Food Chains

Why do we need to eat? To obtain energy

Energy is what makes all of our activities possible. Energy circulates through an ecosystem via food chains and food webs.

Ecosystem is all the organisms in an area that interact with each other and with their environment.

Energy from the sun is the fuel for ecosystems Producers convert energy from the sun into chemical energy through the process of photosynthesis Primary consumers (herbivores) eat plants Secondary consumers (carnivores) eat animals

Food Chain

Detritivores – organisms that feed on the dead bodies of animals, dead plants, and animal dung. Ex. crabs, earthworms, beetles. Decomposers – break down the cells of any dead plant or animal matter and extract the last remaining energy. Ex. bacteria, fungi.

Food Web

If you eat 0.5 kg of food, do you gain 0.5 kg? No. Most of the energy that enters an organism is used by the organism just to stay alive. The organism uses energy to move, to grow, to reproduce, and to carry out all of its activities. Some energy cannot be used and passes out as waste.

Energy Flow

Only a small percentage (~ 10%) of energy is stored in the organism and is available for consumers at the next trophic level. Therefore, the greatest amount of energy is in the 1st trophic level (the producers). There is less energy is the 2nd and even less in the 3rd.

Biomass Pyramid

Because there is less and less energy as you move through a food chain, this usually results in a pyramid of biomass (combination of size and number of organisms) where there are more producers than herbivores, more herbivores than carnivores.