Biogeochemical Quest Answer Key

Biogeochemical Cycles 1. Water Cycle Introduction Precipitation, evaporation, and condensation are all terms that you recognize, but what do they really mean? They are all part of the water cycle, which is a complex process that not only gives us water to drink, and food to eat, but also helps our plants grow. Only about 3% of the Earth’s water is fresh, and 1% of that water can be used for many human purposes. Why can’t we use the other 2% of the fresh water found on the Earth? What about the other 97% of the water found in the world? To find these answers and to discover more, come along for an interactive journey through the water cycle! Questions  Evaporation is the process where a liquid changes from its liquid state to a gas state.  Why is evaporated water so clean? The impurities are left behind  Condensation occurs when a gas Liquid .  Condensation is the opposite of evaporation  are right, When the temperature and pressure the small droplets of water in clouds form larger droplets and precipitation occurs.  Using the terms "evaporation", "condensation", and "precipitation", explain the water cycle in your own words. Liquid water becomes a gas during evaporation. The gas rises and cools and turns back into water through condensation. When the droplets are big enough it will fall back to earth through precipitation.  What factor is most important in determining whether water is a solid, liquid, or gas? Temperature  Is the amount of water on Earth always changing or is it a constant amount? Constant  Explain surface runoff. Precipitation that is not absorbed by the ground runs across the surface and into rivers and eventually the ocean 2. Carbon/Oxygen Cycle Introduction Carbon is an element that is found in all organisms, fossil fuels, soil, the ocean, and the atmosphere. We take part in the carbon cycle by breathing CO2 into the air; autotrophs participate by removing atmospheric CO2 for use in building leaves, stems and other organs is changed into a . through the process of photosynthesis. As we burn more and more fossil fuels, such as oil and coal, we release large amounts of carbon dioxide into the atmosphere- more than can be removed by oceans and photosynthetic organisms. Within the atmosphere, this extra CO2 traps heat. As more CO2 accumulates, the Earth becomes warmer through a process known as the greenhouse effect. Questions  Why do plants and other photosynthetic organisms need CO2 from the atmosphere? Carbon is needed to build leaves, stems and other organs and to make carbohydrates  How can carbon move from “land” to bodies of water? Plants and animals release carbon back into the soil when they decay and this can enter the water systems through runoff  Describe the way human impact has leads to increased levels of CO 2 in the atmosphere. Burning of fossil fuels has lead to an increase in CO2  What is the greenhouse effect? Some gases in the atmosphere like CO2 trap the heat from the sun and keep us warm. Increased CO2 due to fossil fuel use has lead to an increase in temperature on earth  How much carbon is stored in the atmosphere as CO2? 0.04%  What is detritus? Any decaying organic matter  How can human use of fossil fuels be detrimental to the environment? Increased co2 increases temperature which upsets natures balance  Describe one of the many paths a carbon molecule can take through the carbon cycle. Staring in the atmosphere, carbon can be absorbed by a plant through photosynthesis. The plant could die and become buried underground for thousands of years and become a fossil fuel which would then be pumped up and burned in a car are returned to the atmosphere 3. Nitrogen Cycle Introduction The nitrogen cycle represents one of the most important nutrient cycles found in terrestrial ecosystems. Nitrogen is used by living organisms to produce a number of complex organic molecules like amino acids, proteins, and nucleic acids. The majority of nitrogen is found in the atmosphere, where it exists as a gas (mainly N2). Other major reserves of nitrogen include organic matter in soil and the oceans. Despite its large quantity in the atmosphere, nitrogen is often the most limiting nutrient for plant growth. This problem occurs because most plants can only take up nitrogen in two solid forms: ammonium ion (NH4+ ) and the ion nitrate (NO 3- ). Specialized bacteria “fix” nitrogen, converting it to a form that can be used by organisms. By fixing nitrogen, these bacteria are a critical link between atmospheric nitrogen and life on Earth. Questions How is nitrogen important in our lives? DNA, RNA and protiens Why are nitrogen-fixing bacteria contributions to the nitrogen cycle so important? Without them, nitrogen would be stuck in the atmosphere in a form that we cannot use  Nitrogen gas makes up 78% of the air we breathe.  Nitrogen fixing bacteria Ammonia (NH3) converts Nitrogen gas (N2) for organisms to use. to  Another useable form of nitrogen, NH4+ can be converted to by Nitrifying Bacteria for organisms to use. Nitrates and Nitrites and Nitrates and Nitrites  Plants use both Ammonia incorporate nitrogen into DNA, protein, and other molecules. to  Explain how animals get their needed amounts of nitrogen. Eating plants and other animals  Explain how nitrogen cycles through the land and ocean ecosystems. The growth death and decomposition of plants and animals releases nitrogen which then enters river systems  How does the human impact of fertilizers impact the nitrogen cycle? Nitrogen fertilizers runoff the farms into rivers and oceans which leads to excess nitrogen and algal blooms which causes a drop in oxygen levels and dead zones in the water system  Once in plants and animals, explain how does nitrogen return to the atmosphere? When plants and animals die, dec and denitrifying bacteria convert 4. Phosphorous Cycle Introduction Phosphorus is an important chemical for plants and animals. It is part of DNA, certain fats in cell membranes, bones, teeth and shell of animals. Phosphorus circulates through water, the Earth's crust, and living organisms. It is not in the atmosphere and is most likely to enter food chains following the slow weathering of rock deposits. Some of the released phosphates become dissolved in soil water which is taken up by plant roots. Phosphorus is therefore the main limiting factor for plant growth in most soils and aquatic ecosystems. Animals obtain phosphorus by eating plants and/or herbivores. Dead organisms and animal wastes return phosphorus to the soil, to streams, and eventually to ocean floors as rock deposits. Websites: You will have to look these questions up yourself and find your own websites. Questions  Explain why phosphates are a critical part of life. Phosphates are important for DNA, teeth and bones  How is the phosphorus cycle different from other biogeochemical cycles? Explain. Phosphorus cycle does not have a gas phase rock.  The largest reservoir of phosphorus is in sedimentary  Explain how phosphorus travels through the cycle from rock to omnivores. Phosphorus in rocks is released when it rains through weathering. Plants absorb the phosphorus and the plants are then eaten by consumers  Why are excessive concentrations of phosphorus sometimes considered a pollutant? When too much phosphorus enters the rivers and oceans it causes many weedy and plankton species to grow excessively which uses up al of the oxygen and suffocates the organisms. This s called eutrophication  How do humans contribute to these excessive levels of phosphorus? Too much farm fertilizer, cutting down tropical rain forests and some laundry detergents  Phosphorus is mainly stored in the rocks .  How does the soil-based view of the phosphorus cycle compare/contrast with the global-view of the phosphorus cycle? In the soil based view, phosphorus is weathered from rocks, enters the soil and is absorbed by plants. In the global view, the phosphorus enters the rivers and then the oceans and is spread around the globe