Educational worksheet on biogeochemical cycles with questions about the water, carbon, nitrogen, and phosphorus cycles.

- THE WATER CYCLE
1. Drinking, agriculture, industrial processes.
2. Through evaporation, condensation, precipitation, and runoff.
3. Gravity and atmospheric pressure gradients.
4. The process by which water vapor is released from plants into the atmosphere.
5. Soil type, rainfall patterns, and availability of groundwater.
6. A body of permeable rock that can contain or transmit groundwater.
7. Surface runoff and groundwater flow.
8. Water flowing over the land surface, carrying sediment and dissolved substances.
9. Approximately 505,000 cubic kilometers per year.
10. About 100% of precipitation returns as part of the cycle.

- THE CARBON CYCLE
1. Macronutrients: Carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur. Micronutrients: Iron, manganese, zinc, copper, boron, molybdenum, chlorine.
2. a. Primary producers: Fix carbon via photosynthesis (e.g., trees). b. Secondary producers: Consume primary producers, transferring carbon (e.g., deer). c. Decomposers: Break down organic matter, releasing carbon (e.g., fungi).
3. Most carbon is in the oceans as dissolved inorganic carbon and in sedimentary rocks as carbonate minerals.
4. Through photosynthesis by autotrophs and consumption by heterotrophs.
5. Plants absorb CO₂ for photosynthesis, converting it into glucose and releasing O₂.
6. Via respiration, decomposition, and combustion.
7. Organisms that produce their own food using sunlight or chemical energy (e.g., algae).
8. Their organic matter decomposes, releasing carbon back into the environment.
9. They break down dead material, returning carbon to the soil and atmosphere.
10. Formed from ancient organic matter under heat and pressure (e.g., coal, oil).
11. Dissolved CO₂ diffuses into ocean water; marine organisms incorporate it into shells and tissues.

- THE NITROGEN CYCLE
1. Approximately 78%.
2. It is essential for building amino acids, nucleic acids, and chlorophyll.
3. Through consumption of plants or other animals that have assimilated nitrogen.
4. Bacteria that convert atmospheric nitrogen (N₂) into ammonia (NH₃) usable by plants.
5. The soil and aquatic sediments.
6. To synthesize proteins and nucleic acids for growth and metabolism.
7. The microbial conversion of nitrates back into nitrogen gas, returning it to the atmosphere.

- THE PHOSPHORUS CYCLE
1. It is a key component of ATP, DNA, RNA, and phospholipids.
2. It dissolves in water and is taken up by plants through roots.
3. Incorporated into nucleic acids, phospholipids, and bones/teeth during growth.
4. Released as inorganic phosphate through decomposition.
5. Deposited in marine sediments, forming phosphate rock over geological time.
6. Absorbed from water or sediment and incorporated into biological molecules.
7. Phosphorus has no significant gaseous phase; it cycles primarily through water, soil, and living organisms.