Edward Wilson described diversity at all levels of biological organisation ranging from macromolecules inside the cells to biomes. It is of three inter-related hierarchial levels-genetic diversity, species diversity and community ecosystem diversity. Species diversity is the variety in the number and richness of the species of a region. For example, the Western ghats have a greater amphibian species diversity than the Eastern ghats.
The number of species per unit area is called:

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the term that describes the number of species per unit area. This is a key concept in ecology and biodiversity studies.

2. **Identifying the Levels of Diversity**: Edward Wilson described three hierarchical levels of biodiversity: genetic diversity, species diversity, and community ecosystem diversity. The focus here is on species diversity.

3. **Defining Species Diversity**: Species diversity refers to the variety and abundance of different species within a particular region. It includes both the number of different species (richness) and their relative abundance.

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