What Is an Ecosystem?
An ecosystem is a community of living organisms — plants, animals, fungi, and microorganisms — interacting with each other and with their nonliving environment (such as water, soil, sunlight, and air). Ecosystems can be as large as an ocean or as small as a puddle.
In Grade 5 science, understanding ecosystems helps students see how all living things are connected and why changes in one part of an ecosystem can affect everything else.
Living vs. Nonliving Parts of an Ecosystem
- Biotic factors (living): plants, animals, bacteria, fungi
- Abiotic factors (nonliving): sunlight, water, temperature, soil, air
Both biotic and abiotic factors work together to create a balanced system. For example, plants need sunlight and water (abiotic) to grow, and animals need plants (biotic) to eat.
What Is a Food Chain?
A food chain shows the flow of energy from one organism to another in a straight line. Energy always starts with the sun and moves through producers to consumers.
- Producers – Plants and algae that make their own food using sunlight (photosynthesis)
- Primary Consumers – Herbivores that eat producers (e.g., rabbits, caterpillars)
- Secondary Consumers – Animals that eat primary consumers (e.g., frogs, small birds)
- Tertiary Consumers – Top predators that eat secondary consumers (e.g., eagles, wolves)
- Decomposers – Fungi and bacteria that break down dead organisms and return nutrients to the soil
Example Food Chain
Sun → Grass → Grasshopper → Frog → Snake → Hawk
What Is a Food Web?
A food web is a more realistic picture of nature. Most animals eat more than one type of food, so food chains overlap into a complex web of connections. For example, a fox might eat rabbits, berries, and mice — connecting it to multiple food chains at once.
Why Ecosystems Need Balance
When one part of an ecosystem changes, it can cause a ripple effect throughout the entire system. This is called a trophic cascade.
Example: If wolves are removed from a forest ecosystem, deer populations grow unchecked. Deer overeat vegetation, causing erosion, reducing plant diversity, and affecting insects, birds, and water quality — all because one predator was removed.
Types of Ecosystems
| Ecosystem Type | Key Features | Examples of Animals |
|---|---|---|
| Forest | Dense trees, varied rainfall | Deer, owls, bears |
| Ocean | Saltwater, sunlight penetration | Fish, whales, sharks |
| Desert | Low rainfall, extreme temperatures | Coyotes, snakes, lizards |
| Grassland | Grasses, seasonal rainfall | Bison, lions, prairie dogs |
| Freshwater | Rivers, lakes, ponds | Frogs, turtles, trout |
Key Vocabulary to Know
- Habitat – the specific place where an organism lives
- Predator – an animal that hunts other animals
- Prey – an animal that is hunted
- Adaptation – a feature that helps an organism survive in its environment
- Photosynthesis – the process plants use to turn sunlight into food
Remember
Every organism — no matter how small — has a role to play. Even decomposers like worms and fungi are essential because they recycle nutrients back into the soil, allowing new plants to grow and the cycle to continue.