Lesson 2: The Great Transition from Prokaryotes to Eukaryotes

Authors: Meredith Salmon & Dr. Johanna T. Ohlmeyer
[ezcol_1quarter]Main Idea:[/ezcol_1quarter] [ezcol_3quarter_end]Before the first Eukaryotic cells appeared, prokaryotic cells were around for 2 billion years. The prokaryotes, specifically cyanobacteria, are responsible for the Oxygen Revolution. This introduction of oxygen into the atmosphere contributed to the evolution of eukaryotes. In addition, prokaryotes transformation to eukaryotes was accelerated by endosymbiosis. The endosymbiotic theory said that bacteria and archaebacteria come together to form the first eukaryotic cell. This process evolved as a response to the changes in the environment and to the new opportunities for the cell to move, eat, and grow, and communicate. In addition secondary endosymbiotic events occurred, the Eukaryotic cells engulfed prokaryotes that become organelles such as chloroplasts and mitochondria. Over time, multicellular organisms appeared contributing to the great diversity of organisms. Once students understand the importance of prokaryotes and their relationship with eukaryotes, they will be able to learn that Protists are unicellular organisms that are a very important link in the food chain.[/ezcol_3quarter_end]

[ezcol_1quarter]Objectives:[/ezcol_1quarter] [ezcol_3quarter_end] 1. To be able to understand and explain the importance of bacteria during the early history of life on Earth and in our lives. Also, to compare and contrast prokaryotes and Eukaryotes in terms of structure and function.
2. To be able to compare and contrast Prokaryotes and Eukaryotes.
3. To describe how the Endosymbiotic theory explains two prokaryotes, Eubacteria and Archaebacterium, giving rise to eukaryotes.
4. To understand the great variety and diversity of protists.[/ezcol_3quarter_end]

[ezcol_1quarter]Students’ Skills:[/ezcol_1quarter] [ezcol_3quarter_end] Bloom Taxonomy: Knowledge, evaluation, comprehension, application, analysis, synthesis.
NGSS connections: HS-LS4 Biological Evolution: Unity and Diversity. HS-LS4-1: Communicate scientific information that common ancestry and biological evolution are supported by multiple lines of empirical evidence.
Crosscutting concepts: Cause and Effect and Patterns.
Practices: Obtaining, Evaluating, and communicating information.[/ezcol_3quarter_end]

[ezcol_1quarter]Materials:[/ezcol_1quarter] [ezcol_3quarter_end] Textbooks, computers, PowerPoint, worksheets/handouts, pond water, petri dish, microscope. [/ezcol_3quarter_end]

[ezcol_1quarter]Lesson Day 1:[/ezcol_1quarter] [ezcol_3quarter_end]1. Entry card: Working alone, students will be given about five minutes to answer this question, “What are three ideas that come to your mind when you think about bacteria? At least one of these ideas should be positive!” At the end of the five minutes, students will be given the opportunity to share their ideas with the person sitting next to them. If their partner thought of something different that they failed to include, they should include it on their notecard.

2. Before beginning the activity, the teacher will show the students a short video clip about bacteria. As they are watching the movie, students should be taking notes on the different kinds of bacteria that they see (shape, different habitats, different roles in nature, etc.) After the video, the teacher will show a short PowerPoint presentation that explains the defining characteristics of bacteria. The teacher will be sure to emphasize how their structure fits their function. The teacher will focus on their structure and importance in ecosystems.

3. After students have a grasp on the background information about bacteria, the teacher will explain that they will then work in groups to complete the next activity. Each group will be assigned a different bacteria and will have to research several aspects of bacteria on the web, in books, and even in magazines. With the gathered information, they will produce a group poster about their bacteria.

4. Each group will pick their topic at random form a basket and they will be assigned to do research. They will pick at random unless a group has a specific request to research a specific topic that are very interested in. Topics will include: Bacteria’s positive and negative roles in human health, what is Eubacteria and Archaebacterium and where are they found, importance of cyanobacteria in the oxygen revolution, why is bacteria in your gut, how is bacteria used in the production of food, the structure and function of bacterial cells.

5. Once the students have had time to discuss their topics, the teacher will allow them to work for the remainder of class. Each group will present their results to their peers after their poster is complete. They should make a colorful poster complete with descriptions and images.

6. During the poster presentations, each student should contribute and the ones who are not presenting will act as reviewers. That being said, each “reviewer” will think of one comment, suggestion for improvement, or question to ask at the end of the presentation. The teacher will collect these comments and hand them to the group after their presentation so they can get a sense of what their peers thought.

7. During the second class, the student groups will be given time to update and revise their posters based on the ideas and suggestions emphasized by their peers. The teacher will display these posters for everyone to see. Before the end of the lesson, student groups will need to find a bacterium in the news article, summarize it, and present their findings to the class.

8. Exit Card: As a group, students should write down an assessment of how well they worked together as a team. In addition, each student should write down two things they learned in class based on other classmates’ posters and one concept they still have a question on.

9. Homework:  Each student will bring to class a list of 5 characteristics unique to Eukaryotes. [/ezcol_3quarter_end]

[ezcol_1quarter]Lesson Day 2  Endosymbiosis :[/ezcol_1quarter] [ezcol_3quarter_end]1.Entry card: Students will be given a sheet of paper that has a list of bacterial characteristics. Next to the characteristic, they will need to write true or false and correct the false statement to true. The teacher will allow the students to compare with their partners for the last minute and then go over the activity to make sure no one has questions.

2. The teacher will break the class up into two groups. Group one will be responsible for prokaryotes and Group 2 will be responsible for eukaryotes. Each group will have one half of the board, will be able to research their topic, and will be asked to draw and label their cell structure and list its defining characteristics.

3. Comparing and contrasting the structure and function of prokaryotes and eukaryotes will allow students to differentiate between each cell type. After this activity, the teacher will emphasize the similarities and differences between the two by handing out a table provided by the teacher that compares prokaryotes and eukaryotes. Students can work with partners within their groups to go over the information and the teacher will be sure to answer any questions pertaining to the activity.

4. Once the table from step 3 is filled out among students, the teacher will inform the students that they are creating a “Master table” on the board so that they can all compare answers. A whole class discussion will commence and the teacher will ask students for reasons why there are differences between the two cell types. Explain each points of comparison by stating whether it is an advantage or disadvantage for the cell and why. The teacher will work closely with the students and point out that a eukaryotic cell is much more complicated, compartmentalized, and more flexible than a prokaryotic cell.

5. The teacher will explain how the eukaryotic cell arose by the coming together of prokaryotes (Eubacterium and Archaebacterium). They will understand the endosymbiotic theory and the teacher will show a short clip so that they have a visual representation of the process. Students should be able to draw a web diagram and understand this process in their notebook. In addition, it would be helpful if they explained it to the person sitting next to them.

6. Exit card: students will answer the question: How endosymbiosis promoted the rise of the eukaryotic cell?

7. Homework:  Pretend you are a eukaryotic cell. Write a narrative about how you came about and how your structure and function is different from that of a prokaryotic cell. Use the word symbiosis in your narrative. [/ezcol_3quarter_end]

[ezcol_1quarter]Lesson Day 3   Web diagram:[/ezcol_1quarter] [ezcol_3quarter_end] 1. The teacher will start the class by having students discuss their narratives about a eukaryotic cell. The teacher will address any questions that the students have.

2. The teacher will have web diagram worksheets printed out for each student to use. The students will learn that web diagrams should establish a clear relationship between organisms of different backgrounds.

3. Each student will be responsible for working alone at first. Students will have to print out or draw pictures of prokaryotic and eukaryotic cells and structures to put on their web diagram hand out. Each branch will list a specific structure present in both cells and will branch off accordingly. Students will need to establish a relationship between the two cells and explore relationships using arrows/pointers. The pointers go with the label and indicate what other elements can be associated with it in a logical and meaningful way. Students will be encouraged to use many pointers to establish sophisticated and elaborated knowledge networks.

4. Once the students believe that they have finished their web diagram, they will swap papers with the person next to them. They will critique each other’s work and ask questions if they have any.

5. Homework: the students will make sure they understand the context of the web map and write a narrative about the relationships present in their diagram. For a rich, complex narrative, the more linkages and labels the students have the better.

6. For the last class, students will study the diversity and importance of protists. They will start the class by getting into groups of two and each group should obtain a petri dish and sample of pond water from the instructor.

7. Students will spend the remainder of class looking under the microscopes at the pond water and they will describe and draw the protists that they see. They will follow along with a handout that they should fill in carefully. That way, they can use the Internet and books to determine what protists they saw underneath the microscope. Once they determine which protist is which, they will have to individually pick a protist to research.

8. Each student will create an information pamphlet about the protist of their choice and be sure to cover their role in nature. In the next class, the students will set out their brochures and armed with sticky notes, they will post comments, suggestions, and questions on each other pamphlets.

9. The teacher will sum up the lesson by going over the main characteristics of protists and relating to how their structure fits their function. Also, the teacher could lead a summarizing activity on the board by completing a class web diagram that displays the web diagram will show the importance of protists for the environment. Once complete, the students will need to devise a narrative about the relationship between eukaroytes and protists based on the relationships of the pointers. [/ezcol_3quarter_end]

[ezcol_1quarter]Assesment:[/ezcol_1quarter] [ezcol_3quarter_end] 1. Participation in class and during group work.
2. Participation in the poster and pamphlet comment activity.
3. Actively engaged in research.
4. Thoroughness of filling out the handouts assigned in class.
5. Completeness of the Web Diagram activities and narratives.[/ezcol_3quarter_end]

[ezcol_1quarter]Teacher’s Reflections:[/ezcol_1quarter] [ezcol_3quarter_end]1. Were all of the lesson objectives met?
2. Was the importance of structure and function emphasized?
3. Did I compare and contrast prokaryotes and eukaryotes in a clear manner?
4. Did students learn and apply the information in an appropriate manner?[/ezcol_3quarter_end]

[ezcol_1quarter]Notes to the Teacher:[/ezcol_1quarter] [ezcol_3quarter_end]1. This Lesson will take place over two or more class periods.
2. The focus of this lesson is to have students learn and practice to make web diagrams.
3. The teacher should fully explain the purpose of the web diagrams before using them.
4. The teacher should monitor the groups closely and make sure students are engaged.[/ezcol_3quarter_end]

[ezcol_1quarter]Appendix:[/ezcol_1quarter] [ezcol_3quarter_end]Any resources such as charts, tables, and handouts should be used form the lesson plans for middle school. They can be modified for high school students.[/ezcol_3quarter_end]