Download The functional component of ecosystems

The functional component of ecosystems
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Food chain
Food web
Biogeochemical cycle
 Food chain:
• The sequence of food utilization starting with
biomass produce by photosynthetic producers is
called the food chain. In a food chain each organisms
eats smaller organism and is eaten by the larger one.
• At the base of the chain there is always green plants
or other autotrophic (the producers or first trophic
level)
 The detritus food chain:
• The detritus means dead organic matter.
• The detritus food chain starts from dead organic
matter which is eaten by other organisms feeding on
them detritivores.
•In fact, such food chains are less dependent upon the
direct solar energy and mainly depend on the supply of
organic matter produced in the ecosystems.
•For examples woodlouse is depended on the dead
leaves and woodlouse is eaten by a blackbird.
Food web: An ecosystem consists of many
food chains which are interconnected. The
food web is complex network of
interconnected food chains (each starting from
the same point) as shown in figure
Biogeochemical cycle:
• All organisms are made up of basic elements such as
carbon, nitrogen, phosphorus, sulfur, oxygen and
hydrogen. These elements are continuously cycled
between air, water, soil, rock and living organisms. i.e.
the four spheres (atmosphere, biosphere, hydrosphere,
lithosphere) biogeochemical cycles (life-earth- chemical
cycle) are the pathways describing the movement of
these basic elements through the four spheres of the
environment. These cycles driven directly or indirectly
by incoming solar energy and gravity are:
• Hydrological cycle (ii) Oxygen cycle (iii) carbon cycle (iv)
phosphorus cycle (v) sulfur cycle (vi) nitrogen cycle
Hydrological cycle:
• The solar energy evaporates water from the earth’s
surface in to the atmosphere. Some of this water
returns to the Earth as rain or snow.
• Passes through the living organisms, flows in to the
water body and eventually (finally) is evaporated
again to continue to the cycle.
• This constants motion of water is known as
hydrological cycles. The hydrological cycle , showing
the transfer of water from the oceans again shown in
figure
• Evaporation: The conservation of liquid water from oceans,
lakes, streams and other bodies of water to water vapor.
• Transpiration: the process by which the water is evaporated
from the plants leave after it has been extracted from the soil
by roots. The hydrologist use the term evop-transpiration to
described the combine water due to evaporation and
transpiration from the plants leaves.
• Precipitation: it is the process by which water is returned from
the atmosphere back to the earth. The water can fall as rain
hail, snow, slit. However, the most common form ( the
temperate climate) is rain
• Infiltration and percolation: it is the vertical moment of the
water through the soil and permeable rocks to ground water
storage area called aquifers.
• Runoff: it is the water that flow over the surface of Earth, after
falling, to the streams, rivers and oceans to resume the cycle.
The hydrologic cycle differs from most other
nutrients cycles. In this most of the water remains
chemically unchanged and is transformed from
one physical state to another. About 84% of water
remains vapor in the atmosphere comes from the
oceans and the rests comes from the land.
Through the hydrological cycle. Can be viewed as
cycle can be viewed as a cycle of renewal of water
quality.
•Carbon cycle:
•Carbon cycle is a building block of all organic
substance and is the most important for the existence.
It is one of the primary elements forming human tissues
and is essential for plants as well. The carbon is found
on planet in the following major forms.
•As organic molecules in living and dead organisms.
•As carbon dioxide in the atmosphere.
•As organic matter in the soils.
•As fossil fuel and sedimentary rocks deposit such as a
lime stone, dolomite, chalk, etc.
•In the oceans have dissolved atmospheric carbon
dioxide and calcium carbonate shells in a marine
organisms
•The carbon is circulated through the biosphere by the
carbon cycle shown in figure. Trace the flows and paths
in figure. The carbon cycle is based on carbon dioxide
gas, which makes about 0.038% of the volume of the
troposphere is also dissolved in water. The activity such
as aerobic respiration of the living organisms, volcanic
eruption, the weathering of carbonate rocks and the
burning of carbon containing compounds release carbon
dioxide to the atmosphere.
•Photosynthesis is the major driving force for the carbon
cycle shown in figure. the terrestrial and aquatic life
remove carbon dioxide from troposphere to convert in to
glucose and other complex organic compounds and
convert to carbon back to carbon dioxide. Thus
photosynthesis and aerobic respiration circulates carbon
in the biosphere representing major part of the global
carbon cycle.
•The oceans is the major sink of carbon, much of
which is found in the form of dissolved carbon
dioxide gas, and bicarbonate ions. Approximately
85% of world’s carbon is found in the oceans.
•Some carbon takes a long time to recycle, over
million of the years. For examples. Carbon tied up
the fossil fuel, shells & lime stone. Such carbon is
released only when fossil fuel are extracted and
burned and geological disturbance such as
earthquakes, may also release carbon.
Ecosystem model:
All living organisms need nutrients and energy .basic source of energy is
solar radiation, wind and water falls. Energy reaches earth surface and
about 15 percent solar energy is utilized in photo synthesis. Plants obtain
food from carbon dioxide of atmosphere by by process of photosynthesis
at every stage of tropic level there is a loss of energy. About 47 percent of
solar energy reaches the earth’s surface however the nutrients have cyclic
movement.
Two laws of thermodynamics :
First law of conservation of energy: Energy is neither created nor
destroyed. It just changes the forms.
Second law of thermodynamics: when energy is transformed from one to
another form there is increase in entropy and decrease in amount of useful
energy.
Ecosystem depends on surrounding ecosystem. All small ecosystems are
mutually interconnected. The changes in one ecosystem will influence
other ecosystem. More ecosystems occur in space and exist in time.
Ecosystems have dimensions. Ecosystem are time dependent having pasts,
present and future.
Nitrogen cycle
Nitrogen in its gaseous form (N2) constitutes 78% of the
volume of the atmosphere (troposphere).
Nitrogen is crucial component of proteins, many vitamins
and nucleic acids DNA and RNA. However, it cannot be used
directly as a nutrient by most form of life (multi cellular
plants and animals).
Nitrogen gas is converted into the usable from by two
natural processes as shown in figure. Trace the flows and
paths in this diagram.
Nitrogen is cycled via three process namely (i) Nitrogen
fixation (ii) Ammonification (iii) Denitrification
•Nitrogen fixation: The process known as biological
nitrogen fixation is carried out by certain type of bacteria
in aquatic system, in the soil and in the roots of some
plants. The gaseous nitrogen is biological converted to
the ammonia (NH3) which can be used by plants. The
excess ammonia undergoes ‘nitrification’ where it is
converted by specialized aerobic bacteria to ‘nitrate
(NO2) ions’ which are easily used by plants as a
nutrient. Plants assimilate ammonia, ammonium (NH4)
and nitrate (NO3) ions to produce nitrogen containing
organic molecules such as DNA, amino acids and
proteins. Animals get their nitrogen by eating plants.
Fixation also occurs due to lightening where N2 and O2
are converted to the nitrogen oxide .
•Ammonification: The nitrogen rich organic compounds
are returned in the form of wastes and dead bodies.
Specialized bacteria convert this detritus into simpler
nitrogen containing inorganic compounds such as
ammonia and ammonium ions. This process is known
as ammonification.
•Denitrification: Ultimately, nitrogen leaves the soil
through a process called ‘Denitrification’. The
denitrifying bacteria convert ammonia and NH4+ ions
back into nitrogen gas and nitrous oxide (N2O) gas.
These gases enter into the atmosphere to begin the
cycle again.
Oxygen cycle:
Almost all living things need oxygen. They use this oxygen
during the process of creating energy in living cells. Oxygen
cycle is shown in figure.
Just as water moves from the sky to the earth and back in the
hydrologic cycle, oxygen is also cycled through the
environment. Plants mark the beginning of the cycle. Plants
are able to use the energy of sunlight to convert carbon
dioxide and water into carbohydrates and oxygen in a process
called photosynthesis.
This means that plants breathe in carbon dioxide and breathe
out oxygen. Animals from the other half of the oxygen cycle.
They breathe in oxygen which is used to break down
carbohydrates in to energy in a process called ‘respiration’.
Carbon dioxide produced during respiration is breathed out by
animals into the air. So oxygen is created in plants and used up
by animals, as is shown in figure during the day time plants use
some oxygen to break down the carbohydrates, just as animals
do. During night time they. Absorb oxygen from atmosphere for
respiration and give of carbon dioxide. Just as animals do. This
oxygen is cycled in the atmosphere through the process of
photosynthesis and respiration very large surface area. Even
through plants produce approximately ten times as much
oxygen during the day as they consume at night, the night-time
consumption of oxygen by plants can create low oxygen
conditions in some water habitants.
Oxygen in water is cycled through the process of (i) Dissolution
from air & (ii) consumption of organisms, for respiration and
oxidation of organic substances.
Sulfur cycle:
Sulphur is an essential constitute of certain amino acids and vitamins of
the B-complex group. So plants and animals depend on a continuous
supply of sulphur. It is present in the atmosphere as hydrogen sulphide
(H2S) and sulphur dioxide (SO2) gas.
In, nature, these gases are emitted at an alarming rate. In soil, sulphur is
present as a sulphide sulphate and organic sulphur. It is taken by the
plants and through the food chain it returns to the soil . Fungi like
aspergillums and neurospora decompose the sulphur from proteins as
sulphate by aerobic decomposition. This sulphates undergo further
cyclization. In the aerobic conditions, H2S is produced from the
decomposition of the proteins by E.coli.
These days while industrialization and rapid urban development has
increased the concentration in the atmosphere where it reacts with the
moisture and causes acid rain. As a result, soil and aquatic environment
become more acidic and detrimental to organisms the sulphur cycles
shown in the figure.