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 % cow 1% humans

9. 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

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