2.1.1. Trophic level interaction

Trophic level interaction deals with how the members of an ecosystem are connected based on nutritional needs.

Trophic levels (Trophe = nourishment)

I	Autotrophs	Green plants (producers)
II	Heterotrophs	Herbivore (primary consumers)
III	Heterotrophs	Carnivores (secondary consumers)
IV	Heterotrophs	Carnivore (tertiary consumers)
V	Heterotrophs	Top carnivores (Quarternary consumers)

Energy flows through the trophic levels: from producers to subsequent trophic levels. This energy always flows from lower (producer) to higher (herbivore, carnivore etc.) trophic level. It never flows in the reverse direction that is from carnivores to herbivores to producers.

There is a loss of some energy in the form of unusable heat at each trophic level so that energy level decreases from the first trophic level upwards.

As a result there are usually four or five trophic levels and seldom more than six as beyond that very little energy is left to support any organism. Trophic levels are numbered according to the steps an organism is away from the source of food or energy, that is the producer.

The trophic level interaction involves three concepts namely:-

1. Food Chain

2. Food Web

3. Ecological Pyramids