*Natural ecosystem* - It is an ecosystem with no human Interference. - Most natural ecosystems are in a state of equilibrium (balance) because of a variety of producers and consumers living together. Examples of natural ecosystems are rivers and deserts. The biological components of an ecosystem can be divided into: 1. Producers - these are green plants which use light energy from the sun to make their own food by photosynthesis. Examples include grasses, trees and shrubs. 2. Consumers - these depend on other organisms for food. They are not able to make their own food. - Consumers are classified into three; a) Herbivores - these are animals that feed on plants and they are the primary consumers of an ecosystem. Examples include caterpillar, kudu and zebra b) Carnivores - these are animals which feed on other animals, They feed on the primary consumers. These can be secondary or tertiary consumers of an ecosystem. Examples include lion, hyena and vulture. c) Omnivores - these are animalswhich feed on both plants and animals. Examples include human beings and monkeys. 3. Decomposers-they feed on dead plants and animals. They break down dead organic matter into simple nutrients. in the soil which are then absorbed by plants when they make their own food. Examples include bacteria, fungi and earthworms. Note:organisms in a natural ecosystem depend on one another for survival.