is the study of the interactions of living things with each
other and their physical environment. The living
things on earth may be organized into four different levels of
ecological organization. These levels of
organization are indicated in the table below.
||all the members of one species in an area
||all the members of the different
interacting species in an area
||all the members of a community plus the
abiotic (physical) factors influencing them
||entire region of the earth where living
things may be found
of A Community
This is a community of many
different organisms which could exist on milkweed.
The community contains many organisms of different species
in one location.
A Pond Ecosystem
This is a pond ecosystem.
There are many organisms of different species in this
location interacting with the air, water, and land
components of this environment.
ecosystems must have three basic kinds of nutritional
interactions in order to be stable and
self-sustaining. These nutritional interactions
involve producers, consumers, and
organism is one that is capable of trapping the Sun's energy
to make glucose sugar in the process of
photosynthesis. Plants and algae are examples of
producer organisms. Sometimes producer organisms
are called autotrophs. Consumer
organisms depend upon and eat other organisms for their
food. Sometimes consumer organisms are
called heterotrophs. Many different
categories of consumer organisms exist. A herbivore
eats primarily plant material, while a carnivore eats
primarily other animals. An omnivore is a
consumer that eats both plant and animal material.
Humans are an example of an omnivore. A decomposer
is a special category of consumer organism. Decomposers
break down dead organic matter and change it to simpler
nutrients which can be recycled in the
Circle of Life
In order for an ecosystem to sustain life, several
conditions must be met.
Some Conditions for a Stable Ecosystem
- A constant source of energy and a living system capable
of incorporating this energy into organic molecules. (This
means plants and/or algae are needed to convert solar
energy to the energy of sugars by the process of photosynthesis.)
- A cycling of materials between organisms and
their environment. (Some material cycles include
oxygen, carbon dioxide, water, and nitrogen.)
Decomposers, such as bacteria of decay and some fungi are
needed in every ecosystem to return and recycle necessary
materials to the environment.
The greater the number of different populations that
interact within an ecosystem, the more stable and
self-sustaining the ecosystem becomes. The number of different
populations within an ecosystem is sometimes referred to as biodiversity.
These interactions contribute to the overall maintenance of
occurs when two different species or organism living in
the same environment or habitat use the same
limited resources such as food, water, space, light,
oxygen, or minerals. A resource which restricts the
growth of a population is sometimes called a limiting
factor. The more similar the requirements of the
organisms involved, the more intense their competition
will become. If two different species compete for the
same food source, reproductive site, water, or other
limiting factor, one species may be eliminated. This
establishes one species per niche in an ecosystem. A niche
refers to an organismís role, especially its feeding
role, in a community. This allows different species to
coexist and helps to contribute to the overall stability
of the ecosystem.
Three different species of a kind of bird called a
warbler are coexisting in this tree, even though the eat
the same kind of food. These birds are feeding
in different levels of this tree. In this way,
these birds have evolved to occupy different niches.