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 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 Secondary 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