Name:
__________________________ Date: _____________ Per:
____
The Berlese
Extraction:Density/Diversity
of Soil Dwelling Invertebrates
*developed by Maya Merritt based on an experimental design by J. Meyer, NCSU
|
State
Objectives |
Competency Goal 1: The
learner will develop abilities necessary to do and understand scientific inquiry. Competency
Goal 5: The learner will develop an understanding of the ecological
relationship among organisms. |
|
Time
Required |
one 50 minute class period for set-up and to get sample. one-two 50 minute class periods to analyze data. *note:
the sample will take a week to dry out. |
|
Note
to Teachers |
The
variable in this lab is natural vs. disturbed areas. Other variables can be tested including
light vs. shady, southern slope vs. northern slope, wet vs. dry, warmer vs.
cooler areas, etc. |
|
Resources |
visit http://www.cals.ncsu.edu/course/ent591k/berlese.html
for diagrams and Kwik-Key ordering information. |
Materials per lab pair:
soil sample (approx
15 cm by 15 cm)
one gallon plastic milk container
one
mason jar with tight lid
masking
tape and permanent marker
1/4th
inch mesh hardware cloth
stick
and tape
ethanol
(70-95%)
metric
ruler, small shovel, plastic bag (to collect soil sample)
stereoscope
eyedroppers
black
construction paper
Kwik-Key to Soil-Dwelling Invertebrates
Background
Information: If you go for a walk in the woods, you probably notice large organisms. Have you ever stopped to think about the
smaller critters that are living under the places where you step? These often microscopic
organisms are essential in healthy ecosystems, playing a key role in
decomposition. You’ve learned that bacteria
and fungus are important decomposers.
Decomposers are organisms that recycle nutrients, making them accessible
for use by others. But before they can
do their work, organic material must be broken down into more manageable
pieces. This is where soil dwelling
invertebrates come into play.
Your Task: You and
your lab partners have been hired by your school to determine the effect we are
having on soil dwellers living around the area.
Together, you will choose two areas around the school. One area should be one that you consider
natural, having had minimal interference by humans. The other area should be one that you believe
has been disturbed by human actions.
Using the steps of the scientific method as learned in class, you will
formulate a hypothesis related to what you expect to find in those two
areas. For example, you might choose an
area deep in the woods as the natural area and an area in the middle of a
flower bed as the area with disturbance.
If you think adding fertilizers to the area would result in more
diversity, your hypothesis might be……
“Soil
samples taken from a flower bed will contain a greater diversity of soil
dwellers than soil samples taken from a natural wooded area.”
Step 1: Decide
which pair at the lab table will take the sample from the natural area and
which pair will take the sample from the disturbed area. Describe those areas below.
Natural Area:
Area with Interference:
Step 2: Work with
your team to formulate a hypothesis.
Hypothesis:
What
led you to make this hypothesis?
Experimentation Procedure:
1. Label a mason
jar with your names and sample location.
2. Cut the bottom
out of the plastic milk jug and invert it over a mason jar to
make a funnel.
3. Pour about
1.5cm of ethanol into the mason jar.
4. Bend the
corners of the 15 cm x 15 cm hardware cloth so it fits snugly in
the funnel.
5. Go to your
sample site and use the shovel to collect the top layer of a
15 cm x 15 cm surface area. Put the sample in a plastic bag.
6. Transfer the
contents of the bag into the top of the Berlese
funnel. Let
all the lose
material fall through before placing it on the mason jar.
7. Secure the
funnel on the jar using a stick and tape if necessary.
8. Leave in a
safe, warm place to dry out. As the
sample dries, animals will
move down and fall
into the alcohol. After a week or so,
carefully remove
the mason jar and
screw on its lid.
Data
Collection: After the sample has dried out, pour the ethanol containing the
invertebrates into a specimen dish. Put
the dish under the stereoscope and fill out Table 1 related to the organisms
you have found. Use the Kwik-Key to identify all organisms you can. As you classify each organism, use the dropper
to move the organism into the second dish. If you come across an organism you can’t classify,
describe it instead. You may find it
useful to use a piece of black paper to help you better see clear invertebrates.
Table 1: Number/Diversity of Invertebrates
in Natural and Disturbed Areas
|
Organism (identified or described) |
Number in Natural Area |
Number in Disturbed Area |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Total # of
organisms (add
each column) |
|
|
Calculate how many
total organisms you would find in each area if you were to take a m2 sample instead. A 15 x 15 cm sample = 225cm2. Use this formula:
Total number of organisms in m2
= (total number found in 15cm2/0.0225)
Total number of
organisms in a m2 of natural area = __________________
Show your work
here.
Total number of organisms
in a m2 of disturbed area = ________________
Show your work
here.
Conclusion
Questions: Use complete sentences where appropriate.
4.
What are some sources of error that could have affected your results?
5.
What other factors (either human or natural) can you think of to test if you
wanted to know what else effects soil dweller diversity?
6. If you were
to do this experiment again, what would you do differently?
7.
What are some long term effects of humans disturbing natural environments?
What could humans do to minimize these effects?