1. Sixth lecture

2. Trophic relationships Trophic level: how an organism gets its nutrition (energy). –All organisms at a particular trophic level are the same number of transfer steps away from the energy input into the system Food Web: who eats whom in the ecosystem. Interconnected food chains Energy flows through ecosystems via trophic levels within the food web

3. Trophic Levels Primary producers: 1 st trophic level-the autotrophs-capture sun energy (the initial energy source for almost all of earth’s ecosystems) Primary consumers: heterotrophs-herbivores (caterpillars, cows etc), feed on primary producers Secondary consumers: carnivores (birds, wolves etc), feed on primary consumers Tertiary consumers: carnivores that feed on other carnivores

4. Food chains A food chain represents the different links along which food is passed from one organism to another. AT each transfer a large proportion,80 to 90 %, of potential energy is lost as heat. Therefore, the number of steps “links” in a sequence is limited, usually to four or five.

5. Food chains Food chains are of two basic types: 1-The grazing food chain: -It starts with green plants. -The green plants serve as a source of food for herbivores, -which in turn, are eaten by carnivores and for decomposers, which bring about decay in animals and plants.

6. Food chains 2-Detritus food chain, - which goes from dead organic matter into microorganisms. -and then to detritus-feeding organisms (detritivores) and their predators

7. Aquatic food chain:

8. Terrestrial food chain:

9. Food Web Most organisms eat more the JUST one organism. When more organism are involved it is know as a food web. Food webs are more complex and involve lots of organisms.

10. Food webs