The functional component of ecosystems

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.