1. STRUCTURE OF THE ECOSYSTEM
The ecosystem is made of communities and the abiotic factors ( non-living factors e.g.. air, water and soil) and forces with which their members interact.
Species( plural) is a group of organisms: 1. They share characteristics 2. Freely breed 3. Produce fertile off springs.
Populations are made of a group of individuals of a particular species that live in a particular area.
Communities are made of multiple interacting species that live in the same area. Example:……………………………………………………………………….

2. Interaction of species
In contrast to intra specific competition which is really a population level phenomenon. (Intra specific competition is more tense when there are more individuals per unit area). What does this mean? explain
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…………………….. competition can strongly affect the composition of communities. …………………………competitions can give rise to different types of outcomes. If one species is a very effective competitor, it may exclude another species from resources use entirely. This outcome is called competitive exclusion.

3. Alternatively, if neither competitor fully excludes the other the species may continue to live side by side. This result is called species co- existence, this may produce a stable point of equilibrium, in which the relative population sizes of each remains fairly constant through time.
Coexisting species that use the same resources tend to adjust to their competitors to minimise competition with them. Individuals can do this by changing their behavior so as to use a portion of the total array of resources they are capable of using. In such cases,  individuals do not fulfil their entire niche. What is a niche?
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4. The full niche of a species is called its fundamental niche
The full niche of a species is called its fundamental niche. An individual that plays only part of its role or uses only part of its resources because of competition or other types of species interaction is said to display a niche, the portion of its fundamental niche that is actually realized or fulfilled.
Species experience similar adjustment over evolutionary time. Over many generations, the process of natural selection may respond to competition by favoring individuals that use slightly different resources or that use shared resources in different ways. For example, if two bird species eat the same types of seeds, individuals that prefer eating larger or smaller seeds might minimize competition and thereby survive and reproduce more effectively. If the seed eating tendencies are inherited, then these preferences may be passed on to offsprings, and over time natural selection might drive one species to specialize on larger seeds and the other specialize on smaller seeds.