Cycles in Biology.

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Cycles in Biology

A cycle is an interval during which a recurring sequence of events occurs. Cycles are a hugely relevant component of biology. Practically everything has to be recycled as every resource, to some extent, is a non-renewable resource.  There are cycles in all aspects of biology that can be explored.

Life-materials are the basic particles of Earth, called elements, that all living organisms build their bodies from. They are sometimes called "bio-elements." All living organisms are made primarily of six elements, all in the same proportion: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus and Sulphur. Most organisms require small, often tiny, amounts of additional such as iron, copper and iodine. Most plants require a total of twenty-three different nutrients to flourish.

Essential nutrients are limited. We use them for energy to power our bodies (food for metabolism) and as materials to build and renew our bodies. We renew or rebuild our bodies over and over, every day. Nutrients are all recycled so organisms can share them over time. This sharing process is called the Nutrient Cycle. These nutrients have been shared over and over for billions of years. Every organism alive on earth is made of nutrients that have been used and re-used over and over again. Certain human activities may altar the nutrient cycles.  

Living organisms continually release nutrients from their bodies, in the form of wastes, which are really by-products or leftovers from metabolism. Life takes every opportunity to be creative. One organism's wastes become another organism's nutrients. Every animal on Earth releases carbon dioxide as they breathe. It acts as a bi-product, and useless to them; but to every plant on Earth, that carbon dioxide is a necessary nutrient for photosynthesis and continuing life. The plants, in turn, release oxygen into the air, which is necessary for animals. Life on Earth is a balanced process of exchanging each other's leftovers for mutual benefit. Organisms release all their nutrients when they die and are decomposed by fungi and bacteria. Gradually, every part of an organism decomposes and returns to the Nutrient Cycle.

Water is a molecule made of two atoms of Hydrogen (H) and one atom of Oxygen (O). Its chemical formula is H2O. Water is reused over and over again. This recycling of Earth's water has been going on for billions of years and is named The Water Cycle. Heat from the sun changes liquid surface water (oceans, lakes, wetlands rivers) into gas water vapour, which rises into the air, known as evaporation. Above the ocean and rain forests, water vapour gathers into clouds. Winds move the clouds of vapour. The clouds release their water in liquid precipitation (rain) or crystal precipitation (snow). The water runs off, or soaks into the ground, and eventually, some of it flows into the ocean, where the cycle is repeated.

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Another huge source of water vapour in the air is plants. This is called transpiration. Transpiration is the evaporation of water from plants. It occurs chiefly at the leaves while their stomata are open for the passage of CO2 and O2 during photosynthesis. Air that is not fully saturated with water vapour (100% relative humidity) will dry the surfaces of cells with which it comes in contact, so the photosynthesising leaf loses substantial amount of water by evaporation. This transpired water must be replaced by the transport of more water from the soil to the leaves through the xylem of the roots

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