Final answer:
Biodiversity is the subject of this question and it refers to the total number of species in an ecosystem.
Step-by-step explanation:
The subject of the question is Biodiversity. Biodiversity refers to the total number of species in an ecosystem. It encompasses the variety of different species that make up a particular area.
Biodiversity is important for the stability and health of ecosystems and plays a vital role in ecosystem services and human well-being.