Science 9 Notes 1.4_ Biogeochemical Cycles.pdf

Unit 1 Ecology Science 9 Mr. Yeo 2023-2024 Biology STATEMENT OF INQUIRY FOR UNIT 1 ▸ Human interactions with natural systems can have global consequences. KEY CONCEPT: Systems RELATED CONCEPTS: Interactions, Consequences GLOBAL CONTEXT: Globalization and Sustainability Biogeochemical Cycles Recall t...

Unit 1 Ecology Science 9 Mr. Yeo 2023-2024 Biology STATEMENT OF INQUIRY FOR UNIT 1 ▸ Human interactions with natural systems can have global consequences. KEY CONCEPT: Systems RELATED CONCEPTS: Interactions, Consequences GLOBAL CONTEXT: Globalization and Sustainability Biogeochemical Cycles Recall that matter is neither created nor destroyed; but it can transform and be passed on. Biogeochemical cycles: how water, carbon, nitrogen and phosphorus pass from the physical environment to living organisms. Life Earth Atoms and molecules There are 4 essential biogeochemical cycles- the water cycle, the carbon cycle, the nitrogen cycle, and the phosphorus cycle. In order for these materials to be recycled, they must change states and transform! Death and decay also contribute to the biogeochemical cycles. As animals and plants die, bacteria and other decomposers break them down into raw elements, which can be absorbed by plants and then passed on to animals. What you should know for each biogeochemical cycle: The reservoirs (the “places” where each element is ”stored” at each stage of the cycle) Whether the reservoir is part of the geosphere, atmosphere, hydrosphere, or biosphere The form the element is stored in that particular reservoir (e.g. its state, or its chemical name) The specific processes that move the element between different reservoirs The Water (Hydrologic) Cycle All living things require water to survive. Water moves between the ocean, atmosphere and the land, cycling from water vapor to liquid water. Evaporation- liquid water returns to the atmosphere (vaporizes) Transpiration- evaporation of water from plants Water transforming from liquid to vapor Evaporation and transpiration occur during the daytime when the sun heats up the atmosphere. Together they are called evapotranspiration. As the atmosphere cools, the water vapor in the air condenses to form clouds, in a process called condensation. Precipitation- when the water droplets that form clouds become large enough, the water droplets fall to the earth (rain, sleet, snow). Once the water is returned to the earth, some of it is absorbed by plants through their roots. Other water continues to seep into the soil to become ground water in a process known as percolation. Runoff is surface water flowing on land that is eventually carried back to an ocean or lake. Water transforming from vapor to liquid How is water returned to the earth? How is water returned to the atmosphere? The Carbon Cycle Carbon is an essential element for all living things. Carbon is found in living tissues, rocks, the atmosphere, and the ocean. Less than 1% of the carbon found on earth participates in the carbon cycle. Carbon dioxide that is in the air or dissolved in water is used by photosynthesizing plants, algae and bacteria as a raw material to build organic molecules in their bodies such as glucose. Atmosphere à biosphere Carbon may return to the air in 4 ways: Respiration- all living organisms undergo cellular respiration. They use oxygen to break down food to obtain energy; CO2 is a byproduct of the reaction and released back into the atmosphere Decay (decomposition)- when organisms die, decomposers break down their bodies (made of lots of carbon) which forms CO2 that is returned to the atmosphere. Volcanic eruption- CO2 in the mantle (melted rocks) are released into the atmosphere during volcanic eruptions. Combustion- when carbon returns to the atmosphere through combustion or burning of fossil fuels. Combustion of fossil fuels releases CO2, which is a greenhouse gas. Carbon may enter the hydrosphere: Dissolution- large amounts of CO2 naturally dissolve into oceans and lakes. Too much dissolved CO2 makes water acidic and harmful to organisms such as shellfish and corals. When the water becomes saturated (maximum amount of CO2 dissolved), any excess CO2 will go into the atmosphere.. Weathering and Erosion- CO2 can react with rocks, especially in hot and wet conditions over a long period of time. This dissolves the CO2 and the rocks. When conditions dry up, the carbon will precipitate out of the solution (no longer dissolved) and form solid limestone (made of calcium carbonate). Carbon may enter the hydrosphere or geosphere: Burial- sometimes when organisms die, they sink to the bottom of the ocean or get submerged in waterlogged bogs and marshes. Decomposers cannot break down the dead organisms under these conditions so eventually their bodies get buried under sediment and the carbon locked in rocks. (Eventually, the high temperatures and pressures underground will transform the dead organisms into fossil fuels: coal, oil, natural gas. Any shelled remains of organisms will become limestone rock.) Carbon in rocks may be uplifted to the Earth’s surface, dug up, or sink even further into the mantle, where they melt, and can be brought up to the surface in volcanoes. combustion Why do only plants have CO2 going both into and out of them in this diagram? Where do fossil fuels come from? Why does deforestation increase CO2 in the air? Why does deforestation increase CO2 in the air? Removing trees: - Prevents trees from taking up CO2 for photosynthesis - This leads to more CO2 in the air Carbon dioxide + Water à Sugar + Oxygen The Nitrogen Cycle Nitrogen gas (N2) makes up 78% of the atmosphere, however most organisms are unable to use it in this form. Bacteria in the soil are very important because they can use atmospheric nitrogen, and fix it into compounds usable by other living things. Organisms need nitrogen to build proteins and DNA. Nitrogen fixation- nitrogen-fixing bacteria combine nitrogen from the atmosphere with hydrogen to make ammonia (NH3) in the soil. Ammonification- production of ammonia by bacteria during the decay of organic matter. Nitrification- production of nitrates (NO3-) and nitrites (NO2-) from ammonia. Nitrifying bacteria are responsible for nitrification. Plants can use nitrates and nitrites to make proteins. Assimilation- absorption of nitrogen into organic compounds by plants (absorbed through roots). Denitrification- conversion of nitrate to nitrogen gas by denitrifying bacteria, released nitrogen gas back into the atmosphere. Rhizobia are a species of bacteria that have a symbiosis with certain types of plants. They live in their roots and fix nitrogen into ammonia. The Nitrogen Cycle The Phosphorus Cycle Phosphorus is necessary to build DNA molecules. Though phosphorus is necessary, it is not very common in the biosphere and does not enter the atmosphere - it is locked into the land or water. Phosphorous is found in rocks and minerals in the soil. As these rocks gradually wear down, the phosphorus is released in the form of phosphates (PO43-) into the soil or water. When organisms die, decomposers in the soil or water break them down into raw elements, including phosphorus, which can then be reused. When plants absorb phosphate from the soil, it can be passed along from the plants/producers to the other trophic levels. The Phosphorus Cycle Phosphorus is also used in many fertilizers and detergents which can leak into the waterways. Phosphorus makes its way into our waterways from fertilizer runoff (human activity) and when it is released from phosphate-containing rock by weathering Nutrient Limitation The amount of available nutrients directly affects the primary productivity of an ecosystem. -(Primary productivity= rate at which producers produce energy). Sometimes an ecosystem is limited by a single nutrient that is very scarce or cycles slowly. This is called the limiting nutrient. Fertilizers are so popular because they contain 3 important nutrients: nitrogen, phosphorus and potassium. By using fertilizers, farmers can ensure that there are enough nutrients and their crops grow to their fullest potential.