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How do you think understanding the transfer of energy in food webs provides a foundation for more advanced topics in biology in high school and college?
How do you think understanding the transfer of energy in food webs provides a foundation for more advanced topics in biology in high school and college?
Food chains are an entry point for student understanding of how animals and plants interact and how energy moves through an ecosystem. By expanding our view to food webs, we get a more complicated - but also more realistic - view of how ecosystems function and the importance of each piece. By looking at the interactions between different components of the system, students start to understand the interdependence among organisms in nature, and how small changes might impact larger systems.
Key Concept 1: All energy transferred through food webs is derived from the Sun.
Key Concept 1: All energy transferred through food webs is derived from the Sun.
The source of all energy on Earth is the Sun
However, sunlight is not usable food for animals. It must first be changed into a usable form by plants. Animals, not able to produce their own food, are required to eat plants or other animals to gain energy. An example is grass, which absorbs sunlight and is eaten by a grasshopper, which is eaten by a toad, which gets eaten by a snake, which finally gets eaten by a hawk. In time the hawk dies, decays, and is broken down by the decomposers, which return the nutrients back to the soil, which is used again by nearby plants. A food chain shows the transfer of this energy.
Sometimes more than one animal will eat a mouse, for example, and a complex set of energy transfers occur. The interconnected food chains are called a food web.
Regardless of how simple a food chain may be, or how complicated a food web becomes, the Sun is still the original source of energy for all living things.
Key Concept 2: Producers use the Sun’s energy to create their own food through photosynthesis.
Key Concept 2: Producers use the Sun’s energy to create their own food through photosynthesis.
Plants use sunlight, water, and carbon dioxide to make glucose, a type of sugar the plant uses for food. When animals eat plants, the energy stored in the plant is transferred to the animal. Only plants produce their own food, so they are called producersFrom the smallest green algae in a pond to the largest tree on Earth, all plants produce their own food through photosynthesis
Key Concept 3: Consumers and decomposers get their energy from producers or other consumers.
Key Concept 3: Consumers and decomposers get their energy from producers or other consumers.
Some animal consumers get their energy by eating plant producers. Other animal consumers get their energy by eating other consumers (animals). Some animals eat both plants and other animals to obtain energy. (Decomposers, such as bacteria and fungi, are organisms that break down dead organisms and their wastes to get energy.)
Key Concept 4: The different parts of a food web are producers, consumers, and decomposers.
Key Concept 4: The different parts of a food web are producers, consumers, and decomposers.
In order to ensure a successful interactive ecosystem, there must be a proper balancein the populations of organisms within a food web. Any change in the population of any organism in the food web or food chain will affect other organisms. If all the grass in an area were killed in a wildfire, there would be less grass for the deer to eat and they could die off. If there were not enough deer to eat, then the predators (coyotes) would die off. If any population of organisms changes in some way, either increasing or decreasing, it will affect other organisms in the food web. Ultimately decomposers, through their chemical breakdown of the remains of dead plants and animals, return the nutrients in those decaying bodies back to the soil. This decaying material becomes soil humusa rich organic material that supports plant growth, and the food web continues.
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