Example 1. A 6th grader and their pet dog. 2. Head lice living on a human scalp. 3. A bird building a nest in a tree. 4. Bacteria and human intes=nes. 5. Barnacles living on a whale. 6. Flea feeding on a mouse's blood. Parasi-sm (P), Mutualism (M), or Commensalism (C) Food Chains and Food Webs • A food chain is the path that energy takes in traveling from the sun to a chain of organisms and back to the environment. It can be an aqua=c (water) or terrestrial (land) food chain/web. • The arrow always points towards the animal doing the ea=ng…the arrow always shows the direc=on of energy flow. • All food chains begin with the sun…or some source of energy. • REMEMBER: The Law of Conserva=on of MaSer says that maSer/energy/mass cannot be created or destroyed which means that as an organism is eaten it is not destroyed…instead its maSer/mass/energy just gets transferred to another place/
organism. Producers • Use energy from the sun to make food. • Typically store their energy in leaves, stems, and roots. • This is where all other organisms get their energy. • REMEMBER: While most producers are plants, not all of them are. Bacterium, algae, and chemosynthe=c organisms are not plants but can be the beginning organism in a food chain. Consumers • Any form of life that must eat other organisms to survive. • These organisms cannot make their own food. • They are labeled by how far away they are from the producers. We use words like primary, secondary, ter=ary, and quaternary to describe them. Decomposers • Not a producer or consumer but derives its energy from the break down of dead and decaying plant and animal maSer. They help return energy and nutrients back to the environment. • Ex: mushrooms and other fungi. • REMEMBER: This is why fungi are not considered plants…they do not make their own food…they absorb their food from the environment which means they do not need sun to survive. 10% Law • The levels or posi=on in a food chain, food web, or food pyramid are called trophic levels. • As a law, only about 10% of the energy from one trophic level will rise to the next trophic level, the other 90% is lost to the environment (mostly as heat energy) due to metabolism. Food Web • Unfortunately, simple food chains are not the most accurate way to show energy transfer. Most organisms are not eaten by or eat just one organism so it is more realis=c to place them in a web showing mul=ple chains interac=ng