Question 6:What are the different factors that influence

the Green World Hypothesis?

By:Mele Moniz

Nicole Huffman

Green World Hypothesis

• States that terrestrial herbivores consume relatively little plant biomass because

they are held in check by a variety of factors, including predators, parasites, and disease.

• This theory is credited with bringing attention to the role of top-down forces

and indirect effects in shaping ecological communities.

Plants

• Plants have defenses against herbivores such as noxious chemicals and spines.

• Nutrients, not energy supply, usually limit herbivores. Plants give off a low supply of protein, which animals need.

Abiotic Factors

• Changes in temperature and moisture will lower the carrying capacity of herbivores so that they're unable to strip an area of its vegetation.

Intraspecific Competition

• Limits herbivore numbers because they may battle over territory or mates.

Interspecific Interactions

• Such as predation and disease will kill herbivore densities in check. This is said to be the most important limiting factor.

- Predators in a food web suppress the abundance of their prey, thereby releasing the next lower trophic level from predation.

On a Related Note…Trophic cascade• Nelson Hairston, Frederick E. Smith, and Lawrence B. Slobodkin are

credited with the concept of trophic cascade, despite never using the term.

• They argued that predators reduced the number of herbivores and therefore allowed plants to flourish, a.k.a. the green world hypothesis.

• Previously , trophodynamics was used to explain the structure of communities using the bottom-up forces, or resource limitation.

• Hairston, Smith, and Slobodkin argued that ecological communities acted as food chains with three trophic levels. Other models have expanded and shrunk this model.

• Hairston, Smith and Slobodkin formulated their argument in terms of terrestrial food chains, the earliest empirical demonstrations of trophic cascades came from marine and, especially, aquatic ecosystems.