Our Environment · Lesson 2 of 8
Producers, Consumers And Decomposers
“Plants cook, animals eat, decomposers clean up: the ecosystem’s job chart is surprisingly organised.”
• Explain how producers make food using solar energy. • Classify consumers as herbivores, carnivores, omnivores or parasites. • Explain how decomposers break down dead material and wastes. • Trace the movement of materials from decomposers back to producers. • Explain why producers, consumers and decomposers are interdependent.
Imagine an aquarium in which plants grow, fish feed and microorganisms act on dead matter. No single group can keep the system functioning alone. Some organisms bring food energy into the biological community, some obtain that food by feeding, and some return materials from dead matter to the surroundings. These roles are described as producers, consumers and decomposers.
Producers
A Producer is an organism that makes organic food from inorganic substances using energy, usually the radiant energy of the Sun.
Green plants and certain bacteria are producers. Green plants contain chlorophyll and use sunlight during photosynthesis to form organic substances such as sugars and starch from inorganic materials. This process is important because it converts solar energy into chemical energy stored in food.
Other organisms cannot use sunlight directly as food. Producers therefore make captured solar energy available to the rest of the ecosystem. This is why producers form the starting point of feeding relationships.
Consumers
A Consumer is an organism that depends directly or indirectly on producers for food.
A goat feeding on grass depends directly on a producer. A tiger feeding on a deer depends indirectly on producers because the deer obtained its food from plants. Consumers therefore include organisms that eat producers as well as organisms that eat other consumers.
Types Of Consumers
| Type | Feeding Pattern | Typical Example |
|---|---|---|
| Herbivore | Feeds mainly on producers | Goat feeding on grass |
| Carnivore | Feeds on other animals | Tiger feeding on deer |
| Omnivore | Feeds on both plant and animal material | Human eating plant and animal foods |
| Parasite | Obtains nourishment from a host | A parasitic organism living on or in another organism |
Decomposers
A Decomposer is a microorganism, such as a bacterium or fungus, that breaks down dead remains and waste products into simpler inorganic substances.
When plants or animals die, their matter does not simply vanish. Bacteria and fungi act on the dead material and on wastes. They break complex organic substances into simpler inorganic substances that return to the surroundings, including the soil.
Plants can take up these simple substances again. Decomposition therefore helps replenish materials that producers need. Without decomposers, dead organisms and waste would accumulate and the natural return of materials to the soil would be greatly disrupted.
Interdependence
Producers, consumers and decomposers depend on one another in different ways. Consumers depend on producers directly or indirectly for food. Decomposers depend on dead material and wastes from both producers and consumers. Producers benefit when decomposers return simple substances to the environment where they can be used again.
This is why it is misleading to call one group completely independent or unnecessary. Producers are the main entry point for solar energy into the living part of the ecosystem, while decomposers are essential for returning materials from dead organisms and wastes.
Exploring Dependence In An Aquarium
Consider an aquarium containing aquatic plants, small plant-eating organisms, fish, bacteria and fungi. Plants provide food and contribute oxygen during photosynthesis. Consumers feed on plants or other organisms. When organisms die or produce waste, decomposers act on the material. The aquarium becomes more stable when these roles are present in suitable proportions.
Problem
Classify grass, goat, tiger and fungi in a simple grassland system.
- 1.Grass makes food by photosynthesis, so it is a producer.
- 2.Goat feeds on grass, so it is a herbivorous consumer.
- 3.Tiger feeds on another animal, so it is a carnivorous consumer.
- 4.Fungi can break down dead remains, so they act as decomposers.
Problem
Explain how a carnivore can depend on producers even if it never eats a plant.
- 1.The producer captures solar energy and stores it in food.
- 2.A herbivore eats the producer and obtains some of that stored chemical energy.
- 3.The carnivore eats the herbivore.
- 4.Therefore the carnivore depends indirectly on the producer.
Problem
What would happen if decomposers disappeared from an ecosystem?
- 1.Dead plants, dead animals and organic wastes would accumulate.
- 2.Complex organic matter would not be broken down normally.
- 3.Fewer simple inorganic substances would be returned to the soil.
- 4.Plants would lose an important route by which materials are naturally replenished.
- 5.The ecosystem would be disturbed because recycling of matter would be reduced.
Producers bring solar energy into food chains, while decomposers help return matter to the environment. Energy flow and material recycling are connected, but they are not identical processes.
Quiz
Which organisms are producers in the context of this lesson?
A deer that feeds on grass is best classified as a:
Why are decomposers important?
A tiger depends on grass indirectly because:
What would most directly increase if decomposers vanished?
Practice Problems
- Explain how producers convert solar energy into a form that consumers can obtain through feeding.
- Classify cow, lion, human and a parasite into consumer categories and justify each choice.
- Trace the path of material from a dead plant through decomposers back to a living producer.
- Explain why a system containing only producers and consumers but no decomposers would become increasingly difficult to sustain.
- Construct a three-role explanation for a pond using one producer, one consumer and decomposers. Show how each role depends on at least one other role.
Key Takeaways
• Green plants and certain bacteria are producers because they make organic food using solar energy. • Consumers depend directly or indirectly on producers and can be herbivores, carnivores, omnivores or parasites. • Bacteria and fungi act as decomposers by breaking down dead remains and wastes. • Decomposition returns simple inorganic substances to the environment where producers can use them again. • Producers, consumers and decomposers are interdependent parts of a functioning ecosystem.