Material Cycles PDF

**1. Water Cycle** The water cycle describes the continuous movement of water within the Earth and atmosphere. It involves various processes that transfer water between the oceans, atmosphere, and land. **Key Components:** - **Evaporation:** Water from oceans, lakes, rivers, and soil turns...

**1. Water Cycle** The water cycle describes the continuous movement of water within the Earth and atmosphere. It involves various processes that transfer water between the oceans, atmosphere, and land. **Key Components:** - **Evaporation:** Water from oceans, lakes, rivers, and soil turns into water vapor and rises into the atmosphere. - **Transpiration:** Plants release water vapor into the atmosphere through their leaves. - **Condensation:** Water vapor cools and changes back into liquid droplets, forming clouds. - **Precipitation:** Water falls back to the Earth in the form of rain, snow, sleet, or hail. - **Infiltration:** Water seeps into the ground and replenishes groundwater reserves. - **Runoff:** Excess water flows over the land\'s surface into rivers, lakes, and oceans. **2. Carbon Cycle** The carbon cycle regulates the flow of carbon between the biosphere, geosphere, hydrosphere, and atmosphere, ensuring a balance between carbon sources and sinks. **Key Components:** - **Photosynthesis:** Plants and other autotrophs capture carbon dioxide (CO₂) from the atmosphere and use sunlight to convert it into organic compounds (glucose). - **Respiration:** Organisms (plants, animals, and microbes) release CO₂ back into the atmosphere through metabolic processes. - **Decomposition:** Dead organisms and organic matter are broken down by decomposers, releasing stored carbon back into the soil or atmosphere. - **Combustion:** The burning of fossil fuels (coal, oil, gas) releases large amounts of CO₂ into the atmosphere. - **Carbon Sequestration:** Carbon is stored for long periods in carbon sinks such as forests, soils, and the ocean. **3. Nitrogen Cycle** The nitrogen cycle ensures that nitrogen, a critical element for all living organisms, is converted into usable forms, primarily for protein and nucleic acid synthesis. **Key Components:** - **Nitrogen Fixation:** Certain bacteria (in the soil or root nodules of legumes) convert atmospheric nitrogen (N₂) into ammonia (NH₃), which can be absorbed by plants. - **Nitrification:** Soil bacteria convert ammonia into nitrites (NO₂⁻) and then into nitrates (NO₃⁻), which are usable forms of nitrogen for plants. - **Assimilation:** Plants absorb nitrates from the soil to produce proteins and nucleic acids. Animals then consume these plants to acquire nitrogen. - **Ammonification:** Decomposers break down organic matter, returning nitrogen to the soil in the form of ammonia. - **Denitrification:** Denitrifying bacteria convert nitrates back into nitrogen gas (N₂), releasing it into the atmosphere and completing the cycle.