TROPHIC LEVELS
An organisms trophic (feeding) level is determined
by the organism’s source of energy
There are 3 main trophic levels in a food web.1. Autotrophs
2. Heterotrophs
3. Saprotrophs
1. AUTOTROPHS:
• Capture energy from the sun (photosynthetic) or inorganic molecules (chemosynthetic) and converts it into usable energy.
• Also known as (AKA) PRODUCERS– produces food (make energy storing
molecules),
• Eg. Plants, algae and some kinds of bacteria
2. HETEROTROPHS-• AKA CONSUMER
– obtains the energy to build their molecules by consuming plants or other organisms
Includes:
– primary,
– secondary,
– tertiary (etc.) consumers, and
3. SAPROTROPHS/DECOMPOSERS
• An organism that gets it’s energy by feeding off of dead or decaying organic matter
• 2 types:
Detritivores and Scavengers
SCAVANGERS
• Start the decomposition process by finding large quantities of dead material (like corpses) and breaking it down into smaller pieces.
– Eg. Hyenas, Crabs, Vultures.
DETRITIVORES
• Organisms that eat detritus, or dead organic matter.
• Finish the decomposition process by taking the leftovers from scavengers or waste from other organisms and breaking it down to the molecular level.
– Eg. Fungi, Bacteria, Earth Worms
How do you tell the difference between a Scavenger and Detritivore?• Scavengers tend to start the decomposition process by
turning large pieces of food into smaller one. Detritivoresfinish the process by breaking the smaller food into molecules that are recycled into the ecosystem.
• Scavengers are typically larger animals, while Detritvorestypically are smaller microorganisms or invertebrates (though fungi can get quite large).
• Scavengers typically have large ranges that they travel to find corpses. Detritivores typically stay in one general area and eat what ever waste, dead left overs come to them.
Energy Pyramid Model
• Organisms convert food (glucose) into energy.
• This energy is given off as heat which is lost to space.
• Energy is a one way path. It is not a cycle.
Energy Pyramid Model
• An energy pyramid is a diagram that compares energy used by producers, primary consumers, and other trophic levels.
• As a rule each trophic level receives only 10% from the trophic level below.
• In other words each trophic level loses 90% heat to the atmosphere.
Student Task
• Study the food web and convert it into an energy pyramid model.
• The autotrophs in this food web start off with 123,000 kilojoules of energy and the decomposers are included on the outside of the pyramid.
• Also label the levels with the terms on paper
flowers, grasses (seeds, berries)
Marmot, Grouse, Butterfly, Deer, Chipmunk, Bear
Red-tailed hawk,Bear,
Hawk
ProducersAutotrophs
Primary ConsumerHeterotroph, Herbivore
Secondary ConsumerHeterotroph, Carnivore
Carnivore
123,000 kJ
12, 300 kJ
1,230 kJ
123 kJ
SaprotrophsMushrooms, earthworms
Decomposer, Detritivore
Pyramid of Biomass
• Biomass is the mass of organisms minus water.
• Biomass refers to the amount of carbon and other trace elements an organism’s body contains.
Student Task
• Study the food web below and convert it into a biomass pyramid model.
• The autotrophs (phytoplankton) in this food web start off with 5,693,112 Kg of biomass.
• Also label the levels with the terms found on your paper
Phytoplankton
cod, krill, zooplankton
Penguin, Leopard seal, squid, cod
Elephant Seal, Killer Whale
Autotrophs, producers
Primary consumer, herbivore, heterotroph
Secondary Consumer, Carnivore, heterotroph
Tertiary Consumer, Heterotroph, Carnivore
5,693,112 kg
569,311 kg
56,931 kg
5,693 kgWhale
Student Task
Pyramid of Numbers
Illustration of the number of organisms at each level
How can more people be supported on Earth when there is a limited supply of resources?
• It depends on what they are eating.
EXIT SLIP
Plant material eaten by caterpillar
100 kilocalories (kcal)
Feces
50 kcal
Growth
15 kcal
Cellular respiration
35 kcal
Explain this graphic- feel
free to draw it out.
In your answer, make
sure to tell me:
• How much energy did
the plant start with?
• How much energy will
go to the crow? Why?
• What will there be the
most of in this
ecosystem: plants,
caterpillars, or crows?
How do you know?
Top Related