FOOD CHAINS and FOOD WEBS

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

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

1 unit 100 units 10 units 10 units 100 units 1000 units

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

*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 – carnivores or secondary [2o] consumers that eat herbivores

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

2. FOOD WEB - a series of interconnected food chains

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

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

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

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

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

HAWK WEASEL BOBCAT MOUSE GRASSHOPPER FROG SEEDS GRASS VOLE FALLEN LEAVES 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

HAWK WEASEL BOBCAT MOUSE GRASSHOPPER FROG SEEDS GRASS VOLE FALLEN LEAVES 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 Less food for frogs means frogs leave If more voles, more food for bobcats  more bobcats If fewer frogs, less food for bobcats  fewer bobcats

HAWK WEASEL BOBCAT MOUSE GRASSHOPPER FROG SEEDS GRASS VOLE FALLEN LEAVES 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

HAWK WEASEL BOBCAT MOUSE GRASSHOPPER FROG SEEDS GRASS VOLE FALLEN LEAVES 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