Geochemical Cycles

2. 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 mustbe continuously cycled.

3. The Water Cycle • The chemical formula of water is H2O, 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

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

5. 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

6. 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

7. 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) C6H12O6 + 6O2 6CO2 + 6H2O + ATP • Plants take in water to make sugar (photosynthesis) 6CO2 + 6H2O C6H12O6 + 6O2

8. 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: Runoff and Infiltration • Pollution

9. 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)

10. The Carbon Cycle • Carbon is found in… • Our atmosphere (as CO2) • 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 H2O • Ex. Carbon is CO2 in the atmosphere, but C6H12O6 as glucose in plants

11. The Carbon Cycle • The main stages include: • Photosynthesis: plants capture CO2 from the atmosphere and use it to make sugar • Cellular Respiration: CO2 released into atmosphere as waste from metabolism • Consumption: one organism eats another for carbon

12. The Carbon Cycle • The main stages include: • Combustion: CO2 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)

13. 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 CO2 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

14. 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 CO2 in the atmosphere

15. 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 - N2(elemental nitrogen) • Note: Plants and animals can NOT use nitrogen in this form!! • Fossil fuels • Waste • Soil

16. 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

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

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

19. 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.

20. The Nitrogen Cycle • The main stages include: • Denitrification: bacteria convert nitrogen in ammonia to N2 so it can go back into the atmosphere

21. 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. • Bacteriais most important living organism in converting nitrogen to different forms. • Fungi and other decomposers breakdown nitrogen-rich waste and put it in the soil

22. 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