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Understanding Ecosystems: Trophic Structures, Energy Flow, and Human Impact

This lecture explores the intricate relationships within ecosystems through the lens of trophic structures and energy flow. We delve into primary producers, consumers, and decomposers, explaining food chains and webs as pathways for energy transfer. Key concepts include primary productivity (GPP and NPP), ecological efficiency, and biomass pyramids. Additionally, we examine biogeochemical cycles and the impact of human activities, including biological magnification, greenhouse effects, and rainforest destruction. Understanding these principles is essential for comprehending ecosystem dynamics and conservation.

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Understanding Ecosystems: Trophic Structures, Energy Flow, and Human Impact

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  1. Lecture #24 Date ________ • Chapter 54 ~ Ecosystems

  2. Relationships, I • Trophic structure / levels~ feeding relationships in an ecosystem • Primary producers~ the trophic level that supports all others; autotrophs • Primary consumers~ herbivores • Secondary and tertiary consumers~ carnivores • Detrivores/detritus~ special consumers that derive nutrition from non-living organic matter • Food chain~ trophic level food pathway

  3. Relationships, II • Food webs~ interconnected feeding relationship in an ecosystem

  4. Energy Flow, I • Primary productivity (amount of light energy converted to chemical energy by autotrophs) •Gross (GPP): total energy •Net (NPP): represents the storage of energy available to consumers •Rs: respiration • NPP = GPP - Rs • Biomass: primary productivity reflected as dry weight of organic material • Secondary productivity: the rate at which an ecosystem's consumers convert chemical energy of the food they eat into their own new biomass

  5. Energy Flow, II • Ecological efficiency: % of E transferred from one trophic level to the next (5-20%) • Pyramid of productivity: multiplicative loss of energy in trophic levels • Biomass pyramid: trophic representation of biomass in ecosystems • Pyramid of numbers: trophic representation of the number of organisms in an ecosystem

  6. Chemical Cycling • Biogeochemical cycles: the various nutrient circuits, which involve both abiotic and biotic components of an ecosystem • Water • Carbon • Nitrogen • Phosphorus

  7. Human Impact • Biological magnification: trophic process in which retained substances become more concentrated at higher levels • Greenhouse effect: warming of planet due to atmospheric accumulation of carbon dioxide • Ozone depletion: effect of chlorofluorocarbons (CFC’s) released into the atmosphere • Rainforest destruction • Cause: Overpopulation?

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