Food Chains and Food Webs

Food Chains Food Chain: a step-by-step sequence linking organisms that feed on each other All food chains begin with a producer, such as a plant, and continue with animals that feed on the plants and on each other.

Vocabulary Producer: an organism that uses photosynthesis or another form of chemical synthesis to make food Example: plants, trees, grass Consumer: an organism that must eat producers or other consumers to survive Example: deer, wolves, humans, rabbits

Herbivore: an animal that eats only plants Example: deer, rabbit Carnivore: an animal that eats other animals Example: wolf, hawk Decomposer: an organism that eats the waste of living and dead organisms and returns it to the soil as nutrients; where it can be used by other organisms Example: bacteria, worms

Omnivore: an animal that eats both plants and animals Example: human, bear

Food Chains Examine the following food chain: Grass  Deer  Wolf The producer is the grass. The consumers are the deer and wolf. The herbivore is the deer. The carnivore is the wolf.

Grass  Deer  Wolf How would a decline in the wolf population affect the food chain? - the deer population would increase - the grass population would decrease If the grass population were eliminated, what would happen to the deer and the wolf? - the deer would have to look for another food source - if the deer could not find another food source and they died, the wolf would have to look for another food source and could die too

Food Chains Show the Flow of Energy There are limits to the length of a food chain (3 or 4 organisms) because less energy is tranferred as you move higher up in the chain At each step in a food chain, energy is lost: –to support life functions of the organism –as heat to the environment –as waste (urine and feces) to the environment

Energy is Lost in a Food Chain the image below shows how much energy is lost as you move up the food chain

Food Webs A food web is a collection of food chains that interconnect within an ecosystem. A food web is a more accurate representation of an organism’s eating habits because most organisms have more than one food supply. All food webs begin with producers and the arrows point towards the eater. All food webs should end with the top carnivores.

Food Webs