1. CHAPTER 3 How Ecosystems Work

2. The Sun • The sun is the main source of Energy for all life on earth. • The sun is the start of most food chains. • Less than 1% of the sun’s energy that reaches earth is used by living things.

3. CHAP. 3-1 Energy Flow • Feeding Relationships: • Autotrophs – get energy from sun or chemicals to produce food (photosynthetic or chemosynthetic); also called producers • Heterotrophs – depend on autotrophs or other heterotrophs for food; also called consumers

4. Types of Heterotrophs • Herbivores – feed only on plants; ex – rabbits, deer • Carnivores – feed only on animals ex. – tigers and lions Omnivores – feed on plants & animals ; ex. – bears, humans

5. Types of Heterotrophs • Detritivore- feeds on detritus (dead matter) • Scavengers – feed on dead organisms; ex. – vultures, crayfish • Decomposers – feed on dead or decaying plant & animals; ex. – bacteria, protozoa, fungi

6. Feeding Relationships • Food Chain - Model to show how matter & energy flow through an ecosystem • Energy must 1st pass from producers to consumers • Food chains only show 1 possible • route

7. Feeding Relationships • Food webs – show all possible routes • Each organism represents a feeding step or trophic level

8. Trophic Levels Each step in a food web or food pyramid is called a trophic level (energy level) 10% Rule Only 10% of the energy from one trophic level is passed on to the next. 100% grass 10% cow 1% humans

9. Levels of Consumers • Primary consumers • Eat producers • Secondary consumers • Eat herbivore • Tertiary consumers • Eat carnivore • Quaternary consumers • Eats carnivore that ate the carnivore

10. Ecological Pyramids • Diagram that shows the amounts of matter or energy contained at each trophic level • 3 pyramids: • Pyramid of Energy • Pyramid of Numbers • Pyramid of Biomass

11. Pyramid of Energy • Shows the amount of energy which is moving from one level to the next. • Shows that only about 10% of the energy available within a trophic level is transferred to the next trophic level

12. Pyramid of Numbers • Shows the decreasing number of organisms at each successive feeding level

13. Pyramid of Biomass • Biomass- total amount of living tissue in a given trophic level. • Shows the amt. of potential food at each feeding level; decreases at each successive level

14. Biomagnification • The tendency for the concentration of pollutants to increase in animals higher up on the food chain. • Ex: mercury in Tuna, or DDT in Eagles

15. 3-3 Succession • Succession: Changes in an ecosystem over time; include organisms dying out & new ones taking their place • Pioneer species – the 1st species to populate the area • Climax Community- the community that eventually forms if the land is left undisturbed.

16. Primary Succession • Primary succession – occurs on surfaces where no soil existed; ex. – after a volcano erupts

17. Secondary Succession • Secondary succession – follows a disturbance that destroyed an ecosystem but did not destroy the soil; ex. – after a forest fire