Module 9 - Soil formation and biogeochemical cycles

• Matter on the planet is conserved, moving between the biotic (biosphere) and abiotic (atmosphere, lithosphere, hydrosphere) realms.
• Key nutrients are carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur (CHNOPS).
• Biogeochemical cycles involve biological, geological, and chemical processes moving nutrients.

Water Cycle

• Plants obtain water through their roots.
• Animals drink water.
• Water evaporates from oceans, lakes, and streams.
• Evapotranspiration occurs through plant leaves.
• Condensation forms clouds, leading to precipitation and runoff, then the cycle continues,

Carbon Cycle

• Plants get carbon through photosynthesis, including land plants and phytoplankton in the ocean.
• Animals get carbon through their diet by eating plants or other animals.
• Carbon is released back into the atmosphere through cellular respiration as carbon dioxide.
• Carbon can be stored in rock as fossil fuels like coal and oil.
• Combustion releases carbon dioxide back into the atmosphere.

Nitrogen Cycle

• Nitrogen gas is abundant in the atmosphere.
• Nitrogen fixation converts nitrogen into usable ammonia, performed by bacteria in plant roots or added as fertilizer.
• Plants assimilate nitrogen through their roots, and animals obtain it by eating plants.
• After death and decay, bacteria and fungi convert nitrogen into ammonium.
• Nitrifying bacteria convert ammonium into nitrites and then nitrates.
• Nitrates can be leached into the water supply, causing algae blooms due to nitrogen being a limiting nutrient.
• Eutrophication occurs when algae die and are broken down by bacteria, consuming oxygen.
• Denitrifying bacteria return nitrogen back into the atmosphere.

Phosphorus Cycle

• Rocks containing phosphorus are uplifted, then weathered and eroded, moving phosphorus into the soil and water.
• Fertilizers can add phosphorus, promoting eutrophication due to it being a limiting nutrient.
• Plants assimilate phosphorus, and animals obtain it by eating plants.
• Excretion and decay return phosphorus to the water supply, eventually settling in ocean sediments.
• Phosphorus becomes part of phosphate rocks, which are uplifted again. This cycle does not involve the atmosphere.

Sulfur Cycle

• Sulfur moves from the oceans.
• Bacteria convert sulfur into dimethyl sulfide, which becomes sulfur oxide or sulfur dioxide.
• Volcanoes release hydrogen sulfide, which converts to sulfur dioxide.
• Factories also release sulfur dioxide.
• Atmospheric sulfur dioxide falls back to the planet as sulfuric acid and sulfates in rain.
• Plants assimilate sulfur, and consumers obtain it through plants.
• Sulfur returns through the water supply and ends up as sulfur in the oceans.
• The cycle continues or forms fossil fuels, which can be extracted.

Cycles Summary

• Determine how plants acquire nutrients.
• Determine how animals acquire nutrients.
• Understand how nutrients recycle through the atmosphere, hydrosphere, and lithosphere.