🔬 ScienceGrade 4Lesson 2
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Food Webs and Ecosystems
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Learning Objectives
- 1Explain the roles of producers, consumers, and decomposers in an ecosystem
- 2Describe how energy flows through a food web
- 3Identify examples of each role from real ecosystems
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Mini Lesson
An ecosystem is a community of living things interacting with their environment. Every organism plays a role — and energy flows from one organism to the next in a food web.
Producers
- Producers make their own food through photosynthesis.
- Plants and algae are the main producers in most ecosystems.
- They capture energy from the sun and store it in their tissues.
Consumers
- Consumers eat other organisms to get energy.
- Herbivores eat only plants (e.g. rabbits, grasshoppers).
- Carnivores eat only animals (e.g. wolves, eagles, lions).
- Omnivores eat both plants and animals (e.g. bears, humans).
Decomposers
- Decomposers break down dead matter and return nutrients to the soil.
- Examples include fungi, bacteria, and earthworms.
- Without decomposers, dead material would pile up and nutrients would not be recycled.
Food Webs
- A food web shows multiple food chains connected together.
- Energy flows from producers to consumers to decomposers.
- Removing any organism from the web affects the whole ecosystem.
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Tip: remember the order — producers first, then consumers, then decomposers. Energy always flows from the sun through producers to consumers, and finally to decomposers.
Vocabulary
ecosystem
All the living and non-living things in an area, working together.e.g. A pond is an ecosystem with fish, plants, water, and rocks.
producer
A living thing that makes its own food, usually a plant.e.g. Grass is a producer that uses sunlight to grow.
consumer
A living thing that eats other living things for food.e.g. A rabbit is a consumer because it eats grass.
decomposer
A living thing that breaks down dead plants and animals.e.g. Mushrooms and worms are decomposers.
food web
A diagram showing how energy flows between many living things.e.g. A food web shows how plants, rabbits, foxes, and decomposers connect.
energy flow
The path that energy takes as it moves from the Sun to plants to animals.e.g. Energy flows from grass to a rabbit to a fox.
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