Trophic levels refer to the feeding positions that organisms occupy in a food chain or web. Producers such as plants are at the first trophic level. Herbivores that eat plants are at the second level. Carnivores that eat herbivores are at the third level. Top carnivores at the fourth level obtain energy by preying on other carnivores. Energy availability decreases at higher trophic levels as the energy from lower levels is used for metabolism and growth rather than being fully transferred up the food chain.

1. Trophic pyramids Key terms: Producer/Autotroph Consumer / Heterotroph Trophic level Detritivores Omnivores May 29, 2009

2. 1. 4. 3. 2. Trophic levels are Available energy decreases

3. human Leaf Badger Blackbird Fish Caterpillar Grass Hawk Worm

4. 1. Autotrophs 4. Top carnivores 3. Carnivores 2. Herbivores Trophic levels are the feeding levels of the organisms in each component Available energy decreases with level The width of each bar is proportional to the amount of energy stored (biomass)

5. 1. Autotrophs (producers) 4. Top carnivores (omnivores) 3. Carnivores (secondary consumer) 2. Herbivores (primary consumer) Trophic levels are the feeding levels of the organisms in each component Available energy decreases with level Detritivores are consumers that operate at all trophic levels