The correct option is Both A and R are correct, and R is the correct explanation of A
Explanation
The distribution of biodiversity is not uniform across the globe. The most well-known pattern of biodiversity is the Latitudinal Diversity Gradient, which describes how species richness changes with latitude.
Statement-wise Analysis:
- Assertion (A): Correct. Species diversity generally decreases as we move away from the equator towards the poles. The tropics (latitudinal range of 23.5° N to 23.5° S) harbor more species than temperate or polar areas. This pattern is observed in a wide range of taxa, including plants, birds, and mammals.
- Reason (R): Correct. Ecologists propose several hypotheses to explain this gradient. One primary reason is that tropical environments are less seasonal, relatively more constant, and predictable compared to temperate regions. This environmental stability promotes niche specialisation and leads to greater species diversity. Additionally, tropical regions have remained relatively undisturbed for millions of years, allowing a long evolutionary time for species diversification, whereas temperate regions were subjected to frequent glaciations.
Justification for Both A and R are correct, and R is the correct explanation of A
The reason (R) correctly identifies the ecological mechanism (environmental stability and niche specialisation) that results in the pattern described in the assertion (A). Therefore, R is the correct explanation for A.
Key Takeaway:
The Latitudinal Diversity Gradient is driven by factors such as higher solar energy input, greater environmental stability, and a longer evolutionary history in tropical regions compared to temperate or polar zones.