Trophic levels
Definition
Trophic level
The position of an organism in a food chain, shown by a number starting at 1 for the producers.
- Each organism in a food chain belongs to a trophic level, shown by a number that starts at 1.
- Level 1 is the producers, which make biomass by photosynthesis.
- Level 2 is the primary consumers, the herbivores that eat producers.
- Level 3 is the secondary consumers, carnivores that eat the primary consumers.
- Level 4 is the tertiary consumers, carnivores that eat the secondary consumers.
Key Idea
The numbers rise along the chain: producers are level 1, and each animal that eats the one before is the next level up.
Producers, consumers and apex predators
Definition
Consumer
An organism that gets its energy by eating other organisms rather than by making its own food.
- Producers are green plants and algae that make their own food and start every food chain.
- Consumers eat other organisms; the primary consumers are usually herbivores and the later ones are carnivores.
- Apex predators are carnivores at the top of a food chain, with no predators of their own.
Decomposers
Definition
Decomposer
A microorganism, such as a bacterium or fungus, that breaks down dead organisms and waste, returning carbon dioxide to the air and mineral ions to the soil.
- Decomposers are bacteria and fungi that break down the dead bodies and waste of organisms from every trophic level.
- They release enzymes that digest the dead material, then absorb the nutrients.
- This returns carbon and mineral ions to the environment for producers to use again.
Self review
- What is a trophic level?
- Which trophic level are producers, and how do they make biomass?
- What is an apex predator?
- How do decomposers return nutrients to an ecosystem?