Three reasons why tropics show greatest levels of species diversity:
1. Stable climate: The tropics have a warm, stable climate with little seasonal variation. This consistency allows for the evolution and survival of a wide range of species.
2. High primary productivity: The tropical regions, especially rainforests, have high primary productivity due to abundant sunlight, rainfall, and warm temperatures, supporting a wide range of organisms.
3. Ecological niches: The tropics have a diverse range of habitats, creating multiple ecological niches where different species can evolve and coexist.
A battery of emf \( E \) and internal resistance \( r \) is connected to a rheostat. When a current of 2A is drawn from the battery, the potential difference across the rheostat is 5V. The potential difference becomes 4V when a current of 4A is drawn from the battery. Calculate the value of \( E \) and \( r \).