FOOD CHAINS

What is a food chain? A food chain is a linear relationship between producers and consumers.

It represents the transfer of food energy from green plants through repeated stages of eating and being eaten.

Types of Food Chain

1. Grazing food chain – starts with green plants.
2. Detritus food chain – starts with dead organic material (debris or detritus).

Detritivores:

Detritivores feed on organic wastes and dead matter derived from the grazing food chain. Many different types of organisms feed on detritus. They include fungi, protozoa, insects, mites annelids and nematodes.

Examples of Food Chains

Green plants~ aphids ~ lady-bird beetle Green plants ~antelope -lion Algae ~Tilapia ~ kingfisher Plant debris ~bacteria -eprotozoa ~ mosquito larva Phytoplankron-eZooplankton ~ Tilapia ~ Nile perch ~ Human

Food Web

In a natural community, several food chains are interlinked to form a food web. Several herbivores may feed on one plant. Similarly, a given herbivore may feed on different plants and may in turn be eaten by different carnivores.

Decomposers

These are mainly bacteria and fungi. These organisms feed on dead organic matter thereby causing decomposition and decay and releasing nutrients for plants. They form a link between the biotic and the abiotic components.

Pyramid of Numbers

Refers to the number of organisms in each trophic level presented in a graphic form and a pyramid shape is obtained. The length of each bar is drawn proportional to the number of organisms represented at that level.

This is because a herbivore feeds on many green plants. One carnivore also feeds on many herbivores.

In a forest the shape of the pyramid is not perfect. This is because very many small animals such as insects, rodents and birds feed on one tree.

Pyramid of Biomass

This is the mass of the producers and consumers at each trophic level drawn graphically.