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13. 4 Food Chains And Food Webs KEY CONCEPT Food chains and food webs model the flow of energy in an ecosystem. Is this a food chain or food web? What can we infer from this diagram?
13. 4 Food Chains And Food Webs A food chain is a model that shows a sequence of feeding relationships. • A food chain links species by their feeding relationships. • A food chain follows the connection between one producer and a single chain of consumers within an ecosystem. GRAMA GRASS DESERT COTTONTAIL HARRIS’S HAWK What do you notice about the arrows? Which organism is at the top of this food chain?
13. 4 Food Chains And Food Webs • – – – Consumers are not all alike. Herbivores eat only plants. Ex. Rabbit Carnivores eat only animals. Ex. Lion Omnivores eat both plants and animals. Ex. Bear Detritivores eat dead organic matter. Ex. earthworm Decomposers are detritivores that break down organic matter into simpler compounds. Ex. Bacteria, fungi carnivore Decomposer Detritivore
13. 4 Food Chains And Food Webs • Specialists are consumers that primarily eat one specific organism or a very small number of organisms. • Changes in food web can cause extinctions • Ex. Florida snail kites feed mainly on apple snails. Water quality in the FL Everglades has declined and with it, Everglade Snail Kite populations have as well. Why? • Generalists are consumers that have a varying diet. • Changes in the environment/food web are easier to handle since they have alternative means for food
13. 4 Food Chains And Food Webs • Trophic levels are the nourishment levels in a food chain. – Primary consumers are herbivores that eat producers. – Secondary consumers are carnivores that eat herbivores. – Tertiary consumers are carnivores that eat secondary consumers. – Omnivores, such as humans that eat both plants and animals, may be listed at different trophic levels in different food chains.
13. 4 Food Chains And Food Webs Construct a simple food web in your notebook.
13. 4 Food Chains And Food Webs Food web or food chain? Justify your answer.
13. 4 Food Chains And Food Webs A food web shows a complex network of feeding relationships. • An organism may have multiple feeding relationships in an ecosystem. • A food web emphasizes complicated feeding relationships and energy flow in an ecosystem. Which creature consumes the most in this web? The least? Do any have no predator in this web?