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Energy Flow in Ecosystems Environmental Science Fall 2009 Life Depends on the Sun Energy enters an ecosystem when a plant uses sunlight to make sugar (carbohydrates) This process is called photosynthesis 6CO2 + 6H2O + energy C6H12O6 + 6O2 Plants, algae, and some bacteria use sunlight, carbon dioxide, and water to produce sugar and oxygen. Producers Sunlight is the ultimate source of energy for most life on earth Organisms that convert sunlight into chemical energy are called producers Also called autotrophs OR chemotrophs Chemotrophs the exception to the rule – they are found at the bottom of the ocean where no sunlight reaches Bacteria use hydrogen sulfide to create energy Other organisms feed off the bacteria Consumers Organisms that consume other organisms for energy are consumers (heterotrophs) Types of heterotrophs Herbivores – eat only producers Carnivores – eat only other consumers Omnivores – eat producers and consumers More consumers… Detrivores – also called scavengers Eat animal remains and other dead matter Decomposers break down organic matter Include bacteria and some fungus Cellular Respriation The process in which cells use sugar to create energy is called cellular respiration C6H12O6 + 6O2 6CO2 + 6H2O + energy Cells use glucose (sugar) and oxygen to produce carbon dioxide, water, and energy. Cellular respiration occurs inside the cells of most organisms Energy Transfer Each time one organism eats another, energy is transferred Food chains Show one-way flow of energy in an ecosystem Each step on the food chain is called a trophic level Feeding Relationships Food webs Includes more organisms and multiple food chains linked together Trophic Levels Visualization of the loss of energy from one trophic level to the next Often shown as an pyramid Shows relative energy movement in an ecosystem Only 10% of the energy moves to the next level Biomagnification can lead to biomagnification – the concentration of toxic substances in organisms as you move up trophic levels Pollution Ex. DDT and birds of prey; mercury in tuna and sharks