes on a mountain. This is due to

Options

A. increase in temperature
B. decrease in temperature
C. greater seasonal variability
D. Both (b) and (c)

Answer

To solve the question regarding why species diversity decreases from lower to higher altitudes on a mountain, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Species Diversity**:
- Species diversity refers to the variety of different species within a given area, including plants, animals, and microorganisms.

2. **Observation of Species Diversity on Mountains**:
- It is observed that as we move from lower altitudes (like plains) to higher altitudes (like mountain tops), the diversity of species tends to decrease.

3. **Identifying Factors Affecting Species Diversity**:
- The primary factors affecting species diversity at different altitudes are climatic conditions, particularly temperature and seasonal variability.

4. **Temperature Variation**:
- At lower altitudes, temperatures are generally warmer and more stable, which supports a greater variety of life forms.
- As altitude increases, temperatures decrease. Higher altitudes are characterized by colder conditions, which can be harsh for many species.

5. **Seasonal Variability**:
- Higher altitudes experience greater seasonal variability. This means that the climate can change rapidly and unpredictably, making it difficult for species to adapt.
- For example, conditions can shift from sunny to snowy in a short period, which can be detrimental to species that require stable environments.

6. **Conclusion**:
- Both the decrease in temperature and the greater seasonal variability at higher altitudes contribute to lower species diversity.
- Therefore, the correct answer to the question is "both B and C" (decrease in temperature and greater seasonal variability).

### Final Answer:
The species diversity decreases from lower to higher altitudes on a mountain due to both a decrease in temperature and greater seasonal variability. Thus, the correct answer is option D: both B and C.

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