FOOD CHAINS and FOOD WEBS - PowerPoint PPT Presentation

food chains and food webs n.
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FOOD CHAINS and FOOD WEBS

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  1. FOOD CHAINS and FOOD WEBS

  2. FOOD CHAINS Are designed to show the direction that energy flows from producers to top carnivores, in a simplified single pathway.

  3. 10% 10% 90% 90% ENERGY IN FOOD CHAINS energy passed to consumer Producer Primary consumer 2o consumer energy used to live 10% Rule: only 10% of the energy in an organism is passed on to the next trophic level

  4. 1 unit 100 units 10 units 10 units 100 units 1000 units

  5. FOOD WEBS & TROPHIC LEVELS 1. TROPHIC LEVEL - the place in a food chain that an organism feeds a. FIRST TROPHIC LEVEL - producers or autotrophsthat feed themselves

  6. *Any organisms found at the second trophic level or higher are considered to be heterotrophs i.e. they do not produce their own food b. SECOND TROPHIC LEVEL - herbivores or primary[1o] consumers that eat producers c. THIRD TROPHIC LEVEL – carnivoresor secondary [2o] consumers that eat herbivores

  7. d. FOURTH TROPHIC LEVEL – carnivore or tertiary [3o] consumers that eat other carnivores

  8. 2. FOOD WEB - a series of interconnected food chains

  9. HAWK BOBCAT WEASEL FROG MOUSE GRASSHOPPER VOLE GRASS FALLEN LEAVES SEEDS We will use this simpler food web to answer a series of questions

  10. HAWK BOBCAT WEASEL FROG MOUSE GRASSHOPPER VOLE GRASS FALLEN LEAVES SEEDS Identify an autotroph produces its own food Identify a primary consumer eats a producer

  11. 2o consumer HAWK 1o consumer BOBCAT WEASEL FROG MOUSE producer GRASSHOPPER VOLE GRASS FALLEN LEAVES SEEDS 3o consumer Identify a secondary consumer a carnivore that eats herbivores 1o Consumer Identify a tertiary consumer a carnivore that eats other carnivores

  12. HAWK BOBCAT WEASEL FROG MOUSE GRASSHOPPER VOLE GRASS FALLEN LEAVES SEEDS Identify an organism at the fourth trophic level [show how it is at this level]

  13. HAWK BOBCAT WEASEL FROG MOUSE GRASSHOPPER VOLE GRASS FALLEN LEAVES SEEDS Identify a decomposer something that eats dead things Identify an omnivore something that eats both plants & animals

  14. HAWK BOBCAT WEASEL FROG MOUSE GRASSHOPPER VOLE GRASS FALLEN LEAVES SEEDS Explain, what would be the effect on grasshoppers if fewer leaves Over a longer time less food means some voles leave fewer fallen leaves means less food for voles voles now eat more grass voles eat more grass fewer voles means less food for bobcat less grass for grasshoppers to eat bobcats now eat more frogs fewer grasshoppers as they leave area as less food fewer frogs means weasels eat more grasshoppers fewer grasshoppers

  15. HAWK BOBCAT WEASEL FROG MOUSE GRASSHOPPER VOLE GRASS FALLEN LEAVES SEEDS Explain what would be the effect on bobcats if fewer grasshoppers Fewer grasshoppers means less grass & seeds being eaten and less food for frog, weasels & mice Over a longer time If more grass, more food for voles If more voles, more food for bobcats  more bobcats Less food for frogs means frogs leave If fewer frogs, less food for bobcats  fewer bobcats

  16. HAWK BOBCAT WEASEL FROG MOUSE GRASSHOPPER VOLE GRASS FALLEN LEAVES SEEDS Explain what would be the effect on hawk if fewer bobcats. Fewer bobcats means more voles and frogs Over a longer time More voles eat more grass more frogs means more grasshoppers eaten Fewer grasshoppers means less food for mice & weasels [although weasels can eat frogs] Less grass for grasshoppers & mice Fewer grasshoppers & mice, less food for hawks  fewer hawks Overall, less food for hawks  fewer hawks

  17. HAWK BOBCAT WEASEL FROG MOUSE GRASSHOPPER VOLE GRASS FALLEN LEAVES SEEDS Explain what would be the effect on voles if fewer hawks Fewer hawks means more weasels and more mice More mice & weasels eat more grasshoppers So now fewer grasshoppers so they eat less grass Now more grass, so more food for voles  more voles

  18. References • Investigating Science – Pearson • A. Dercho