An ecosystem is all the living and nonliving things in a certain area. All the plants and animals, even the microorganisms that live in the soil, are living parts of an ecosystem. Air, water, and rocks are nonliving parts of an ecosystem.
Ecosystems are smaller parts of all the living environments on Earth. Earth’s entire living environment is called the biosphere. The biosphere is made up of large areas called biomes. Land biomes include grasslands, deserts, coniferous forests (forests of cone-bearing trees), deciduous forests (forests of trees that shed their leaves), and tropical rain forests. There are also biomes in bodies of water, such as the ocean.
The biomes, in turn, are made up of many ecosystems. The desert biome, for example, covers all the deserts of the world. Each individual desert is an ecosystem. The Mojave Desert in California is a desert ecosystem.
Some ecosystems are huge, and some are small. A tropical rain forest ecosystem might cover hundreds of square miles. A mangrove swamp ecosystem might stretch only a few miles along the shore of an island.
A place can have more than one ecosystem. A rain forest and a mangrove swamp could be on the same island. A coral reef ecosystem might be in the water around the island.
All things in an ecosystem are connected with one another. These connections come through food and energy. The energy comes from the Sun. Plants use the energy in sunlight to make food. Animals eat the plants. Other animals eat the plant-eating animals. The way energy flows in food from plants to animals is called a food chain. Food chains that overlap are called food webs.
Let’s look at an ecosystem in a forest. Water flowing in a river makes the riverbanks wet. Plants that need lots of water grow along the riverbanks. Insects feed on plants in or along the river. A salmon swimming by eats the insects that fall in the water. A brown bear that lives in the forest wades into the river and swipes its paw in the water. The bear catches and eats the salmon.
The bear tosses the salmon bones and some meat onto the riverbank. Bacteria and fungi now go to work. The tiny bacteria and fungi feed upon the remains of the salmon. They break down the salmon into chemical nutrients. Nutrients from the salmon go into the soil.
The roots of plants along the riverbank take up the nutrients. They use the nutrients to make food. In this way, nutrients get recycled back through the ecosystem.
Any change in one living or nonliving part of an ecosystem can cause changes in other parts. Droughts, storms, and fires can change ecosystems. Some changes harm ecosystems. If there is too little rainfall, plants will not have enough water to live. If a kind of plant dies off, the animals that fed on it may also die or move away.
Some changes are good for ecosystems. Some pine forests need fires for the pine trees to reproduce. The seeds are sealed inside pinecones. Heat from a forest fire melts the seal and lets the seeds out.
Polluting the air, soil, and water can harm ecosystems. Building dams on rivers for electric power and irrigation can harm ecosystems around the rivers. Bulldozing wetlands and cutting down forests destroys ecosystems.
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