Biodiversity decreases, and the overall health of the ecosystem decreases.
Answer: Option D
Explanation:
In a niche when two different species occupy a niche competition arises between them. In due course both the species fight for existence and nature selects the best adaptable one to win. The other species either reduces in its population or gradually in struggle for existence they deteriorate and die.
Hence a decrease in bio diversity happens here due to natural selection. If the biodiversity is decreased in a particular niche it affects the growth of different species which in turn affect the whole ecosystem resulting in decrease of the overall health in an ecosystem.