Unit: Organization General Task. How Are Cells Differentiated?

Transcription

1 The following instructional plan is part of a GaDOE collection of Unit Frameworks, Performance Tasks, examples of Student Work, and Teacher Commentary. Many more GaDOE approved instructional plans are available by using the Search Standards feature located on GeorgiaStandards.Org. Unit: Organization General Task How Are Cells Differentiated? Overview: Making microscopic observations of different types of cells, students will compare and contrast cell organelles and their functions and relate how these structures maintain homeostasis in all living things. Standards (Content and Characteristics): SB1. SB3. Students will analyze the nature of the relationships between structures and functions in living cells. a. Explain the role of cell organelles for both prokaryotic and eukaryotic cells, including the cell membrane, in maintaining homeostasis and cell reproduction. Students will derive the relationship between single-celled and multi-celled organisms and the increasing complexity of systems. b. Compare how structures and function vary between the six kingdoms (archaebacteria, eubacteria, protists, fungi, plants, and animals). d. Compare and contrast viruses with living organisms. SCSh2. Students will use standard safety practices for all classroom laboratory and field investigations. a. Follow correct procedures for use of scientific apparatus. b. Demonstrate appropriate technique in all laboratory situations. c. Follow correct protocol for identifying and reporting safety problems and violations. SCSh4. Students use tools and instruments for observing, measuring, and manipulating scientific equipment and materials. a. Develop and use systematic procedures for recording and organizing information. SCSh5. Students will demonstrate the computation and estimation skills necessary for analyzing data and developing reasonable scientific explanations. d. Consider possible effects of measurement errors on calculations. Biology 9-12 Organization August 17, 2007 Page 1 of 11

2 Enduring Understandings: Cells have particular structures that underlie their functions. Regardless of cell type, cellular components function together to maintain homeostasis. All organisms and systems are organized from simple parts into complex systems that must maintain homeostasis in order to survive. Essential Questions: 1. How are unicellular and multicellular organisms similar and different? 2. How are prokaryotic and eukaryotic cells similar and different? 3. How do organelles work together to maintain homeostasis in the cell? 4. Why is cell differentiation necessary for the survival of multicellular organisms? Pre-Assessment: Placemat Activity: Group students into 4, have a placemat for each group. The placemat can be a piece of butcher paper divided into four sections. Label sections as : Characteristics of Eukaryotes, Examples of Eukaryotes, Characteristics of Prokaryotes, Examples of Prokaryotes. Give students 5 minutes to brainstorm as much as they know for their placemat. See Placemat template below. A different placement could be created to pre-assess student knowledge of the characteristics and types of plant and animal cells. Outcome / Performance Expectations: Compare cell types and describe the function of individual cell organelles in cell functioning and reproduction Describe homeostasis as involving the transport of materials in a cell and in an organism Explain the role and mechanisms of homeostasis in maintaining life as they relate to cell structure General Teacher Instructions: This activity will take approximately two full block periods. The instructions in this lab may need to be adjusted depending on the type of microscopes available for student use (compound microscope or digital microscope) and the skill levels of your students. The focus of second part of this activity is to compare structures from multi-cellular organisms with those of the less complex organisms. The students are NOT to be assessed on the different types of cells. The assessment should be on the organization necessary for the complex organisms to carry out the life processes and survive. Materials Needed: Part 1 Compound microscope or digital microscope prepared slide of bacteria Methyl blue paper towel ruler (clear) August 10, 2007 Page 2 of 11

3 Elodea or Lettuce Yogurt with active culture 2 slides and coverslips Iodine stain Onion eyedropper Cover slips Toothpicks Prepared slides of human epithelial tissue. Part 2 Compound microscope Prepared slides Leaf (cell types vary in the formation of this organ, lead students to see the variety of cells) Stem (either monocot or dicot, do not focus on the difference between these two, the focus is on differentiation of cells) Root (meristem) Epithelial Cardiac muscle Nerve Smooth muscle Bone Safety Precautions: Follow correct microscope handling directions. Follow glass safety rules (handling slides/ slip covers) Follow chemical safety rules for toxic chemicals Wear goggles and aprons. Methyl blue and Iodine stain clothes. Task with Student Directions: Procedures: All students should complete the following sections and put all observations, measurements and calculations in their lab notebooks. Part 1 1. Measuring the field of view: Turn on the microscope's light source. Adjust the amount of light for your eyes using the diaphragm located underneath the stage. Calculate the total magnification of each objective by multiplying the power of the objective (the even number printed on the objective) by the ocular (the number that has an "x" behind it printed on the eye-piece). Record value in a data table. Place a clear ruler on the stage and determine the diameter of the field of view while using the low power objective (generally 10x). Record value in a data table. August 10, 2007 Page 3 of 11

4 Teacher note: The small size of bacteria may prohibit direct student observations. Set up a station for students to view bacterial cells (prepared slide). Have a poster or some other visual aid showing the structure of a bacterial cell. Teacher note: the size of a single cell can be determined by dividing the diameter of the field of view by the approximate number of cells that fit across that diameter. Teacher note: Skin cells from the underside of the wrist can be obtained with a small piece clear tape eliminating the use of toothpicks. The tape can be placed directly on a slide and stained as described. Calculate the diameter of the high power field of view by dividing the low power field of view diameter by the number of times the low power magnification can be divided into the high power magnification. Record value in a data table. Example: If the low power field of view is 2mm or 2000 microns, the low power magnification is 10x and the high power magnification is 40x, then the high power field of view is 2000 microns divided by 4 = 500 microns. Record value in a data table. 2. Viewing Prepared Slides: Bacteria Place the prepared slide of bacteria on the stage of the microscope. Using the low power objective (usually 10x) find and focus on some bacteria cells. Adjust the slide so that the bacteria cells are in the center of the field of view. Using the ruler determine the distance between the bottom of the objective and the slide and record the information on the data sheet. Adjust the microscope to high power (not the oil immersion objective) and refocus on the cells. If necessary re-adjust the position of the cells so that they are again the in center of the field of view. If your microscope has an oil immersion objective (100x), adjust the microscope to oil immersion with the assistance of your teacher and again refocus and adjust the position of the cells if necessary. Draw a circle on the data sheet to represent your field of view at this magnification then draw several bacteria cells in that circle. Indicate the total magnification that you are using and estimate the size of one of the cells. Human epithelial cells Slide: If necessary, the teacher can prepare the human epithelial slide and have it setup for students to view. Gently scrape the inside of the cheek with a toothpick. Wash cells from toothpick to slide using a pipette of distilled water, or stir toothpick into a drop of water on a slide. Dispose of toothpick properly. Add a coverslip. Add iodine or methyl blue by drawing the stain under the coverslip using a paper towel. Place the prepared slide on the stage of the microscope. August 10, 2007 Page 4 of 11

5 Teacher note: Instruct students to dip only the tip of a toothpick into the yogurt, and transfer that small drop onto the slide. Observe the cells as you have done in the previous portions of this activity. Record your observations on the data sheet. Again after making the circle in the space, make a drawing of the cell and label all of the structures that you see. Indicate the total magnification you are using and estimate the size of one of the cells. 3. Preparing Your Own Slides: Slide One: Yogurt Place a very small dollop of yogurt on a microscope slide. Mix the yogurt in a drop of water, add a coverslip, place the slide on the stage of a compound microscope. First focus using the low-power objective. Then, rotate to the high-power, and focus. Finally, use the oil immersion objective to Draw a perfect circle in the space on the data sheet to represent your field of view at this magnification and draw three cells (labeling all the parts that you can see) in that circle. Give as much detail as you can. Indicate the total magnification and estimate the size of one of the bacteria cells. Slide Two: Onion Place a drop of water in the middle of a clean slide. Remove a section of the skin from the inside layer of the onion and place it on the slide in the drop of water. Make sure the skin is smooth and is not folded or twisted. Place the cover slip over the top by placing the edge of the cover slip on the end of the drop of water, and then gently lower the cover slip down on the drop of water. Observe through the microscope (by first using low-power and working up to high-power). Are any of the organelles moving? Record your observations on the data sheet. Draw a perfect circle in the space on the data sheet to represent your field of view at this magnification and draw the cells you see (labeling all the parts that you can see) in that circle. Give as much detail as you can. Indicate the power that you are using and estimate the size of one of the cells. Place one drop of iodine on the slide just to the side of the cover slip. Using a small piece of paper towel on the opposite side, draw the stain under the cover slip. Let the slide set for 3 minutes letting the iodine stain the cells. Again observe the cells through the microscope. August 10, 2007 Page 5 of 11

6 Draw a perfect circle in the space on the data sheet to represent your field of view at this magnification and draw the cells you see (labeling all the parts that you can see) in that circle. Give as much detail as you can. Indicate the total magnification and estimate the size of a single onion cell. Clean and dry the slide and cover slip when done. Slide 3: Elodea Place a drop of water on the slide again, and put an Elodea leaf or a small piece of leafy lettuce in the water. Put the cover slip in place as you did before and observe the leaf through the microscope (again going from the scanning objective to high-power). Observe the cells. You may have to use a lower power to see all of one cell at a time. Again after making the circle in the space, make a drawing of the cell and label all of the structures that you see. Indicate total magnification and estimate the size of a single Elodea cell. Clean and dry the slide after your observations and data collection. Complete the following analysis items using the drawings and data collected over the two days. Analysis: Indicate the diameter of the field of view of low and high power Calculate the total magnification power of the microscope with each objective. Give the size of the cells observed (estimated) and indicate the type of cell each represents Bacteria (prepared) Bacteria (yogurt) Onion Elodea or Lettuce Human skin cell Visit this website: html August 10, 2007 Page 6 of 11

7 Pick a virus from the website and sketch a diagram of your virus. Label the parts and give their function. Compare the structure of a virus to that of a cell. Compare the size of virus to that of a cell and an organelle( ribosomes, for instance.) Compare eukaryotic and prokaryotic cells using a graphic organizer. Compare plant and animal cells using a graphic organizer. From the estimated cell size, have the student measure their height and width to determine how many cells it would take to make a body their size. Show calculations. Make a composite drawing of the largest cell observed with the other cells drawn inside of it in proportion to see that many bacteria cells can fit inside a human cell. In an essay type format, students will compare and contrast the cell organelles and their functions to the single-celled organisms and how these structures maintain homeostasis in all living things. Students should also include a diagram (flow chart) of how organisms are organized. Students will need to include in their discussions why multi-cellular organisms require differentiation to maintain homeostasis. Inquiry Using the Digital Microscopes Part I. All students will show proficiency with the microscope (either digital or compound) prior to completing the activity by: Measuring the field of view: Turn on the microscope's light source. Adjust the amount of light for your eyes using the diaphragm located underneath the stage. Place the clear ruler on the stage and determine the diameter of the field of view while using the low power objective (the shortest one). Record value in a data table. Adjust to high power (do not use the oil immersion objective 100x) and calculate the diameter of its field of view using the directions provided above. Record value in a data table. August 10, 2007 Page 7 of 11

8 Calculate the total magnification of each objective by multiplying the power of the objective (the even number printed on the objective) by the ocular (the number that has an "x" behind it printed on the eye-piece). Record value in a data table. Part 2 Provide students with a variety of prepared slides of both prokaryotic and eukaryotic cells as well as materials to make their own slides. Using the digital microscope each group will: Capture and save an image of each of the following: Prokaryotic Cell Eukaryotic Cell Plant Cell Animal Cell Bacteria Cell Place the images and the following information into a multimedia or word processing document. Incorporate the information listed below. Type of cell Magnification used when image was captured Size of each cell Label any organelles visible Method for preparing each slide Create a graphic organizer to compare eukaryotic and prokaryotic cells Create a graphic organizer to compare plant and animal cells Resources: Homework / Extension: Conclusion: In an essay type format, students will compare and contrast the cell organelles and their functions to the single-celled organisms and how these structures maintain homeostasis in all living things. Students should also include a diagram (flow chart) of how organisms are organized. Students will need to include in their discussions why multicellular organisms require differentiation to maintain homeostasis. Students complete Cell_Venn Diagram OR- Have students visit this website: Research organelles and determine the basic functions of each organelle. August 10, 2007 Page 8 of 11

9 In a paragraph, describe the role each organelle plays in maintaining homeostasis in the cell. Instructional Task Accommodations for ELL Students: Instructional Task Accommodations for Students with Specific Disabilities: Pair with more advanced native language speaking partner (allow for translation in native language for comprehension) as needed Provide paragraph summary template ( fill in the blank format) Provide bilingual support using word to word translation such as dictionaries, and glossaries Provide native language text books and support material whenever possible Keep language simple, eliminate unnecessary text, modify difficult text ( use visual representations of texts Give a written example of what observations measurements and calculations in their lab notebooks should look like Highlight / or color code key points in directions of microscope viewing, measuring, and calculating Review and Implement IEP accommodations for specific student needs Other Accommodations may include Word banks, and /or sentence starters for written lab report Provide step by step check off sheet for activities Verbal responses to explain student s detailed drawings and or graph Highlight / or color code key points in directions of microscope viewing, measuring, and calculating Instructional Task Accommodations for Gifted Students: Students may view, measure, and make calculations of additional cell types and record in lab notebooks Research size of viral particles; include drawing of a virus indicating the appropriate scale. August 10, 2007 Page 9 of 11

10 Pre-assessment Placemat Template: One Stop Shop For Educators Characteristics of Eukaryotes Examples of Eukaryotes Examples of Prokaryotes Characteristics of Prokaryotes August 10, 2007 Page 10 of 11

11 Cell Venn Make a Venn diagram using the following organelles for prokaryotic and eukaryotic cells. Then use the same organelles for plant and animal cells. 1. cell membrane 6. endoplasmic reticulum 2. cell wall 7. vacuole 3. nucleus 8. mitochondria 4. ribosomes 9. chloroplast 5. cytoplasm 10. lysosomes Prokaryotic Cells Eukaryotic Cells Plant Cells Animal Cells August 10, 2007 Page 11 of 11