Geochemical Cycles Geochemical cycles represent the movement of

Geochemical Cycles • Geochemical cycles represent the movement of a particular form of matter through the living and nonliving parts of an ecosystem. – The 3 main cycles that we will study are: • Water (Hydrologic) • Carbon • Nitrogen Since matter can neither be created nor destroyed, and Earth is a closed system, these essential nutrients must be continuously cycled.

The Water Cycle • The chemical formula of water is H 2 O, and this is necessary for the life processes of all living things. • Water is found in… – Earth’s surface (including oceans, lakes, rivers, etc. ) • 97% is in the ocean! • Of the 3% that is freshwater, 2% is frozen in glaciers – Under Earth’s surfaces (groundwater, aquifers) – In the atmosphere – In living organisms

The Water Cycle • This cycle is driven by the sun, which causes evaporation from reservoirs and organisms.

The Water Cycle • The main stages include: – Precipitation: water falls to Earth as a liquid (usually rain, sleet or snow) – Runoff: liquid water that isn’t infiltrated runs along the surface and collects in puddles, lakes, oceans, or other bodies of water. – Infiltration: some water seeps from the surface of the Earth to underground aquifers

The Water Cycle • The main stages include: – Evaporation: sun heats liquid water to vapor and it rises to the atmosphere – Transpiration: water rises back into the atmosphere as water vapor from plants – Condensation: water condenses to form clouds before precipitating again

Living Organisms and the Water Cycle • All organisms take in water for nutrient transport, chemical reactions, diffusion, etc. – Which means, they also have to eliminate water too (urine/feces) • All organisms release water when breaking down food for energy (cellular respiration) C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + ATP • Plants take in water to make sugar (photosynthesis) 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2

Think about it… • What about human participation in the water cycle? How do we contribute to the cycle as living organisms? How do we negatively impact the cycle? • Negative Human Impact: – Deforestation: transpiration – Paving/Building/Development: Infiltration – Pollution Runoff and

The Carbon Cycle • Carbon is another molecule necessary for life to exist. • Carbon is found in… – Macromolecules, which are large molecules necessary for life. • • Proteins (muscle, skin, etc…) Carbohydrates (food, sugars) Lipids (fats) Nucleic acids (DNA and RNA)

The Carbon Cycle • Carbon is found in… – Our atmosphere (as CO 2) – Minerals and rocks – Fossil fuels (coal, oil, natural gas) – Organic (living) materials in soil or aquatic sediments • Note: Carbon changes forms as it cycles, unlike water, which is always H 2 O – Ex. Carbon is CO 2 in the atmosphere, but C 6 H 12 O 6 as glucose in plants

The Carbon Cycle • The main stages include: – Photosynthesis: plants capture CO 2 from the atmosphere and use it to make sugar – Cellular Respiration: CO 2 released into atmosphere as waste from metabolism – Consumption: one organism eats another for carbon

The Carbon Cycle • The main stages include: – Combustion: CO 2 released into atmosphere from burning – Decomposition: decomposers break down carbon from dead organisms, allowing it to be recycled in the soil – Fossilization: converts carbon from once-living organisms into a fuel source through intense heat and compression, including natural gas, oil, and coal (fossil fuels)

Living Organisms and the Carbon Cycle • Decomposers (like bacteria and fungi) break down dead materials and return the nutrients (like Carbon) to the soil • Photosynthetic organisms (like plants and algae) remove CO 2 from the atmosphere and convert it into simple sugars. • Animals, plants and fungi do cellular respiration in order to break down carbon-rich foods for energy

Think about it… • What about human participation in the carbon cycle? How do we contribute to the cycle as living organisms? How do we negatively impact the cycle? • Negative Human Impact: – Combustion: when wood or fossil fuels, which contain carbon, are burned causing major of CO 2 in the atmosphere

The Nitrogen Cycle • Nitrogen is the last molecule necessary for life to exist that we will focus on. • Nitrogen is found in… – Two Macromolecules: Proteins and Nucleic acids – In the atmosphere in the form of a gas - N 2 (elemental nitrogen) • Note: Plants and animals can NOT use nitrogen in this form!! – Fossil fuels – Waste – Soil

The Nitrogen Cycle • The main stages include: – Nitrogen fixation: Bacteria (or lightning!) in the soil or water convert nitrogen (from the air or water) into forms that plants can use

The Nitrogen Cycle • The main stages include: – Decomposition: decomposers like bacteria break dead matter down, returning nitrogen to the soil.

The Nitrogen Cycle • The main stages include: – Ammonification: Bacteria convert nitrogen from waste (urine and feces) into ammonia.

The Nitrogen Cycle • The main stages include: – Nitrification: Bacteria convert nitrogen in ammonia into nitrates and nitrites to be absorbed by plants in their roots. • This is how nitrogen enters the food chain, and eventually reaches us.

The Nitrogen Cycle • The main stages include: – Denitrification: bacteria convert nitrogen in ammonia to N 2 so it can go back into the atmosphere

Living Organisms and the Nitrogen Cycle • The nitrogen cycle is different from other geochemical cycles, in that no step is completed without the help of living organisms. – Bacteria is most important living organism in converting nitrogen to different forms. – Fungi and other decomposers breakdown nitrogen-rich waste and put it in the soil

Think about it… • What about human participation in the nitrogen cycle? How do we contribute to the cycle as living organisms? How do we negatively impact the cycle? • Negative Human Impact: – Fertilizers: The use of fertilizers adds WAY too much nitrogen to the soil, creating an imbalance • This excess nitrogen can get into groundwater which can be dangerous to drink – Combustion: not as major of an impact on the nitrogen cycle as the carbon cycle, but burning fossil fuels does release excess nitrogen into the atmosphere