Explain why there is ecosystems diversity in the biosphere ?
Every ecosystem is adapted to a different climate. Rainforest plants are adapted to heavy rainfall, high humidity, and high temperatures, so they have big leaves that transpire a lot so they don't get oversaturated with water, and their roots don't need to be as deep since the water from vapor and rain is enough to sustain them.
The problem is if you put a rainforest in any climate other than an equatorial, humid, rainy climate, it would die off very quickly. Similarly, if you tried to put a desert in a rainforest climate, the plants would become waterlogged because they're adapted to conserving water to withstand drought, not use transpiration to get rid of it as fast as possible.
Climate has fostered the evolution of a diverse set of ecosystems that are adapted to handle the temperature, humidity, precipitation, and seasonal changes they are in.