In a given habitat,we have $20$ plant species and $20$ animal species. Should we call this 'diversity' or 'biodiversity'? Justify your answer.

(N/A) This should be called 'biodiversity'.
Biodiversity is the term used to describe the combined diversity of all living organisms (plants,animals,and microorganisms) present in a specific habitat or on Earth.
Since the habitat contains both plant species and animal species,the term 'biodiversity' is appropriate as it encompasses the variety of life forms present in that ecosystem.