Chapter 18
Section 3
Energy
Transfer
Producers
Producers are autotrophs that
are capable of converting
chemical energy into organic
molecules.
Photosynthetic producers such
as plants, protists and some
bacteria convert solar energy
into carbohydrates.
Chemosynthetic producers
such as bacteria and archaea
convert inorganic, sulfur-based
molecules into carbohydrates.
Producers
The rate at which photosynthetic producers convert solar to organic
energy is called gross primary productivity (GPP).
The organic matter produced by autotrophs is called biomass.
Only some of the energy stored as biomass is available to other
organisms and some must be used by the producers.
Producers
Net primary productivity (NPP) measures the rate at which biomass
accumulates in an ecosystem.
GPP is like a person’s monthly salary before taxes and NPP is
like the actual amount in their actual paycheck.
R=
Respiration
Producers
Net primary productivity varies greatly between ecosystems.
Biomes that have high levels of light, temperature, nutrients and water
have the highest NPP.
Biomes like tropical rainforests and estuaries (river meets ocean) have
a high diversity of producers that support other organisms.
Consumers
Consumers are heterotrophs that cannot synthesize organic molecules
from inorganic energy sources.
Consumers either ingest (eat) or absorb nutrients from producers or
other consumers.
Decomposers are fungi or bacteria that break down producers and
consumers after they die to make inorganic compounds available to the
ecosystem again.
Consumers
There are three levels of consumers that are based on what they eat.
Primary (1°) consumers eat producers and can be either herbivores or
omnivores.
Secondary (2°) consumers eat
primary consumers and can be
either carnivores or omnivores.
Tertiary (3°) consumers eat
secondary consumers and are
carnivores only.
Quaternary (4°) consumers
are also carnivores that are
the top predators.
Consumers
Detritivores can occur at any level because they consume dead
organisms.
They are scavengers that feed on detritus or waste products in addition
to carcasses.
They are different from decomposers because they do not break the
parts down into simple compounds do not cycle nutrients back to the
ecosystem
Energy Flow
Trophic levels can be used to indicate an organisms position in a food
chain and show the direction of energy transfer.
All producers are in the first level, while all primary consumers are in
the second level.
The third and fourth levels contain secondary and tertiary consumers.
Energy Flow
A food web is used to illustrate the many possible feeding relationships
among the organisms in an ecosystem.
The more organisms there are at each trophic level, the greater the
stability of the ecosystem.
Energy Flow
When one organism consumes another one, not all of the energy gets
transferred as biomass.
Things like undigestable bones or shells, or waste products such as shed
skin or feces do not become part of the consumer.
Most of the energy is lost as heat through the process of metabolism.
Energy Flow
Only 10% of the energy in one trophic level is transferred to the next.
A biomass pyramid is used to show the amount of organisms at each
trophic level.
Fewer consumers can be supported at each level because of the
inefficiency of energy transfer.