We will be discussing different trophic levels, food chains, food webs, and ecological pyramids. A food chain is a linear network of links in a food web starting from producer organisms and ending at an apex predator species, detritivores, or decomposer species. A food chain also shows how organisms are related to each other by the food they eat. Each level of a food chain represents a different trophic level.
1. Please place guided
reading in the basket.
2. Get out the notes from
Food Chains, Food Webs, and
• A food chain is the simplest path that
energy takes through an ecosystem.
• Energy enters from the sun.
• Each level in the transfer of energy is a
• Organisms at each level use energy in
cellular respiration and heat loss and store
The 1 Trophic Level
• Consists of primary producers
• Primary producers include land plants and
phytoplankton in aquatic environments.
2 Trophic Level
• Consists of primary consumers
• Primary consumers that eat green plants
• Examples: grasshoppers, rabbits,
The 3rd and Any Higher Trophic
• Consists of consumers.
• Carnivores and omnivores
• Examples: Humans, wolves, frogs, and
flow of energy
• A food web
various paths that
energy takes through
• Models that show how energy flows through
• Pyramids can show the relative amounts of
energy, biomass, or numbers of organisms at
each trophic level in an ecosystem.
• The base of the pyramid represents producers.
• Each step up represents a different level of
• The number of trophic levels in the pyramid is
determined by the number of organisms in the
chain or web.
Energy pyramids compare energy used by
producers and other organisms on trophic
• Between each tier of an
energy pyramid, up to 90
percent of the energy is
lost into the atmosphere
• Only 10 percent of the
energy at each tier isenergy
transferred from one lost
trophic level to the next.
Other pyramid models illustrate an
ecosystem’s biomass and distribution of
• Biomass is a measure of the total dry mass of organisms in
a given area.
• Even though a biomass pyramid shows
the total mass of organisms at each level,
it doesn’t necessarily represent the
amount of energy available at each level.
• For example, the skeleton and beak of a
bird will contribute to the biomass but
aren’t available for energy.
• A pyramid of numbers shows the numbers of individual
organisms at each trophic level in an ecosystem.
• A vast number of producers are required to support even a
few top level consumers.