Biodiversity refers to species richness, genetic diversity of populations within a species and variety of ecosystems present on the earth. Hence, biodiversity is the variety present at all the levels of biological organization.
A group of individuals that can interbreed to produce fertile progeny is referred to as species.
Sum total of all living beings present in a region, climatic and edaphic factors makes an ecosystem. Living beings make the biotic component of the ecosystem while climatic and edaphic factors are abiotic components.