Biogeochemical Cycles “To understand biology is to understand that all life is linked to the earth from which it came.” Rachael Carson, 1961

Where does the stuff on this planet come from? Is there any more stuff coming? Could I be part dinosaur? Hubble Space Telescope: Protoplanetary Disks around Newborn Stars

Elements that Matter the chemistry of beings C – carbon H – hydrogen O – oxygen N – nitrogen P – phosphorus K - potassium S - sulfur 96% All living things on earth contain the elements carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur 3%

The Carbon / Oxygen Cycle Atmospheric CO2 1 Photosynthesis 2 Respiration CO2 Only plants can incorporate CO2 into living sustaining molecules that organisms use to build and power their bodies. They do this through the process called photosynthesis. Plants capture CO2 by using sunlight to bind it to water molecules and arrange them to make sugar. Oxygen is released as a byproduct that animals use to breathe. When fossil fuels are burned, CO2 is released back into the atmosphere to reenter the carbon cycle. CO2 allows the sun’s infrared rays to penetrate through the atmosphere. It also acts as a heat trap, insulating the earth. Increasing the amount of CO2 in the atmosphere, increases the amount of retained heat, elevating the earth’s temperature. This phenomenon is termed the “greenhouse effect”. 5 Burning of Fossil fuels Plants Animals 4 3 Fossil fuels Dead organisms

The Nitrogen Cycle 4 1 5 6 2 3 6. Denitrification Atmospheric N2 Animals decay and waste Plants N2 fixing bacteria Legumes Nitrogen Fixation Denitrifying bacteria 1 Decomposition The nitrogen cycle is slightly different. Plants cannot capture nitrogen directly from the atmosphere. Rather they must get it from the soil after bacteria have transformed it into a useable compound. Bacteria extract the nitrogen from the atmosphere and through a series of internal chemical reactions, create nitrogenous compounds that plants can assimilate. Once the nitrogen is captured in plants, it is available to animals in the form of amino acids and proteins. Bacterial Decomposers 5 Ammonia (NH3) and Ammonium (NH4) 6 Denitrification 2 Nitrification 3 Nitrifying bacteria Assimilation Nitrates (NO3)

The Phosphorus Cycle Phosphorus enters the cycle as rain and water dissolve it from rocks and minerals. The dissolved phosphorus is taken up by plants and assimilated by animals eating the plants. This is an animal’s sole source of phosphorus, a main chemical ingredient in DNA and RNA. Phosphorus is recycled through decomposition of plants and animals. Phosphorus is a limiting resource in most terrestrial and aquatic ecosystems. Excess phosphorus in the environment leads to eutrophication – bacteria and algal blooms which deplete water of oxygen necessary for most organisms.