Food Webs and Energy — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
An herbivore is an animal that eats only meat, such as a lion or hawk.
Corrected: An herbivore is an animal that eats only plants, such as a rabbit or deer.
The corrected sentence is: "An herbivore is an animal that eats only plants, such as a rabbit or deer.". The original sentence "An herbivore is an animal that eats only meat, such as a lion or hawk." contained an error that needed to be fixed.
2. Fix the sentence:
Energy increases as it moves up each level of a food chain.
Corrected: Energy decreases as it moves up each level of a food chain because some energy is lost as heat at every level.
The corrected sentence is: "Energy decreases as it moves up each level of a food chain because some energy is lost as heat at every level.". The original sentence "Energy increases as it moves up each level of a food chain." contained an error that needed to be fixed.
3. Fix the sentence:
A top predator like an eagle is a producer because it is at the top of the food chain.
Corrected: A top predator like an eagle is a consumer because it gets energy by eating other animals, not by making its own food.
The corrected sentence is: "A top predator like an eagle is a consumer because it gets energy by eating other animals, not by making its own food.". The original sentence "A top predator like an eagle is a producer because it is at the top of the food chain." contained an error that needed to be fixed.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. An animal that eats both plants and animals is called an omnivore.
Omnivores eat both plant and animal matter. Examples include bears, raccoons, and humans.
2. A prey is an animal that is hunted and eaten by a predator.
In a predator-prey relationship, the prey is the organism being hunted; the predator does the hunting.
3. Energy in a food chain flows from producers to consumers.
Producers make energy; consumers obtain it by eating producers or other consumers.
4. An animal that eats only plants is called an herbivore.
Herbivores eat only plant matter. Examples include rabbits, deer, cows, and grasshoppers.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Why are there usually more producers than top predators in an ecosystem?
Sample answer: Each level of the food chain passes on less energy than it received. Many producers are needed to support fewer herbivores, and even fewer predators can be supported at the top.
The 10% energy rule: only ~10% of energy transfers up each trophic level, so each higher level supports fewer organisms.
2. Give an example of a simple food chain with at least three organisms.
Sample answer: Grass is eaten by a rabbit, and the rabbit is eaten by a hawk. The sun provides energy to the grass, which passes through each organism.
A basic 3-organism food chain: sun → grass (producer) → rabbit (primary consumer) → hawk (secondary consumer).