Food Chains & Food Webs

Food chain  Food chain: A model that shows how energy and matter move through an ecosystem AcornSquirrelRed-tailed hawk AcornSquirrelRed-tailed hawk  Arrows point to the CONSUMER  Need to start with a PRODUCER  Only up to 5 organisms in a food chain (only shows 1 feeding relationship at a time)

Energy  Energy (E): the ability to do work  In food chains/webs, all energy (E) comes from the Sun  Sun’s E trapped by producers & convert to chemical E (in photosynthesis)  Sun’s E trapped by producers & convert to chemical E (in photosynthesis)  The E moves from producers to consumers along the food chain (only moves in 1 direction)  Some energy is “lost” along the way in the form of heat  Some energy is “lost” along the way in the form of heat

Rule of 10%  Only 10% of the energy gets passed on to the next level of the food chain. 90% of the energy is lost as heat or used by the organism  In our example of the food chain, if the acorns were 100 calories…how many of those 100 calories would the red-tailed hawk get?  1 calorie!

Matter  Matter: is anything that has mass and takes up space  Atoms are the “building blocks” of matter  4 most important elements in living organisms: hydrogen (H), oxygen (O), nitrogen (N), and carbon (C)  The Earth has a limited amount of matter, so matter must be RECYCLED!!

Carbon Cycle

Nitrogen Cycle

Water Cycle

Remember…  Energy FLOWS through the ecosystem  Matter RECYCLES in the ecosystem

Trophic Levels  Trophic level: the feeding level in the ecosystem  P = Producer  1 = 1 st level consumer (feeds on producers)  2 = 2 nd level consumer (feeds on 1 st level con.)  3 = 3 rd level consumer (feeds on 2 nd level con.)  Levels can go higher (not usually above 5)  Possible for an organism to be on more than 1 trophic level (in other food chains or food webs)

Example  Wetland Food Chain Phytoplankton Blue gill Heron Alligator (P) (1) (2) (3)

Food Webs  Food web: a pattern of feeding in an ecosystem consisting of interconnected and branching food chains  All the same rules apply (arrows, trophic levels, etc)