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Ecology 3
Main Idea : How do Energy and
Nutrients flow through an Ecosystem?
A.
Introduction
1. All organisms use energy (directly or
indirectly) from the sun to power their
life processes.
a. Producer organisms capture energy
from the sun and store it in the
chemical bonds of the food molecules
they make.
2. This energy, however, does not remain
in the organism forever.
a. As the organism
performs its life
processes, it uses
energy.
b. In addition, as the
energy in food is
converted to the useable
form known as ATP, most
of the energy is
converted to heat and is lost to the
environment.
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3. If the organism is a producer, it
must make food (through photosynthesis)
continually. If the organism is a
consumer, it must obtain food
continually. Why?... because its energy
is either:
a. Used during life processes.
OR
b.
Lost to the environment as heat.
4. Only the energy stored in the body
tissues of each organism is passed on to
the next consumer in the food chain.
5. Because of this loss of energy, most
of the original stored energy is lost in
just 5 steps of the food chain. (a food
chain, or pyramid will never be larger
than 5 steps, because all the energy is
lost by that point)
6. An energy pyramid
is a diagram that
shows the transfer of
energy through a food
chain or web.
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a. Each block of the energy pyramid
represents the amount of energy that
is available to the organisms in the
next higher block.
b. Each level is smaller due to the
loss of
heat as the organisms
carry on their life activities.
c. Producer organisms contain the
most energy because they capture
energy directly from the sun and
store it in the chemical bonds of the
food molecules they make.
d. In spite of this constant loss of
energy to the environment, life
continues because the sun continues
to provide energy.
B. Recycling and Reusing Materials
1. Decomposers extract the last bit of
energy contained in dead organisms (as
well as the energy in their waste
products) and use it to carry out their
own life processes.
a. In the process of doing this,
decomposers return the raw materials
(contained in the once-living
organism) to the soil.
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b. Decomposition (Definition) – the
process of breaking down dead
organisms, and their waste products,
into raw materials and returning
those raw materials to the ecosystem.
c. Examples of decomposers are
bacteria and fungi
.
2. Because of the actions of
decomposers, the atoms and molecules in
living things cycle through both the
living (biotic)and nonliving (abiotic)
parts of the biosphere.
a. Chemical elements such as carbon,
hydrogen, oxygen, and nitrogen, (the
four most abundant elements that make
up the earth and the bodies of living
things) pass through food webs and
are combined and recombined in
different ways in different living
organisms.
b. For example, plants
trap carbon dioxide
and water molecules in
energy rich compounds
(such as glucose and
starch) during the
process of
photosynthesis. When
plants need energy for
their life activities
or are eaten by a
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consumer, these molecules may be
broken down and used by the organism.
During respiration, molecules (such
as glucose and starch) are broken
down by the cells and returned to the
environment in the form of carbon
dioxide and water (and energy (ATP)
is released).
There will be a quiz on this entire packet on ________and a
TEST on _____.
.
Unit XIV Ecology Student Notes [NOTES 2000 #8]