Functioning of Ecosystems
Level 11 Guiding Question: |
What systems in the environment allow Agroecology to function properly and why are they vital to our existance?
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Ecosystem function refers to the dynamic processes occurring within ecosystems: the movement of matter and energy and the interactions and relationships of the organisms and materials in the system. It is important to understand these processes in order to address the concepts of ecosystem dynamics, efficiency, productivity, and development, especially in agroecosystems where function can determine the difference between the success and failure of a particular crop or management practice.
The two most fundamental processes in any ecosystem are the flow of energy among its parts and the cycling of nutrients.
Gliessman, Stephen R.. Agroecology: The Ecology of Sustainable Food Systems, Third Edition, 3rd Edition. CRC Press
Level 11 Investigations
Flow of EnergySolar energyis fixed by the phototrophs, called primary producers, like green plants. The energy is passed on from trophic level to trophic level and each time about 90% of the energy is lost, with some being lost as heat into the environment (an effect of respiration) and some being lost as incompletely digested food. Therefore, primary consumers get about 10% of the energy produced by autotrophs, while secondary consumers get 1% and tertiary consumers get 0.1%. This means the top consumer of a food chain receives the least energy, as a lot of the food chain's energy has been lost between trophic levels. This loss of energy at each level limits typical food chains to only four to six links (producers,pirmary, secondary and tertiary consumers, decomposers).
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Carbon CycleThe carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, geosphere, hydrosphere, and atomsphere of the Earth. Along with the nitrogen cycle and the water cycle, the carbon cycle comprises a sequence of events that are key to making the Earth capable of sustaining life; it describes the movement of carbon as it is recycled and reused throughout the biosphere by the processes of photosyntheisis and respiration.The global carbon budget is the balance of the exchanges (incomes and losses) of carbon between the carbon reservoirs or between one specific loop (e.g., atmosphere <-> biosphere) of the carbon cycle.
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Nitrogen CycleThe nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of
Earth's atomsphere (78%) is nitorgen, making it the largest pool of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems. The nitrogen cycle is of particular interest to farmers because nitrogen availability can affect the rate of key ecosystem processes, including primary production and decomposition. |
Investigation 1: Energy Flow
Investigation 2: Carbon Cycle (Plant Respiration and Photosynthesis)
Read the instructions in the left hand column and collect all the equipment and supplies before you watch the video. After you have read the lab procedures please watch the the video as the presentor demonstrates how the lab is to be organized and carried out. Please ask the instructor if you have any questions before you begin the experiment.
Carbon dioxide is necessary for the process of photosynthesis to occur, and it is an end product of cellular respiration. In plants, CO2 is captured during photosynthesis and converted into carbohydrates. These energy-rich storage molecules are then available to the plant that made them or to organisms that eat the plants. These organisms convert the carbohydrate molecules to glucose molecules that they then use to produce usable energy molecules, such as adenosine triphosphate (ATP), which are needed for the organism to survive. The process by which the glucose molecules are converted to ATP is cellular respiration. These two processes are also very important to the carbon cycle.
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Investigation 3: Nitrogen Cycle (Soil and tissue testing)In this investigation we will explore how to take and accurately record nitrogen levels in plant tissues and soil. Why it is important will also be discusssed. Read the following instructions (on the right hand column) carefullly and take 3-5 soil and tissues samples and post them on the BLOG site, please include if the nitrogen is deficient or abundant and what will you have to apply or do to correct the problem.
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Instructions on how to use test vials to determine nitrogen level in soil and plant tissues. |
LaMott Soil Test Instructions
Level 11 Video
This video is about the relationship between photosynthesis and respiration and illustrates how both processes are important to the Carbon Cycle.
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The above video helps explain what happens in the dark and light cycles of photosynthesis.
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Level 11 Elaborate
Watch the Nitrogen Cylce animation and draw and label the phases and chemical equations that take place in Nitrogen Cycling in your "Know Books". This will help you complete your website on Agroecology.
Level 11 Review
Read the website below to review the Nitrogen Cycle. After you have completed the "Reading" section please proceed onto the "Quiz" seciton and practice for the Unit Summary. Don't forget to have the quiz scored online to see how you have done.
Level 11 Summary