Chapter 3 Section 2: Energy Flow
•Identify the source of energy for life processes
•Trace the flow of energy through living systems
•Evaluate the efficiency of energy transfer
among organisms in an ecosystem.
Producers
• Sunlight is the ultimate source of energy for most life on
Earth. (this is from less than 3% of the sunlight that actually
reaches the Earth)
• Some types of organisms rely on the energy stored in
inorganic chemical compounds.
• All organisms that use energy from their environment to
fuel the assembly of simple inorganic compounds into
complex organic compounds are called autotrophs.
• Because they make their own food, they are also called
producers.
• They are essential to the flow of energy through the
biosphere.
Types of Consumers
• Many organisms (animals, fungi, and many
bacteria) can not make their own food and
must acquire energy from other organisms.
• These organisms are called heterotrophs or
consumers.
• There are many types of heterotrophs
Herbivores
•Obtain energy by eating only plants
•Examples include cows, caterpillars, and deer
Carnivores
•Obtain energy from eating animals
•Examples include snakes, dogs, and owls
Omnivores
•Obtain energy from eating plants and animals
•Examples include humans, bears, and crows
Detritivores
•Obtain energy from feeding on plant and animal remains and
other dead matter
•Examples include mites, earthworms, snails, and crabs
Decomposers
•Obtain energy by breaking down organic matter
•Examples include bacteria and fungi
Food Chains
• A food chain is a series of steps in which organisms transfer
energy by eating and being eaten.
• The energy in a food chain flows from the sun or inorganic
compound to autotrophs and then to heterotrophs.
Food Webs
•A food web links all
the food chains in an
ecosystem together
•The energy in a food
web flows from the
sun or inorganic
compound to
autotrophs and then
to heterotrophs.
Trophic
Levels
•Each step in a food
chain or food web.
•Producers make up
the first trophic level
•Consumers make up
the second, third, or
higher trophic level.
•Each consumer
depends on the
trophic level below it
for energy.
Ecological
Pyramids:
Energy Pyramid
Only about 10
percent of the
energy available
within one trophic
level is transferred
to organisms at the
next trophic level.
Ecological
Pyramids:
Biomass Pyramid
A biomass pyramid
represents the
amount of
potential food
available for each
trophic level in an
ecosystem
Ecological
Pyramids:
Pyramid of
Numbers
•An ecological pyramid
which is used to
represent the number
of individual
organisms at each
trophic level.
•A pyramid of
numbers isn’t always
necessarily a
“pyramid” because
you might have fewer
individual producers
than you have
herbivore consumers.