Life in a Drop of Water
Teacher’s Guide
Grade Level: 6-8 Curriculum Focus: Life Science Lesson Duration: Four class periods
Program Description
Life in a Drop of Water—Hundreds, even thousands, of microscopic organisms can live in a single
drop of pond water. This program features incredible close-up photography that reveals bacteria,
protozoa, metazoa, diatoms, algae, and their fascinating world. It also visually demonstrates that,
while these organisms appear strange, they have a lot in common with you and me. Students learn
how to identify common microorganisms, how to collect and maintain cultures, and why scientists
study these important forms of life.
Discussion Questions
• What are the smallest life-forms on Earth?
• What tiny creatures live in pond and lake water?
• What do microorganisms have in common with people?
• Why do scientists study microorganisms?
Lesson Plan
Student Objectives
• Understand that many life-forms and entire ecosystems, invisible to the naked eye, exist in most
lakes, streams, and ponds.
• Name various microorganisms found in pond water.
• Identify and draw three microorganisms and write a report about the life cycle of one of them.
Materials
• Life in a Drop of Water video
• Computer with Internet access
• Microscopes, slides, and clean bottles or jars for collecting pond water (optional)
• Drawing paper and pencils, pens, or markers
• Print and Internet resources about freshwater microorganisms and how to identify them
Life in a Drop of Water
Teacher’s Guide 2
Procedures
1. Review information from the video with the class.
• What do we call a life-form that is so small we need to look at it through a microscope in
order to see it? (a microorganism)
• How many microorganisms can live in one drop of water? (hundreds or even
thousands)
• What do humans have in common with the smallest microorganisms? (We are all made
of cells.)
• What is a cell? (the basic unit of which all living things are composed)
• How many cells does it take to make a living organism? (Single-celled microorganisms
have only one cell; larger organisms can have billions.)
• How many cells are there in a human body? (billions)
• What parts do all cells contain, regardless of what organism they belong to? (a nucleus,
the control center of the cell; a substance called cytoplasm surrounding the nucleus,
where many cell functions occur; a membrane, the sack-like container that holds the cell
together)
• What are the smallest microorganisms you can see with an ordinary microscope?
(bacteria)
• Why are bacteria important? (They are an essential food for other microorganisms.)
• What is another important food source for many pond organisms? (algae)
• What are algae? (plantlike organisms that appear in a variety of forms and belong to a
larger group of organisms called protists)
• What are protists? (Protists belong to a group of organisms that are neither plant nor
animal.)
• How do algae obtain their food? (through photosynthesis)
• What is photosynthesis? (a process by which plants and algae convert water and carbon
dioxide into food using the energy of sunlight)
• What is the green substance found in most algae? (chlorophyll)
• What are clusters of algae called? (colonies)
• What are protists that possess flagella called? (flagellates)
• What are protozoa and what does their name mean? (Protozoa are common one-celled
organisms found in pond water; their name means “first animals.”)
• What are protozoa that possess cilia called? (ciliates)
Published by Discovery Education. © 2005. All rights reserved.
Life in a Drop of Water
Teacher’s Guide 3
• What structures in protozoa allow them to take in and expel water? (contractile
vacuoles)
• How do most protozoa reproduce? (through fission)
• What is the name of the process during which protozoa exchange cell material?
(conjugation)
• What is the enclosure a protozoan forms when it enters a state of suspended animation?
(a cyst)
• How does an amoeba move? (by sending out streams of cytoplasm called pseudopods)
• What are the bubbles that protozoa form to surround food? (food vacuoles)
• In what ways are protists important? (They form the bottom of the food chain; some are
responsible for producing most of the air we breathe; many are used in scientific studies;
some are carriers of disease.)
2. Ask students to name some of the microorganisms they might find in a drop of pond water.
Record their responses and read any below not offered by students.
• bacteria
• algae
• protozoa
• paramecium
• blepharisma
• spirostomum
• dileptus
• stentor
• lacrymaria olor
• vorticella
• bursaria
• didinium
• amoebas
• rotifers
• daphnia (water flea)
• cyclops
• hydras
• giardia
Published by Discovery Education. © 2005. All rights reserved.
Life in a Drop of Water
Teacher’s Guide 4
3. Challenge students to learn more about the microorganisms in pond water. Activity Option One
(for use w