Food webs
In this topic you will:
- draw and interpret food webs that include microorganisms as decomposers
- think about how microorganisms contribute to food webs.
Key words
- dung
- nutrients
Roles of decomposers
No-one would want to eat a rotten apple. The microorganisms that make an apple decay have spoiled the food.
But most of the time, decay by microorganisms is useful. Microorganisms break down dead bodies and animal waste. They decompose this material. Almost all decomposers are microorganisms. Fungi and bacteria are the most important decomposers.
If the dead bodies and waste are not broken down by decomposers, they would just build up. There would be heaps of dead plants, dead animals and animal dung everywhere.
But there is an even more important reason why decomposers are useful. The dead bodies and waste contain substances that living organisms can use to supply them with energy, or to help them to grow. These substances are called nutrients.
When microorganisms decay organic matter, they return the nutrients to the soil. Plants can then use the nutrients to help them to grow. This is really helpful for the plants.
This also helps animals, because there are more plants to eat.
Common mistake
Many people think that only animals break down waste. In fact, most decomposers are microorganisms such as fungi and bacteria. They do most of the work in recycling nutrients back into the soil.
Decomposers in food webs
Decomposers feed on almost every organism after it dies. They also feed on waste from animals. This is how decay microorganisms get their energy. Energy from the dead organisms and their waste is transferred to the decomposers.
You can show this by adding decomposers to food chains or food webs. You do not usually do this because you have to draw an arrow from every organism in the food chain or food web to the decomposers. This makes it look very complicated. The diagram shows a simple food web with decomposers added to it.
Questions
Show Answer
Example: Grass → Grasshopper → Frog → Snake → Microorganisms
Decomposers break down the dead snake and recycle nutrients into the soil.
Show Answer
Decomposers are consumers because they get their energy by feeding on dead organisms and waste, not by producing their own food like producers do.