Download 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.
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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.
 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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 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.