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What are food webs? 0 In most food chains, each type of organism is eaten by more than one type of consumer-this can make organisms a part of more than one food chain 0 FOOD WEB- a network of food chains that have some links in common 0 Food webs are just several food chains put together. 0 A food web tells you a lot about the living things in an ecosystem 0 COMPETITION is the struggle between organisms for the same resource 0 Life in an ecosystem is a constant struggle How can food webs change? 0 When one population in a food web changes, ALL the other populations in the food web can be affected 0 When top carnivores are removed, prey populations are no longer controlled 0 Prey populations increase in number, they need more producers to supply them with food. 0 Page 149 Sea otters eat several animals in the kelp-forest but in the 1800s too many sea otters were hunted for their fur. The sea urchin population was soon out of control How do new organisms change food webs? 0 Humans can change ecosystems by introducing new species 0 EXOTIC SPECIES- are non-native plant and animal species that have been introduced into an environment 0 These plants and animals can threaten native species 0 In a food web, organisms compete with each other for food and other resources. When an exotic species is introduced into an ecosystems, it also competes with native species for resources ALL FOOD CHAINS MUST HAVE BALANCE!!!