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Preview text The carbon and nitrogen cyclesPage:The element carbon is the present in all living organisms. It's recycled throughvarious processes, which are described in the carbon cycle.Nitrogen is essential for the formation of amino acids to make proteins. Thenitrogen cycle describes the ways in which nitrogen is recycled.Carbon cycleMost of the chemicals that make up living tissue contain carbon. When organisms die thecarbon is recycled so that it can be used by future generations. The model that describes theprocesses involved is called the carbon cycle.Steps in the carbon cycle1.Carbon enters the atmosphere as carbon dioxide from respiration andcombustion.2.Carbon dioxide is absorbed by producers to make carbohydrates inphotosynthesis.3.Animals feed on the plant passing the carbon compounds along the food chain.Most of the carbon they consume is exhaled as carbon dioxideformed duringrespiration.
The animals and plants eventually die.4.The dead organisms are eaten by decomposers and the carbon in their bodies isreturned to the atmosphere as carbon dioxide. In some conditions decompositionis blocked.
The plant and animal material may then be available as fossil fuel inthe future for combustion.Carbon cycle in the sea - higher tier onlyIn the sea, marine animals may convert some of the carbon in their diet to calciumcarbonate which is used to make their shells. Over time the shells of dead organisms collecton the seabed and form limestone. Due to Earth movements this limestone may eventuallybecome exposed to the air where it's weathered and the carbon is released back into theatmosphere as carbon dioxide. Volcanic action may also release carbon dioxide.WHAT IS THE CARBON CYCLE?The carbon cycle is the process through which carbon is cycled through the air, ground,plants, animals, and fossil fuels. People and animals inhale oxygen from the air andexhale carbon dioxide (CO2), while plants absorb CO2 for photosynthesis and emitoxygen back into the atmosphere.
Carbon dioxide is also exchanged between theatmosphere and the oceans. This natural system of processes keeps CO2 levels in theatmosphere stable over time. The figure below depicts the carbon cycle by showing howcarbon moves between land, the atmosphere, and the ocean through various naturaland human-initiated processes. On land, carbon is contained within rocks, the soil,plants, and animals. When these decompose, the carbon can be emitted to theatmosphere as CO2. Once in the atmosphere, the carbon can then be absorbed by theoceans or by a land/ocean-based plant or shell-bearing animal.
It is important to notethat only a small amount of the Earth’s carbon moves through the carbon cycle eachyear.Natural and Anthropogenic Carbon FluxesOzone Layer Depletion, Greenhouse Effect & Global Warming1. A molecule containing three atoms of oxygen is called ozone. Ozone is very rare in ouratmosphere, averaging about three molecules of ozone for every 10 million airmolecules. In spite of this small amount, ozone plays a vital role in the atmosphere.2. 2. Ozone is mainly found in two regions of the Earth's atmosphere. Most ozone (about90%) resides in a layer that begins between 6 and 10 miles (10 and 17 kilometers) abovethe Earth's surface and extends up to about 30 miles (50 kilometers).
This region of theatmosphere is called the stratosphere. The ozone in this region is commonly known asthe ozone layer.3. 3. Ozone present in the stratosphere plays a beneficial role by absorbing most of thebiologically damaging ultraviolet sunlight. The absorption of ultraviolet radiation by ozonecreates a source of heat.
Ozone thus plays a key role in the temperature structure of theEarth's atmosphere. Without the filtering action of the ozone layer, more of the Sun's UVradiation would penetrate the atmosphere and would reach the Earth's surface. Manyexperimental studies of plants and animals and clinical studies of humans have shownthe harmful effects of excessive exposure to UV radiation.16. 16. Global warming refers to an unequivocal and continuing rise in the averagetemperature of Earth's climate system. Most of global warming is being caused byincreasing concentrations of greenhouse gases produced by human activities.
Futureclimate change and associated impacts caused by global warming will vary from regionto region around the globe. Global warming can be prevented by reducing the emissionof greenhouse gases.17. 17. Increase in spread of disease. Warmer waters and morehurricanes. Increase in droughts and heat waves.
Economic consequences. Melting ofpolar ice caps.
Fires and wildfires. Death by smog. Increase in volcanic activities. Loss of biodiversity and animalextinction.18. 18. Melting and breaking down of polar ice caps.19. 19. Artist’s illusion of New York city underwater.20.
20. Artist’s illusion of backwards evolution in case of polar bears.