Nutrient Cycles Lesson #5

Nutrient Cycles Nutrients are chemicals required for plant and animal growth as well as other life processes. Salts, amino acids, sugars, vitamins, etc.

Where are nutrients found? Nutrients can be found just about anywhere. Examples: land (soil), ocean, atmosphere, living organisms These locations are called stores. Nutrients can stay in a store for a short time or long time, and everywhere in between.

Nutrient Cycles Nutrient cycles describe the flow of nutrients in and out of stores as a result of biotic and abiotic processes. The three main nutrient cycles are: Carbon Cycle Nitrogen Cycle Phosphorus Cycle

Carbon Cycle Carbon is the key element in all living things Carbohydrates - source of energy Proteins - structural parts of bodies Fats/Lipids - insulation, long term energy store

Where do we find Carbon? Sources of Carbon Atmosphere Oceans All living things Fossil fuels and many more places!

Where do we find Carbon? Carbon reservoir – store carbon and release it slowly Carbon sink – reservoirs that absorb more carbon than they release (ex. Oceans)

What is the Carbon Cycle? The carbon cycle describes the process where carbon is recycled through ecosystems Mostly through photosynthesis and cellular respiration. Products of one are reactants for the other. These processes keep the balance of O2 and CO2 in the biosphere.

Photosynthesis

Photosynthesis Carbohydrates formed are passed through food chains and food webs. Decomposition releases carbon into the soil Carbon can be stores as fossil fuels and marine sediments

Cellular Respiration

Cellular Respiration Carbon is released back into the atmosphere Carbon is also released from combustion of fossil fuels Oxygen is also cycled through photosynthesis and cellular respiration

Nitrogen and Phosphorus Cycle Lesson #3

Nutrient Cycles The three main nutrient cycles are: Carbon Cycle Nitrogen Cycle Phosphorus Cycle

Nitrogen Cycle All living things need nitrogen to form nucleotides (DNA and RNA) and amino acids (proteins). Nitrogen gas makes up 78% of the atmpsohere, but most organisms can’t break the strong bonds of N2 molecules so the nitrogen cycle is needed.

First Step - Nitrogen Fixation A process carried out by nitrogen-fixing bacteria found in nodules on the roots of legumes such as peas, peanuts, and soybeans. On average there is 100 lightening strikes worldwide per second, 8 million per year. National Severe Storms Laboratory

First Step - Nitrogen Fixation Also in cyanobacteria and in lichens Plants and bacteria have a symbiotic relationship Nitrogen (N2) is fixed (combined with H2) to give ammonia (NH3) Excess ammonia is dissolved in water as ammonium (NH4+) ions. On average there is 100 lightening strikes worldwide per second, 8 million per year. National Severe Storms Laboratory

Second Step - Nitrification A process where nitrate (NO3-) ions are produced from ammonium by bacteria in soils Plants need both NH4+ ions and NO3- ions to grow Plants use nitrates to make amino acids and DNA. Animals get amino acids by digesting plant proteins and nucleic acids, and remake their own proteins and DNA.

Third Step - Denitrification When organisms produce waste or die and decompose, the material are broken down to release ammonium and nitrates. Anaerobic bacteria convert ammonium and nitrate back to nitrogen gas. This process speeds up in low oxygen, acidic environments such as peat bogs

Nutrient Cycles The three main nutrient cycles are: Carbon Cycle Nitrogen Cycle Phosphorus Cycle

Phosphorus Cycle Phosphates are important molecules in living things DNA and RNA have sugar phosphate backbones. Animals have phosphates in shells, bones and teeth. Cell membranes are made of phospholipids (fat molecules) Energy in all organisms stored in ATP (adenosine triphosphate).

Phosphorus Cycle All phosphate originates from weathering of sedimentary and metamorphic rocks. There is no phosphate in the atmosphere! Phosphate ions dissolve in water, get absorbed by producers then eaten by consumers.

Short Cycle When organisms die and decompose the phosphates are released and dissolve in water and are available to producers again.

Long Cycle When organisms die and decompose in the ocean, the phosphates and other elements sink to the bottom and are covered in sediments These sediments eventually become sedimentary rocks and the phosphates remain trapped until a geological event exposes them to weathering.

Human Impact on the Phosphorus Cycle Human activities add phosphate to ecosystems in several ways Commercial fertilizers Animal manure used to enrich soil Output from sewage treatment plants and industrial waste