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energy and nutrients.docx

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McMaster University
Kim Dej

September 26 , 2012 Biology 2F03: Fundamental and Applied Ecology Energy and nutrients (1) Energy and nutrients - sources of energy: light, organic and inorganic molecules - rate of energy acquisition is limited - optimal foraging theory helps explain choice and location of food items Question - how on earth life is being fed Energy use and kingdoms - how energy is obtained? - Heterotrophic: uses organic matter, bacteria, protest, plants, fungi, animals - Photosynthetic: uses light, bacteria, protest, plants, animals - Chemotrophic: consumes molecules, bacteria - Who captures the most? - What is the message here: plant and protest seem to be doing more photosynthetic acquisition of energy and are at the foundation - What is PAR: photosyntectically active radiation, energy that arrives on earth which pigments can use to convert to organi2 matter, measured by photon flux, the number of photons striking 1m /second.) Visible light (400-700 nanometers) carries ~45% of solar energy at sea level. Three pathways for using this energy:  C3 (photosynthesis) – C3 plants  C4 – C4 plants  CAM (crassulacean acid metabolism) - Many animals use symbiotic algae in there tissues to absorb energy, photosynthesize Question - what ecological implications do these biochemical pathways of photosynthesis have? C vs C plants 3 4 - C4plants use lower concentration of CO : 2  Can afford to open stomata less than C pla3ts  Conserve water  Do better in environments where water is limited - the two pathways involve different number of carbon atoms in the initial photosynthate (3 vs 4): C p4ants are better in drier and hotter environments and may be moving northward in Canada - CAM plants combine day and night phases with C pathway – very efficient 3 water use - CAM plants open their stromata and take in CO at ni2ht when temperatures are lower and humidity higher: water potential between plant and air is much less during the day as a result they lose much less water - CAM plants close their stomata during the day when temperature are high and humidity is low, therefore they grow much slower Question - are needs for nitrogen different between plants and animals? If yes, why? - Need proteins, need nitrogen - Yes - Animals need more because we need to move, need proteins, activities that animals engage in that plants don’t therefore need more nitrogen Why does nitrogen take center stage? - can you get nitrogen from the air: no plants cannot get it from the air - what is it for: proteins - so how do we get it: from plants, not very efficient, eating other animals easy way of getting nitrogen - do all organisms contain the same amount of nitrogen: plants d
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