FOOD CHAINS & WEBS

FOOD CHAINS& WEBS

the ultimate energy source

Energy Flow in EcosystemsEnergy flows from where into the

biological world?

Energy Flow• How does the sun’s energy enter

the biological world?• What is photosynthesis?

consumer 1

Energy Flow• The sun’s energy flows into organisms

that can change the sunlight into food then into organisms that eat them.

• This flow is:

sunlight producer consumer 2

Word to Know

producer

detritivore

omnivore

carnivoreherbivore

consumer

decomposer

autotroph heterotroph

PRODUCERS• What are producers?• Autotrophs that trap solar energy into

organic molecules during photosynthesis; can produce their own food

• Ex. Plants, algae and some bacteria

``

sunlight producer consumer 1 consumer 2

CONSUMERS• What are consumers?• Heterotrophs that eat other organisms

to obtain energy• Examples: deer, rabbits, cows, mice,

lions, humans, hawks, snakes


HERBIVORES• What are herbivores?• Organisms that eat

plants• Primary Consumers• Ex. Cows, caterpillars, bunnies


CARNIVORES• What are carnivores?• Organisms that eat meat (other

animals/consumers)• Secondary Consumers• Ex. tigers, wolves, snakes, hawks


TOP CARNIVORES• What is a top-level carnivore?• Top-level carnivores eat secondary

consumers; usually nothing feeds on them

• Ex. killer whale eating a sea lion or hawk eating a snake.

consumer 3


OMNIVORES• What are omnivores?• Consumers that eat both plants and

animals• Primary and Secondary Consumers• Ex. bears and humans

Where do allthe dead things go?

• They are eaten. YUMMMM!

• They decay. SMELLY!

decomposerdetritivore

Detritivore vs Decomposers• Detritivores and decomposers both feed

on the remains of dead plants and animals and other dead matter (detritus)

• They rely on dead tissues for nutrients.

decomposerdetritivore

• Detritivores eat the remains of dead plants and animals

• Decomposers breakdown (decay) organic matter and feed on itCrabs, mites,

earthworms, snails

Bacteria & fungi

Detritivore vs Decomposers

• What is a scavenger?• A scavengers is a

type of detritivore that feeds on carrion (dead animal remains).


Ex. vultures, sharks, maggots, hyenas

• Why would they be called the environmental “recyclers”?

• They decompose excrement, dead bodies and leaf litter, returning nutrientsto the physical environment.

decomposer


consumer 3


Energy Flow• The series of steps in which

organisms transfer energy by eating and being eaten is called a Food Chain


Food Chains & Food Webs• The steps in the transfer of energy from

organism to organism in feeding relationships are called Trophic Levels.

• How does a food chain describe this path of energy? (arrows)

producer consumer 1 consumer 2 consumer 3

Food Chains & Food Webs

• Name the number of the trophic levels in the food chain below.

• How do the trophic level numbers correspond with the “eating terms”?

TrophicLevel 1 2 3 4


Food Chains & Food Webs• What important energy transfer is not

shown in a food chain?• Why is it that some energy is lost from one

level to the next level?• How much energy is actually passed on to

the next level? (rule of thumb)


Food Chains & Food Webs• What vital “recycler” is not shown in

this food chain?• Upon which organism(s) would it

feed?

decomposer


Food Chains & Food Webs• If all of the snakes in this chain died, what

would happen to the hawk?

consumer 2

decomposer

producer consumer 1 consumer 3

• To the decomposers?

Food Chains & Food Webs• Most organisms feed on more than one

trophic level and feed on several different species at each trophic level. This is a food web.

Antarctic Food Web

Making a Food Web• Use these organisms for Food Chains and

Food Web Practice worksheet.

Ecological Pyramids

Ecological Pyramids

• Instead of representing trophic levels in a food web, an ecological pyramid can be used.

Grass (10,000 kcal)

Grasshopper (1,000 kcal)

Frog (100 kcal)

Snake (10 kcal)

Hawk(1 kcal)

1

2

3

4

5

Ecological Pyramids• Does this pyramid represent a food chain

or web?

• How could this pyramid be changed to represent a food web?

Grass (10,000 kcal)


Frog (100 kcal)

Snake (10 kcal)

Hawk(1 kcal)

1

2

3

4

5

Ecological Pyramids

• What do the big numbers represent?

• What does the kcal mean?

Grass (10,000 kcal)


Frog (100 kcal)

Snake (10 kcal)

Hawk(1 kcal)

1

2

3

4

5

Pyramid of Energy• What happens to the energy as you go

up?• How much

energy is available for the next level? (What %)

Grass (10,000 kcal)


Frog (100 kcal)

Snake (10 kcal)

Hawk(1 kcal)

1

2

3

4

5

Pyramid of EnergyPyramids of energy show the relative amount of energy available at each trophic level of a food chain or food web. Grass (10,000 kcal)


Frog (100 kcal)

Snake (10 kcal)

Hawk(1 kcal)

1

2

3

4

5

Pyramid of Energy

Pyramid of Energy

Ecological Pyramids• How is this pyramid different from the

previous ones?

• What could the multiple pictures of the species at each level represent?

Pyramid of Biomass

A pyramid of biomass illustrates the relative amount of living organic matter available at each trophic level

Biomass-the total amount of living tissue within a given trophic level.

Pyramid of Biomass• What information would this pyramid

include if it were a pyramid of biomass?

• How do they get a number total for the biomass of a population?

Pyramid of Biomass

Pyramid of Biomass

Pyramid of Numbers

A pyramid of numbers shows the relative number of individual organisms at each trophic level.

Pyramid of Numbers• What information would this pyramid

include if it were a pyramid of numbers?

• How do they get a number total for a population of organisms?

Pyramid of Numbers

Pyramid of Numbers

Pyramids of Aquatic Ecosystems

• Numbers

• Biomass

• Energy

Phytoplankton are microscopic and weigh very little

Pyramids of Temperate Forests

• Numbers

• Biomass

• Energy

Trees are huge but not as numerous as many smaller forest creatures.

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FOOD CHAINS & WEBS