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Ecology lec 6 (coping with energy variation) summary.docx

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Western University
Biology 2483A
Hugh Henry

Ecology Lec 6- Coping with Energy variation Autotroph- Energy from sunlight (photosynthesis) or from inorganic compounds (chemosynthesis) - Convert energy to chemical energy in bonds of organic molecules Heterotroph- Energy from consuming organic compounds originating from autotrophs - some hetero’s consume nonliving organic matter - Parasites & herbivores- consume live hosts (not necessarily kill them) - Predators- consume live hosts Holoparasites- plants with no photosynthetic pigment, get E. from other plants (e.g wrap around) - e.g. dodder- reduces biomass of agriculture Hemiparasite- photosynthetic, but gets water, nutrients & some E. from another plant Sea slugs- get E. from separated functional chloroplasts from algae they eat. Photosynthesis- E. from sunlight to take up CO2 & make organic compounds (most avail E. on earth) Chemosynthesis- E. from inorganic compounds used to make carbs - important in nutrient cycling bacteria & hydrothermal vents Photosynthesis- 2 major steps - Light rxn: light used to split H2O & provide electrons to make ATP & NADPH - Dark rxn: CO2 fixed into carbs (Calvin cycle) Light response curve- Saturation point: when photosynthesis no longer increases as light increases Compensation point: where CO2 uptake = CO2 loss by resp. Net Photosynthesis = 0. Plants acclimatize to low light by shifting the light curve; morphological & physiological change - Low light grown= Saturates at lower photosynthetic rate, Compensation point at lower light intensity - High light grown= thicker leaves, more chloroplasts (enough energy to invest in thicker leaves) Tradeoff- Low water availability, close stomata to preserve water, but also limit CO2 supply (energy) - Closed stomata- no CO2, no calvin cycle, energy accumulates & damages (use carotenoid pig.) Enzymes- diff climates = diff enzymes temp. optima - acclimatize by synthesizing diff isozymes Nutrients- Most N is associated with rubisco (& other enzymes); ↑N = ↑photosynthesis - But N supply is low, & increasing N in leaf = more herbivores will like to eat them Rubisco- 2 competing rxns- Carboxylase rxn- Photosynthesis - Oxygenase rxn- Photorespiration- O2 taken up, carbs broken, CO2 released - Good-
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