Teacher’s guide
1. Purpose
- The purpose of this lab is to introduce students to the
microorganisms that live in a freshwater ecosystem. This lab uses
water from a lake but other common sources are ponds, rivers, etc.
This lab is meant to be an introduction to a unit on ecosystems, and
to get students thinking about how there are many different factors
that must work together to maintain a stable ecosystem.
2. Concepts
- Biotic and abiotic factors
- Fresh Water Ecosystem
- Microorganisms (and their importance to an ecosystem)
- Taxonomy (emphasis on phylum)
3. Objectives/Standards
- Define biotic and abiotic.
- Provide examples of biotic and abiotic factors
- Describe microorganisms that are found in a fresh water ecosystem
- Compare and contrast microorganisms of similar and different
phyla.
- Stage H, 12B, 1
- Stage H, 12A, 3
4. Materials
- Slides & cover slips
- Microscopes
- Medicine droppers or pipettes
- Pond or Lake water
- Dixie cups
- Biology textbooks
- Computers with internet access
5. Preparation guide, distribution of materials, refill instructions, etc.
- Water that is to be examined should be collected from a lake or
pond prior to the lab. It is recommended to collect water near plant
material relatively close to when the lab will be conducted.
- Students should be paired up or work in groups of no more than
three. One group will be at each station. The station should include
one microscope, and students will be given a lab packet. Students
may also need their textbook.
- At the front of the room there will be slides and cover slips,
medicine droppers/pipettes, and the lake water sample with Dixie
cups. Each group should come up and obtain their own sample of
the lake water and transport it to their station via the Dixie cup.
Students will also need to grab one slide and cover slip, and one
medicine dropper/pipette to bring back to their station.
- There should be no need to refill as long as plenty of lake water is
obtained. Students may need plenty of pipette tips.
- Lab packets and assignment hand outs are included below.
6. Time/length of lab
- Prelab discussion (5 minutes)
- Lab activity and Postlab discussion of what students saw (20 – 30
minutes)
- Microorganism Research Assignment (30 - 40 minutes)
- Group reports (15-20 minutes)
- This lab would be a 2 day activity with students finishing up the
assignment on the second day.
7. Safety issues
- There are no major safety issues with this lab other than students
should not drink the water.
- It also may be a good idea to have students wash their hands after
working with the water.
- All materials can be disposed in the sink.
8. Prelab discussion guide
- Announce to students that we will be starting a unit on ecosystems
and the first ecosystem that will be studied is freshwater.
- On one side of the board write abiotic and on the other side of the
board write biotic. The discussion should be started by asking
students if they know what these mean, and they can be guided to
the right answer.
- After it is established what abiotic and biotic mean, have students
make a list of abiotic and biotic factors that would be found in a lake
ecosystem.
- Lead the students to include microorganisms as an important biotic
factor in the ecosystem. Have them come up with a list of any
microorganisms they can think of that would live in lake water.
- Introduce the lab activity
9. Postlab discussion guide
- Students should discuss what they saw under the microscope.
- Go over answers to the postlab questions to make sure students
answered them correctly. Clear up any misconceptions.
- Introduce the Microorganism Research Assignment.
10. Any special notes
- It is probably a good idea to do a sample slide of water to make
sure there are microorganisms in the water that you collected. If
not, then you may need to find another source of water.
- To move the lab along faster, you can obtain many containers of
lake water so that each group has their own. This eliminates the
need for Dixie cups.
- To also save on time, you can have the microscopes out and set up
at each station. It also might be a good idea to dismiss groups one
at a time to come up and collect the materials that they will need to
avoid chaos.
- Computer lab should be reserved ahead of time if you do not have
one in your classroom.
11. Diagram of the lab set up
Lake water
sample
Microscope
Lab packet to
record
observations &
answer
questions
Slide and
cover slip
Pipette/medicine
dropper
Fresh Water Organism Identification Lab
Ecosystems are the combined physical and biological components of an environment.
Physical factors of the environment are referred to as abiotic factors, and biological
factors are referred to as biotic factors. Abiotic and biotic factors work together to
create a stable ecosystem. Ecosystems have many different kinds of organisms living
and working together. These organisms can be rather large such as fish or ducks, or
they can be invisible to the naked eye.
For this lab you will be working in pairs. You and your partner will examine a sample of
lake water taken from a fresh water ecosystem. You will use a microscope to identify
microorganisms that live in the lake water. Record your observations in the table below,
including the name of the organism and how many were found in your sample. Then
answer the questions at the end of your lab packet.
To help you indentify the organisms in the lake water, you and your partner will be
given an identification key.
Observations
Organism Name
Number
Found in
Sample
Other Observations (movement, color, etc.)
Questions
1. What organism in your lake water sample was the most abundant? Least
abundant?
2. Some of the organisms that you may have observed might have appeared to be
a green color. What is causing the organism to appear green? What is the
function of that substance?
3. Describe the importance of microorganisms (including bacteria) and what would
happen if all microorganisms would suddenly disappear from the lake.
4. Describe the movement of the organisms that you observed with the microscope.
Did they all move in the same way? How was their movement different?
5. List two abiotic factors that can affect a fresh water ecosystem. Describe how
these might also affect the microorganisms that live in this water.
Organism Identification Sheet
Microorganism Research Assignment
Now that you have seen first-hand what the microorganisms in a fresh water
ecosystem look like, you and your partner will research these organisms to learn
more about them. Each group will be assigned a microorganism to research
using the following website:
http://www.microscopy-uk.org.uk/
Once you are at the website you will want to click on the “Pond Life ID Kit” link.
You will also need to visit the “Virtual Pond Dip” link.
You and your partner will need to use this website to answer the questions
below. After all groups are finished researching their microorganism, each group
will share their findings with the class.
1. Is this microorganism single-celled or multicellular?
2. Where would you most likely find this microorganism?
3. What is the relative size of your microorganism compared to other
microorganisms found in fresh water ecosystems?
4. Describe the appearance of your microorganism. What does it look like?
5. List three special characteristics about your microorganism.
6. What kingdom and phylum does this microorganism belong to?
7. List two other microorganisms that are found in the same phylum. How
are these microorganisms similar to the one that you have been
researching?
8. List two other microorganisms that are NOT found in the same phylum.
How are these microorganisms different to the one that you have been
researching?