TROPHIC LEVELS • Determined by the organism’s source of energy • There are 3 main trophic levels in a food web. • Organisms are identified by their trophic level according to their name. • Autotrophs • Heterotrophs • Saprotrophs
1. AUTOTROPHS: • Capture energy from the sun (photosynthetic) or inorganic molecules = chemicals (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 • decomposers and detrivores
Saprotrophs • Include detrivores and decomposers
DETRIVORES • Organisms that eat detritus, or dead organic matter. • Eg. Earthworm, vulture, crab
DECOMPOSERS • A kind of detrivore • Break down organic matter into simpler compounds. • release essential nutrients back into the environment to be recycled. • Eg. Fungus
Pyramid Models: graphs which illustrate the trophic levels in a community.
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.
Decomposer Detrivore, carnivore Mushrooms earthworms 123 kJ Secondary Consumer Heterotroph, Decomposer, detrivore, carnivore Red-tailed hawk, grizzly bear, Mushrooms and earthworms 1,230 kJ Primary Consumer Heterotroph, herbivore 12, 300 kJ Marmot, grouse, butterfly, deer, chipmunk Producers autotrophs 123,000 kJ flowers, grasses (seeds, berries)
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.
Tertiary Consumer, Heterotroph, Carnivore 5,693 kg Elephant Seal, Killer Whale 56,931 kg Penguin, Leopard seal, squid Secondary Consumer, Carnivore, heterotroph Primary consumer, herbivore, heterotroph 569,311 kg Squid, cod, krill, zooplankton 5,693,112 kg Phytoplankton Autotrophs, producers
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.