CYCLES IN THE bIOSPHERE

Nutrients Cycling Matter may be transformed from one type to another, but it cannot be created or destroyed. This is called the LAW OF CONSERVATION of MATTER. Nutrients are matter that organisms require for their life processes. Macronutrients – those nutrients that are required in large amounts. (nitrogen, carbon, phosphorus) Micronutrients – those nutrients needed in smaller amounts.

What goes in must come out? Materials on the planet are constantly being used and re-used. Those materials are moved through different phases on the planet in biogeochemical cycles. Biogeochemical means “life-earth-chemical”. Different items and elements require different amounts of time to cycle through the environment. The amount of matter cycled by biogeochemical cycles is gigantic! For example, about 90 million metric tons (1 metric ton = 1,000 kg or 2,210 lbs) of nitrogen are cycled per year. 90% of it is done by bacteria. The major biogeochemical cycles are: the carbon cycle, the water cycle, the nitrogen cycle, and the phosphorus cycle.

The Nitrogen Cycle The nitrogen cycle is the process in which nitrogen is cycled between the atmosphere, bacteria, and other living things. All living things need nitrogen to build proteins, which are used to make new cells. Nitrogen makes up 78% of the atmosphere. BUT…living things cannot use the nitrogen in the atmosphere…so how do we get what we need?

The Nitrogen Cycle Nitrogen in the atmosphere must be “fixed” by nitrogen fixing bacteria in the ground before it can be used by plants and animals. These bacteria live in little nodules on the roots of plants called legumes (ie: beans, peas, clover) or in the soil. Once the nitrogen is converted into the right form, animals get that nitrogen by eating plants that contain it. Plants get that nitrogen by absorbing it through their roots in the soil.

The Nitrogen Cycle There is a good amount of nitrogen in decaying matter and waste. Decomposers such as fungus and bacteria break down animal waste, leaves, dead trees, dead animals, etc. During decomposition, nitrogen that was once in living things is returned to the soil and some is returned to the atmosphere. If decomposers did not exist, nitrogen would build up in waste and dead organisms rather than being returned to the soil to be used again.

The Phosphorous Cycle The phosphorous cycle involves the geosphere and the oceans. It is a key component of cell membranes, DNA, and RNA. Although phosphorous is found in living things…tons more of it is found in rocks, soil, sediments, and the ocean. It is released naturally when rocks are broken down by water or wind. This makes it difficult for phosphorous to be released. Plants can only take up phosphorous through their roots when it is dissolved in water.

The Carbon Cycle The carbon cycle is the process in which carbon is cycled through the land, water, and living things. On average it takes one carbon atom 300 years to complete the full carbon cycle. Carbon is an essential part of proteins, fats, and carbohydrates. Carbon is found in all living things.

The Carbon Cycle Carbon dioxide found in the atmosphere is used by plants and trees to carry out photosynthesis. During that process, carbohydrates and oxygen are made. All living things carry out cellular respiration, breathing in the oxygen and using it to create energy. Living things breath out and release carbon dioxide back into the atmosphere.

The Carbon Cycle All living things eventually die and decay = C returned to the ground. C is compacted into fossil fuels over millions of years. Those fossil fuels such as oil, gas, and coal were once living things. Fossil fuels are burned to make vehicles move, heat homes, provide electricity, etc. When those fossil fuels are burned, carbon dioxide is released into the atmosphere.

The Water Cycle The water cycle is the movement of water from the atmosphere, to waterways, the ground, and back to the atmosphere. Water is continuously in motion on our planet.