170 likes | 369 Vues
CHAPTER 3 How Ecosystems Work. 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 i s used by living things. CHAP. 3-1 Energy Flow. Feeding Relationships:
E N D
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.
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
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
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
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
Feeding Relationships • Food webs – show all possible routes • Each organism represents a feeding step or trophic level
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
Levels of Consumers • Primary consumers • Eat producers • Secondary consumers • Eat herbivore • Tertiary consumers • Eat carnivore • Quaternary consumers • Eats carnivore that ate the carnivore
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
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
Pyramid of Numbers • Shows the decreasing number of organisms at each successive feeding level
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
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
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.
Primary Succession • Primary succession – occurs on surfaces where no soil existed; ex. – after a volcano erupts
Secondary Succession • Secondary succession – follows a disturbance that destroyed an ecosystem but did not destroy the soil; ex. – after a forest fire