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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
carnivore
herbivore
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
sunlight producer consumer 1 consumer 2
HERBIVORES• What are herbivores?• Organisms that eat
plants• Primary Consumers• Ex. Cows, caterpillars, bunnies
sunlight producer consumer 1 consumer 2
CARNIVORES• What are carnivores?• Organisms that eat meat (other
animals/consumers)• Secondary Consumers• Ex. tigers, wolves, snakes, hawks
sunlight producer consumer 1 consumer 2
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
sunlight producer consumer 1 consumer 2
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).
Detritivore vs Decomposers
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
Detritivore vs Decomposers
consumer 3
sunlight producer consumer 1 consumer 2
Energy Flow• The series of steps in which
organisms transfer energy by eating and being eaten is called a Food Chain
sunlight producer consumer 1 consumer 2
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
producer consumer 1 consumer 2 consumer 3
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)
producer consumer 1 consumer 2 consumer 3
Food Chains & Food Webs• What vital “recycler” is not shown in
this food chain?• Upon which organism(s) would it
feed?
decomposer
producer consumer 1 consumer 2 consumer 3
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)
Grasshopper (1,000 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)
Grasshopper (1,000 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)
Grasshopper (1,000 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)
Grasshopper (1,000 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.