What is a Microorganism?
Introduction to Microorganisms
NPS/MARC NEIDIG
National Park Service
U.S. Department of the Interior
Zion National Park
Zion National Park, April 2014 What is a Microorganism? 2
Theme
Though they cannot be seen with the
naked eye, there are millions of diverse
microorganisms living everywhere around us,
performing a variety of important functions.
Focus
This activity guide provides the definition, and
explores examples of microorganisms, and the
places microorganisms are found.
Activities
How Small is Small?
By using a large scale, students will be able
model the size of specific microorganisms and
compare them with the size of a human hair.
Mystery Microorganisms
Students will learn about the five categories of
microorganisms by classifying a set of species
(their “Mystery Microorganisms”).
Microorganisms Are Everywhere –
Even in Zion National Park!
Students will use a description and photo
to categorize a species of microorganism
and determine where it might live in Zion
National Park.
Background
Just as there are millions of different
species of plants and animals in the world,
there are millions of different species of
microorganisms. Microorganisms can survive
in environments where humans are unable
to live. Microorganisms exist throughout the
world, from Antarctica to your kitchen, from
inside animals, like humans, to the expansive
wilderness in Zion National Park.
Introduction
This guide contains background information about what microorganisms
are and directions for three activities that will help students better
understand microorganisms and how they relate to everyday life and
Zion National Park. The activities are most beneficial to students when
completed in order. This guide is specifically designed for sixth grade
classrooms, but the activities can be modified for students at other levels.
A microorganism is defined as a living thing
that is so small it must be viewed with a
microscope. Some microorganisms like viruses
are so small they can only be seen with special
electron microscopes.
There are five different categories of
microorganisms—bacteria, algae, protozoa,
fungi, and viruses—explained in further detail
in Mystery Microorganisms. Microorganisms
cover almost all the kingdoms of life. Bacteria
and some algae are in the Monera kingdom
(sometimes divided into the separate
Eubacteria and Archaebacteria kingdoms),
algae and protozoa are in the Protista
kingdom, and fungi make up their own
kingdom. There is ongoing debate about how
to classify most microorganisms (for instance,
some scientists put some types of algae in the
Plant kingdom while others do not).
Microorganisms of all kinds can be found in
Zion National Park and southern Utah. In
many cases, these microorganisms can actually
be seen at work, such as the fungi, algae, and
bacteria that build up the fragile spires of
biological soil crust, or the algae which gives
the Emerald Pools a green color.
Microorganisms are also prevalent inside us.
While we like to think of ourselves as being
made up of human cells, we are actually
90% microbial: there are 10 times more cells
from microorganisms in our bodies than
human cells. That means there are trillions
of microorganisms living inside us every day.
Most are helpful to us, such as bacteria that
help us digest our food. Scientists now think
that a diversity of microorganisms inside of us
help us resist many diseases.
Core Connections
Utah Core Curriculum
Sixth Grade Science
Standard 5: Students
will understand that
microorganisms range from
simple to complex, are found
almost everywhere, and are
both helpful and harmful.
Objective 1: Observe and
summarize information about
microorganisms.
Objective 3: Identify positive
and negative effects of
microorganisms and how
science has developed positive
uses for some microorganisms
and overcome the negative
effects of others.
Activity Materials
Corresponding materials
which may include images,
worksheets, and answer keys
are available for each activity.
Materials can be downloaded
from the lesson plan webpage,
found here.
Zion National Park, April 2014 What is a Microorganism? 3
How Small is Small?
Duration
45 Minutes
Location
Outside or inside area with a large open space
Key Vocabulary
organism, microorganism, single-celled, algae,
bacteria, fungi, protozoa, virus
Objectives
Students will be able to conceptualize the size
of microorganisms and give a definition of
what a microorganism is.
Method
By using a large scale, students will be able
model the size of specific microorganisms and
compare them with the size of a human hair.
Background
The average human hair is 0.1 millimeters
wide, and barely discernable with the naked
eye. Microorganisms are many hundreds to
thousands of times smaller and by definition
can only be seen under a microscope.
Most microorganisms consists of only one
cell and they are known as single-celled
organisms (in comparison, humans consist
of trillions of different cells). Different
species of microorganisms vary in size, shape,
appearance, and way of surviving.
The largest microorganisms are most fungi
and many species of protozoa. Viruses are
by far the smallest of all microorganisms. If
a virus was the size of a baseball, an average
bacterium would be the size of a pitcher’s
mound, and one single human cell would be
the size of the entire stadium!
Materials
• meter stick or ruler
• magnifying glass
• marking material for ground (i.e. sidewalk
chalk, markers, or string)
• a hair from a human head
• 5 meters of butcher paper (if inside)
Suggested Procedure
1. Introduce the idea of what microorganisms
are and that they cannot be seen with the
naked eye.
2. Have students examine a human hair (one
can be passed around and/or students can
examine their own). Students can look
at how thin the hair is with and without
magnifying glasses.
3. Go outside or into your open space, and
use the meter stick to measure an area 1
meter long. Mark it with chalk, string, or
tape (depending on your location). One
meter represents the 0.1 millimeter width
of a hair using the scale of 10,000 :1.
4. Using the information below, add different
microorganisms to the ground or paper.
Students can measure out the size and label
the different cells and microorganisms:
Human red blood cell (.01 mm) = 10 cm
Paramecium (protozoa) (0.2 mm) = 2 m
Euglenoids (algae) (0.4 mm) = 4 m
Scenedesmus (algae) (0.03 mm) = 30 cm
E. coli bacteria (.002 mm) = 2 cm
Staphylococcus bacteria
(.0005 mm) = 0.5 cm
Polio virus (.00002) = .2 mm (a tiny dot)
5. When finished measuring out all the
microorganisms, compare their sizes.
Notice how viruses are the smallest type
but other types vary in size depending on
the species. Students can draw their own
reference models on paper to keep.
6. Finish by asking students (verbally or in
writing) why scientists have to use models
like this (because some microorganisms
are too small to be seen under regular
microscopes and it is difficult to
compare sizes and features of a variety of
microorganisms because of their size).
Extension
Have students research the size of other
microorganisms to compare size and practice
math skills using the 10,000:1 scale.
Find large items to compare microorganisms
to such as a pencil, a school bus, or a football
field. For instance, if the 2,000 foot tall cliffs of
Zion Canyon were on the scale, they would be
over 3,800 miles long, the distance from Las
Vegas to Chicago and back!
The rod shape of E. coli can be
clearly seen under a scanning
electron microscope.
Micrasterias americana algae at
400x magnification.
NIH
PROYECTO AGUA
Zion National Park, April 2014 What is a Microorganism? 4
Digital interpretation of
rhinovirus.
Aspergillus fumigatusas, a fungi,
visible under a microscope.
Algae color the water green at
the Emerald Pools.
Mystery
Microorganisms
Duration
45 Minutes
Location
Inside
Key Vocabulary
organism, microorganism, single-celled, algae,
bacteria, fungi, protozoa, virus, producer,
decomposer
Objectives
Students will be able to list the five different
types of microorganisms and share the specific
attributes of at least one type.
Method
Students will learn about the five categories of
microorganisms by classifying a set of species
(their “Mystery Microorganisms”) as one of
the types of microorganisms.
Background
Generally, there are five categories of
microorganisms (simpler definitions are
located in the glossary for student use):
Bacteria: These microorganisms are the
oldest living things on Earth, and have been
around an estimated 3 billion years (scientists
have found fossils of cyanobacteria). They
come in a variety of shapes (spheres, rods,
or spirals) and are a diverse set of organisms.
However, all of them are prokaryotes (they
lack a nucleus). Bacteria is plural, bacterium is
singular.
Algae: While not all algae are green, all
algae are capable of photosynthesizing and
are producers. However, most algae are not
plants, and the majority are in the Protista
kingdom. Like plants, algae produce oxygen
and account for about 70% of all the oxygen
produced on Earth. Algae can be single-celled
or multicelled. Algae mostly grow in water and
include seaweed and “pond scum.” Algae is
plural, alga is singular.
Fungi: All fungi are decomposers, breaking
down dead matter for nutrients, and they
cannot produce their own food. Fungi are
distinguished from other decomposers in that
they reproduce using spores, tiny, seed-like
cells. Most fungi are multicellular, but others
such as yeast are single-celled. Most cells of
fungi are loosely connected through thread-
like filaments called hyphae. Fungi is plural,
fungus is singular.
Protozoa: The name protozoa means “first
animal,” and describes this microorganism’s
ability to move and hunt. Protozoa are
members of the Protista kingdom. Ciliates,
amoebae, and flagellates all are categories
of protozoa and all are single-celled. Most
protozoa do not cause disease but there are
a few that cause harm to humans, including
Plasmodium (malaria) and Giardia. These
protozoa are considered parasites. Protozoa is
plural, protozoan is singular.
Viruses: There is some debate on whether
viruses are actually organisms at all; that is,
whether they are alive or not. While they
have DNA or RNA and infect a host like
other parasites, viruses have no true cells and
cannot reproduce on their own. Viruses is
plural, virus is singular.
Materials
• Mystery Microorganism Clues sheets
• Large (8.5 x 11) envelopes
Suggested Procedure
1. Prepare “mystery packets” ahead of time
using the Mystery Microorganism Clues
sheets. Print one set of each and put them
in large envelopes labeling them “Mystery
Microorganism #1,” etc. Each packet
should have two or three photos all from
the same grouping (virus, bacteria, etc.). If
students have access to laptop computers
or tablets, photos could be loaded and
viewed digitally.
Mystery Microorganism #1 (Virus)
• HIV/AIDS
• The common cold
• Chickenpox
Mystery Microorganism #2 (Bacteria)
• Yogurt
• E. Coli
• Streptococcus
NPS/BRYANNA PLOG
HHS
ROBIN S
Zion National Park, April 2014 What is a Microorganism? 5
Mystery Microorganism #3 (Protozoa)
• Malaria (Plasmodium)
• Amoeba proteus
Mystery Microorganism #4 (Fungi)
• Bread mold
• Penicillin
• Mushrooms
Mystery Microorganism #5 (Algae)
• Algae on a pond
• Algae (microscope photos)
2. Write the five different categories of
microorganisms on the board, with the
definition underneath (write on a white
board or print out and put up). Go over the
definition of each type of microorganism
with the class:
Bacteria: single-celled organisms that are
shaped like spheres, rods or spirals
Protozoa: single-celled parasites that act
like animals (feed on and destroy bacteria
and other organisms)
Fungi: decomposers that break down
matter, including bacteria
Algae: single-celled and plant-like
Viruses: non-living; cause many diseases
3. Divide the class into five groups and give
each group one of the mystery packets.
Each group has to figure out the category
for their microorganisms. Give each group
a few minutes to determine which category
of microorganism they think they have.
Tell them to be prepared to share their
reasoning with the class.
4. Once allotted time is up (5 minutes or
when all groups are finished), groups will
share their conclusions. You can go group
by group (i.e. which microorganism do you
think your group has?), or by the type of
microorganism (which group thinks they
have algae?). Have each group come to
the front and explain how their examples
fit the definition for their microorganism.
If there is room on the board, have each
group place their photos up under the
correct label and definition.
Extension
Ask the class a question to help further
define the different categories and have the
group stand up if the description fits their
microorganism. Questions could include: Is
yours a decomposer? A producer? Which
ones are alive? Which ones can cause disease?
Which can be treated by antibiotics?
Have students explore different types of
organisms online. Suggested site: “What
and where are micro-organisms” on: http://
www.childrensuniversity.manchester.ac.uk/
interactives/science/microorganisms/micro-
organisms/
Zion National Park, April 2014 What is a Microorganism? 6
Microorganisms Are
Everywhere Even in
Zion National Park!
Duration
45 Minutes
Location
Inside
Key Vocabulary
algae, bacteria, fungi, protozoa, virus,
decomposer, producer
Objectives
Students will be able to use their knowledge
of different types of microorganisms to
successfully categorize and describe specific
microorganisms and infer what type of
environment they might live in.
Method
Students will use a description and photo to
categorize a species of microorganism and
determine where it might live in Zion National
Park.
Background
Microorganisms are found all over the world
and can survive in a variety of extreme
conditions. They are found in steam vents,
boiling mud pots, and Antarctica. Some can
even survive radiation levels 10,000 times
higher than humans. Certain microorganisms
prefer water, others soil, and still others live
inside other living things.
Trillions of microorganisms live inside humans
and other animals. Most microorganisms are
helpful to us (and other animals), such as the
bacteria that help us digest food. Scientists
now think that a diversity of microorganisms
inside our bodies help us resist many diseases.
One reason microorganisms have been around
for billions of years is because they are able
to thrive in all types of environments. In one
gram of soil, for instance, there are around 40
million individual bacteria.
In dry areas like Zion National Park, bacteria
pair with cyanobacteria (blue-green algae),
fungi, algae, lichens, and mosses to create a
fragile soil crust called biological soil crust.
Biological soil crusts help prevent erosion
and retain water and serve many important
functions in Zion National Park and other
desert areas. Microorganisms can also be
seen in Zion National Park in areas like
the Emerald Pools where algae grow in
abundance.
NPS/BRYANNA PLOG
Zion National Park, April 2014 What is a Microorganism? 7
Materials
• Microorganisms Are Everywhere photos
and reference sheet
• Microorganisms in Zion Descriptions
and Worksheet
Suggested Procedure
1. Go over and show some of the different
and extreme places microorganisms
can live throughout the world (“Where
Microorganism Live” document). Explain
that microorganisms thrive everywhere:
some can live in the most extreme of
environments, but different species thrive
in different environments. Alternatively,
students could present each environment
in turn instead of the teacher.
2. Randomly assign students one of the
five microorganisms on the
Microorganism Descriptions sheets
(Rhizobia, Streptococcus bovis, Spirogyra,
Aspergillus, and Giardia). Hand out
printed copies or display the
“Microorganism Descriptions” sheets
about each microorganism so students can
see the information.
3. Give each student a “Microorganisms in
Zion” worksheet and have them use the
information from the Microorganism
Descriptions sheets to complete the
information. Allow them around 15
minutes to work.
4. Once students are done, group them
together by the microorganism. Allow them
time to discuss their answers with each
other and sort out any disagreements.
5. Have each group present their findings and
their microorganism.
Extension
Students can further research their
microorganism and write or share more
information about it with the class (e.g.
why the role of nitrogen-fixing bacteria like
Rhizobia is important or how to prevent
getting sick from Giardia).
Grand Prismatic Spring in
Yellowstone National Park
Biological soil crust forms when
bacteria, algae, and fungi
combine.
NPS
NPS/BRYANNA PLOG
Zion National Park, April 2014 What is a Microorganism? 8
Glossary
algae: single-celled plant-like organisms. They
produce their own food using photosynthesis.
bacteria: single-celled organisms that belong
to the Monera kingdom. They can be shaped
like spheres, rods, or spirals and can do
everything from decompose dead leaves to
cause disease.
decomposer: an organism that feeds on dead
or decaying organisms. They cannot produce
their own food but get their energy from
breaking down dead organisms.
fungi: a type of decomposer that reproduces
through tiny seed-like cells called spores.
While some fungi like mushrooms and molds
are large, other types of fungi are single-celled.
microorganism: an organism that is so small
it can only be viewed under a microscope
(not with the naked eye). They usually are
not plants or animals and come in a variety of
types, species, sizes, and shapes.
organism: any living thing, large or small. All
organisms need air, water, and energy and can
grow and reproduce.
producer: an organism which can produce
its own food using the energy from the sun to
photosynthesize.
protozoa: single-celled parasites that act
like animals (feed on and destroy other
microorganisms).
single–celled: an organism that is made up of
only one cell; in contrast, humans are made up
of trillions of cells.
virus: non-living agent of disease. Can
multiply and cause harm to the living thing it
infects.
References
American Society for Microbiology. “Let’s Get
Small.” Last modified 2006.
http://archives.microbeworld.org/
resources/experiment/experiment_lets_
get_small.aspx
Genetic Science Learning Center. “Extreme
Environments: Great Salt Lake. Last
modified January 2014. http://learn.
genetics.utah.edu/content/gsl/
Microscopy UK. “Pond Life Identification
Kit.” Last modified 1999. http://www.
microscopy-uk.org.uk/pond/protozoa.
html
National Park Service: Arches National Park
and Canyonlands National Park. “Lesson
Plans: Microorganisms in the Desert.”
http://www.nps.gov/arch/forteachers/
classrooms/6th_microorganisms.htm
The University of Manchester. “Micro-
organisms.” Last modified 2012.
http://www.childrensuniversity.
manchester.ac.uk/interactives/science/
microorganisms/micro-organisms/
Utah Education Network. Utah Core
Standards: “Science, 6th Grade
Core.” http://www.uen.org/core/core.
do?courseNum=3060
