Grade 4
The Human Knowledge Project
Unit 14 — Ecosystems and Living Things
Welcome back!
Every living thing depends on other living things and on its environment.
A forest, a pond, a prairie, and even your backyard are examples of ecosystems where plants, animals, fungi, and microorganisms interact.
Today you will learn how ecosystems work and why protecting them is important.
What Is an Ecosystem?
An ecosystem is a community of living things interacting with one another and with their physical environment.
An ecosystem includes:
- plants
- animals
- fungi
- microorganisms
- soil
- water
- air
- sunlight
All of these parts work together.
Producers, Consumers, and Decomposers
Living things play different roles in an ecosystem.
Producers
Producers make their own food, usually through photosynthesis.
Examples include:
- grasses
- flowers
- trees
- algae
Consumers
Consumers cannot make their own food.
They obtain energy by eating plants or other animals.
Examples include:
- deer
- rabbits
- wolves
- hawks
- humans
Decomposers
Decomposers break down dead plants and animals.
Examples include:
- fungi
- many bacteria
- earthworms
They return nutrients to the soil, helping new plants grow.
Food Chains
A food chain shows how energy moves through an ecosystem.
Example:
Sun
↓
Grass
↓
Rabbit
↓
Fox
↓
Decomposers
Energy begins with the Sun and passes from one organism to another.
Food Webs
Most ecosystems contain many connected food chains.
Together they form a food web.
Food webs better represent the many feeding relationships found in nature.
Habitats
A habitat is the natural home of an organism.
A habitat provides:
- food
- water
- shelter
- space
Different organisms require different habitats.
Adaptations
Adaptations help organisms survive.
Examples include:
- thick fur for cold climates
- camouflage
- sharp claws
- long roots
- waterproof feathers
Adaptations develop over many generations and help species survive in their environments.
Human Impact
People affect ecosystems in many ways.
Positive actions include:
- planting trees
- protecting wildlife
- reducing pollution
- conserving water
- recycling
Negative actions may include:
- habitat destruction
- pollution
- overuse of natural resources
Responsible choices help protect ecosystems for future generations.
Activity
Choose one ecosystem.
Examples include:
- rainforest
- desert
- pond
- forest
- grassland
- ocean
Create a report describing:
- producers
- consumers
- decomposers
- important habitats
- one food chain
- one way people can help protect this ecosystem
Practice
Answer these questions.
What is an ecosystem?
What is the difference between producers and consumers?
What do decomposers do?
How is a food web different from a food chain?
What is a habitat?
How can people help protect ecosystems?
Review
Today you learned:
- ecosystems connect living and nonliving things
- producers make food
- consumers obtain energy by eating other organisms
- decomposers recycle nutrients
- food webs describe many feeding relationships
- habitats provide what organisms need
- people can positively or negatively affect ecosystems
Healthy ecosystems support all forms of life on Earth.
Looking Ahead
Next we will explore engineering and technology, discovering how people use science, mathematics, and creativity to solve problems and improve everyday life.