Ecosystems Topic 4.5: Biogeochemical Cycles. Part of the Local Ecosystems Module Spotlight Biology Preliminary Text Chapter 4 Authors: D. Heffernan, J. Bastina , B. Grieve, K. Humphreys, A. Sartor Science Press 2002. Biogeochemical Cycles.
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Part of the Local Ecosystems Module
Spotlight Biology Preliminary Text Chapter 4
Authors: D. Heffernan, J. Bastina, B. Grieve, K. Humphreys, A. Sartor
Science Press 2002
We have studied that animals obtain the energy crucial to life by ingesting organic molecules carrying that energy. In this process they are also obtaining essential nutrients they need to construct their own body tissues.
In this section we are going to look at how essential nutrients are cycles through our environment. These cycles are called Biogeochemical Cycles and include:
For good health, most organisms require about 25 chemical elements known as essential elements. The six listed below are required in large amounts.
Calcium, magnesium, sulfur, iron, sodium and manganese are required in lesser quantities.
Trace elements are those required in even smaller quantities and vary greatly between organisms. These include:
We know that energy and nutrients are passed from one organism to another by the same complex molecules, but the paths they take through ecosystems are very different.
Energy flows steadily through an ecosystem. From the sun it passes from one trophic level to the next and is lost to the environment along the way. However the Earth does not receive a consistent supply of chemical elements from the sun or space.
Nutrient elements are not produced or used up they instead are passed around from one organism to another in closed loops called nutrient cycles.
Because most of these cycles involve the movement of elements through living organisms and out planets geological features, they are often referred to as biogeochemical cycles.
Nutrient cycling and recycling have been going on since life began. So the nutrient elements circulating today have been used before, probably many times before.
Atoms of carbon that are in your body right now might have once been part of rocks on the ocean floor, of single celled organisms (zoo or phytoplankton) floating in the ocean or the nose of an extinct dinosaur!
The cycling of water through clouds, rain, snow and rivers is the most familiar and visible of the biogeochemical cycles. You would have studied these processes before
The water cycle is driven by solar energy, both allowing the evaporation of water from lakes and oceans and driving transpiration (the loss of water vapour) in plants.
Carbon is an element found in many compounds. When it is bonded to hydrogen and oxygen, it is the backbone of the organic molecules on which life is based, as well as an important component of carbonate rocks. Carbon dioxide in the atmosphere helps keep the Earth at a constant Temperature.
The movement of carbon through the biosphere is vital to life on Earth. We have understood the basics of the carbon cycle for along time but there are many questions unanswered about how much carbon travels along which part of the pathway at any particular time.
We know that carbon dioxide in the air becomes part of plants during photosynthesis. The carbon and oxygen then pass along the food chain until they are released back into the atmosphere.
Almost all organisms consist of 49% carbon by dry mass. (if you were to remove all of the water from our body, it would be our dry mass) The organic compounds in both organisms alive today and the fossil remains of ancient organisms are important carbon storage sites in the biosphere.
Carbon can be stored as fossils when an animal or plant is buried. Over time its remains are converted into oil, natural gas or coal. Carbon can also be deposited a calcium carbonate (limestone) by coral.