The variety of life in the world or in a particular habitat or ecosystem is called

Biodiversity

Explanation:

The life originated from a single common ancestor on Earth but the variety of habitats and the environmental condition led to the formation of a variety of organisms On Earth through the process of evolution.

This can be explained as there are about more than 8 million species on Earth living in a variety of ecosystem. The ecologists explained these varieties of species in one term called the "Biodiversity" that is the varieties of life in a particular habitat.

The Biodiversity directly affects the ecosystem in terms of the energy, matter and maintains the continuous flow of these cycles.

Thus, Biodiversity is correct.