Lesson 2. Investigating Nutrition, Digestion, and Circulation in Unicellular Organisms
Estimated Time: 2 days
Objective: To compare and contrast how unicellular ad multicellular organisms perform the life
processes of nutrition, digestion, and circulation
EQ: How is nutrition, digestion, and circulation in a unicellular organism different from that of
a multicellular organism?
Bridge: (recall) Have students briefly describe the process that a human needed to go through
to get nutrients to a cell.
Mini Lesson: Have students share out their responses. (Start with one student then have others
fill in blanks or things that were left out to get a quick reminder of the processes. Make sure that
the students mention the HCl in the stomach that is creating the acidic environment for the
pepsin to work-this is very important for the lab and tracking the digestion of food by the
paramecium!).
Expectations for work period: obviously unicellular organisms do not have the organs that
multicellular organisms do, yet they still have to get nutrients, digest these nutrients, and get
them where they need to go within the cell.
1. You will be following a given procedure to observe how one unicellular organism
obtains, digests, and circulates their nutrients.
2. Compare and contrast your observations to the information that you gathered yesterday
on these processes in humans.
3. Prepare some wet mount slides and develop a procedure to see if all single celled
organisms carry out nutrition, digestion, and circulation the same as the paramecium
Work Period: Complete the investigation and questions
Summary: Answer the EQ, using evidence from your experiments to support your answer.
Closing: You have observed how humans obtain, digest, and move nutrients through their
bodies as well as how some unicellular organisms perform the same functions. However,
humans are not the only animals on earth and they certainly are not the same as plants and
fungus. Do you think that the other groups of vertebrates (fish, birds, amphibians, reptiles) carry
out these three processes the same way or differently from mammals (like humans)? Explain
your reasoning.
SPED & ELL Modifications:
1. For lower functioning students give them a diagram of the digestive system to use as a
visual cue for the bridge
2. For the Mini Lesson: Students can watch the Amoeba eat the Paramecium in this video:
http://www.youtube.com/watch?v=pvOz4V699gk&feature=related
3. Students could work with partner to complete the questions during the work period.
4. Pre-record the reading for the independent practice or pair students with reading partners
to be able to read the background information for them.
Apps and Internet Activities:
Youtube App: Students can use the iPads or Netbooks to find two videos of both
unicellular and multicellular digestion and
MindMeister App: Students can use either iPads or Netbooks as it is a Web2.0 Tool and
create comparison charts of the multicellular vs Unicellular digestion (keep in mind for
both the 2.0 tool and App students will need to create an account.
Popplet App: Could be used to make a comparison chart as well
Independent Practice: The background reading provided information on paramecium,
including their importance in what was called “detritus- based food webs in aquatic ecosystems”.
Using this description and your knowledge of biology, create a food web that has at least 6
organisms in it (one being the paramecium) to show the nutrient/energy flow and
interdependence.
Paramecium Feeding Lab Tips
To make the stained yeast suspension, prepare a thick suspension of yeast that has been mixed
with water. Add a small amount of congo red to the yeast suspension. It should be a bright red
color. Bring the yeast/congo red suspension to a gentle boil for 5 minutes. Allow the suspension
to cool before using in the experiment.
Methyl cellulose solution can be purchased or made by adding 3 g of methyl cellulose to 100 ml,
of distilled or deionized water.
A rich culture of Paramecia will guarantee that students will witness a Paramecium feeding.
Good microscope focusing technique and light regulation will be required for this lab. Review
these techniques with students prior to the lab.
Yeast/Congo red suspension:
 Add 3 g dry yeast to 10 ml water and stir. Add 0.3 g Congo Red.
 Boil gently for 10 minutes. This will keep in the refrigerator for a week.
 This thick solution may be diluted by buffer prior to use.
Preparation Notes for this lab:
You will have to collect pond water samples for the experimental design section. I did not
include an identification key here since the microorganisms you will collect will vary from
collection locations and with the temperature. You will need to create this yourself or allow time
for the students to find the organisms online (that takes a LOT of time)
I usually get my paramecium from the pond water as well, although this is very time consuming
to pick them out of the sample (from Mendon Ponds but most creeks or fresh water bodies in the
area have tons of microorganisms in them) and I start collecting pond water in August (make my
own kids separate out the paramecium) and then culture it in an “artificial pond” which is just a
big clear glass jug, throughout the year (same with the Daphnia) but you can order paramecium
cultures from Wards or Carolina. To really cut back on time if you planned ahead and have a
budget in your school for supplies, you could choose 3-4 different microorganism cultures, mix
them together, and throw in some Elodea and just tell the students its pond water 
**If you are strapped for time/money on this lab, the first part of the yeast digestion can be
achieved through this 2 minute video:
http://www.youtube.com/watch?v=l9ymaSzcsdY&feature=related
And then have them do the guided inquiry lab piece (second part) only.
Name ________________________________________________________
School
Living Environment
Date ______________________
Digestion in Unicellular Organisms
Background Information:
Paramecia (singular: paramecium) are a slipper shaped ciliates which is found in
oxygenated aquatic environments feeding near vegetative matter. Paramecia are unicellular
microorganisms belonging to the protoctist phylum Ciliophora. Members of this phylum
(ciliates) are characterized by their external covering of continuously beating, hair-like cilia.
Cilia are motility organelles homologous to the undulating tails of sperm cells and the epithelial
cilia which line our respiratory tracts: they help the paramecia to move. These single celled
organisms must perform all of the same functions as a multicellular organism without specialized
cells found in multicellular organisms, and it is their ability to fulfill these requirements along
with their elaborate cell parts, making them among the most functionally complex cells.
Viewed through a microscope you can see many structures the paramecium use to
perform these life functions. The buccal cavity, or oral region, is located toward the anterior of
the cell. This orifice (opening) is lined with highly organized rows of beating cilia which draw
food particles into the cytopharynx (equivalent to the throat of the cell) where they are
incorporated into food vacuoles and digested. Also visible within the cytoplasm are two, large,
sporadically contracting vacuoles at either end of the cell. The contraction of these vacuoles
expels water from the cell as a means of balancing its salt concentration.
Paramecia are a key link in detritus-based food webs in aquatic ecosystems. Most
paramecia are bacteriovorous and feed voraciously on bacteria that accompany decaying organic
matter. These bacteria-gorged cells are then consumed by other protists and small animals, which
are in turn preyed upon by larger organisms. The oldest reported fossil Paramecium was
discovered in a piece of amber dating back to the Cretaceous period, over 65 million years ago.
Question: How does a paramecium get food from its environment and how does it break the
food into nutrients?
Prediction/Hypothesis:
Experimental Design:
Materials
Paramecium culture
coverslips
yeast culture
microscope
Methyl cellulose solution (3%), cotton fibers (pulled from a cotton ball is fine) or Protoslo
microscope slides
Congo red (stain and indicator for this lab)
Procedure:
1. Prepare a stained yeast suspension by adding a few drops or 0.3g of Congo Red to the yeast
suspension. Boil the yeast and Congo red for approximately 10 minutes and allow to cool before
adding this to the paramecia on your slide. (you may want to do this the day before the lab or
your instructor may have done this for you already)
2. Place a ring of methyl cellulose or cotton fibers on a clean microscope slide.
3. Place a small drop of Paramecia culture in the center of the methyl cellulose ring or on cotton
fibers.
4. Add a small drop of stained yeast suspension to the Paramecia drop.
5. Cover with a clean coverslip and immediately observe with a microscope.
6. Locate a Paramecium and observe what happens to the stained yeast cells. The Paramecia will
ingest some of the yeast cells very quickly, perhaps within 10 seconds of adding the yeast.
7. Study the food vacuole formed inside a Paramecium and observe it for at least 10 minutes.
Hint: You will have to continuously focus up and down "through" the Parameciumand regulate
the light carefully.
8. Record the color of the ingested yeast in your data table every two minutes for a total of 10
minutes.
9. Draw a sketch of the Paramecium and show the path of the ingested yeast and include & label
the nucleus, cell membrane, oral groove, food vacuole, and cilia in your sketch (see the diagram
in the background information for help if needed).
Data
Create a data table for your results.
Use your procedure and your question
to help you figure out what you should
include.
With your data, consider the following
questions (especially when moving to
the data analysis section!):
Paramecium Sketch:
How is the yeast different from the Paramecium?
How did the yeast cells get to the inside of the
Paramecium?
What color and shape were the yeast cells initially?
What does the color tell you about the pH?
About how long does it take for the food vacuole to
cycle through Paramecium?
Was there any change in the shape of the yeast cells
over time? What was it?
Was there any change in color of the yeast cells over
time? What does the change in color, if any, tell you?
Data Analysis
Evaluation
How does digestion in the paramecium compare to what we saw yesterday in multicellular
organisms?
Design an experiment to see if ALL unicellular organisms carry out these three life functions the
same as the paramecium does. Use your lab template for recording purposes. You will find
multiple unicellular organisms in the pond water samples you will be drawing from. Use the
picture key and characteristics that you observe to figure out what unicellular organism(s) you
are looking at.