Relating Structure to Function in Cells Grade 12

Transcription

1 Ohio Standards Connection: Life Sciences Benchmark A Explain how processes at the cellular level affect the functions and characteristics of an organism. Indicator 2 Explain why specialized cells/structures are useful to plants and animals (e.g., stoma, phloem, xylem, blood, nerve, muscle, egg and sperm.) Lesson Summary: In this lesson, students will investigate specialized structures in both plants and animals. They will relate structure to function, as they determine why the specialization is necessary and useful to the living organisms involved. They will use microscopes to look at cells and they will investigate the differences between different types of cells. Estimated Duration: Four hours Commentary: This lesson addresses the basics of cell structure and function. Students are able to view a variety of cells and evaluate why the structure of the cell exists, in relation to the function that it must perform. One teacher in the field reviewed this lesson and commented: It is very adaptable to various skill/grade levels of students. It could be modified for advanced level students, as well as for those still struggling to master the basic knowledge of the standard. Pre-Assessment: Write the following questions on the board. Instruct students to answer the questions on a sheet of paper. 1. What makes blood cells different from nerve cells? 2. What is meant by cell specialization? 3. Give an example of a specialized cell and explain its purpose. 4. Why do we need different types of cells in order to maintain homeostasis? Scoring Guidelines: 1. What makes blood cells different from nerve cells? Blood cells are specialized for carrying oxygen or fighting disease, while nerve cells conduct nerve impulses from the body, to the brain, and back to the body 2. What is meant by cell specialization? Cell specialization is the design of cells of an organism specifically for a certain function. 1

2 3. Give an example of a specialized cell and explain its purpose. White blood cells fight disease; red blood cells carry oxygen to the body; cnidocysts for defense in cnidarians, contain nematocyst, a stinging cell. 4. Why do we need different types of cells in order to maintain homeostasis? Different cells perform different functions. Success of these functions is crucial for maintenance of homeostasis. Use the pre-assessment as an indicator of student prior knowledge on the indicator and a guide for instruction. It can be a springboard for class discussion. Post-Assessment: Have students examine several examples of different types of cells and explain how the structure of each cell relates to its function. Distribute Attachment A, Post-Assessment to provide guidelines for this assessment. Scoring Guidelines: Use Attachment B, Post-Assesment Scoring Guidelines to assess student work. Instructional Procedures: Part One - Introduction 1. Discuss responses to the pre-assessment questions with students. This can be a whole class discussion, think-pair-share, or other method of generating conversation about the topic with the students. 2. Explain to students that many cells have special structures for certain functions. Give the students examples from both the plant and animal kingdom. Instructional Tip: Some examples include: xylem and phloem cells in plants, stoma in plants; blood cells, muscle cells, and various other types of cells in animals, such as villi and microvilli in the stomach (to increase the surface area and enhance absorption). Stress the importance of structure and function in these specialized structures. Part Two Mosses vs. Vascular Plants 3. Provide students with examples of mosses and vascular plants. Have them make a T- chart listing the observable characteristics of both mosses and vascular plants. See Attachment C, T-Chart. Instructional Tip: Make an overhead of the T-chart. With the class, compare and contrast mosses and vascular plants. Work across, writing one statement for mosses, and then a comparison or contrasting statement for vascular plants. 4. Define vascular tissue, xylem, and phloem for students. Review diffusion and osmosis. 2

3 5. Have students use the microscope to look at cross-sections of vascular plants. Have students draw a diagram of their slide and identify the xylem and the phloem on the slide. Instructional Tip: Use prepared slides, or have students make their own slide with a VERY thin section of stem from a plant such as a Swedish Ivy. 6. Have students look at a cross-section of moss under the microscope and draw it. Have students compare Swedish Ivy and moss. Students should observe and note that there is no xylem or phloem on the slide of moss. 7. Ask students, How do you think mosses transport food and water if they have no vascular tissue? Have students share their answers with the class. 8. Explain to students that the size of the moss is directly related to the fact that they don t have vascular tissue. They should understand that mosses must be small, because they are unable to transport water great distances. Part Three Stomata Instructional Tip: A leafy plant such as leaf lettuce works well for this activity. 9. Provide students with a copy of Attachment D, Observing Stomata. Have students research the function of stomata in plant cells. 10. Using a leaf, have students snap the leaf in two and carefully use forceps to pull the BOTTOM membrane from the leaf. They should mount this on a clean slide, cover with a drop of water and add a cover slip. 11. Have students view their slide under the microscope. Instruct them to draw a diagram of what they see and label stomata and guard cells on their diagram. 12. Have students repeat the preparation of the slide using the TOP of the leaf. View the slide under the microscope and draw a diagram of what they see. 13. Ask students to compare the two slides. (The slide of the top of the leaf has no stomata and guard cells.) 14. Ask students to explain why they think the plant only has stomata and guard cells on one side of the leaf. Have them share their answers with the class. 15. Ask students, Why are the guard cells important for the plant? What do they control? Have students share their answers. 16. Ask students, What types of things might move into or out of the guard cells? How are these things important for photosynthesis? Have students share their ideas with the class. Reinforce the idea that oxygen is released by the plant as a product and carbon dioxide is taken in by the plant as a reactant for photosynthesis. 3

4 Part Four Blood cells 17. Using the microscope and a prepared slide of a human blood smear, have students identify different types of cells. They should see many red blood cells, such as pink/red circles, but relatively few white blood cells in their sample. Instructional Tip: Blood carries many pathogens that students should not handle. Use professionally prepared slides to avoid exposure. 18. Have students complete Attachment E, Blood Cells. Students should go to their textbook as a resource and investigate the difference in function between red and white blood cells. 19. Ask students to brainstorm, in pairs, why they think the cells are different in appearance even though they are both types of blood cells. Give them five to ten minutes to discuss. Ask them to share answers and keep a list on the board. 20. Upon completion of this part of the activity, have students use their text to verify or refute the list of answers given by the class. 21. Make sure that you go over student results of this part of the activity. Stress to students that they are researching why specialized cells are important and should be finding out why red and white blood cells look the way they do (how structure is related to function). Ask students to brainstorm why cardiac cells might have a large number of mitochondria. Have them share answers with the entire class. Discuss with students the fact that cardiac muscle needs a lot of energy to function properly, so it has a large number of mitochondria. Part Five Synthesis of information 22. Give students a copy of Attachment G, Cell Specialization Graphic Organizer and have them fill it out. You may choose to do this in the form of notes, or have students do this independently. Make an overhead sheet of the blank graphic organizer, and provide a copy for each student. 23. Discuss this graphic organizer with students. Ask if any students have any questions. Explain anything that needs to be clarified 24. Students should begin to work on the post-assessment. Give each student a copy of Attachment A, Post-Assessment. Differentiated Instructional Support: Instruction is differentiated according to learner needs, to help all learners either meet the intent of the specified indicator(s) or, if the indicator is already met, to advance beyond the specified indicator(s). Have students work in pairs while doing microscope work to enable those who are proficient at using the microscope to help teach others how to focus and make accurate drawings. 4

5 If necessary, provide students with the cell specialization graphic organizer with the notes already filled in. Have these students highlight sections as they are discussed, to keep them on task. Provide students with a vocabulary list of the words in this lesson. Have them write the definitions, making sure that they use the words correctly throughout the lesson. Provide students with the blank graphic organizer at the beginning of the activity, and have them fill it in as the lesson is completed. Have students research some of the specialized structures of invertebrate animals to use in their essays, providing examples of importance of the specialized structures for defense, nutrition, response to the environment, etc. (Suggested examples: flame cells in planaria; cnidocytes, ocelli, statocysts, water vascular system in sea stars) Extension: Have students look at different tissue samples, such as cuboidal epithelium, pseudostratified columnar epithelium, adipose tissue, muscle, cartilage, etc. Have them identify similarities and differences and relate structure to the function of each of these types of tissue. This can be completed with samples from the Internet. Homework Options and Home Connections: Provide students with a handout on different types of tissue. Have them research (in their text) the function, and find out if there is a key part of structure related to function in these tissues. Materials and Resources: The inclusion of a specific resource in any lesson formulated by the Ohio Department of Education should not be interpreted as an endorsement of that particular resource, or any of its contents, by the Ohio Department of Education. The Ohio Department of Education does not endorse any particular resource. The Web addresses listed are for a given site s main page, therefore, it may be necessary to search within that site to find the specific information required for a given lesson. Please note that information published on the Internet changes over time, therefore the links provided may no longer contain the specific information related to a given lesson. Teachers are advised to preview all sites before using them with students. For the teacher: For the students: microscopes, slides, cover slips, lens paper, forceps, water, pipette/dropper, prepared slides of blood smear, plant leaves (onetwo leaves per lab group), vascular plant stem cross section slides, moss cross section slide microscopes, slides, cover slips, lens paper, forceps, water, pipette/dropper, prepared slides of blood smear, plant leaves(onetwo leaves per lab group), vascular plant stem cross section slides, moss cross section slide 5

6 Vocabulary: xylem phloem guard cell stomata osmosis vascular plant red blood cell white blood cell cell wall cell membrane chloroplast photosynthesis mitochondria Technology Connections: Have students investigate the Web for microscopic images of cells that illustrate the specificity of the structures is related to the function of the cell. Research Connections: Marzano, R., Pickering, D., Pollock, J. (2001).Classroom Instruction that Works: Research-Based Strategies for Increasing Student Achievement, Alexandria, Va: Association for Supervision and Curriculum Development. Identifying similarities and differences enhances students understanding of and ability to use knowledge. This process includes comparing, classifying, creating metaphors and creating analogies and may involve the following: Presenting students with explicit guidance in identifying similarities and differences; Asking students to independently identify similarities and differences; Representing similarities and differences in graphic or symbolic form. General Tips: If possible, provide each student with a microscope, especially students who have not had experience with microscopes. This way, all students will gain proficiency at the use of the instrument and the amount of time spent waiting for someone else to finish will be minimized. Check with local medical research labs, universities and community colleges for prepared slides. They may have some prepared slides that they are willing to donate to your school. Check with the American Red Cross about free literature that they may have on blood and blood disorders/diseases. You can view stomata on leaves, that don t have an easily removable membrane, by putting two swipes of clear nail polish on the underside of the leaf and allowing it to 6

7 dry for minutes. Peel it off and you have an imprint of the cells of the underside, including the guard cells. When using the graphic organizer for note-taking, have students draw in a diagram of each structure covered in the notes. Attachments: Attachment A, Post-Assessment Attachment B, Post-Assessment Scoring Guidelines Attachment C, T-Chart Attachment D, Observing Stomata Attachment E, Blood Cells Attachment F, Blood Cells Key Attachment G, Cell Specialization Graphic Organizer Attachment H, Cell Specialization Graphic Organizer Key 7

8 Attachment A Post-Assessment Relating Structure to Function Directions: Provide five examples of cells or tissue and explain how the structure of the cell relates to its function and aids the organism as a whole. Your essay will be evaluated using the scoring guidelines below. Depth of Understanding Communication Level 4 Level 3 Level 2 Level 1 Scientific Scientific Scientific Scientific information and information and information information ideas about cell ideas about cell about cell about cell specialization are specialization are specialization specialization accurate and accurate. has occasional has major thoughtfully Scientific inaccuracies or is inaccuracies or explained. connections simplified. is overly Scientific about cell Scientific simplified. connections about specialization connections Scientific cell specialization are identified. about cell connections are correctly specialization about cell identified and may be implied. specialization discussed. are unclear or absent. Scientific information about cell specialization is communicated clearly and precisely, but may also include inventive/expressive dimensions. Presentation is effectively focused and organized. Scientific information about cell specialization is communicated clearly. Presentation is effectively focused and organized. Scientific information about cell specialization has some clarity. Presentation has some focus and organization. Scientific information about cell specialization is unclear. Presentation lacks focus and organization. Adapted from Council of Chief State School Officers State Collaborative on Assessment and Student Standards (SCASS) Science Project, April

9 Attachment B Post-Assessment Scoring Guidelines The scoring guidelines for the essay can be found in the students directions. Below are the type of specialization features that could be highlighted in the essay. This is only a partial list. Students could include other examples. Specialized cells provide a unique function in the organism in which they are found; Red blood cells are specialized because they carry oxygen to the body parts and return carbon dioxide to the lungs; White blood cells are specialized because they recognize chemicals secreted by microorganisms and are able to leave the blood to go to the area of the body where microorganisms are located to initiate the immune response; Xylem is a specialized plant tissue that transports water through the plants; Phloem is a specialized plant tissue that transports food through the plant; Ocelli are specialized structures in cnidarians and planarians that help them recognize light; Statocysts are specialized structures in cnidarians that help them recognize gravity. 9

10 Attachment C T-Chart Mosses Vascular Plants 10

11 Name Attachment D Observing Stomata Observing Stomata Plants contain many unique cellular structures that have specific functions. Two of these structures are guard cells and stomata. A stoma (plural, stomata) is a pore in the leaf. It is surrounded by two guard cells. In this activity, you will investigate the location, structure and function of stomata and guard cells. Materials: clean slides, cover slips, lens paper, plant leaf, forceps, microscope Procedure: 1. Make sure that your slides are clean and free of fingerprints. 2. Gently break the leaf. Using the forceps, carefully peel the membrane on the underside of the leaf and place it on your slide. 3. Cover the slide with a cover slip and view under high power. Make a detailed drawing of what you see in the space below. Be sure to label your drawing correctly. 4. Repeat steps one to three, using a membrane from the top of the leaf. 5. Identify the guard cells and stoma on each sample and answer the questions below. Data collection: The purpose of stomata is to: Underside of leaf High Power Top side of leaf High Power 11

12 Attachment D (Continued) Observing Stomata Questions: 1. What is different about the top side and the underside of the leaf? 2. Why do you think the two sides are different? 3. Identify the stoma and the guard cells. 4. Using your textbook, identify the function of the stoma and the guard cells. 5. Think about the structure/shape of the guard cells and the stoma. How does this relate to the function of these structures? 12

13 Name Attachment E Blood Cells Anatomy and Physiology Blood cells Directions: Look at the slides of blood. Focus them on low power, then switch to high power before you draw them. Draw each, and answer the questions that follow. Questions: 1. On the drawing of the blood, label some red blood cells and some white blood cells. 2. What is the function of the red blood cell? 3. What is the function of the white blood cell? 4. What are the types of white blood cells that you can see in your slide? 5. What happens within your body if you have too many red blood cells? Explain. 6. What is happening within your body if you have too many white blood cells? Explain. 13

14 1. Bloodsmear drawing with cells labeled. Attachment F Blood Cells Key 2. Red blood cells deliver oxygen and remove waste. 3. White blood cells are part of the immune system and they help to fight disease. 4. Lymphocytes and neutrophils will be the most common cells. 5. Too many red blood cells can result in a condition called polycythaemia. Excess red blood cells cause the blood to thicken and blood clots become problematic. 6. Too many white blood cells indicates that the body is fighting an infection or disease. If the white blood cell count remains consistently high, it may be an indication of leukemia. 14

15 Attachment G Cell Specialization Graphic Organizer Cell Specialization DRAFT 15

16 Attachment H Cell Specialization Graphic Organizer Key Cell Specialization Stoma and Guard Cells Vascular Tissue, Plant Blood Cells Nematocysts Stoma pore in plant cells on underside of leaf to allow passage of gases such as CO2 Guard Cell one of two cells that surround stoma and control the size of the stoma. Stoma is larger during the day, when plant takes in large amounts of CO2 for photosynthesis. Tissue specialized for carrying water and nutrients in plants. Xylem for transport of water from roots to leaves; formed from tracheids to be one long, straw-like tube in plant. Phloem transport nutrients and carbohydrates made by photosynthesis from leaves to stem and roots of plant. Red blood cells contain no nucleus; made in red bone marrow; specialized to carry oxygen throughout the body; found in very large numbers in blood samples. White blood cells contain a nucleus and DNA, specialized to fight disease; numbers of white blood cells varies with the health of the individual. Specialized cells in jelly fish that contain poison stingers that jet outward when the jellyfish is threatened. Nematocyst stingers turn inward, unless the jellyfish is threatened, then they shoot outward with their poison. Diagram of stoma and guard cells Diagram of vascular tissue Diagram of red and white blood cells Diagram of nematocysts DRAFT 16