Ch 14 covers ecosystem structure and function — producers, consumers, decomposers, energy flow, food chains/webs, ecological pyramids, nutrient cycling, productivity, and ecological succession.
Energy flow: unidirectional (sun → producers → herbivores → carnivores). 10% law (Lindeman): only ~10% energy transfers to next trophic level. Food chains: grazing (starts with producers) and detritus (starts with dead organic matter). Food web: interconnected food chains. Ecological pyramids: of number (can be inverted — tree ecosystem), biomass (inverted in aquatic), energy (always upright).
GPP (Gross Primary Productivity) = total photosynthesis. NPP = GPP − Respiration (available to consumers). Decomposition: fragmentation → leaching → catabolism → humification → mineralisation. Nutrient cycling: carbon cycle (photosynthesis/respiration, fossil fuels), nitrogen cycle (fixation by Rhizobium, nitrification, denitrification), phosphorus cycle (sedimentary, no gaseous phase).
Primary succession: starts on bare rock/land (xerosere: lichen → moss → herbs → shrubs → trees). Secondary succession: starts where community existed (faster, soil present). Climax community: stable, self-sustaining. Hydrarch: in water → land. Xerarch: on dry land.
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The pyramid of energy is always upright because at each trophic level, a significant amount of energy (about 90%) is lost as heat through respiration and metabolic activities. Only about 10% is passed to the next level. Since energy is always lost and never gained at successive levels, the bars always decrease from bottom to top, making the pyramid invariably upright. This follows the laws of thermodynamics.
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