"I bequeathe
myself to the dirt, to grow from the grass I love;
If you want me again,
look for me under your boot-soles."
- Walt Whitman
In my first post I made mention
of the ecosystem in passing. Now I am going to dilate on it focusing on how it
works.
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, grassland. The
boundaries are not fixed in any objective way, although sometimes they seem
obvious, as with the shoreline of a small pond.
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. Thus the two main factors that cause the ecosystem to
function are:
·
ENERGY TRANSFORMATION
·
BIOGEOCHEMICAL CYCLING
ENERGY TRANSFORMATION
Energy enters the biological
system as light energy, or photons, is transformed into chemical energy in
organic molecules by cellular processes including photosynthesis and
respiration, and ultimately is converted to heat energy. This energy is
dissipated, meaning it is lost to the system as heat; once it is lost it cannot
be recycled. Without the continued input
of solar energy, biological systems would quickly shut down. Thus the earth is
an open system with respect to energy.
The transformations of energy in
an ecosystem begin first with the input of energy from the sun. Energy from the
sun is captured by the process of photosynthesis. Carbon dioxide is combined
with hydrogen (derived from the splitting of water molecules) to produce
carbohydrates (CHO). Energy is stored in the high energy bonds of adenosine
triphosphate, or ATP.
Energy from the sun, captured by
plant photosynthesis, flows from trophic level to trophic level via the food
chain. A trophic level is composed of organisms that make a living in the same
way, that is, they are all primary producers (plants), primary consumers
(herbivores) or secondary consumers (carnivores). Dead tissue and waste
products are produced at all levels. Scavengers, detritivores, and decomposers
collectively account for the use of all such "waste" -- consumers of
carcasses and fallen leaves may be other animals, such as crows and beetles,
but ultimately it is the microbes that finish the job of decomposition. Not
surprisingly, the amount of primary production varies a great deal from place
to place, due to differences in the amount of solar radiation and the
availability of nutrients and water.
Energy from the sun, captured by
plant photosynthesis, flows from trophic level to trophic level via the food
chain. A trophic level is composed of organisms that make a living in the same way
that is they are all primary producers (plants), primary consumers (herbivores)
or secondary consumers (carnivores). Dead tissue and waste products are
produced at all levels. Scavengers, detritivores, and decomposers collectively
account for the use of all such "waste" -- consumers of carcasses and
fallen leaves may be other animals, such as crows and beetles, but ultimately
it is the microbes that finish the job of decomposition. Not surprisingly, the
amount of primary production varies a great deal from place to place, due to
differences in the amount of solar radiation and the availability of nutrients
and water.
BIOGEOCHEMICAL CYCLING
Cycling of elements is controlled
in part by organisms, which store or transform elements, and in part by the
chemistry and geology of the natural world. The term Biogeochemistry is defined
as the study of how living systems influence, and are controlled by the geology
and chemistry of the earth. Thus biogeochemistry encompasses many aspects of
the abiotic and biotic world that we live in.
In biological systems, elements
are referred to as "conservative". These elements are often
nutrients. By "conservative" it means that an organism can change
only slightly the amount of these elements in their tissues if they are to
remain in good health.
Biogeochemists use is a simple
mass balance equation to describe the state of a system. The system could be a
snake, a tree, a lake, or the entire globe. Using a mass balance approach we
can determine whether the system is changing and how fast it is changing.
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 i.e. ponds, forests
etc. The two main factors that cause it to function are energy transformation (flow)
and biogeochemical cycling.
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