Photosynthesis in Opuntia is done by

They are dominant plants of the cold desert

In most animals, the metabolic reactions proceed in a ...$A$... temperature range (in humans, it is $37^{\circ} C$ ). But there are microbes (archaebacteria) that flourish in hot springs and deep sea hydrothermal vents where temperature far exceed ...$B$...

Choose the correct option for $A$ and $B$

Many fishes of freshwater can't live in sea water and vice -versa because of

Ecological factors which prevent a species from producing at its maximum rate is termed as