Food Chains Food Webs Food Pyramids March 30

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Food Chains, Food Webs & Food Pyramids March 30, 2011

Food Chains, Food Webs & Food Pyramids March 30, 2011

Review from last day • Producer: makes its own food (e. g. , plants)

Review from last day • Producer: makes its own food (e. g. , plants) • Consumer: feeds on other organisms (e. g. , humans)

Scavenger • Do not kill their own food • Eats abandoned carcasses (e. g.

Scavenger • Do not kill their own food • Eats abandoned carcasses (e. g. , vultures)

Food Chains • Feeding relationships that describe eating patterns of organisms • Placement of

Food Chains • Feeding relationships that describe eating patterns of organisms • Placement of the organism in the food chain depends on what role they play in the ecosystem

Food Chains (con’t) • Each step in a food chain is called a trophic

Food Chains (con’t) • Each step in a food chain is called a trophic level • Approximately 90% energy loss at each step • Any change in one level affects all other levels

Food Chain Example Organism Role Grasshopper Frog Snake Hawk Producer Primary Consumer Secondary Consumer

Food Chain Example Organism Role Grasshopper Frog Snake Hawk Producer Primary Consumer Secondary Consumer Tertiary Consumer Top Consumer Trophic Level 1 st 2 nd 3 rd 4 th 5 th

Practice Drawing Food Chains • In an alpine meadow, clover is eaten by a

Practice Drawing Food Chains • In an alpine meadow, clover is eaten by a ground squirrel. The ground squirrel is eaten by a grizzly. Create the appropriate food chain. • Clover Ground Squirrel Grizzly

Food Webs • Most feeding relationships are more complex than just a single chain

Food Webs • Most feeding relationships are more complex than just a single chain because: 1) Most organisms eat more than 1 type of food 2) Most organisms are eaten by more than 1 type of consumer • Food webs show many connected food chains

Food Web Example

Food Web Example

Practice Food Web • Arrange these food chains into a single food web 1)

Practice Food Web • Arrange these food chains into a single food web 1) Grass Rabbit Hawk 2) Clover Rabbit Fox 3) Grass Mouse Snake Hawk Fox Snake Mouse Grass Rabbit Clover

Food Pyramids • Show the quantity of organisms involved • There are three types

Food Pyramids • Show the quantity of organisms involved • There are three types 1) Pyramid of Numbers 2) Pyramid of Biomass 3) Pyramid of Energy

Pyramid of Numbers • Shows the number of organisms at each trophic level •

Pyramid of Numbers • Shows the number of organisms at each trophic level • Easy to construct • Not useful to show amount of energy because it does not take into account the sizes of individual organisms

Pyramid of Biomass • Shows total mass of the organisms at each trophic level

Pyramid of Biomass • Shows total mass of the organisms at each trophic level • Takes number and size into consideration • Good estimate of energy in ecosystem • Does not take reproductive rates into consideration • Reduction of biomass in pyramid occurs because: – Not everything in the lower levels gets eaten – Not everything that is eaten is digested – Energy is always being lost as heat weasels

Pyramid of Energy • Shows available energy at each level • Most accurate but

Pyramid of Energy • Shows available energy at each level • Most accurate but very to difficult to model • Energy is lost as heat along the food chain • Energy decreases as you move up the food chain