associate professor university of oregon ph.d. in …ph.d. in zoology university of georgia michelle...

Unit Three Single-celled Organisms

©Project Oceanography Spring 2002 75

Michelle Wood

Associate Professor Department of Biology University of Oregon

Ph.D. in Zoology University of Georgia

Michelle attended the University of Corpus Christi where she earned B.A. degrees in Biology and Speech. After graduating from the University of Georgia with a Ph.D., she continued her work as a postdoctoral student at the University of Chicago. She studied genetics and the evolutionary ecology of recently discovered photosynthetic organisms. After her postdoc, she continued as part of the research faculty in Ecology and Evolution Department until 1990. She then moved to the University of Oregon where she is now an Associate Professor. Dr. Wood’s research interests include studying picocyanobacteria from an evolutionary viewpoint. She is looking at how these microorganisms can survive in a wide range of marine environments. For instance, in the Arabian Sea, she and her student, Nelson Sherry, found that these organisms could reproduce several times a day and reach population sizes of more than a million cells per milliliter. These were free-living picocyanobacteria that bloomed during the summer Monsoon season. In the winter she found many examples of picocyanobacteria living symbiotically with dinoflagellates. She would like the students to know that people who study the ocean are a community of creative, curious, and wonderful people. She says, “If you are a student interested in ocean science, rest assured that there are many wonderful people out here who want to help you follow your dreams.”



Unit III Single-celled Organisms On the cutting edge… Dr. Wood at the University of Oregon is on the edge of scientific discovery as she explores some of the microscopic inhabitants of the marine environment. She is studying the relationship between a cyanobacteria and a dinoflagellate. She is interested in learning more about how these organisms create a symbiotic relationship that helps them succeed in nutrient-poor tropical waters.

Introduction to Single-celled Organisms Lesson Objectives: Students will be able to do the following: • Compare and contrast three types of symbiotic relationships • Describe the relationship between zooxanthellae and coral • Explain the effects of nitrogen-fixing bacteria on their symbiotic partners Key concepts: symbiosis, commensalism, parasitism, mutualism, dinoflagellate, nitrogen-fixing cyanobacteria

Symbiotic Relationships

The word symbiosis in its simpliest terms means “living together”. This word describes a partnership between two

different kinds of organisms such as a sea anemone and a hermit crab or a squid and a bacterium. These relationships are long-term associations that are usually advantageous to at least one member of the partnership. These symbiotic relationships often occur because of the nutritional needs of the members. There are many examples of symbiosis to be found in nature. For example, some hermit crabs have shells covered with sea anemones. The crab is

camouflaged from predators and protected with the sea anemones’ tentacles while the anemones are carried to various locations where food gathering is easier. The bobtail squid harbors light emitting bacteria. These bacteria help create light patterns that camouflage the squid during hours of feeding. Symbiotic relationships can be divided into three broad categories: commensalism, parasitism, and mutualism. These categories describe how each partner benefits from the relationship. In commensalism, one member benefits while the other is neither helped nor harmed. A good example



of this type of relationship is the remora that can attach itself to a

shark. The remora gets a free ride and eats the scraps left by the shark. It does not harm or help the shark. In

parasitism, one member is helped while the other member is harmed. An example of a parasitic relationship is a tapeworm in a human. The parasite, the tapeworm, lives inside the human or host. The parasite is helped, because it gets nutrition from the food in the human’s intestine. The human can slowly starve, because the tapeworm is using the nutrition from the food the human eats. In mutualism, both organisms benefit as in the case of the fish and the cleaner shrimp. The fish enters a “cleaning station” where the shrimp removes parasites from the fish’s body. The fish gets

cleaned and the shrimp gets a free meal. Symbiotic relationships occur between organisms of all sizes in all environments. Some partners are vastly different in size as evidenced by the whale and its special barnacle partner that lives in its skin. Some symbiotic partners are similar in size like the hermit crab and the sea anemone. We often think of symbiotic relationships that include organisms that we can see without using a microscope, but symbiosis occurs in the micro-world as well. Some microorganisms such as diatoms with their glasslike outer coverings, dinoflagellates with their whiplike projections, and even the tiniest bacteria are involved in symbiotic relationships. Some of these relationships involve only microorganisms while others can include much larger animals. We will take a closer look at an example of mutualism between a dinoflagellate and a much larger animal that lives in the marine environment.

Dinoflagellate/Coral Symbiosis

Dinoflagellates are common members of the phytoplankton found in the ocean. There are nearly 2000 species of these single-celled organisms that have been identified. They come in a variety of sizes but are considered the mid-sized members of the micro world. They are generally smaller than the diatoms and larger than the photosynthetic bacteria. Dinoflagellates derive their name from their two distinct flagella or

whiplike projections that are used for locomotion. Most of these organisms are covered with armored plates called thecal plates. Scientists use these plates to help classify these organisms. Dinoflagellates also have different lifestyles. Some of them are photosynthetic, producing their own food, while



others must find food. A good example of a symbiotic relationship involving a photosynthetic dinoflagellate is the partnership between a zooxanthellae and a coral. Corals are animals that are

related to sea anemones and form the huge geologically important coral reefs.

“Zooxanthellae” are a type of dinoflagellate that specializes in living symbiotically within the tissues of animals. In this mutualistic relationship, the zooxanthellae live inside the coral. The zooxanthellae is called an endosymbiont and the coral is the host. These two partners recycle the waste products from living processes to continue their relationship. The endosymbiont uses energy from the sun to power the process of photosynthesis. The zooxanthellae produces sugar from carbon dioxide in the water and releases oxygen. The food or sugar produced by this process gives the coral energy. The presence of the zooxanthellae also helps the coral produce calcium carbonate. This material is used to build a cup-shaped skeleton to

support the coral animal. This skeleton becomes a coral reef. The oxygen released during photosynthesis is used by the coral for respiration. Carbon dioxide released during the coral’s respiration is used by the zooxanthellae during photosynthesis. The corals also produce waste products such as ammonium. Some of these products are used as nutrients by the zooxanthellae. As you can see both organisms benefit from this relationship, but they must also give up something. The dinoflagellate gives up some of its photosynthetic energy to the coral. In return the coral must use a portion of that energy to keep its surface clean and grow branched colonies. This provides the dinoflagellate with adequate sunlight for photosynthesis. The zooxanthellae’s light requirements also restrict the coral to depths at which the coral can grow. Why would organisms enter into a relationship where they had to give up something? In this instance, coral reefs are found in nutrient-poor waters, so this relationship provides both members with sufficient nutrition.

. Cyanobacteria

We are going to take a closer look at some very small members of the microscopic world, because they are important in symbiotic relationships. The cyanobacteria are sometimes called “blue-green algae” because of

their color and because they also photosynthesize. These organisms are not algae but rather a special kind of bacteria. These bacteria are unicellular, but they may combine to form colonies or filaments. Some of



these colonies are large enough to be seen without a microscope.

Typical cyanobacteria get their color from a bluish

pigment called phycocyanin. Many

marine cyanobacteria

contain an additional, pink pigment called

phycoerythrin. These pigments are used by the cyanobacteria to capture sunlight during photosynthesis just as most plants use the chlorophyll pigment. These very simple, unicellular organisms are found in nutrient-poor waters. They are fascinating to study, and some of them have a unique ability. Some cyanobacteria species are among the few organisms that can change atmospheric nitrogen into forms that can be used by plants and animals. Organisms that can do this are called nitrogen-fixing bacteria. Why is it important to have nitrogen-fixers? Nitrogen is the third most abundant element found in organisms. While it is abundant as nitrogen gas in the atmosphere, only nitrogen-fixing organisms can convert nitrogen gas to forms that can be taken up by plants and converted to food that animals can eat. So, nitrogen-fixing organisms ultimately provide the nitrogen required by all other organisms in the food chain. Since nitrogen-fixers provide an essential nutrient plants require, many photosynthetic organisms have

developed symbiotic relationships with a microbe that can fix nitrogen. These relationships between a nitrogen-fixer and a plant partner can be found in all types of environments from forested areas to open ocean waters. Some plants will even create special homes for these bacteria within their roots or stems in return for the nitrogen they produce. In exchange, the plant provides the bacteria with some of the energy needed to change atmospheric nitrogen into these usable forms. Cyanobacteria also form symbiotic relationships with other microscopic organisms. One of these organisms is a diatom. Diatoms are single-celled, photosynthetic organisms found in all types of freshwater and marine environments. They are a primary component of marine plankton, but they can also be found in the deep ocean sediments. These organisms are known for their intricate outer skeletons made of silica. These silica walls or frustules are composed of two overlapping parts that fit together. It is important to note that diatoms can make their own food, but they must find a source of nutrients. Nutrients provide the building blocks for cells. Without nutrients organisms cannot carry on life processes such as growing. Most



plants get their nutrients from the soil, but diatoms live in the ocean. Where will they get their nutrients? Just as the kelp, diatoms will have to find their nutrients in the water. Unfortunately for some species of diatoms, they live in very clean, pure water that may not contain enough nitrogen. For the diatom, the lack of nitrogen can be limiting. That means that they may not be able to grow even if they have enough food in the form of sugar. In this case, a symbiotic relationship could solve the problem. If the diatom and the cyanobacteria live together, perhaps they could both get what they need. The diatom and the cyanobacteria are both

photosynthetic, so there will be plenty of food for both organisms. The diatom, being much larger than the cyanobacteria, provides a home for the smaller organism. The cyanobacterium in turn uses its special nitrogen-fixing ability to make usable forms of nitrogen for itself and the diatom. This is exactly what happens in the case of the cyanobacteria and a diatom called Rhizosolenia. These microscopic symbiotic relationships also occur between cyanobacteria and dinoflagellates. These dinoflagellates are a little bit different than the zooxanthellae that we discussed earlier, and next time we’ll see how scientists study one of these interesting relationships.



Activity: Feeding Friends

Some animals develop associations that are advantageous to both of the partners. This type of relationship is a special kind of symbiosis called mutualism. These types of partnerships can be found in all habitats and can include the largest animals to the smallest bacteria. Many times these mutualistic relationships are formed because of the nutritional needs of the members. Objectives: Students will be able to do the following: 1. Describe a mutualistic relationship. 2. Demonstrate a mutualistic relationship. 3. Analyze the advantages and disadvantages of a

mutualistic relationship. Materials: • Items to represent food (stuffed animals, folded pieces of paper, items that

can be picked up using only elbows, or combinations of these items, etc.) Approximately two items per student is adequate (of course the more items the longer the rounds). These amounts can be adjusted to suit your needs.

• Spot markers (poker chips, paper squares, etc.) Note to Teacher: This activity requires some students to move with their eyes closed. Always show students how to move safely with their eyes closed prior to the activity. If students are having difficulty, the activity can be done by a few students at a time instead of the whole group. Procedure: 1. Discuss symbiotic relationships. Have students brainstorm reasons for

organisms having such relationships. What are the advantages and disadvantages of these partnerships?

2. Explain that in this activity students will be organisms (either No See Ums or Ferocious Feelers) that must gather food within their habitat. At first they will hunt for food on their own. Later they will take part in symbiotic relationships.

3. Have students choose partners. (Partners should stand next to each other.) 4. Have students form a circle by joining hands and moving apart until their arms

are fully extended. Have students drop hands and take two giant steps backwards. The area inside the circle becomes the habitat. (Playing area can be adjusted for groups of various sizes. The area should allow ample room between players on the field.)

5. Place a “spot marker” next to each pair of students. 6. Explain that the inside of the circle represents a habitat. The organisms that

are participating will be hunting for food within this habitat. Explain that people that are not organisms during the round are helping to keep their partner safe. They can only speak to warn their partner if someone is coming too close, but they cannot direct anyone to or away from food.



7. Explain the following parameters for the activity. (It is helpful to have a

student demonstrate the appropriate behavior as the parameters are read.) • Organisms are hunting for food in the habitat. (Show students the items

that will be used for food.) • Both types of organisms move by crawling. • Both types of organisms move very slowly as if they are in slow motion. • Organisms that move quickly die from overexertion and must sit outside of

the habitat. • The No See Ums must close their eyes while they are in the habitat. They

collect food using their hands. • The Ferocious Feelers can see, but they can only use their elbows to pick

up food. • Food that cannot be held by the organism may be stockpiled on their “spot

marker”. 8. Before the round begins:

• Have one partner from each pair step into the circle. Have students that are in the circle choose the type of organism they want to be. (Try to have some of both types of organisms for each round.)

• Have student participants sit randomly in the habitat. No See Ums must have their eyes closed. Ferocious Feelers should have their elbows ready.

• Distribute food randomly in the habitat. 9. Give a signal for the round to begin.

• At the signal, students crawl throughout the habitat gathering food according to their restrictions.

• After all the food is gathered, have students return to their “spot marker”. 10. Repeat using the other half of the students. 11. Discuss the limitations of each type of organism as they tried to gather food.

Did one type of organism get more food than the other type? 12. Explain that in the next round organisms will develop symbiotic relationships. 13. Explain that the following parameters apply for this round:

• The partners in each pair will work together as one organism. • In this round food gathered by either partner can be used by both

partners. • Each pair will consist of a No See Um and a Ferocious Feeler. • The partners must stay in contact at all times during this round. (It is up to

the partners to decide how to safely accomplish this task.) • Once the partners have chosen a point of contact, they cannot change

during the round. For example, if one organism places his hand on his partner’s back, then he cannot change to putting his hand on his partner’s arm during the round.

• Remind students that the No See Um still cannot see and the Ferocious Feeler can still only collect food with their elbows.

14. Give partners time to decide which organism each will be and how they will stay in contact. (One hand is enough.)



15. When students are ready, have symbionts enter the playing area. (The

playing area can be enlarged to accommodate more students simply by distributing the food in a larger area. Students still have their “spot markers” to identify home.)

16. Have student partners “connect” and take their starting positions. (No See Ums have their eyes closed. Everyone is still.)

17. Remind students that excess food can be stockpiled on their “spot marker”. 18. At the signal, have students collect food following the parameters given. 19. Discuss ways that various partners solved problems. Was feeding more

efficient this time? (Hopefully students will realize that the No See Um is the best food gatherer and the Ferocious Feeler is the best director but other solutions may occur.) Discuss the advantages and disadvantages of being in a symbiotic relationship. What did the partners have to give up to be in this symbiotic relationship?

Possible Extensions: 1. Older students may prefer to walk instead of crawl. For this adaptation, use

food items that students may feel as they walk such as stuffed animals rather than flat items such as poker chips. Be sure that these items are soft and will not cause a tripping or falling hazard. The Ferocious Feelers can also be given arm extenders such as sand shovels or tongs to replace their elbow feeding devices. Remember that partners should be watching out for each other’s safety. Teach students how to maneuver safely with their eyes closed using the “bumpers up” position. In this position the arms are partially extended at chest height, fingers pointing upward, palms facing outward. This gives the sightless person a “bumper” to help them feel people or objects in their way.

2. After each round designate a new number of food items necessary to live. Was it easier to get the necessary items with a partner or alone?

3. After one round, designate one item as poisonous. How many organisms were killed? Apply this information to real world situations.



Student Information: Amazing Associations

Everywhere we look in nature, we can see different kinds of organisms living together.

The gopher tortoise shares its home with a snake. The algae live within the body of the coral animal. The whale swims through the water with barnacles attached to its skin. In these relationships the partners live together for long periods of time. At least one of the partners will benefit from this association. Scientists use the word “symbiosis” to describe these partnerships. Symbiotic relationships can be found in all types of environments from the largest wooded forest areas to the smallest corner of the deep ocean bottom. Partners in these relationships can be similar in size as in the case of the crab that carries anemones on its back. The partners can be vastly different in size such as the whale and the barnacle or the microscopic algae that lives inside the coral animal. In some of these relationships the smaller partner will live inside

the other partner. In this case the smaller partner is called an endosymbiont. The larger partner is called the host. Symbiotic relationships can occur between all types of living organisms. Animals can develop partnerships such as the remora fish and the shark. A photosynthetic organism and an animal can live together as the algae and the coral. Some unicellular organisms with characteristics of both plants and animals can be found in symbiotic partnerships. Even the tiniest microscopic organisms called bacteria have important symbiotic relationships. Some of these unicellular organisms are cyanobacteria, commonly called “blue-green algae”. Some cyanobacteria are really special; they are among the few organisms that can “fix” nitrogen. That means that they can take nitrogen from the atmosphere and change it into forms that can be used by other living organisms. Even humans can’t do that!



Single-celled Organisms and Symbiotic Relationships

Lesson Objectives: Students will be able to do the following: • Describe an experimental method used by scientists • Compare and contrast two studies involving the same symbiotic relationship • Identify at least two technologies used in these particular studies Key Concepts: experimental design, enzyme, antibody, transmission electron microscopy, autoradiography

Methods Used by Scientists

Scientists study the natural world. They look for answers to questions they might have about something they have observed in nature.

In scientific research, a process is used to answer these questions. This process is not always the same, but it generally contains these steps: observation, questioning, using the results of previous scientific research, developing a testable prediction, creating and carrying out an experiment, gathering results, and drawing conclusions. From observation and research scientists begin to develop a conceptual model. This is a model in your head based on connected units of information or a concept. Then it is time to make a testable prediction based on the model. These predictions are testable hypotheses that help scientists evaluate their model. Researchers then design and carry out experiments to test their hypotheses. The experimental design depends on the type of

question being asked. Usually researchers try to design experiments with a control, which means that they can make comparisons between the experimental group and nonexperimental group. Sometimes experiments indicate that the scientist’s hypothesis was falsified. This means that the hypothesis could not be shown to be true in that particular instance. In this case, researchers refine their question and continue to conduct other experiments. Sometimes important scientific breakthroughs are discovered accidentally. In other cases practical applications may result from studying the natural world. These practical applications of scientific discovery are called technology. Let’s take a closer look at two specific examples of how scientists work and design research experiments.



Research Design 1

These research designs represent the steps that two scientists used to find answers to their questions. The thinking sections give a more detailed view of the process.

The Carpenter Research Team’s Experiment Observation: Some dinoflagellates have cyanobacteria living inside them. Thinking: This observation made the team curious. They began to ask questions. Broad Questions: Why would these two organisms live together? Does this relationship benefit either partner? Is it a mutualism?

Thinking: The research team knew that some other cyanobacteria could both do photosynthesis and fix nitrogen. They knew that the sugars and nitrogen produced by these processes were used by organisms. They also knew that some symbioses involving cyanobacteria were mutualisms that involved the cyanobacterium providing nitrogen to the host. They wondered if the same thing could be happening in this situation. So they came up with the following question. Specific Question: Does the cyanobacteria provide sugars from photosynthesis and nitrogen from nitrogen fixation to the dinoflagellate? Thinking: The research team knew that special molecules called enzymes are required for carbon fixation (part of photosynthesis) and nitrogen fixation. Each type of enzyme is specific for a target molecule. When the enzyme finds its target molecule, it will bind to it and create a new complex. The research team used this information to come up with their hypotheses. Hypotheses: 1. If the cyanobacteria are fixing carbon (carrying on photosynthesis), then they

will have the key enzyme that fixes carbon (Rubisco) in their cells. 2. If the cyanobacteria are fixing nitrogen, they will have the key enzyme for

nitrogen fixation (nitrogenase), in their cells. 3. In addition, if the dinoflagellate depends on the cyanobacterium for both

carbon and nitrogen, then the Rubisco and nitrogenase enzymes will only occur in the cyanobacterium and not in the dinoflagellate.



Thinking: Now the team had to come up with a plan to test their hypotheses. They drew on their knowledge about the way substances react with one another to develop their design. They knew that they could make special reagents called antibodies that would recognize the Rubisco and nitrogenase enzymes. If the enzymes were present in the sample, the antibodies would connect with their target molecule. The antibody and its enzyme would stick together creating complexes. A tracer could be added to the sample that would connect to the antibody complex and allow it to be seen using a transmission electron microscope. Scientists would also be able to see where the complexes were localized within the cells. If the enzymes were not present, the antibodies could easily be washed out of the cells after the experiment. They would not be seen in the sample viewed by electron microscopy. Plan: Antibodies specific for rubisco and nitrogenase would be made. These antibodies would be introduced to the sample. The antibodies would attach to the target enzymes present in the sample. A second reagent would be created with gold beads attached to it. This second complex would act as a tracer. When it attached to the original enzyme-antibody complex, the gold’s reflective properties would allow it to be seen with a transmission electron microscope. If the enzymes were not present, the complexes would not be seen using the microscope. Procedure: The samples were collected from the seawater. They were exposed to the antibodies. They were viewed using a transmission electron microscope. Results: 1. Enzymes for carbon fixation (Rubisco) were only found in the cyanobacteria. 2. Enzymes for nitrogen fixation (nitrogenase) were not found in either organism. Conclusions: 1. Hypothesis one was supported. The cyanobacteria were capable of

photosynthesis because they had the Rubisco enzyme; the dinoflagellate probably was not capable of photosynthesis since it did not have the enzyme Rubisco.

2. Hypothesis two is falsified. Neither organism had the enzyme nitrogenase. This means that the cyanobacteria are probably not providing the products of nitrogen fixation to the dinoflagellate.



Research Design 2

Dr. Wood spends a lot of time studying cyanobacteria and their close relatives. Most of the time she finds these organisms free-living in the water column as independent individuals. But a few years ago, while she was studying cyanobacteria in the Indian Ocean, she found some dinoflagellates that she had never seen before. Upon closer inspection of these organisms, she found that they had cyanobacteria living inside of them.

Dr. Wood’s Experiment

Observation: Some dinoflagellates living in the Indian Ocean have cyanobacteria living inside of them. Broad Question: What do scientists know about this symbiotic relationship? Thinking: She began to do some research to find out what other scientists might know. She found that only a few people had written papers about this relationship, and no one had figured out how the relationship was helpful to its members. She became particularly interested in Dr. Carpenter’s team and their research. Building on what Dr. Carpenter’s team had learned she continued to develop their model that the symbiosis was some form of mutualism in which both partners got a benefit from living together. She formulated another question. Specific Question: Is the enzyme for fixing carbon (Rubisco) that is found in the cyanobacteria actively fixing carbon; and, if it is, is the carbon fixed by the cyanobacteria transferred to the dinoflagellate? Thinking: Dr. Wood knew that during carbon fixation (part of the photosynthetic process), carbon enters the cell as carbon dioxide. Carbon dioxide is a gas that is soluble in water. The processed carbon dioxide becomes part of the sugar made during photosynthesis. If the carbon is now part of the cell material it cannot be easily washed away. She also knew that she could trace the carbon in carbon dioxide and find out if it was turned into sugars by labeling it with a radioactive form of carbon. Hypothesis: 1. If the cyanobacteria were actively fixing carbon then the labeled carbon from

carbon dioxide would be incorporated into cell material during photosynthesis.



2. If the model of mutualism that involves the cyanobacteria providing sugar to

the dinoflagellate is true, then labeled carbon would first appear in the cell material of the cyanobacteria and only later in the dinoflagellate.

Thinking: An autoradiographic technique could be used to label the carbon. This would allow us to trace it through the cell. Autoradiography is similar to photography. In photography, a special chemical (photographic emulsion) on the film is exposed (or turns dark) when light hits it. This creates a negative. In autoradiography, the radioactive material acts as the light. Wherever there is radioactivity, the film is exposed and has dark spots on it. Plan: Using autoradiographic techniques, trace carbon flow in samples that have been incubated in sunlight and compare to a known photosynthetic cyanobacteria for verification (a control).

Procedure: 1. Collect and prepare specimens from the ocean. 2. Add radioactive carbon dioxide (a tracer) to the sample. 3. Incubate in the light for about one hour (for photosynthesis to take place). 4. Remove the soluble carbon dioxide and expose the sample to photographic

emulsion. 5. Run a control on a photosynthetic cyanobacterium using the same

experimental technique.

Results: 1. The control shows that dark spots would indicate photosynthetic activity. 2. The autoradiographic techniques show evidence of fixed carbon (in the form

of dark spots) in the area of the cyanobacteria.

Conclusions: The results of the two experiments seem to indicate that the cyanobacteria are contributing products of photosynthesis to the dinoflagellate. It appears that the dinoflagellate cannot do this on its own. It appears that at least one side of a mutualistic relationship is being described by the experiments that Dr. Wood and Dr. Carpenter and their colleagues have done.



Activity: Symbiosis Search

Scientists generally follow the scientific method to set up an experiment. This method has several steps but there are also variations within the method depending on the type of problem to be solved or the information that the scientist is seeking. One important part of any scientific endeavor includes research. Scientists gather materials to find out what has all ready been done in their field. They look for information that will help them with their next scientific experiment. Today, with so much information available, it is critical for scientists to consider the source of their information and its reliability. Objectives: Students will be able to do the following: 1. Search the internet to find answers to questions. 2. Compare information from two sources. 3. Propose criteria for determining sources of reliable information. Materials: • Internet access • Question page • Writing instrument Procedure: 1. Have students use the following websites to answer the questions in the

Symbiosis Search. • Source 1-http://oceanworld.tamu.edu/students/coral/coral3.htm • Source 2-

http://mgd.nacse.org/hyperSQL/lichenland.html/biology/meeting.html • Source 3-http://www.imm-km.unibe.ch/projekte/symbiosis/Sym.html • Source 4-http://www.seacave.com/sym.html

2. Have students look for the answer to either question 3 or 4 in another resource. (Use other websites, written materials, human sources, etc.) What conflicting information (if any) did they find?

3. Brainstorm with students how to determine the best source when conflicting information is given.

4. Devise a plan to test the proposal. Did it take into account all variables? Does it need to be revised? Where in the real world do we find similar problems?

Answer Key: The number in parentheses indicates the internet source for the answer. 1. alga and fungus (2) 6. seawater (3) 2. bacteria (Vibrio fischeri) (3) 7. lichen (coral, etc.) (2) 3. “sym” means together and “biosis” means life (1) 8. mucous coating (4) 4. less than 1% (1) 9. Cnidaria (1) 5. thallus (2) 10. antibiotics, food, dye (2)



Symbiosis Search

1. What two organisms join together to make a lichen? 2. What kind of organism produces light for the Hawaiian squid? 3. What does the word symbiosis mean? 4. What percent of the world’s oceans are covered by coral reefs? 5. What is the name of the lichen “body”? 6. Where does the squid find its bioluminescent symbionts? 7. Name one organism (from the website) that is an indicator

organism? 8. How is the anemone fish protected from the anemone’s sting? 9. To what phylum does the coral animal belong? 10. Name one use for a lichen.



Activity: Can You Fix This?

Organisms need to have all of the components of their living tissues in order to live and grow. One important nutrient that all living things need is nitrogen. Nitrogen is commonly found in the atmosphere, but this nitrogen cannot be used directly by organisms. It must be changed into another form. Organisms that can change atmospheric nitrogen into usable forms are called nitrogen-fixers. Objectives: Students will be able to do the following: 1. Construct organic molecules using the correct ratios of nutrients. 2. Describe a limiting factor. 3. Analyze the importance of nitrogen-fixers. Materials: • Items that can be connected and come in a variety of colors such as colored

paper clips, legos, gum drops and toothpicks, etc. If nothing else is available, paper squares of various colors can be stacked or glued together.

• Four colors of the chosen item • Plastic or paper bags to hold items-one per group • One extra bag for the nitrogen-fixer Prior to the Activity: (Paper clips will be used for this demonstration. Any four colors may be used.) Prepare the nitrogen-fixer by placing at least 30 green paper clips into a bag. Prepare one bag for every four students using the following ratios of paper clips. You may make doubles if necessary. • 36 white, 8 yellow, and 3 blue • 36 white, 8 yellow, and 2 blue • 36 white, 8 yellow, and 1 blue • 36 white, 8 yellow, and 0 blue Procedure: 1. Discuss the importance of nutrients to living organisms. Explain that these

nutrients are incorporated into organic molecules that make up living tissue. In order to construct the correct molecule, the components must be combined in a particular ratio. Explain that the job of the nitrogen-fixer is to change one of these components, nitrogen, into a form that can be used in these organic molecules. In this activity, the molecule being made consists of 9 white paper clips, 2 yellow paper clips, and 1 blue or green paper clip. (This information can be written on the board.) The blue or green paper clip represents the nitrogen that is necessary to complete the molecule.

2. Give the nitrogen-fixer bag to one student. (This student will not be part of a group.)



3. Give one bag to every four students, and tell them that they will be given a

limited amount of time to construct their molecules using the correct number and colors of paper clips.

4. Give students a signal to begin. 5. Have students build their molecules with only the paper clips they have in

their bags. Discuss what problems they encountered and how many organic molecules they were able to complete. Record their results.

6. Explain that nitrogen is the limiting nutrient in this case. If organisms could get more nitrogen, they could use all of their other nutrients (paper clips). Ask for ideas on how they could get more nitrogen.

7. Tell them that in this round they will again only have a limited amount of time to build their substances. This time they may signal the nitrogen-fixer to supply them with nitrogen. The trick is that nitrogen can only be asked for when the rest of the molecule is complete. Each group may only receive one nitrogen at a time. (This limits the number of compounds that can be completed, because the nitrogen-fixer can only move so fast. This represents processing time.)

8. Have students take their materials apart and redistribute bags to other groups.

9. Give students a limited amount of time to complete their molecules. (This will vary will group size.) Remind students that they may ask for nitrogen from the “fixer”.

10. When time is up, have students compare the results from the first round to the results in the second round. Could they build more substances in round two? What would happen if there were more than one nitrogen-fixer? Can they relate this to what happens in real life?

Possible Extensions: 1. Have students build a complex compound for instance start with having them

build a sugar (C6H14) and then put in phosphate or nitrogen to make other compounds. Try this with and without a nitrogen-fixer.

2. Supply students with varying amounts of paper clips and try using a variety of time periods to complete the task. Are there other limiting factors in addition to the amount of nitrogen available?



Student Information: The Case of the Curious Observer

Are you curious and creative? Do you like to explore nature and try to

figure out how things work? This is what scientists do. They observe things in nature and become interested in learning more about what they observed. They begin to ask questions. They want to know why things happen or maybe how they happen. They begin to look up information. Scientists may find books at the library or information on the internet. They look for papers written by other scientists, and they talk with their colleagues. They gather lots of information and begin to form an idea about what is happening. Scientists try to fit all the pieces together in a conceptual model. Then they try to predict what will happen if the model is true. They develop a testable prediction based on the model; this is called a hypothesis. This hypothesis helps the scientists focus their research. Next they need to design an

experiment to test their hypothesis. This takes planning and careful study of what scientific knowledge already exists. Once the planning is finished, the real fun begins. Researchers get to conduct the experiment! Each experiment is designed to test a particular hypothesis. Researchers may use the latest technical equipment or simple tools developed in the past while conducting their experiments. After the experiment, the scientists study their results. Researchers ask more questions. What do the results tell us? Did the results support or falsify the hypothesis? What new prediction can we make to test the model in a different way? Do we need to change the model based on the results? At this point, scientists create new experiments or redesign old ones. They continue to search for answers. Does this sound like something you would like to do?



Single-celled Organisms Vocabulary

Algae-aquatic, photosynthetic organisms ranging in size from single-celled forms to the giant kelp Antibody- proteins that are produced in the bloodstream in reaction to foreign substances; As part of an animal’s natural immune system, antibodies help neutralize foreign substances and produce immunity. Their property of targeting specific substances can be used for many kinds of research if the antibodies are purified from the blood of the animal that made them. Autoradiography-a technique that uses radioactive materials to trace substances through a system Bacteria-unicellular or filamentous organisms with a simple cellular organization (also called prokaryotes); the oldest forms of life on Earth Catalyst-a substance that modifies the rate of a chemical reaction without being used up in the process Camouflage-blending in with the environment Chlorophyll-a green pigment used in photosynthesis Commensalism-symbiotic relationship in which one member is helped and the other member is neither helped nor harmed Conceptual Model-a way of thinking about something that uses interconnected ideas or units of information to make an abstract representation of a system or process Control-a standard used to verify the results of an experiment Cyanobacteria-the group of bacteria that are capable of oxygen-producing photosynthesis; The chloroplasts of green plants appear to have evolved from cyanobacteria. Diatom-unicellular algae with cell walls made of silica Dinoflagellate-marine algae having two flagella and a cell wall made of cellulose; Many are photosynthetic, some are bioluminescent, and some can cause red tides. Endosymbiont-the member of the symbiotic relationship that lives inside the other member



Enzyme-protein that acts as a catalyst for chemical processes that take place in living systems Flagellum-an organ of motility in unicellular organisms (In dinoflagellates it is flexible and whiplike.) Frustule-a cell wall made of silica and composed of two parts Host-the organism on or in which a parasite lives Hypothesis-a testable prediction Mutualism-symbiotic relationship in which both members benefit Nitrogenase-the enzyme that converts atmospheric (elemental) nitrogen to ammonia as the first step of nitrogen fixation Parasite-an organism that benefits by living in or on another organism and contributes nothing to the other organism Parasitism- a symbiotic relationship in which the host is harmed and the parasite is helped Photosynthesis-the biologically-mediated chemical process that uses carbon dioxide, water, nutrients, and energy from the sun to produce food and oxygen Plankton-organisms that drift or swim weakly, generally carried about by currents Radioactive-property of the atoms of some molecules that involves emitting energetic particles by disintegration of the nucleus of the atom Rubisco-ribulose 1,5 bis-phosphate carboxylase; the enzyme that converts carbon dioxide to a three-carbon organic molecule as the first step in the photosynthetic production of glucose (a six carbon sugar) Silica-a crystallized compound that occurs as sand, quartz, and other minerals Soluble-capable of being dissolved Symbiosis-a long-term association between two different types of organisms Technology-the application of science to commercial enterprise, medicine, environmental restoration, and other human activities



Single-celled Organisms References

“Bacteria”. Online at http://www.ucmp.Berkeley.edu/bacteria/bacteria.html 13 November 2001. “Cyanobacteria”. Encarta. Online at http://www.encarta.msn.com/find/Concise Asp?z=1&pg=2&ti=761574227 9 October 2001. “Cyanobacteria”. Online at http://www.ucmp.Berkeley.edu/bacteria/

cyanointro.html 8 October 2001. “Diatom.” Online at http://www.ucmp.berkeley.edu/chromista/bacillariophyta.html 14 Nov. 2001. “Dinoflagellate”. Online at http://www.ucmp.berkeley.edu/protista/

dinoflagellata.html 14 November 2001. Douglas, A. E., Symbiotic Interactions. Oxford: Oxford University Press, 1994. Janson, S., E. J. Carpenter, and B. Bergman. “Immunolabelling of phycoerythrin, Ribulose 1,5-bisphophate carboxylase/oxygenase and nitrogenase in the Unicellular cyanobionts of Ornithocercus spp. (Dinophyceae).” Phycologia. 34.2 (1995): 171-176. McFall-Ngai, M. J., and E. G. Ruby. “Sepiolids and Vibrios: When First They Meet.” BioScience. 48.4 (April 1998). “Microorganisms”. NASA poster. NW-2000-10-155-HQ. “Reef Symbiosis”. Online at http://www-geology.ucdavis.edu:8000/~gel3/

symbiosis.html 3 Nov. 2001. Sherry, N. D., and A. M. Wood. “Phycoerythrin-containing picocyanobacteria in the Arabian Sea in February, 1995: diel patterns, spatial variability, growth Rates.” Deep-Sea Research 48 (2001): 1263-1284. “Symbiosis”. Encyclopedia Britannica. Online. 3 November 2001. “Symbiosis in the Marine World”. Online at http://www.petplace.com/Articles/ artShow.asp/artId=2425 3 November 2001. “Symbiosis”. http://www.ultranet.com/~jkimball/BiologyPages/S/Symbiosis.html Online. 3 November 2001. Wood, Michelle. Written correspondence. 15 November 2001.

associate professor university of oregon ph.d. in …ph.d. in zoology university of georgia michelle...

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