Question

2. Before the 1960s, most ecologists thought that the number of producers in an ecosystem was the only variable that limits the number of herbivores. The idea was that every level was regulated by the amount of food from the trophic level below it. How did the green world hypothesis differ from this “bottom-up” view?

3. Imagine a simple food chain: Grass -> Grasshoppers -> Mice. If snakes that eat mice are added to the ecosystem, how would you redraw the food chain to represent this change?

4. After the snakes are added, would you expect the amount of grass to increase or decrease? Explain your reasoning.

Answer 1

2.

  The green world hypothesis states that terrestrial herbivores consume little plant biomass, which holds them in check due to predators, parasites, and diseases. The green world hypothesis differs from this bottom up view by stating that regulation of terrestrial herbivores is due to species above them on the food web not below.

3.

If snakes that eat mice are added to the ecosystem,I would add snakes to the top of this food chain.

4.

I would expect the amount of grass to decrease because more mice would be eaten leading to less grasshoppers being eaten thus more grass would be consumed.