Who helps in maintaining species diversity in a biological community?

What are the effects of biodiversity on ecosystem functioning?

Which of the following statements are true?
$I$. Species diversity provides stability to the ecosystem.
$II$. Communities with more species tend to be more stable than those with fewer species.
$III$. Ecosystems with higher biodiversity are more productive than ecosystems with lower biodiversity.
$IV$. Biodiversity is not essential for the maintenance and health of the ecosystem.
Choose the correct option.

Outdoor plot experiments were conducted by

Can you think of a scientific explanation,besides the analogy used by Paul Ehrlich,for the direct relationship between diversity and stability of an ecosystem?

State the contributions of the following scientists:
$(i)$ Alexander von Humboldt
$(ii)$ David Tilman
$(iii)$ Paul Ehrlich