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:
Consumers make their own food using sunlight and water.
Corrected: Producers make their own food using sunlight and water. Consumers must eat other organisms to get energy.
The original sentence mixed up consumers and producers. Producers like plants make their own food through photosynthesis, while consumers cannot make food and must eat other living things to get energy.
2. Fix the sentence:
A food chain has many branching paths where energy can travel in different directions.
Corrected: A food chain has only one straight path of energy. A food web has many branching paths where energy can travel in different directions.
A food chain follows just one straight line from producer to top predator. The description of many branching paths actually fits a food web, which links multiple food chains together.
3. Fix the sentence:
Scavengers hunt and kill live animals to get their energy.
Corrected: Scavengers eat animals that are already dead rather than hunting live prey.
Scavengers like vultures feed on animals that have already died, so they do not hunt live prey. Hunting and killing live animals is what predators do, not scavengers.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. Energy enters most ecosystems through photosynthesis performed by plants.
Photosynthesis is the process plants use to turn sunlight into food energy. This is how almost all energy first enters an ecosystem before being passed along to animals.
2. A primary consumer eats producers like grass or algae.
"Primary" means first, so a primary consumer is the first level of animal that eats directly from producers like grass or algae.
3. Fungi and bacteria break down dead organisms and are called decomposers.
Fungi and bacteria earn the name decomposers because they decompose, or break down, dead plants and animals into simple nutrients that return to the soil.
4. At each level of a food chain, some energy is lost as heat.
When animals use energy to move, grow, and stay warm, much of that energy escapes as heat. That is why less energy is available at each higher level of a food chain.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Name three types of consumers and explain what each one eats.
Sample answer: Herbivores eat only plants, carnivores eat only animals, and omnivores eat both plants and animals.
The three main consumer types are herbivores (plant-eaters like deer), carnivores (meat-eaters like wolves), and omnivores (both plants and animals, like bears). Each type gets energy from different food sources.
2. What might happen to a food web if a disease killed most of the frogs in a pond?
Sample answer: The insects that frogs eat would increase because fewer frogs would be eating them. The snakes and birds that eat frogs would have less food and their numbers might drop.
Removing frogs would cause a ripple effect. Insect populations would grow because fewer frogs are eating them, while snakes and birds that depend on frogs for food would struggle and their numbers would likely drop.