CHAPTER-13 BIO-GEO CHEMICAL CYCLE
- All living organisms require Carbon, Hydrogen, Oxygen, Nitrogen,Sulphur, Phosphorous, Potassium and Calcium in large amounts.
- They get the nutrients from air (Atmosphere) water (Hydrosphere) and soil (Lithosphere).
- The nutrient elements derived from the earth by the living organisms for use in their growth and development are called bio-geo chemicals.
- The cyclic flow of elements or compounds between non-living environment (soil, rock, air, water) and living organisms is known as bio- geo chemical cycle.
Life and Non-Life Interactions (Biotic and Abiotic Factors)
- The branch of biology which deals with the interr-relationships oforganisms and their environment is called Ecology
- The organisms and the physical environment of the habitat form anecological complex termed ecosystem
- Ecosystem (Environmental system) includes two essential components:
- Abiotic components
- Biotic components
Abiotic Components
- The abiotic components of the environment are air, water, soil, light andtemperature.
Biotic Components
- Include all living organisms including human beings. Plants and animals are interdependent.
- Bees depend for their food on pollen and nectar from flowers.
- Flowers depend on bees for pollination. ‘=
- The energy trapped by green plants is relayed through a series of heterotrophic organisms. This forms the food chain.
- Grass – Rabbit – Fox – Tiger
Water Cycle
- Oceans are the biggest store houses of water from which water evaporates to form clouds.
- Plants absorb water from the soil or water reservoir and add it to the air (atmosphere) as vapour by transpiration.
- Mammals excrete water as sweat which evaporates from their bodies.
- Water is also added to the environment by death and decay of organisms.
- About two-thirds of our body is made up of 97% oceans, 2% of ice-caps, 1% fresh
- ground water. .
- In 20 minutes, one thunderstorm can send down over over 125,000,000 gallons of water. (One gallon is equivalent to 4.5 litres)
Nitrogen cycle
- Nitrogen is essential element required by organisms to synthesizeproteins and nucleic acids
- Though atmosphere contains about 78% of Nitrogen, it cannot be utilizedby living organism unless it is converted into ammonia, amino acids or These compounds which are available in the soil are cycled andrecycled through the ecosystem.
- The Nitrogen Cycle involves
Nitrogen fixation
- Nitrogen assimilation
- Ammonification
- Nitrification
- Denitrification
Nitrogen fixation
- During nitrogen fixation, nitrogen is oxidized to oxides by lightningthese oxides get dissolved in rain water and get precipitated.
- The nitrogen fixing bacteria such as Azotobacter, Rhizobium and blue green algae like Noshoc convert gaseous nitrogen to ammonia and nitrates
Nitrogen assimilation
- The nitrates absorbed by plants is utilized for making organic matter suchas proteins, nucleic acids etc.
Ammonification
- When the plants and animals die, their protein are broken down to release ammonia by the action of bacteria and fungi
Nitrification
- The ammonia is converted into nitrates and nitrates by soil bacteria such as Nitrobacter and Nitrosomonas which are then absorbed by plants
Dentrification
- Free living soil bacteria such as pseudomonas reduce nitrate ions of soil into gaseous nitrogen
Organisms involved in Nitrogen cycle
Activity | Name of organism |
Nitrogen Fixation | Rhizobium, Azotobacter and Nostoc
|
Ammonification | Ammonifying bacteria and fungi
|
Nitrification | Nitrosomonas and Nitrobacter
|
Denitrification | Pseudomonas
|
Carbon Cycle
- The three main sources of carbon are
- CO2 of the air and CO2 dissolved in oceans
- Carbonate rock in the earth’s crust and
- Fossil fuels like coal and petroleum
- The atmospheric carbon dioxide enters into the living world, i.e, greenplants, through the process of photosynthesis.
- The respiratory activities at each trophic level return carbon dioxidequickly to the atmosphere.
- Carbon dioxide is also returned to the atmosphere through decomposition of dead organic materials, burning of fossil fuels volcanic activities.
Oxygen Cycle
- All living organisms require oxygen for respiration Oxygen isone of theconstituents of water and forms about 20% of the air in the atmosphere.
- Oxygen enters the living world through respiration
- The carbon dioxide is utilized by the plants to produce food materials during the process of photo synthesis and oxygenisreleased.
- These compounds after breaking down, release oxygen in the atmosphere and maintain balance in the Environment