Environmental Problems, Their Causes, and Sustainability 1

Figure 4-15 Feeding relationships between producers,consumers, and decomposers.Soil and WaterNutrientsBreak downorganic matterfor recyclingDecomposers(bacteria, fungi)Producers(plants andphytoplankton)ConsumersFeeding onLiving OrganismsPrimaryConsumersFeeding onProducers(rabbits, zooplankton)Secondaryand HigherConsumers Feeding onOther Consumers(foxes, turtles, hawks)ConsumersFeeding onDead Organismsor the Organic Wastes ofLiving OrganismsScavengers(vultures, hyenas)A few producers, mostly specialized bacteria,can convert simple compounds fromtheir environment into more complex nutrientcompounds without sunlight. Thisprocess is called chemosynthesis.All other organisms in an ecosystemare consumers, or heterotrophs(“other feeders”) thatget the energy and nutrientsthey need by feeding on otherorganisms or their remains.Decomposers (mostly certaintypes of bacteria and fungi)are specialized consumersthat recycle organic matter inecosystems. They do this bybreaking down (biodegrading)dead organic material orDetritus Feedersdetritus (“di-TRI-tus”, meaning“debris”) to get nutrients.(crabs, termites)This releases the resultingsimpler inorganic compoundsinto the soil and water, where producerscan take them up as nutrients.Life works in circles.Figure 4-15 shows the feeding relationshipsamong producers, consumers feeding onlive or dead organisms or their wastes, and decomposers.Trace the flows of matter and energy in this diagram.Some consumers, called omnivores, play dualroles by feeding on both plants and animals. Examplesare pigs, rats, foxes, bears, cockroaches, and humans.When you had lunch today were you an herbivore, acarnivore, or an omnivore?Detritivores consist of detritus feeders and decomposersthat feed on detritus. Hordes of these wasteeaters and degraders can transform a fallen tree trunkinto a powder and finally into simple inorganic moleculesthat plants can absorb as nutrients (Figure 4-16,p. 66). In natural ecosystems, there is little or no waste.One organism’s wastes serve as resources for others,as the nutrients that make life possible are recycledagain and again. In nature waste becomes food.Producers, consumers, and decomposers use thechemical energy stored in glucose and other organiccompounds to fuel their life processes. In most cellshttp://biology.brookscole.com/miller1465