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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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CHAPTER 3 How Ecosystems Work

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Chapter 3 how ecosystems work

CHAPTER 3 How Ecosystems Work

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% cow1% 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

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