Ecosystems and Habitats

Grade 3 · Science · Study Guide

Learn how living and nonliving things work together in ecosystems and why habitats are important for survival.

An ecosystem is all the living and nonliving things in a particular area that interact with each other. Living things include plants, animals, fungi, and bacteria. Nonliving things include water, sunlight, soil, air, and rocks. Every part of an ecosystem is connected.

A habitat is the specific place where an organism lives and finds everything it needs — food, water, shelter, and space. Different organisms are suited to different habitats. A fish needs a water habitat with oxygen dissolved in the water. A cactus wren lives in desert habitats. A polar bear thrives in Arctic habitats.

In every ecosystem, energy flows through a food chain. Producers, usually plants, use sunlight to make their own food through photosynthesis. Consumers are animals that eat plants or other animals. Herbivores eat only plants, carnivores eat only animals, and omnivores eat both. Decomposers like fungi and bacteria break down dead organisms and return nutrients to the soil.

All living things depend on other living things to survive. This interdependence keeps ecosystems balanced. If one species disappears or a new one is introduced, it can affect the entire ecosystem. For example, if all the wolves in a forest disappear, deer populations might grow too large and eat too many plants.

Common ecosystems include forests, grasslands, wetlands, oceans, deserts, and freshwater lakes and rivers. Each has its own unique community of living things.

Key terms

Ecosystem: All the living and nonliving things in an area that interact with each other.
Habitat: The specific environment where an organism lives and gets what it needs to survive.
Producer: A living thing, usually a plant, that makes its own food using sunlight through photosynthesis.
Consumer: An organism that gets energy by eating other organisms.
Decomposer: An organism such as fungi or bacteria that breaks down dead plants and animals, returning nutrients to the soil.
Food chain: A sequence showing how energy passes from one organism to another through eating.

Flashcards

Ecosystem: All living and nonliving things in an area that interact with each other.
Habitat: The place where an organism lives and finds food, water, shelter, and space.
Producer: Organisms like plants that make their own food using sunlight through photosynthesis.
Consumer: An organism that eats other organisms for energy.
Decomposer: Organisms like fungi and bacteria that break down dead material and recycle nutrients.
Food chain: A diagram showing the flow of energy from one organism to another through eating.
Herbivore: An animal that eats only plants.
Carnivore: An animal that eats only other animals.

Questions

Which of the following is a nonliving part of an ecosystem?
1. A tree
2. A rabbit
3. Sunlight
4. A mushroom
Show answer
Answer: Sunlight
Sunlight is a nonliving (abiotic) part of an ecosystem. Trees, rabbits, and mushrooms are all living organisms.
Plants are called producers because they make their own food using sunlight.
Show answer
Answer: True
Plants are called producers because they produce their own food through photosynthesis, using sunlight, water, and carbon dioxide.
An animal that eats only plants is called a ______.
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Answer: herbivore
Herbivores are animals that only eat plants. Examples include rabbits, deer, and caterpillars.
What role do decomposers play in an ecosystem?
1. They hunt and eat large animals
2. They make food using sunlight
3. They break down dead organisms and return nutrients to the soil
4. They migrate to warmer climates in winter
Show answer
Answer: They break down dead organisms and return nutrients to the soil
Decomposers break down dead and decaying organisms, releasing nutrients back into the soil where plants can use them again.
A habitat provides an organism with food, water, shelter, and space.
Show answer
Answer: True
A habitat must provide all four basic needs for an organism: food, water, shelter, and adequate space to live.

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