Trophic Levels

[2025-09-22 Mon]

1. Trophic Levels

1.1. Definition

A trophic level is a step or position in a food chain that shows how energy and nutrients flow through an ecosystem. Each level depends on the one below it for energy.

1.2. Main Levels

Producers (1st level)
- Plants, algae, some bacteria.
- Use sunlight or chemicals to make food (photosynthesis/chemosynthesis).
Primary Consumers (2nd level)
- Herbivores that eat producers (e.g., deer, rabbits, zooplankton).
Secondary Consumers (3rd level)
- Carnivores/omnivores that eat herbivores (e.g., foxes, fish).
Tertiary Consumers (4th level)
- Top predators that eat other carnivores (e.g., hawks, sharks).
Decomposers (work across all levels)
- Fungi, bacteria, detritivores recycle matter back into the system.

(see: Trophic Levels Diagram, )

1.3. Energy Flow

Only about ~10% of energy passes from one level to the next. (see: The 10% rule)
Energy decreases as you move up → explains why food chains are usually short. (see: Food chains)

1.4. Representation

Food chain: linear sequence.
Food web: interconnected chains (more realistic).
Energy pyramid: shows decreasing energy at higher levels.

(see: Energy Pyramids, Food chains, Food webs)

1.5. Example

Grass → grasshopper → frog → snake → hawk.

Grass = producer.

Grasshopper = primary consumer.

Frog = secondary consumer.

Snake = tertiary consumer.

Hawk = apex predator.

1.6. Key Idea

Trophic levels reveal the structure of Ecosystems and how energy limits population size at higher levels.

2. Elsewhere

2.1. References

2.2. In my garden

Notes that link to this note (AKA backlinks).