Biogeochemical Cycles

1. Biogeochemical Cycles

2. What Sustains Life on Earth? • Solar energy, the cycling of matter, and gravity sustain the earth’s life. Figure 3-7

3. MATTER CYCLING IN ECOSYSTEMS • Nutrient Cycles: Global Recycling • Global Cycles called biogeochemical cycles, are cycling of nutrients from the abiotic reservoirs to biotic reservoirs. • Nutrients are the elements and compounds that organisms need to live, grow, and reproduce. • Biogeochemical cycles move all nutrients through air, water, soil, rock and living organisms over millions of years.

4. MATTER CYCLING IN ECOSYSTEMS • Nutrient Cycles: Global Recycling • Abiotic – nonliving cycles like rock cycle, water cycle and other chemical cycles. • Biotic – living organism involved cycles like carbon and nitrogen cycle. • All cycles enable a specific chemical element or nutrient to be taken and reused through various forms.

5. Carbon & Nitrogen Cycles • https://youtu.be/NHqEthRCqQ4

6. Carbon Cycles: • One of the most complex cycles on Earth. • It is the movement of atoms and molecules containing the element carbon between sources (release CO2 to atmosphere) and sinks (absorb CO2).

8. 4 Steps • 1st Step: carbon enters the atmosphere as carbon dioxide from respiration (breathing)  and combustion (burning). • 2nd Step: carbon dioxide is absorbed by producers (life forms that make their own food e.g. plants) to make carbohydrates in photosynthesis . These producers then put off oxygen.

9. 3rd Step: animals feed on the plants. Thus passing the carbon compounds along the food chain. Most of the carbon these animals consume however is exhaled as carbon dioxide. This is through the process of respiration. The animals and plants then eventually die. • 4th Step: the dead organisms (dead animals and plants) are eaten by decomposersin the ground. The carbon that was in their bodies is then returned to the atmosphere as carbon dioxide. • In some circumstances the process of decomposition is prevented. The decomposed plants and animals may then be available as fossil fuel in the future for combustion. 

11. Carbon Cycles: • Carbon just like all other nutrients cycles from one reservoir to another through many years. • Eg: Carbon enters plants as CO2 which is incorporated into organic molecules by a process called photosynthesis • When organisms respire, a portion of this carbon is returned to the atmosphere as CO2.

12. Carbon Reservoir pools: Where Carbon is stored • Organic molecules – in living and dead organisms. • Carbon Dioxide (CO2) in atmosphere. • Organic matter in soil. • Fossil fuels and sedimentary rock like limestone. • CO2 in ocean/water bodies. • Calcium carbonate in the shells of marine organisms.

13. Anthropogenic Effectson the Carbon Cycle • We alter the carbon cycle by adding excess CO2 to the atmosphere through: • Burning fossil fuels. • Clearing vegetation faster than it is replaced. • Just Breathing Figure 3-28

14. Sources vs Sinks Activity • Provide at least 5 examples of sources and sinks with your table. • Remember sources (release CO2 to atmosphere) and sinks (absorb CO2). • We will discuss on the board. • You have 5 minutes.

15. The Nitrogen Cycle • Nitrogen is the second largest nutrient cycle on the planet, second only to carbon. • It is the movement of atoms and molecules containing the element nitrogen between sources and sinks.

17. 4 Steps • 1st Step: Nitrogen Fixation • The process in which atmospheric nitrogen is converted into a form of nitrogen (primarily ammonia) that is available for uptake by plants and that can be synthesized into plant tissue. • 2nd Step: Nitrification • The transition of ammonia to nitrite and then nitrate through oxidation.

18. 3rd Step: Ammonification • The plant or animal dies and is converted back into ammonium by decomposers (bacteria and fungi that break down dead organisms). • 4th Step: Denitrification • Nitrates in the soil are converted back into nitrogen (N2) to go out into the atmosphere.

20. Nitrogen Storage • Most of the reservoirs in which nitrogen compounds occur in the nitrogen cycle hold those compounds for a short amount of time. • The atmosphere is the major reservoir of nitrogen.

21. Effects of Human Activities on the Nitrogen Cycle • We alter the nitrogen cycle by: • Adding gases to atmosphere that contribute to acid rain. • Adding nitrous oxide to the atmosphere through farming practices which can warm the atmosphere and deplete ozone. • Contaminating ground water from nitrate ions in inorganic fertilizers. • Releasing nitrogen into the troposphere through deforestation.

22. Anthropogenic Effectson the Nitrogen Cycle • Human activities such as production and use of fertilizers now “fix” (put into environment) more nitrogen than all natural sources combined. Figure 3-30

23. Phosphorus Cycle • https://youtu.be/wdAzQSuypCk

24. Phosphorous Cycle • Movement of atoms and molecules containing the element phosphorus between sources and sinks. • The major reservoirs of phosphorous are rock and sediments that contain phosphorus-bearing minerals. • Essential nutrient for plants and animals.

25. 3 Steps • 1st Step: Weathering • Since the main source of phosphorus is found in rocks, the first step of the phosphorus cycle involves the extraction of phosphorus from the rocks by weathering. Weather events, such as rain and other sources of erosion, result in phosphorus being washed into the soil. • 2nd Step: Absorption by Plants and Animals • Once in the soil, plants, fungi, and microorganisms are able to absorb phosphorus and grow. In addition, phosphorus can also be washed into the local water systems. Plants can also directly absorb phosphorus from the water and grow. In addition to plants, animals also obtain phosphorus from drinking water and eating plants.

26. 3rd Step: Return to the Environment via Decomposition • When plants and animals die, decomposition results in the return of phosphorus back to the environment via the water or soil. Plants and animals in these environments can then use this phosphorus, and step 2 of the cycle is repeated.

28. No Atmospheric Component • There is no atmospheric component in the phosphorus cycle, and the limitations this imposes on the return of phosphorus from the ocean to land makes phosphorus naturally scarce in aquatic and many terrestrial ecosystems. In undisturbed ecosystems, phosphorus is the limiting factor in biological systems.

29. Effects of Human Activities on the Phosphorous Cycle • Phosphorous Cycle has been greatly affected by human activity in the last 100 years. • We remove large amounts of phosphate from the earth to make fertilizer. • We reduce phosphorous in tropical soils by clearing forests. • We add excess phosphates to aquatic systems from runoff of animal wastes and fertilizers.

30. Water Cycle • https://youtu.be/TWb4KlM2vts

31. The Water (Hydrologic) Cycle • Movement of water in its various solid, liquid, and gaseous phases between sources and sinks. • Powered by the sun. • The oceans are the primary reservoirs of water at the earth’s surface, with ice caps and groundwater acting as much smaller reservoirs.

32. Water’s Unique Properties • There are strong forces of attraction between molecules of water. • Water exists as a liquid over a wide temperature range. • Liquid water changes temperature slowly. • It takes a large amount of energy for water to evaporate. • Liquid water can dissolve a variety of compounds including rock. • Water expands when it freezes.

34. 4 Steps • 1st Step: Evaporation • Heat from the Sun causes water on Earth (in oceans, lakes etc) to evaporate (turn from liquid into gas) and rise into the sky. This water vapor collects in the sky in the form of clouds. • 2nd Step: Condensation • As water vapor in the clouds cools down it becomes water again, this process is called condensation. • 3rd Step: Precipitation • Water falls from the sky in the form of rain, snow, hail, or sleet, this process is called precipitation. • 4th Step: Collection • Oceans and lakes collect water that has fallen. Water evaporates into the sky again and the cycle continues.

35. Anthropogenic Effects on the Water Cycle • We alter the water cycle by: • Withdrawing large amounts of freshwater from the ground causing salt water to contaminate reservoir. • Withdrawing large amounts from rivers and streams changes flow of nutrients • Clearing vegetation causes eroding soils that clogs streams. • Polluting surface and underground water. • All of this contributes to climate change.