Question

What is the green world hypothesis?

Answer 1

Hint: The green world hypothesis is concerned with the population check of the plants. If the growth of the herbivores is not checked, then the plants would be eaten all around. This is controlled by a variety of factors like predators, parasites and diseases.

Complete answer:
The green world hypothesis was proposed in 1960 by the scientists Nelson Hairston, Frederick Smith and Lawrence Slobodkin. This hypothesis is impossible to test till now. The hypothesis states that the predators, diseases and parasites keep a check on the population of herbivores. If the population of herbivores is not checked, it would consume all the plants. The scientists also stated that the number of trophic levels in the food chain affects the productivity of the ecological community.

The green hypothesis holds good because it is concerned with pointing out the role of top-down forces
like predators, parasites, diseases and also the indirect effects in building ecological communities.
However, this theory is being criticised due to several reasons like the herbivore population can be checked by the availability of mate, food, nesting sites etc. The complex food web and cannibalism also is the reason for the criticism of this hypothesis.

Note: The controversy to this theory is that the plants also have certain mechanisms to prevent themselves from being eaten up. For example, some plants have thorns which protects them from being eaten up, some plants secrete alkaloids and other chemicals which serve as toxic to the herbivores. They even are potent in killing the animals.