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 when classroom microscopes are available and pond water can be collected): Supply the students with clean bottles or jars and take a field trip to a pond to observe any visible signs of life, such as pond scum or algae. Collect samples of clear water. Back in the classroom, have students prepare microscope slides with the pond water they collected and study the slides under their microscopes. Tell them to identify at least three of the organisms on their slides by finding detailed microscopic photographs of various microorganisms in print and on the Web. Activity Option Two: Have students use print and Web resources to find detailed microscopic photographs of various microorganisms. Ask them to choose three they would like to study further. The following Web sites are good starting points: • Micro*Scope http://starcentral.mbl.edu/mv5d/portal/index.php?option=com_azorganism&Itemid=56 • Cells Alive! http://www.cellsalive.com/ • Microscope Forum: Digital Image Galleries http://www.microimaging.ca/forum.htm • Protists http://www.microbe.org/microbes/protists1.asp • What is a Microbe? http://www.microbe.org/microbes/what_is.asp • Amoebas Are More Than Blobs http://www/microscopy-uk.org.uk/mag/artsep01/amoeba.html • Protist Images and Information http://megasun.bch.umontreal.ca/protists/gallery.html • Zoo Lab: Protozoan Form and Function http://bioweb.uwlax.edu/zoolab/Table_of_Contents/Lab-2b/lab-2b.htm • Microbes in Drinking Water http://www.waterbornediseases.org/FactSheets/microbes.htm • Waterborne Pathogens and the Diseases They Cause http://www.microbeworld.org/htm/cissues/waterq/wqual_1.htm 4. When students have identified or chosen three microorganisms for further study, ask them to draw realistic, detailed illustrations of each one, labeling its various parts and the function of each part. Then ask them to choose one of the three microorganisms they have drawn, research it further, and write a one-page report explaining its life cycle. Tell them the report should answer these questions: What is the name of the microorganism? To what larger family of organisms does it belong? Where does it grow? Does it have only one cell or is it a multi-cellular Published by Discovery Education. © 2005. All rights reserved. Life in a Drop of Water Teacher’s Guide 5 organism? How does it eat? What does it eat? What eats it? How does it reproduce? What other interesting facts have you learned about it? 5. Have students choose partners. Ask them to share their life cycle reports and illustrations with their partners and answer any questions. Then have each student summarize his or her partner’s report for the class, using the illustration to help explain it and mentioning at least three interesting facts. Assessment Use the following three-point rubric to evaluate students’ work during this lesson. • 3 points: Students were highly engaged in class discussions; produced high-quality illustrations and a complete report, including all of the requested information; accurately summarized partner’s report and illustration and cited at least three interesting facts. • 2 points: Students participated in class discussions; produced adequate illustrations and an adequate report, including most of the requested information; satisfactorily summarized partner’s report and illustration and cited two interesting facts. • 1 point: Students participated minimally in class discussions; created unsatisfactory illustrations and an incomplete report with little or none of the requested information; were unable to summarize partner’s report, discuss the illustration, or recall any interesting facts. Vocabulary algae Definition: Microscopic, plantlike organisms Context: Algae appears in a variety of forms. amoeba Definition: Among the best known type of protozoa Context: The stream of cytoplasm an amoeba sends out is called a pseudopod, which means false foot. bacteria Definition: The smallest organisms visible with an ordinary microscope Context: Bacteria provide food for many other microorganisms. cell membrane Definition: The sack-like container that holds a cell together and gives it shape Context: The cell membrane controls what goes into and comes out of a cell. cells Definition: The tiny uniform structures of which all living things are composed Published by Discovery Education. © 2005. All rights reserved. Life in a Drop of Water Teacher’s Guide 6 Context: The cells that make up a human being have much in common with single-cell microscopic creatures. chlorophyll Definition: A green substance in plants that is similar to blood in animals Context: Like plants, most algae are filled with chlorophyll. cilia Definition: Short, hairlike strands used by some protozoa to move Context: A protozoan that has cilia on any part of its body is called a ciliate. conjugation Definition: The action of two microscopic organisms joining at the sides in order to exchange cell material Context: Conjugation enables organisms to live longer and to better adapt to their environment. contractile vacuoles Definition: Round structures on the interior of a protozoan that open and close Context: Contractile vacuoles work like pumps to maintain the proper amount of water within a protozoan. cyst Definition: A state of suspended animation in which protozoa resemble spheres Context: Many protozoa form cysts to enable themselves to survive unfavorable conditions, such as drought. cytoplasm Definition: Fluid substance surrounding the nucleus of a cell Context: Many cell reactions occur within its cytoplasm. diatoms Definition: Organisms closely related to algae Context: Diatoms have hard outer walls and are found in both freshwater and oceans. euglenas Definition: Protists filled with green chlorophyll, closely related to algae Context: Euglenas rely on photosynthesis to obtain much of their food. fission Definition: The process through which some microscopic organisms reproduce themselves by dividing Context: A paramecium can reproduce through fission up to three times a day. Published by Discovery Education. © 2005. All rights reserved. Life in a Drop of Water Teacher’s Guide 7 flagella Definition: The thin, barely visible tails some microscopic animals use to propel themselves through water Context: Protists that possess flagella are called flagellates. food vacuole Definition: A bubble an amoeba forms around its food Context: If you examine an amoeba’s cytoplasm, you might see still-living organisms struggling inside a food vacuole. nucleus Definition: The control center of a living cell Context: The nucleus controls all of a cell’s activities, including reproduction. oral groove Definition: A channel some microscopic organisms have along the sides of their bodies, that directs food into their gullet or stomach Context: Paramecia have oral grooves instead of mouths. photosynthesis Definition: A process by which plants convert water and carbon dioxide into food Context: Like plants, algae produce food by photosynthesis. protists Definition: Organisms that are neither plant nor animal Context: Algae belong to a larger group of organisms called protists. protozoa Definition: Common one-celled organisms found in freshwater Context: There are thousands of different kinds of protozoa. Academic Standards National Academy of Sciences The National Academy of Sciences provides guidelines for teaching science in grades K–12 to promote scientific literacy. To view the standards, visit this Web site: http://books.nap.edu/html/nses/html/overview.html#content. This lesson plan addresses the following national standards: • Life Science: Structure and function in living systems; Reproduction and heredity; Regulation and behavior; Populations and ecosystems; Diversity and adaptations of organisms Published by Discovery Education. © 2005. All rights reserved. Life in a Drop of Water Teacher’s Guide • 8 Science as Inquiry: Abilities necessary to do scientific inquiry; Understandings about scientific inquiry Mid-continent Research for Education and Learning (McREL) McREL’s Content Knowledge: A Compendium of Standards and Benchmarks for K–12 Education addresses 14 content areas. To view the standards and benchmarks, visit http://www.mcrel.org/compendium/browse.asp. This lesson plan addresses the following national standards: • Science—Life Sciences: Understands the principles of heredity and related concepts; Understands the structure and function of cells and organisms; Understands relationships among organisms and their physical environment; Understands biological evolution and the diversity of life • Science—Nature of Science: Understands the nature of scientific knowledge; Understands the nature of scientific inquiry • Language Arts—Viewing: Uses viewing skills and strategies to understand and interpret visual media Support Materials Develop custom worksheets, educational puzzles, online quizzes, and more with the free teaching tools offered on the DiscoverySchool.com Web site. Create and print support materials, or save them to a Custom Classroom account for future use. To learn more, visit http://school.discovery.com/teachingtools/teachingtools.html. Credit Renne Leatto, education and curriculum writer Published by Discovery Education. © 2005. All rights reserved.