Answer: The world is green because herbivores are kept in check by their predators (top-down control), not by plant food supply.
- A Plants are sometimes thought to dominate ecosystems mainly because sunlight is universally abundant everywhere in general practice
- B The world is green because herbivores are kept in check by their predators (top-down control), not by plant food supply
- C Every trophic level in an ecosystem is sometimes thought to be limited primarily by available food supply alone as frequently described
- D Producer biomass is sometimes thought to consistently outcompete consumer biomass in nearly any ecosystem in most textbook accounts
Correct answer: B. The world is green because herbivores are kept in check by their predators (top-down control), not by plant food supply
Explanation: HSS hypothesis: despite abundant plant food, herbivores rarely eat all vegetation because predators control them from the top down. Evidence: carnivore removal often triggers herbivore explosions and overgrazing.
Energy pyramid showing a simple food chain (producer to herbivore to carnivore) with energy decreasing roughly tenfold at each trophic level.
Concept context
Ecosystems, food chains, energy flow, nutrient cycles, biodiversity, and conservation.