Lect. 06 nutrient-energy web

Lect. 06 nutrient-energy web - Energy and Carbon Sources...

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Unformatted text preview: Energy and Carbon Sources • Organisms classified by trophic (feeding) levels. – Autotrophs use inorganic carbon and energy. • Photosynthetic : CO 2 = carbon source, sunlight = energy. • Chemosynthetic : CO 2 = carbon source, inorganic molecules = energy – Heterotrophs use organic molecules for carbon and energy. Most of Biosphere is Solar - Powered • Light propagates as waves and photons. – Infrared (IR) Long-wavelength, low energy. – Ultraviolet (UV) Short wavelength, high energy. • Can destroy biological machinery. – Photosynthetically Active Radiation (PAR) • Between two extremes. Solar - Powered Biosphere • Chlorophyll absorbs light as photons. • PAR measured as… – photon flux density. • # of photons per m 2 per second. • Landscapes, water, and organisms can change amount and quality of light. Photosynthetic Pathways • C 3 Photosynthesis – Used by most plants and algae. – CO 2 + recycled 5-C sugar = 3 carbon acid (X2) • To fix carbon, plants open stomata to let in CO 2 . – Water escapes = stress in arid environments. Photosynthetic Pathways • C 4 Photosynthesis – More efficient at fixing CO 2 . • Need fewer stomata open than C3s. – Lose less H 2 O....
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Lect. 06 nutrient-energy web - Energy and Carbon Sources...

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