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Confused about the difference between food chains and food webs? Don't worry, you're not alone. But we can help you sort it out. Here's everything you need to know about food chains and food webs, and how ecologists use them to better understand the role of plants and animals in the ecosystem.
What is a food chain? A food chain follows the path of energy as it is transferred from species to species within an ecosystem. All food chains begin with the energy produced by the sun. From there they move in a straight line as the energy is moved from one living thing to the next.
Here's an example of a very simple food chain:
Food chains show how all living things get their energy from food, and how nutrients are passed from species to species down the chain.
Here is a more complex food chain:
Trophic Levels of a Food Chain
All living creatures within a food chain are broken down into different groups, or trophic levels, that help ecologists understand their specific role in the ecosystem. Here's a closer look at each of the trophic levels within a food chain.
Producers: Producers make up the first trophic level of an ecosystem. They earn their name via their ability to produce their own food. They do not depend upon any other creature for their energy. Most producers utilize the Sun's energy in a process called photosynthesis to create their own energy and nutrients. Plants are producers. So are algae, phytoplankton, and some types of bacteria.
Consumers: The next trophic level focuses on the species that eat the producers. There are three types of consumers.
- Herbivores: Herbivores are primary consumers that eat only plants. They may eat any or all parts of the plant, such as leaves, branches, fruit, berries, nuts, grass, flowers, roots, or pollen. Deer, rabbits, horses, cows, sheep, and insects are a few examples of herbivores.
- Carnivores: Carnivores eat only animals. Cats, hawks, sharks, frogs, owls, and spiders are just a few of the world's carnivores.
- Omnivores: Omnivores eat both plants and animals. Bears, humans, raccoons, most primates, and many birds are omnivores.
There are various levels of consumers that work there way on up the food chain. For example, primary consumers are the herbivores that eat only plants, while secondary consumers are the creatures that eat the secondary consumers. In the example above, the mouse would be a secondary consumer. Tertiary consumers eat secondary consumers - on our example that was the snake.
Finally, the food chain ends at the apex predator - the animal who resides at the top of the food chain. In the example above, that was the hawk. Lions, bobcats, mountain lions, and great white sharks are more examples of apex predators within their ecosystems.
Decomposers: The last level of the food chain is made up by the decomposers. These are the bacteria and fungi that eat decaying matter - dead plants and animals and turn them into nutrient-rich soil. These are the nutrients that plants then use to produce their own food - thus, starting a new food chain.
Simply put, a food web describes all of the food chains in a given ecosystem. Rather than forming a straight line that goes from the sun to the plants to the animals that eat them, food webs show the interconnectedness of all of the living creatures in an ecosystem. A food web is made up of many interconnected and overlapping food chains. They are created to describe species interactions and relationships within an ecosystem.
Here are some examples:
Food web within the Chesapeake Bay.
Food web of marine habitat in Alaska
Food web of a soil-based ecosystem
Food web of a pond