A4 - Biogeochemical Cycles (Updated 2024) PDF

A4 - Biogeochemical Cycles I can… Explain water’s primary role in biogeochemical cycles, considering its chemical and physical properties (i.e. universal solvent & hydrogen bonding) Explain the cycling of carbon, oxygen, nitrogen, and phosphorus and relate this to the general...

A4 - Biogeochemical Cycles I can… Explain water’s primary role in biogeochemical cycles, considering its chemical and physical properties (i.e. universal solvent & hydrogen bonding) Explain the cycling of carbon, oxygen, nitrogen, and phosphorus and relate this to the general reuse of all matter in the biosphere Explain the interrelationship of energy & matter in maintaining homeostasis, and how human activity impacts this balance in different ecosystems Necessity of Cycles There is a limited amount of matter in our ecosystem, therefore, chemicals must be recycled constantly ○ Recycling of matter through biotic and abiotic parts of ecosystems allows all organisms to obtain essential nutrients The main biogeochemical cycles are: ○ Oxygen and carbon ○ Nitrogen ○ Sulfur ○ Phosphorus The Carbon Cycle The Carbon Cycle Carbon also accumulates and is stored in various reservoirs for long periods of time, where it is unavailable to organisms until it is released ○ This cycling through carbon sinks is referred to as slow cycling ○ Fossil fuel deposits are an example of slow cycling, it can take millions of years before the carbon is available again Carbon sinks include trees, fossil fuel deposits, the ocean, and limestone rock Carbon is released from these reservoirs both quickly (e.g. forest fires) and slowly (e.g. weathering) through natural processes The Carbon Cycle Carbon and oxygen are closely related in our ecosystem Carbon plays a key role in metabolic processes (cellular respiration and photosynthesis); is thus directly linked to the oxygen cycle Moves from producer to consumer to decomposer, and back to the atmosphere through rapid cycling Human Impacts on the Carbon Cycle Mining fossil fuels Clearing away vegetation (this increases the amount of CO2 in the atmosphere) ○ Most CO2 released into the air eventually becomes dissolved in the ocean, but oceans only hold so much! The Greenhouse Effect: The gases trap the heat from the Sun and warm Earth’s surface ○ A certain amount is essential for survival on Earth. Without them, the average temperature on Earth would be 15°C to -18°C. Global warming: CO2 levels have tripled over the last 30 years due to increased production and industrialization Albedo: Snow and ice have a high albedo, melting means more light and radiation which increases temperature on Earth The Carbon Cycle Largest carbon sink in the biosphere are Earth’s oceans Water in ocean contains billions of tonnes of dissolved CO 2 The Nitrogen Cycle Nitrogen makes up 78.1% of Earth’s atmosphere It is required by organisms to make proteins and DNA However, atmospheric nitrogen (N2) can’t be used for this purpose ○ Must therefore be converted to ammonia (NH3) through a process called nitrogen fixation The Nitrogen Cycle Bacteria convert nitrogen gas (N2) into ammonia (NH3) through nitrogen fixation This ammonia is then converted into nitrates (NO3), which can then be used by plants Animals can only obtain nitrogen by eating plants Excess nitrates in the soil are converted back into atmospheric nitrogen by anaerobic bacteria, this process is called denitrification The Nitrogen Cycle The Sulfur Cycle Sulfur-containing compounds are found primarily in the ground in the form of rocks, coal, and oil. 1. Through volcanic activity, geologic uplift, or the mining & burning of fossil fuels, sulfur is then released into the air in the form of sulfur dioxide (SO 2) 2. Sulfates do not stay in the air for very long; they are returned to the earth through acid precipitation (caused primarily by the burning of fossil fuels) 3. Bacteria in the soil then allow the sulfates to be used by plants. These sulfur compounds return to the soil once the plants die and decompose 4. Some of the sulfur returned to the ground is also re-deposited in rocks, and the cycle continues Acid Decomposition Acid deposition (or acid rain): Occurs when slow-cycled sulfur deposited in rocks, oil, or coal is released into the atmosphere SO2 reacts with CO2 and H2O(g) (water vapor) in the atmosphere to form sulfuric acid and sulfurous acid ○ Results in acid decomposition, therefore returning sulfur to oceans and soils ○ Acid can leach nutrients from soil and change water pH, making it impossible for organisms to survive The amount of sulfur that is released due to human activities (such as the burning of fossil fuels) is far greater than the amount that is released through natural processes (such as weathering or volcanic activity) The Sulfur Cycle Sulfur is an important component of proteins and vitamins Plants and algae incorporate sulfur into their tissues and cells ○ When dead, decomposers return sulfur to soil/atmosphere Many bacteria use sulfur components in photosynthesis and some types of cellular respiration ○ Bacteria are an essential part of the sulfur cycle ○ Release sulfur that is in forms that can’t be used by the organisms Sulfur in the Atmosphere The distinctive “rotten egg” smell of sulfur is caused by decomposers who are hard at work producing hydrogen sulfide gas H2S can be dangerous in high concentrations… thankfully, it’s easy to detect because of the smell The Phosphorus Cycle Phosphorus is required for bones, teeth, and cellular materials, such as DNA, phospholipids, and ATP, but is in limited quantities in the environment Doesn’t cycle in the atmosphere, but is found in soil and H 2O Can be added to crops as fertilizer Large amounts of phosphorus are stored in rocks and released during weathering and erosion The Phosphorus Cycle The phosphorus cycle links to the water cycle due to: Percolation: The movement of a liquid through a porous material, such as soil particles ○ Eventually, water fills the lower levels of soil (sand, gravel, bedrock, clay) Leaching: The removal of soluble minerals by percolation The Phosphorus Cycle Animals obtain phosphorus by consuming foods such as milk, grains, and meat Plants use phosphorus in the form of phosphate (PO43−) from H2O Most of the world’s phosphorus is locked in rock and sediments causing limited growth of plants Large amounts of nitrates & phosphates can be harmful, leading to the overgrowth Algal bloom in a lake. of algae, called an algal bloom Eutrophication Eutrophication: Overabundance of nutrients, namely phosphorus, that results in explosive growth of plants and algae ○ Organisms such as algae take over, resulting in an algal bloom Algal bloom: Prevents sunlight from reaching organisms deeper in the water As large amounts of deep-water organisms die, process of decaying results in decreasing levels of oxygen (hypoxia) Lack of oxygen leads to death of more living organisms within all areas of the lake and subsequently, increases population of decomposers Energy and Matter Transfer Energy is involved in each step of these cycles Water is a necessary component of these cycles, so biogeochemical cycles are linked together through energy and water