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Nutrient Cycling and Retention (2).docx

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McMaster University
Kim Dej

November 19 , 2012 Biology 2F03: Fundamental and Applied Ecology Nutrient Cycling and Retention (2) Question - what is nitrogen needed for? - Which organisms can obtain nitrogen directly from air - Plants get nitrogen from soil, nitrogen that is dissolved in water Nitrogen: main pathways and storage - needed for amino acids, RNA, DNA, chlorophyll, haemoglobin - main storage is in the atmosphere - air>soluble compounds: nitrate, ammonia>plants>animals>sediments (including organic)>denitrification goes back into the atmosphere - N fixers (bacteria free and symbiotic, blue-green algae), lightning, synthetic fertilizers - Lightning has so much energy that as it passes through the nitrogen atmosphere it binds to oxygen and bonds to create nitrate ion picked up by plants, or can be reduced to ammonia and picked up by plants - Mean biotic life ~600 years - Additional chemical details:  Ammonia based or nitrogen based fertilizers based on the type of crop Bloom due to nitrogen (Oct 2000) - remote sensing of green pigments permits tracking of algal blooms in the ocean - such blooms result from land originated nutrient, mostly N Question - which element is most abundantly used: carbon - and how is it lost from biota? Carbon cycle: main points Carbon cycle: main points - building material of life: lost via respiration - cycles fast in organic molecules 2nd CO Building material of life: lost via re-piexists in manyheat balance  in water: carbonate – exchanges with plants and atmosphere Cycles fast in organic molecules and CO  in2rocks: calcium carbonate – very slow recycling via volcanic activity, uplifting and erosion  humans add a lot: from fossil fuels; processing of plants and animals; Exists in many forms: accelerated rock weathering in water: carbonate – exchanges with p-animpact on heat balance of atmosphere atmosphere in rocks: calcium carbonate – very slow recycling via volcanic activity, uplifting and erosion Humans add a lot: from fossil fuels;Decomposition Details in Fig. 20.4 processing of plants and animals; - respiration is the business of returning CO to the atmosphere and involves a accelerated rock weathering lot of decomposition 2 - re-use of P, N, C by a new batch of creatures requires decomposition (or respiration) - decomposition depends on water availability, decomposition is not good if there’s no water - how do we know it depends on water availability: if you bury a bag of leaves in a dry forest, there is a 62% mass loss after 24 months, in a wet forest, there is a 94% mass loss in 24 months, more irregularity
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