Title: Energy Transfer in Producers and Primary
Consumer
All living organisms have the ability to transfer energy
as a result of their metabolism. According to the first
law of bioenergetics, energy cannot be created or
destroyed only converted from one form to another. In
tracing energy flow, the ultimate source of energy for
most of the energy on this earth is the sun. Primary
productivity is the amount of light energy converted to
chemical energy by an autotroph in a given time period.
Total primary production is known as gross primary
production (GPP), or it is the amount of light energy
that is converted into chemical energy.
While autotrophs have the ability to fix carbon dioxide
into organic compounds, they also oxidize or break
down those very same organic compounds they made
during the process of cellular respiration. The net
primary production (NPP) is equal to gross primary
production minus the energy used by the primary
producers for respiration (R). Net primary production
can be literally “seen”. If a field of cotton is more
productive than another field of cotton, then there
would be more plants and the plants would be larger
and more robust. In other words, the more productive
cotton field would have more biomass. One should also
note that productivity includes a time factor and net
productivity is biomass of vegetation added to the
ecosystem per unit area per unit time. The term
standing crop total is biomass of photosynthetic
autotrophs present in at a given time.
In terrestrial ecosystems, net productivity can be
indirectly assessed by determining the change in the
biomass of plants for a specific time period.
Productivity involves the fixation of carbon dioxide and
does not include water. That being the case when
studying productivity, productivity involves changes in
dry biomass. This means that the plant or other
organisms involved must be dehydrated.
One can examine the productivity in primary and
secondary consumers. Secondary productivity of an
ecosystem is the amount of chemical energy in food
converted to new biomass in various consumers during
a given period of time. Food used by a consumer is
converted into one of three destinations:
• released as heat energy
• used in the production of new biomass
• not used and excreted
• Net secondary production is the energy stored in
biomass represented by growth and
reproduction. When a caterpillar feeds on a leaf,
only about one-sixth of the leaf’s energy is used
for secondary production. An organism’s
production efficiency is the fraction of energy
stored in food that is not used for respiration.
_____________________________________________
Purpose: This inquiry investigates the net primary
productivity of mung beans and the net secondary
productivity of pill bugs.
_____________________________________________
Materials:
1 lb. Mung beans
1 egg carton /group
3 cups of potting soil/ group
1 large potato/group
5 petri dishes per group
25 coffee filters/group
25 cup cake paper/group
Grow light
Balance that measures to the 0.001 g
Transparent tape
_____________________________________________
Background: Heat energy is often measured calories.
One calorie is the amount of energy it takes to increase
the temperature of one gram of water one degree
Celsius. A kilocalorie (or Calorie) is equal to 1,000
calories. A calorie is equal to 4.18 Joules of energy. A
watt is the amount of energy used per unit time. A watt
is equal to one Joule/second.
_____________________________________________
Primary Productivity: Investigating mung beans
• Write several paragraphs about its life cycle,
niche, and importance in agriculture.
• Explain what is contained in a mung bean.
• Determine the best method for germinating
and growing mung beans.
• Obtain 12 mung beans and make observations
about mung beans. List five observable
differences among your mung beans.
• Determine the mass of each of your 12 mung
beans.
• Determine the number of calories in each of
your 12 mung beans.
• Research the number of calories found in 1 tbs.
of dried mung beans.
• Determine the number of calories per gram of
mung beans.
• Record this data.
• Determine the primary productivity of your
mung beans for a 7 day and 14 day period
• Research information about Von Helmut’s
Experiment. Explain where does biomass come
from and does the term carbon fixation mean.
How can you verify Von Helmut’s experiment in
this inquiry? Design an inquiry to determine
the net primary productivity of mung beans
over for a seven day period and a 14 day period.
____________________________________________
Secondary Productivity: Investigating pill bugs
• Write several paragraphs about its life cycle,
niche, and importance in the ecosystem.
• Determine the dry biomass of the food that
will be given to pill bugs (potato or carrot
pieces groups).
• Explain how pill bugs consume energy.
• Explain what types of energy transfers occur
once the pill bug consumes energy.
• Obtain 10 pill bugs and make observations
about your pill bugs. List five observable
differences among your pill bugs.
• Determine the percentage of dried biomass in
your 10 pill bugs based on the information
given below. DO NOT DEHYDRATE YOUR PILL
BUGS (it will kill them!).
• Determine the percentage of dry biomass in the
energy source transferred to your pill bugs.
• Determine the secondary productivity of your
pill bugs.
• Design an inquiry to determine the net
secondary productivity of pill bugs over for a
seven day period and a 14 day period.
DATA COLLECTION
•
Needed Information:
• The amount of energy in dried mung bean
tissue (leaves)
• The amount of energy in dried mung bean
seeds
• Percent dried biomass in mung beans
• Percent dried biomass in potatoes
• Percent dried biomass in pill bugs
• Information Mass of 10 live pill bugs
• Mass of 10 dehydrated pill bugs = 0.206 g
Mung Beans
Mass (g)
Observations
Mass (g)
Observations
1
2
3
4
5
6
7
8
9
10
11
12
Pill Bugs
1
2
3
4
5
6
7
8
9
10
Remember, you will need more data input as the lab
progresses
TO HAVE SUCCESS IN YOUR LAB YOU NEED TO:
READ, READ, READ, AND READ