New News Biology #67

Trophic Levels

Trophic levels are just different levels of a food chain.

If we use trophic levels to organize the food chain:

Trophic level 1: the grass - a producer (a plant or algae)

Trophic level 2: the rabbit - a primary consumer (herbivores)

Trophic level 3: the snake - a secondary consumer (carnivore)

Trophic level 4: the hawk - a tertiary consumer (carnivore)

Usually there won’t be more than 4 or 5 trophic levels, as there wouldn’t be enough energy to sustain organisms in a higher trophic level (energy gets lost as it goes up the food chain - normally only 10% is passed on to the next trophic level).

The carnivores at the top of the chain (regardless of how many trophic levels there are) have no predators to eat them, so they are known as ‘apex predators’.

There is a group of organisms that don’t fit neatly into this pattern though, and they are the omnivores, which eat both producers (plants) and other animals.

It is common to put them in the third trophic level, as they eat the primary consumers (other animals), though it is not a perfect fit because they also eat trophic level 1 (the producers) as well.

Lastly, there are detritivores and decomposers. Detritivores consist of small animals like worms, while decomposers consist of bacteria and fungi. They have a thing in common, which is they decompose the dead plant and animal matter in the environment. This allows them to recycle nutrients from animals and plants back to the ground and these nutrients can get reabsorbed by the producers to be used again in the cycle.