How Do We Survive in Balance? Ecosystems and Food Chains

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Updated on: Educator Review By: Michelle Connolly

Ecosystems are like small worlds inside our big world. In fact, our entire world is an ecosystem that includes countless smaller ecosystems, and these ecosystems keeps life going on our planet. 

So, what does the ecosystem mean?

Ecosystem is an environment where living organisms, like plants and animals, and non-living things, like water and soil, live and interact with each other. The living organisms survive when their specific needs are met. These needs include food, shelter, temperature, water and air.

So, the ecosystem includes two major components: Biotic and Abiotic. Biotic means the living organisms in the system. Abiotic means the non-living elements in the system. Living organisms interact with non-living things, and depend on each other for survival.

Ecosystems have no particular size. An ecosystem can be small, like inside a tree trunk, medium like a pond, or large like the ocean.

Food Chain

It is agreed that the living organisms need food to survive, but how do the living organisms in the ecosystem get food?

The food chain explains how living things get the food they need. Each living thing in an ecosystem has a role to play, either a producer, a consumer or a decomposer. 

  1. Producers are the living things that make their own food. Plants are producers. They do not depend on other organisms for food, instead they make their own food through a process called photosynthesis, in which they use sunlight, carbon dioxide and water to produce food.
  2. Consumers are the organisms that eat other living things. They do not produce food within themselves. Humans and animals are consumers. They eat plants or other animals.
  3. Decomposers are living things that break down waste and dead animals or plants, and return nutrients to the soil, so that new plants grow. Bacteria and fungi, like mushrooms, are examples for decomposers. They like to eat dead things, which increases the soil’s fertility.

So, the way that producers, consumers, and decomposers provide nutrients for one another is called a food chain. Decomposers break down dead things, which helps nourish the soil. The better soil helps producers, which are plants. Then, consumers eat the producers, other consumers, or both, depending on their type. After the consumers die, the decomposers break them down to help the soil, and the cycle goes on.


In the ecosystem, the water, water temperature, plants, animals, air, light and soil all work together. For example, if there is not enough water or light, or if the soil does not have the right nutrients, the plants will die. If the plants die, the animals that depend on plants for food will die. If those animals die, other animals that depend on those animals will die. So, all the parts in an ecosystem work together to make a balanced system. When the balance in the ecosystem is disrupted, organisms cannot thrive.  

A healthy ecosystem should be diverse. Diversity means different kinds of organisms play different roles. An ecosystem depends on different kinds of organisms to keep it in balance. However, introducing new organisms can upset the natural balance of an ecosystem. 

Invasive Species

The newly introduced organisms that are not naturally found in a specific ecosystem are called invasive species. When invasive species enter an ecosystem, three possible things can happen there:

  1. The existing animals adapt and stay in their ecosystem.
  2. The existing animals die.
  3. The existing animals move somewhere else to find a new home.

So, invasive species cause changes and upset the natural balance in the ecosystem.  

Human Impacts

Humans are part of many ecosystems. While humanity relies on balanced ecosystems for living, there are often negative consequences of human interaction. Possible disruptions caused by humans include: 

  1. Pollution is one of the main causes of disruptions in the ecosystem. It causes increased temperature, acid rain and drought, which makes it difficult for the living organisms to survive. Polluted soil can become infertile and unsuitable for plants, which in turn will affect other organisms in the food chain.
  2. Removing too many resources, such as water, threatens the lives of the organisms living in the ecosystem. 
  3. Throwing waste into an ecosystem by humans can lead to imbalance of nutrients.
  4. Overfishing leads to disrupted food chains in the ocean.
  5. Cutting down trees threatens to destroy thousands of ecosystems in the forests.
  6. Using too much fertilizer can damage ecosystems. Pesticides can sometimes kill a lot more bugs than they are intended to. This means less bugs to eat for some animals, which causes a disruption in the balance of the whole ecosystem.
Ecosystem disruption

Natural Disruptions

It is important to remember that not all disruptions are caused by humans, some happen naturally such as:

  • Climate changes. If climate changes too quickly, the living organisms will not have time to adapt. Climate change can also cause more wildfires, more floods, warmer rivers and decreased plant life.
  • Imbalance in the prey-predator relationship. If the prey population in an ecosystem grows, predator numbers will increase as well. Growing predator numbers will eventually reduce the food until it can no longer sustain the predator population. Decreased number of preys will lead to their extinction.

Examples for Ecosystems

  • In a pond ecosystem, there are plants, insects, larvae, fish, crocodiles and microbes. Microbes decompose the dead material and increase the soil fertility. Fertile soil helps plants grow. Insects feed on these plants. Larvae feed on the insects. Fish eat the larvae. Crocodiles eat the fish. When crocodiles die, microbes decompose their dead tissue again, and the cycle goes on.
  • Flowers in a garden ecosystem provide nectar for butterflies, bees and other insects. Insects transfer pollen between plants, helping the plants reproduce and survive.
  • In a lake ecosystem, the sun hits the water and helps the algae grow. Algae produces oxygen for animals, and it also provides food for microscopic animals. Small fish eat the microscopic animals, absorb oxygen and expel carbon dioxide. Then, plants use the carbon dioxide to breathe and grow. 
  • Rainforest ecosystems contain lots of plants. Plants provide food and even homes for some animals, such as birds and butterflies. For example, birds build nests in plants, bugs eat the leaves of the plants, and butterflies drink nectar from flowers.

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