There are $..........$ species of orchids on Earth.

Which of the following is $NOT$ a characteristic of a stable biological community?

According to the representation of global biodiversity proportions for the number of species of major taxa of vertebrates,select the appropriate option for the labels $X$,$Y$,and $Z$ in the given figure.

Most of the industrialized nations are rich $............$ but poor in $............$.

In the $Rivet$ $Popper$ hypothesis,what do the rivets represent?

The largely tropical Amazonian rain forest in South America has . . . . . . numbers of bird species.