ECO SYSTEM
An
ecosystem consists of the biological community that occurs in some locale, and
the physical and chemical factors that make up its non-living or abiotic
environment. There are many examples of ecosystems
- a pond,
- a forest,
- an estuary
- a grassland
The boundaries are not fixed in any objective way, although
sometimes they seem obvious, as with the shoreline of a small pond. Usually the
boundaries of an ecosystem are chosen for practical reasons having to do with
the goals of the particular study.
The study of ecosystems mainly consists of the study of
certain processes that link-
- The living, or biotic, components to
- The non-living, or abiotic, components.
Energy transformations and biogeochemical cycling are the main processes that
comprise the field of ecosystem ecology. As we learned earlier, ecology generally is defined as the
interactions of organisms with one another and with the environment in which
they occur. We can study ecology at the level of the individual, the
population, the community, and the ecosystem.
- Studies of individuals are concerned mostly about physiology, reproduction, development or behavior
- Studies of populations usually focus on the habitat and resource needs of individual species, their group behaviors, population growth, and what limits their abundance or causes extinction.
- Studies of communities examine how populations of many species interact with one another, such as predators and their prey, or competitors that share common needs or resources.
In ecosystem ecology we put all
of this together and, insofar as we can, we try to understand how the system
operates as a whole. This means that, rather than worrying mainly about
particular species, we try to focus on major functional aspects of the system.
These functional aspects include
such things as-
- The amount of energy that is produced by photosynthesis
- How energy or materials flow along the many steps in a , or
- What controls the rate of decomposition of materials or rate at which nutrients are recycled in the system
STRUCTURE OF AN ECOSYSTEM
You are already familiar with the parts of an ecosystem.
From this course and from general knowledge, you have a basic understanding of
the diversity of plants and animals, and how plants and animals and microbes
obtain water, nutrients, and food. We can clarify the parts of an ecosystem by
listing them under the headings "abiotic" and
"biotic".
Usually, biological communities include the
"functional groupings" shown above. A functional group is a biological category composed of
organisms that perform mostly the same kind of function in the system; for
example, all the photosynthetic plants or primary producers form a functional
group. Membership in the functional group does not depend very much on who the
actual players (species) happen to be, only on what function they perform in
the ecosystem.
FUNCTION OF AN ECOSYSTEM
Ecosystem function is the capacity of natural processes and
components to provide goods and services that satisfy human needs, either
directly or indirectly (de Groot et al 2002). By following this definition,
ecosystem functions are conceived as a subset of ecological processes and
ecosystem structures. Each function is the result of the natural processes of
the total ecological sub-system of which it is a part. Natural processes, in
turn, are the result of complex interactions between biotic (living organisms)
and abiotic (chemical and physical) components of ecosystems through the
universal driving forces of matter and energy.
PRODUCERS,
CONSUMERS AND DECOMPOSERS
Producers or autotrophs are organisms that make their own
organic material from simple inorganic substances. For most of the biosphere
the main producers are photosynthetic plants and algae that synthesis glucose
from carbon dioxide and water. The glucose produced is used both as an energy
source and combines with other molecules from the soil to build biomass. It is
this biomass that provides the total theoretical energy available to all non- photosynthesizing
organisms in the ecosystem.
Consumers or heterotrophs are organisms that obtain
organic molecules by eating or digesting other organisms. These are the herbivores and
carnivores of the ecosystem. By eating other organisms they gain both food as
an energy supply and nutrient molecules from within the biomass ingested. For
instance to build new protein consumers have to eat protein contain amino
acids.
Decomposers are
the waste managers of any ecosystem. They are the final link in a food web
breaking down Dead Organic Matter (DOM) from producers and consumers and
ultimately returning energy to the atmosphere in respiration and inorganic
molecules bake to the soil during decomposition. Decomposers can be divided
into two groups based on their mode of nutrition. DETRITIVORES
are organisms that ingest non-living organic matter.These can include
earthworms, beetles and many other invertebrates. SAPROTROPHS are organism that
lives on or in non- living organic matter, secreting digestive enzymes into it
and absorbing the products of digestion. These include Fungi and bacteria.
