Ecosystems — Answer Key
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
In a food chain, the arrow points from the predator to the prey it eats.
Corrected: In a food chain, the arrow points from the prey to the predator to show energy flow.
The corrected sentence is: "In a food chain, the arrow points from the prey to the predator to show energy flow.". The original sentence "In a food chain, the arrow points from the predator to the prey it eats." contained an error that needed to be fixed.
2. Fix the sentence:
A food chain always begins with a consumer like a deer or rabbit.
Corrected: A food chain always begins with a producer like grass or algae.
The corrected sentence is: "A food chain always begins with a producer like grass or algae.". The original sentence "A food chain always begins with a consumer like a deer or rabbit." contained an error that needed to be fixed.
3. Fix the sentence:
A hawk is a primary consumer because it is the first animal to eat prey.
Corrected: A hawk is a tertiary consumer because it eats animals that eat other animals.
The corrected sentence is: "A hawk is a tertiary consumer because it eats animals that eat other animals.". The original sentence "A hawk is a primary consumer because it is the first animal to eat prey." contained an error that needed to be fixed.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. A food chain shows one linear path of energy from organism to organism.
A food chain shows a single straight path: producer → primary consumer → secondary consumer, etc.
2. Energy enters most food chains through sunlight from the Sun.
Sunlight is the ultimate energy source for almost all ecosystems through photosynthesis.
3. An animal that only eats plants is called a herbivore or primary consumer.
Herbivores eat only plants. They are primary consumers, the first level after producers.
4. A secondary consumer is an animal that eats primary consumers.
The feeding order: producers → primary consumers → secondary consumers → tertiary consumers.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Write a simple four-step food chain that could occur in a grassland ecosystem.
Sample answer: Grass is eaten by a rabbit, the rabbit is eaten by a fox, and the fox is eaten by a hawk. The food chain is grass, rabbit, fox, hawk.
A grassland food chain: producer → herbivore → small predator → top predator.
2. Why does a food chain always start with a producer and not a consumer?
Sample answer: A food chain starts with a producer because producers are the only organisms that can convert sunlight into food energy. All consumers depend on that energy, so the chain must begin where the energy enters the ecosystem.
Producers capture new energy from sunlight. Consumers just pass along existing energy.