OWL PELLET AND ENERGY PYRAMID LAB Online
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You will need a camera for this lab.
Main heading for your post: Owl Pellet and Energy Pyramid Lab
Subheadings: Part 1 Owl Pellet Dissection, Part 2 Ecological Pyramids
See what to submit under each part. You will only work with one pyramid in Part 2.
Objectives
1.
2.
3.
4.
5.
6.
7.
8.
Demonstrate an understanding of the nature of science and the scientific process.
Classify animals according to type of skeletal structure.
Identify bones that compose the skeletal system.
Trace the flow of energy through the trophic levels and energy pyramids.
Explain how organisms interact within an ecosystem and how owls affect an ecological community.
Demonstrate analysis of data to produce visual results and written explanations.
Perform calculations to determine patterns.
Demonstrate collaborative skills.
Introduction
Owl pellets are the undigested remains of prey ingested by an owl. The owl swallows its prey whole, and during
the process of digestion, the soft parts of the prey are dissolved and passed on to the intestine for absorption.
The hard, non-digestible parts-bones, teeth, fur, feathers, and chitonous remains of insects are compressed in
the gizzard and passed on to the proventriculus, the first chamber of the owl’s stomach, where the pellet
remains until it is expelled. These pellets are not eliminated as feces, but are regurgitated through the mouth.
The Common Barn Owl feeds in early morning and early evening and will usually produce one to two pellets per
day. Glossy black when fresh, the pellet remains smooth and dark in color when dry. Your pellet has been
fumigated to eliminate the presence of any insects and then individually wrapped for preservation. Unless
otherwise stated, the pellets in this lab are from the family Tytonidae and more specifically, the Common Barn
Owl, Tyto alba.
View this video to learn more about owls and pellets, http://youtu.be/JdrbSzC6Jcg.
View these slideshows to learn more, http://www.barnowltrust.org.uk/infopage.html?Id=193.
Safety
1. Be careful with sharp tools and bones.
2. Wash hands after activity.
Materials
Owl pellet
Camera
Dissecting surface
Scale
Bone sorting charts
Other small tools, as supplied
Glue
Sheet of plain paper or cardboard for mounting bones
Part 1 Owl Pellet Dissection
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What to submit for this part:
o Table 1 (1 points)
o Photo of chart with sorted bones (2 points)
o Photo of reconstructed skeleton (2 points)
o Table 2 (1 points)
o Graph of species numbers (2 points)
o Comments about other species found
Procedure
1. Remove the pellet from the aluminum foil.
2. Measure the length and width of the pellet and record these measurements in Table 1.
Table 1. Owl Pellet Measurements
Length
Width
3. Place the pellet on the dissecting surface. Carefully separate the bones from fur or feathers onto
another part of your surface using your fingers and available tools.
4. Carefully clean the bones by picking or scraping off debris and sort them according to type—skulls, jaws,
vertebrae, etc.
5. When you are sure that all bones have been separated, dispose of the other materials in the trash.
6. Identify the animals found in your pellet by matching the bones in your pellet with those in the Bone
Sorting Chart.
7. Place each bone beside the matching bone on the Bone Sorting Chart.. You may have many of each type
of bone sorted and glued or just a few.
8. Take a photo of your chart with the sorted bones.
9. Reconstruct a partly complete skeleton of one prey animal. Glue the parts on a sheet of paper and take
a photo.
10. Record the types and numbers of animals in Table 2.
Table 2. Kinds and Number of Animals Found in Owl Pellets
No. Voles
No. Shrews
No. Birds
Your Data
11. Make note of any other species you can identify.
2
No. Moles
No. Rats
12. Construct a bar graph of the data in Table 2, using the grid below or another source.
Part 2 Ecological Pyramids
The amount of energy or matter in an ecosystem can be illustrated by a drawing called an ecological pyramid. In
this activity you will construct three types of ecological pyramids, a number pyramid, a biomass pyramid, and an
energy pyramid.
Each pyramid you construct will consist of four trophic levels. The top of each will relate to your owl, the only
tertiary consumer (3o). The next level down will relate to the owl’s prey, the secondary consumers (2o). For the
purposes of this activity, assume the prey found in the owl pellets are secondary consumers. The next trophic
level down will relate to the organisms eaten by the owl’s prey, the primary consumers, (1o). The base of each
pyramid will relate to the organisms eaten by the primary consumers, the producers. Use the information
obtained from your owl pellet dissection to construct the ecological pyramids below.
A. Number Pyramid for a 24-hour Period
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Only students with last names starting with A through H perform this part.
What to submit for this part:
o A drawing or depiction of the completed number pyramid. You may not copy and paste
someone else’s pyramid. (5 points)
o Calculations for number 3, 4, and 6 (3 points)
o Answers to questions 1-4. (4 points)
A number pyramid is an ecological pyramid that indicates the total number of organisms in each trophic
level.
1. Draw your pyramid on a separate piece of paper, labeling the number of 3o, 2o and 1o consumers.
Reminder, there is only 1 owl, which is the 3o consumer.
2. From the number of skulls in your pellet (same type or different types) determine the number of
prey consumed. One skull = one prey animal.
3. Determine the ratio, R, of the number of 2o consumers to the number of 3o consumers.
R = # 2˚ Consumers
3
# 3˚ Consumers
4. Use R to calculate the number of 1o consumers by multiplying the number of 2o consumers by R.
# 1o Consumers = R (# 2˚ consumers)
5. Label your pyramid with the number of 1o consumers.
6. Calculate the number producers by multiplying the number of 1o consumers by R.
# Producers = R (# 1˚ consumers)
7. Finish your pyramid by labeling it with the number of producers.
1. What are owl pellets?
2. During the nesting season the young need an enormous amount of food for growth. If the nest
contains three young and each of the young eat five mice per night for a month and the two
adults eat four per night, how many mice would the parents have to capture in 30 days?
3. The pellets are from what owl family?
4. Environmentalists are concerned about the accumulation of certain poisons in predators. Why
do you suppose owls, eagles, swordfish, humans and lions are often the most threatened
organisms of a community that are exposed to DDT or mercury?
B. Biomass Pyramid for a 2.5-year Lifespan.
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Only students with last names starting with I through P perform this part.
What to submit for this part:
o Completed Table 3 (3 points)
o Drawing or depiction of your biomass pyramid. You may not copy and paste someone
else’s pyramid. (2 points)
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Calculations for number 3, 5, and 7 (3 points)
Answers to questions 1-4 (4 points)
A biomass pyramid is an ecological pyramid that indicates the total mass of organisms in each trophic
level.
1. Complete Table 3.
Table 3
A
B
C
Prey types
Biomass
No. found
in pellet
House
Mouse
20 g
Vole
40 g
D=
C x 365
No. eaten
per year
(1 pellet
per day
for 365
days)
4
E=
BxC
F=
E x 365
Biomass
eaten per
24 hours
(g)
Biomass
eaten per
year (365
days) (g)
G=
F x 2.5
Biomass
eaten
over a 2.5
year
lifespan
(g)
Shrew
5g
Brown Rat
240 g
Bird
80 g
Other
Total
2. Draw your biomass pyramid on a separate piece of paper. Label the total biomass of the 3o
consumer. Assume the owl’s biomass is 500 g.
3. Determine the new ratio, R, of the total biomass of the 2˚ consumers to the total biomass of the 3˚
consumers.
R = Biomass of 2˚ consumers
Biomass of 3˚ consumers
4. Add the biomass of the 2o consumers to your pyramid.
5. Use your ratio, R, to calculate the total biomass of the 1˚ consumers by multiplying the total biomass
of the 2˚ consumers by R.
Biomass of 1˚ consumers = R (biomass of 2˚ consumers)
6. Add the total biomass of the 1˚ consumers to your pyramid.
7. Calculate the total biomass of the producers by multiplying the total biomass of the 1˚ consumers by
R.
8. Finish your pyramid by labeling it with total biomass of the producers.
Answer these questions.
1. What happens to the soft parts of the prey?
2. These pellets are not eliminated as _________________, but are regurgitated through
the ___________________.
3. In terms of energy flow in an ecosystem, why is the amount of energy passed from one trophic level to
the next so small? Since we know energy cannot be destroyed, account for the loss of energy that
occurs between the prey and the owl.
4. Describe any pattern you see.
C. Energy Pyramid for a Trophic Level.
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Only students with last names starting with Q through Z perform this part.
What to submit for this part:
o Drawing or depiction of your energy pyramid. You may not copy and paste someone else’s
pyramid. (5 points)
5
o
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Calculations for number 2 and 3. (2 points)
Answer questions 1-5 (5 points)
An energy pyramid is an ecological pyramid that indicates the amount of energy in each feeding level.
According to the terms of thermodynamics, only about 10% of the energy available within one trophic
level is transferred to organisms at the next trophic level.
1. Assume that the producers in this pyramid (plants) contain a total of 500,000 Calories of food
energy. Draw an energy pyramid and label the base with this value.
2. Calculate the amount of energy for the 1˚ consumers by multiplying the food energy of the
producers by 0.10. Write this value in your pyramid.
3. Complete your energy pyramid by calculating and labeling the energies for the top two trophic
levels. Assuming that the barn owl regurgitates one pellet per day, how many prey items would the
owl that produced your pellet consume per year?
Answer these questions.
1. Where does the pellet remain until it is expelled?
2. List 6 other birds that are known to regurgitate pellets.
3. Placing the owl at the highest trophic level, create a food web using the following items: vole, deer
mouse, mole, house mouse, weasel, shrew, snake, starling, frog, salamander, spider, grubs, earthworms,
centipedes, crane fly, seeds, plants, roots.
4. Why does the number of organisms decrease as you move up the pyramid level?
5. We know that about 50% of the energy in an organism is not digested by the consumer and is simply
passed through as waste or feces. Is the energy stored in the feces lost to the ecosystem? Why or why
not?
6
How to
measure
the jaw
Tooth
types
Jaw Length
Lobed
Angled
Pointed
Rat
Vole
Mouse
Shrew
Bird
Jaw Length (mm)
17-30
15-20
10-15
7-14
15-40
Tooth Type
Lobed
Angled
Lobed
Pointed
None
Skull and Jaw
Shoulder Blade
Hip
Upper Leg
Lower Leg
Rib
Vertebra
Foot
2