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CHAPTER 3 How Ecosystems Work

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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:

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the sun
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
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
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 heterotrophs1
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
Feeding Relationships
  • Food Chain - Model to show how

matter & energy flow through an


  • Energy must 1st pass from

producers to consumers

  • Food chains only show 1 possible
  • route
feeding relationships1
Feeding Relationships
  • Food webs – show all possible routes
  • Each organism

represents a

feeding step

or trophic


trophic levels
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
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
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
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


pyramid of numbers
Pyramid of Numbers
  • Shows the


number of


at each


feeding level

pyramid of biomass
Pyramid of Biomass
  • Biomass- total amount of

living tissue in a given trophic


  • Shows the amt. of potential

food at each feeding

level; decreases at

each successive level

  • 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
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
  • Primary succession – occurs on surfaces where no soil existed; ex. – after a volcano erupts
secondary succession
Secondary Succession
  • Secondary succession – follows a disturbance that destroyed an ecosystem but did not destroy the soil; ex. – after a forest fire