Download - Food Chain, Webs, and Pyramids
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Food Chain, Webs, and Pyramids
H. Biology
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Relationship of Organisms• Organisms are resources /
“food” for other organisms• Food is energy which
allows the survival and reproduction of populations
• Food chains and food webs show how energy is transferred from one organism to another
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Energy Roles• The sun is the original source of all energy!• Producers: “Harness” energy from the sun– Ex. plants
• Consumers: Organisms that eat something else– Ex. animals
• Decomposers: return energy to the environment– Ex. fungus, bacteria
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Vocab You Need to Know!• Producer - usually a green plant that produces its own food by
photosynthesis• First-order Consumer - the organism that eats the producer• Second-order Consumer - the organism that eats or derives
nutrients from the first-order consumer • Herbivore - a plant eater• Carnivore - an organism that obtains nutrients from the blood or
flesh of an animal• Omnivore - an organism which eats both plant and animal matter• Scavenger - an consumer that eats dead animals (e.g. crab)• Detritivore - a consumer that obtains its nutrients from detritus• Decomposer - an organism such as bacteria and fungi that breaks
down dead organisms and their wastes
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Trophic StructureEcosystems divided into trophic levels (feeding
levels)Primary producers—autotrophs (mostly
photosynthetic but can be chemosynthetic)Primary consumers—herbivoresSecondary consumers—carnivores that eat
herbivoresTertiary consumers—carnivores that eat other
carnivoresDetrivores/Decomposers—consumers that eat
dead or decaying matter
Ecosystems
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Producers• Plants harness energy from the sun through
photosynthesis• Producers are the base of every food chain– Meaning they are the source of food for all other
animals
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Consumers• 4 Types of Consumers:– Herbivore: Eat only plants
• Ex. Cows, horses
– Carnivore: Eat only meat• Ex. Polar bear
– Omnivore: Eat plants and animals• Ex. Humans, grizzly bears
– Scavenger: Carnivores that feed on bodies of dead organisms• Ex. Vultures
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Decomposer• Decomposers break down waste and dead organisms
and return the raw materials to the environment– Ex. Bacteria, fungi
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Energy Flow through Biological Systems
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Which Way Will the Energy Flow Go?!
Grass ------ Cow ------ Human
Plant ------ Mouse ------ Snake
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Food Chain• Food Chain – series of
organisms showing feeding relationships. – almost always begins
with a green plant (producer) which is eaten by an animal (consumer).
– The arrow means 'is eaten by', and points to the animal doing the eating!
– This shows the flow of matter and energy along the food chain.
– There are no decomposers in a food chain.
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Food Web• Food Web is a network of interrelated food chains in a
given area– Includes decomposers
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Toxins in the Environment• In some cases, harmful
substances persist for long periods in an ecosystem
• One reason toxins are harmful is that they become more concentrated in successive trophic levels
• In biological magnification, toxins concentrate at higher trophic levels, where biomass is lower
Zooplankton0.123 ppm
Phytoplankton0.025 ppm
Lake trout4.83 ppm
Smelt1.04 ppm
Herringgull eggs124 ppm
Con
cent
ratio
n of
PC
Bs
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BiomagnificationWhat happens as levels of toxins (like DDT and mercury) as they move up trophic levels?
• Toxin INCREASES in concentration from one link in a food chain to another– B/c they’re insoluble
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Energy Pyramid
• 2nd Law of Thermodynamics: 100% of the energy from one organism is NOT transferred to the next – Most of the energy (90%) is lost to the
environment / used by the organism to carry out its life processes or it is lost to the environment
• Energy Pyramid shows the amounts of energy that moves from one level to the next
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Sample Energy Pyramid
Only 10% is passed on from one level to the next…the rest is LOST (usually as heat)
What happens as
levels of toxins (like DDT) move up trophic
levels?
Pyramid of Net Productivity:
~10% of energy at each level converted
to new biomass
CALLED 10% rule (trophic efficiency)
LOTS OF BIOMASS HERE