The movement and transformation of chemical elements and compounds between living beings, atmosphere and earth's crust is called biogeochemical cycle. In this lesson, you will learn about following cycles.
- Water Cycle
- Nitrogen Cycle
- Carbon Cycle
- Oxygen Cycle
1: (a) Water cycle, 2: (b) Lightning, 3: (d) Chickpea, 4: (d) Ammonia, 5: (c) Protein, 6: (a) Oxygen, 7: (c) Photosynthesis, 8: (b) Photosynthesis, 9: (d) Stratosphere, 10: (a) Chlorofluorocarbons
The water cycle is also known as the hydrologic cycle. It involves the continuous movement of water on, above, and below the surface of the earth. Water changes into different states of matter during water cycle.
Water on earth changes into vapor through evaporation. Water vapor goes up into the atmosphere and changes into clouds after condensation. After that precipitation occurs and water falls on earth in the form of rain and snow.
The nitrogen cycle is the biogeochemical cycle that describes the transformations of nitrogen and nitrogen-containing compounds in nature.
Living beings cannot utilize the gaseous form of nitrogen. Hence, gaseous nitrogen needs to be changed into a form so that plants can take up and utilize nitrogen. The process of converting gaseous nitrogen into a suitable form for green plants is called nitrogen fixation.
- Some fixation of nitrogen occurs during lightning strikes. Due to energy from lightning, nitrogen gas in atmosphere changes to oxides of nitrogen. The oxides of nitrogen then reach the soil along with rainwater.
- Most part of the nitrogen fixation is done by free-living or symbiotic bacteria. These bacteria have the nitrogenase enzyme. This enzyme changes gaseous nitrogen into ammonia. Ammonia is further converted into organic compounds.
- Some nitrogen fixing bacteria live in symbiotic association in root nodules of leguminous plants. Rhizobium is one such example. Such bacteria get shelter and food in root nodules of leguminous plants. In lieu of that, these bacteria help in nitrogen fixation in soil.
- After that, plants utilise nitorgen compounds from soil, to make protein.
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth.
Photosynthesis is the major process through which carbon dioxide reaches the living world.
Some gases trap infrared radiation in atmosphere. This results in a general rise of atmospheric temperature. This is called greenhouse effect. Examples of greenhouse gases are; carbon dioxide, methane and water vapor.
The oxygen cycle is the biogeochemical cycle that describes the movement of oxygen within and between its three main reservoirs: the atmosphere (air), the biosphere (living things), and the lithosphere (earth’s crust). The main driving factor of the oxygen cycle is photosynthesis, which is responsible for the modern Earth's atmosphere and life.
All the above mentioned cycle can be grouped or explained as energy cycle on this earth. The sun is the main source of energy for every activity on earth. This energy facilitates the everlasting cycle of all resources in the biosphere. This system ensures that whatever we take from earth and its atmosphere we return it in some way or other.
The ozone layer is a layer in earth’s atmosphere which contains relatively high concentrations of ozone. This layer absorbs 93-99% of the sun’s high frequency ultraviolet light, which is potentially damaging to life on earth. Over 91% of the ozone in Earth's atmosphere is present here. It is mainly located in the lower portion of the stratosphere from approximately 10 km to 50 km above Earth's surface, though the thickness varies seasonally and geographically.
Because of heavy use of CFCs (Chlorofuorocarbons) in refrigerators and pressurized cans by human the ozone layer has broken at some places. This has caused an alarming rise in ultraviolet radiation leading to increased cases of skin cancers.