Look at this food chain: Grass → Grasshopper → Frog → Snake. If frogs disappear from this ecosystem, what will happen to the population of grasshoppers and snakes? Why?
If frogs disappear from this food chain, the grasshopper population will increase because frogs are their predators. Without frogs to eat them, more grasshoppers will survive and reproduce.
The snake population will decrease because frogs are their food source. Without frogs, snakes will have less food available, leading to starvation, reduced reproduction, or migration to other areas in search of food.
This demonstrates how the removal of one organism from a food chain affects both the organisms below it (which increase) and the organisms above it (which decrease).
Explanation
The chapter explains food chains in Section 12.5 and shows how organisms at different trophic levels depend on each other. Activity 12.9 demonstrates how changes in one population (frogs being harvested) led to cascading effects—fewer frogs meant more insects (pests). The same principle applies here: frogs control grasshopper populations and serve as food for snakes. Their removal disrupts the balance in both directions of the food chain.
Solution Steps
Frogs are predators of grasshoppers, so without frogs, the grasshopper population will increase due to fewer being eaten.
Frogs are a food source for snakes, so without frogs, the snake population will decrease due to lack of food.
The removal of one organism from a food chain creates cascading effects: organisms below (prey) increase, while organisms above (predators) decrease.