Cell Structure and Function

Transcription

1 Biology, Quarter 2, Unit 2.1 Cell Structure and Function Overview Number of instructional days: 14 (1 day = 50 minutes) Content to be learned Explain/justify the relationships between and among the specialized structures of the cell and their functions. Describe how the malfunction of cell organelles can lead to disease. Demonstrate an understanding of energy transfer in cells during photosynthesis and cellular respiration, tracking overall ATP use and production. Essential questions How do specific cell organelles produce/ regulate what the cell needs for survival? What is the relationship between structure and function in organelles? Science processes to be integrated Use data and observations to question, predict, and hypothesize. Analyze and interpret data (quantitative and qualitative). Use evidence to draw conclusions. Communicate understanding of ideas. Create and analyze models, diagrams, and/or graphs. Make connections between structure and function. What is the relationship between the reactants and products of photosynthesis and respiration? How does the cell membrane regulate the movement of materials using osmosis, diffusion, and active transport? 13

2 Biology, Quarter 2, Unit 2.1 Cell Structure and Function (14 days) Written Curriculum LS1 - All living organisms have identifiable structures and characteristics that allow for survival (organisms, populations, & species). LS1 (9-11) INQ+SAE+FAF -1 Use data and observation to make connections between, to explain, or to justify how specific cell organelles produce/regulate what the cell needs or what a unicellular or multi-cellular organism needs for survival (e.g., protein synthesis, DNA replication, nerve cells). LS1 (9-11)-1 Students demonstrate understanding of structure and function-survival requirements by 1a explaining the relationships between and amongst the specialized structures of the cell and their functions (e.g. transport of materials, energy transfer, protein building, waste disposal, information feedback, and even movement). LS1 (Ext)-1 Students demonstrate understanding of structure and function-survival requirements by 1aa describing how the malfunction of cell organelles can lead to disease (e.g. leaky lysosomes and rheumatoid arthritis) Clarifying the Standards Prior Learning In grades K 4, students learned how to cite evidence to distinguish living from nonliving things. They identified the basic needs of plants and animals (e.g., water, air, food, space). Students understood what living things need to reproduce, and they learned how the physical structures of an organism allow it to survive in its habitat/environment. In grades 5 and 6, students recognized that different organisms have different features (e.g., gills or lungs) and behaviors (e.g., hibernation or migration) to meet their needs for survival. Students should have been able to describe and compare how different organisms have mechanisms that work in a coordinated way to allow them to obtain energy, grow, move, respond, defend themselves, reproduce, and maintain internal balance. They described structures and/or behaviors that help organisms to survive in their habitat/environment. In grades 7 and 8, students were introduced to the cell as the basic unit of life. They learned that a single cell has all of the same survival requirements as a whole organism. Students had the opportunity to observe and describe cells, as seen through a microscope. They learned about cell parts, including the cell membrane, cell wall, nucleus, and chloroplasts. At this point, students recognized that genetic material is located in eukaryotic cells nucleus. 14

3 Biology, Quarter 2, Unit 2.1 Cell Structure and Function (14 days) Current Learning The level of instruction for this unit is developmental/reinforcement of concepts. Although students have been exposed to basic cell structures, at this level they learn how these structures function to produce/ regulate what the cell needs for survival. They also learn the functional interdependence of the various organelles within a cell. This could be accomplished by using analogies such as a factory, city, etc. Students use data and observation to explain and justify how specific cell organelles produce and regulate what the cell needs for survival. This could be accomplished by investigating the structure and function of membranes within the cell, importance of enzymes, recurring theme of surface area to volume ratio, etc. Teachers may review and integrate teaching major biological molecules (lipids, carbohydrates, proteins, and nucleic acids) and their roles in various cell parts. Students then explain and justify the relationships and interdependence between and among the specialized structures of the cell and their functions. A good way to illustrate this interdependence is with the endomembrane system within a mitochondrion and chloroplast. Another way to do this, while linking to prior knowledge from Unit 1, is to explain the role of key cell parts in the energy conversions of photosynthesis and respiration. Students should demonstrate an understanding of energy transfer in cells during photosynthesis and cellular respiration, tracking overall ATP use and production. It is not essential for students to know the specific stages of these two processes; however, they should understand the conversion of light energy to chemical energy and the overall input/output of the processes. Students apply their knowledge to predict how the malfunction of cell organelles can lead to disease. This could be accomplished through the study of a specific malfunction (e.g., leaky lysosomes or membrane proteins). It is important that they demonstrate an overall understanding of how structure and function of living things meet the requirements for survival in the natural world. Students use data and observations to question, predict, and hypothesize the role of various cell structures and functions in relation to survival. They should analyze and interpret data (quantitative and qualitative) to draw conclusions about the importance of structure to function. A way to accomplish this quantitatively is by allowing students to investigate the need for more or less of certain organelles (i.e., number of mitochondria in muscle cells versus skin) and qualitatively by viewing cells from various parts of organisms and noticing that not all cells contain the same organelles (i.e., plant versus animal). Students should communicate understanding by creating and/or analyzing models, diagrams, and graphs. This unit lends itself well to an introduction to the tools and techniques of biologists (i.e., microscopy, slide preparation, etc.). In the classroom during this unit of study, students might learn proper microscope and slide preparation techniques. They could use microscopes in their inquiry of organelles and miscellaneous cell types. Students could also create and/or analyze graphs, diagrams, and/or models. Investigation into cell structure and function might also involve computer modeling (webquests, transport simulations, etc.). Many teachers use this opportunity to discuss and demonstrate the roles of osmosis and diffusion (emphasizing the importance of these in transport). A good way to accomplish this might be a laboratory activity dealing with osmosis. It is quite common for teachers to use a creative learning experience that allows students to describe the roles of various cell parts and their interdependence. For example, Cells are like or Cell City are common analogy-based projects used here. It is important, however, that students focus on the 15

4 Biology, Quarter 2, Unit 2.1 Cell Structure and Function (14 days) relationship between the structure and function of the organelle or the interdependence between organelles. Additionally, students may demonstrate their knowledge of diffusion, osmosis, and active transport using any of the following: computer simulations, dialysis bags, grapes, and various items yielding the effects of each phenomenon through the cell membrane. Many teachers in high school build upon the basic knowledge that students acquired during middle and high school chemistry. At this point, students move beyond an introductory understanding of cell parts to focus on explaining the relationships and interactions between cell parts. They also describe the way that these parts function at the foundational level. For example, when considering the movement of a glucose molecule across a membrane, students need to explain how the structure of the cell makes this possible. They also go on to predict how an error (malfunction) of one cell part could lead to disease in the organism. Future Learning This is a foundational unit (a springboard) to future units of study. In Unit 2.2, this concept will be taken to the next level (unicellular to multicellular life). Again during homeostasis (Unit 2.3), students will use this knowledge to look at internal balance in living things. The entire work of Quarter 3 will rely heavily on this background knowledge. Students can only understand the cell cycle and reproduction if they understand how a cell functions. Without an understanding of the nucleus, ribosomes, and endoplasmic reticulum, students will have a great deal of difficulty comprehending how DNA s code becomes protein. A solid understanding of biochemistry and cell function will be extremely useful in possible future courses such as biotechnology, forensics, anatomy, physiology, etc. Additional Findings One challenge that teachers need to address when teaching this unit depends on whether students have had some experience learning about chemical reactions. Research shows that an understanding of cell functions requires a prior understanding of both chemical reactions and the structure of atoms and molecules. Further, an understanding of the structure of major biological molecules (i.e., proteins) is a necessary precursor to the study of cell function. (Atlas of Science Literacy, Volume 1, p. 73) Because molecular biology will continue well into the 21st century as a major frontier of science, students should understand the biochemical basis of life in order to take informed positions on moral and ethical issues. (National Science Education Standards, p. 181) Research indicates that it may be easier for students to understand that the cell is the basic unit of structure (which they can observe) than that the cell is the basic unit of function (which has to be inferred from experiments). Research also shows that high school students may hold various misconceptions about cells after traditional instruction. (Atlas of Science Literacy, Volume 1, p. 72) Pupils seem to suffer from interference between the concepts of cell and molecule. When asked to sketch a molecule, many drew something that resembled a cell. Students felt that most items studied in biology (including proteins, carbohydrates, and water) were made of cells. (Making Sense of Secondary Science, p. 25) When using models to help students understand the structure and function of cell organelles, it is important to remember that students in middle and high school view models as physical copies of reality and not as conceptual representations. Teachers need to help students understand the limitations of models. (National Science Education Standards, p. 116) 16

5 Biology, Quarter 2, Unit 2.2 Unicellular and Multicellular Life Overview Number of instructional days: 10 (1 day = 50 minutes) Content to be learned Use data and observation to make connections between, explain, or justify what a multicellular organism needs for survival. Use data and observation to make connections between, explain, or justify what a unicellular organism needs for survival. Explain that most multicellular organisms have specialized cells to survive. Explain that unicellular organisms perform all survival functions and are not specialized. Compare the roles of various subcellular structures in unicellular organisms to comparable structures in multicellular organisms. Essential questions What are the necessary functions of life for all living things? How does a unicellular organism carry out all of life s functions in only one cell? Science processes to be integrated Use data and observations to ask questions. Analyze and interpret data (quantitative and qualitative). Use evidence to draw conclusions. Communicate understanding and ideas about interdependence and other aspects of the natural world. Create and analyze models, diagrams, and/or graphs. Use tools and techniques to investigate order and organization. How do specialized cells in a multicellular organism work together to carry out life s functions? How are various subcellular structures in a unicellular organism comparable to related structures in a multicellular organism? 17

6 Biology, Quarter 2, Unit 2.2 Unicellular and Multicellular Life (10 days) Written Curriculum LS1 - All living organisms have identifiable structures and characteristics that allow for survival (organisms, populations, & species). LS1 (9-11) INQ+SAE+FAF -1 Use data and observation to make connections between, to explain, or to justify how specific cell organelles produce/regulate what the cell needs or what a unicellular or multi-cellular organism needs for survival (e.g., protein synthesis, DNA replication, nerve cells). LS1 (9-11)-1 Students demonstrate understanding of structure and function-survival requirements by 1b explaining that most multicellular organisms have specialized cells to survive, while unicellular organisms perform all survival functions. (e.g. nerve cells communicate with other cells, muscle cells contract, unicellular are not specialized). LS1 (9-11)-1 Students demonstrate understanding of differentiation by 1c comparing the role of various sub-cellular structures in unicellular organisms to comparable structures in multicellular organisms (e.g. oral groove, gullet, food vacuole in Paramecium compared to digestive systems in multicellular organisms). Clarifying the Standards Prior Learning In grades K 4, students learned how to cite evidence to distinguish living from nonliving things. They identified the basic needs of plants and animals (e.g., water, air, food, space). Students understood what living things need to reproduce, and they learned how the physical structures of an organism allow it to survive in its habitat/environment. In grades 5 and 6, students recognized that different organisms have different features (e.g., gills or lungs) and behaviors (e.g., hibernation or migration) to meet their needs for survival. Students should have been able to describe and compare how different organisms have mechanisms that work in a coordinated way to allow them to obtain energy, grow, move, respond, defend themselves, reproduce, and maintain internal balance. They described structures and/or behaviors that help organisms to survive in their habitat/environment. In grades 7 and 8, students were introduced to the cell as the basic unit of life. They learned that a single cell has all of the same survival requirements as a whole organism. Students had the opportunity to observe and describe cells, as seen through a microscope. They learned about cell parts, including the cell membrane, cell wall, nucleus, and chloroplasts. At this point, students recognized that genetic material is located in eukaryotic cells nucleus. 18

7 Biology, Quarter 2, Unit 2.2 Unicellular and Multicellular Life (10 days) Current Learning The instructional level for this unit is developmental in terms of understanding unicellular life forms, but it reinforces the previous unit s knowledge of subcellular structures. Students now compare and contrast unicellular and multicellular organisms, developing an understanding of how each is able to perform all of life s functions. Students use data and observation to make connections between, explain, or justify what a unicellular or multicellular organism needs for survival. This could involve a study of the various needs such as nutrients, removal of wastes, or reproduction. Students then explain that most multicellular organisms have specialized cells to survive, while unicellular organisms perform all survival functions and are not specialized. One way to approach this is to compare the roles of various subcellular structures in unicellular organisms to comparable structures in multicellular organisms. For example, students could compare the way that nutrients are obtained by a bacterium, protist, plant, fungus, and simple and complex animals. Students use data and observations to question the role of various subcellular structures in unicellular organisms and comparable structures in multicellular organisms in relation to survival. They analyze and interpret data to draw conclusions about the comparisons between unicellular and multicellular life. A way to accomplish this is through viewing and analyzing various unicellular and multicellular life forms. This could be through the use of live specimens, prepared slides, or images. Students should be expected to evaluate differences and similarities amongst these organisms. Students communicate understanding and ideas by creating and/or analyzing models, using diagrams and/or graphs, or participating in discussion of these ideas. This unit lends itself to drill and practice in the use of tools and techniques of biologists (i.e., microscopy, slide preparation, etc.). Students compare and contrast the structures and functions of various unicellular and multicellular organisms. They could use microscopes, models, diagrams, or images to accomplish this. Within multicellular organisms, students consider different types of specialized cells and how this specialization provides for their function. Additionally, they recognize the interdependence of these different cell types, which work in a coordinated way that allows for survival. In a classroom, students might be found researching and then presenting information about various ways in which unicellular and multicellular organisms accomplish the same function of life. For example, waste removal as carried out by a bacterium, protist, plant, fungus, or simple and complex animal. In this unit, students explore unicellular life for possibly the first time. In earlier grades, they had a clear understanding that living things have needs; however, most of their experience was limited to plants and animals. Although students previously studied the structures and functions of the cell, they were not considering the cell as an independent living thing with all of the same needs as a multicellular organism. Students are now expected to make the connections between subcellular structures in a unicellular organism and related levels of organization in a multicellular organism. Additionally, they now explore the interdependence of specialized cells in multicellular organisms, which helps bridge to the next unit. Future Learning The next unit of study is homeostasis, which will require knowledge of the interdependence of specialized cells in a multicellular organism. It will also require an understanding that unicellular organisms have the same basic survival needs as a multicellular organism, including homeostasis. 19

8 Biology, Quarter 2, Unit 2.2 Unicellular and Multicellular Life (10 days) This exploration of diversity (unicellular to multicellular) will set the stage for later investigation of evolution and classification. Additional Findings Among 16-year-old students, there is some confusion about levels of organization. Responses suggest that pupils thought that molecules of protein are bigger than the size of a cell and that single-celled organisms contain intestines and lungs. The pupils in the study had been taught about cells in the previous year and superficially knew a number of correct statements about them. However, over a third of responses revealed inadequate alternative ideas about cells. (Making Sense of Secondary Science, p. 25) In a study of children ages 5 16, researchers found that almost all children recognized animal examples as living; percent of 12- to 15-year-olds regarded a particular plant as living. Almost all the children attributed growth to plants, but apparently considered this a prerequisite of life. (Making Sense of Secondary Science, p. 19) The familiar description and depiction of cells in blood sometimes lead students to the notion that organisms contain cells rather than that organisms are mostly made up of cells. Imagining the large number of cells is also a problem for young students. Large organisms are composed of about a trillion cells, but this number means little to middle school students. Students may have even more difficulty with the idea that cells are the basic unit in which life processes occur. Neither familiarity with functions of regular-sized organisms nor observations of single-celled organisms reveal much about the chemical activities going on inside single cells. (Benchmarks for Science Literacy, p. 110) 20

9 Biology, Quarter 2, Unit 2.3 Homeostasis Overview Number of instructional days: 14 (1 day = 50 minutes) Content to be learned Explain how the immune system works to maintain homeostasis in the human body. Explain how the endocrine system works to maintain homeostasis in the human body. Explain how the nervous system works to maintain homeostasis in the human body. Draw conclusions about how these three systems interact to maintain homeostasis in the human body. Investigate the factors (positive and negative feedback systems) that affect homeostasis in human body systems. Essential questions How does the immune system help the human body maintain homeostasis? How does the endocrine system help the human body maintain homeostasis? How does the nervous system help the human body maintain homeostasis? Science processes to be integrated Analyze the role of interdependence and equilibrium as it pertains to the human body. Use logical cause-and-effect reasoning. Evaluate the effect of interactions with the natural world on human body equilibrium (homeostasis). How do body systems interact to help the human body maintain homeostasis? What are the factors that affect homeostasis? 21

10 Biology, Quarter 2, Unit 2.3 Homeostasis (14 days) Written Curriculum LS 4 - Humans are similar to other species in many ways, and yet are unique among Earth s life forms. LS4 (9-11) SAE+FAF -10 Explain how the immune system, endocrine system, or nervous system works and draw conclusions about how systems interact to maintain homeostasis in the human body. LS4 (9-11)-10 Students demonstrate an understanding of human body systems by 10a explaining how the roles of the immune, endocrine, and nervous systems work together to maintain homeostasis. 10b investigating the factors that affect homeostasis (e.g. positive and negative feedback). Clarifying the Standards Prior Learning In grades K 4, students identified what the physical structures of humans do or compared the physical structures of humans to similar structures of other animals. They demonstrated an understanding of the human body by identifying the five senses and using the senses to identify objects in the environment. They observed, identified, and recorded the external features of humans and other animals. Additionally, they identified the senses necessary to meet survival needs for a given situation. Students went on to make connections between external and internal body structures of humans, understanding how they help humans to survive. They compared and analyzed external features of humans and other animals. In grades 5 and 6, students used data and observations to support the concept that environmental or biological factors affect human body systems. They went on to make predictions about how these biotic and abiotic factors could affect human body systems. Pupils demonstrated an understanding of human health/disease by identifying the biotic and abiotic factors that cause disease and affect human health (e.g., radiation, carcinogens). In grades 7 and 8, students identified biotic factors such as microbes, parasites, and food availability, which have an effect on human body systems. They also identified abiotic factors such as drugs, weather, and pollution that have an effect on human body systems. Students went on to research and report on how these factors cause human disease and affect human health. Current Learning This unit of study is primarily at the developmental level. Although students have a basic understanding of other body systems and human health/disease, they have not studied these three particular body systems. Further, they do not have an understanding of homeostasis. Students explain how the immune, endocrine, and nervous systems work to maintain homeostasis in the human body. They then draw conclusions about how these three systems interact to maintain homeostasis 22

11 Biology, Quarter 2, Unit 2.3 Homeostasis (14 days) in the human body. Once students have a foundational knowledge of homeostasis, they investigate the factors that affect homeostasis in human body systems. Students analyze the role of interdependence and equilibrium as it pertains to the human body. They are expected to use logical cause-and-effect reasoning regarding these three systems that interact to maintain homeostasis in the human body. They then evaluate the effect of interactions with the natural world on human body equilibrium (homeostasis). In the classroom, students might be observed exploring the three body systems included in this unit of study. They first need to gain a general understanding of each of the three individual systems and then compile knowledge to understand how the three work together. This might be accomplished by using a case study or example of an injury or other homeostatic imbalance and then applying knowledge to evaluate how the three body systems coordinate to return the body to homeostasis. The initial phase of learning (obtaining knowledge of the three systems) is probably accomplished by a combination of teacher-led instruction and small-group work. The evaluation of a case study and/or injury could be done individually and/or in small groups. By the end of this unit, students should have a conceptual understanding of homeostasis and the interaction of these three body systems more than a detailed content knowledge of each individual system. In middle school and/or health class, students learned about other body systems, but they have not been exposed to the immune, endocrine, and nervous systems as part of the required curriculum. They most likely have a very basic knowledge of the immune and nervous systems, but many may not have had any exposure to the endocrine system. Additionally, students have not learned about homeostasis as it pertains to the human body. Future Learning Knowledge from this unit will be important in other courses such as health and anatomy/physiology. More importantly, the knowledge from this unit will be used throughout life. To be an educated member of society (or a parent), it is important to understand the role of fevers, allergies, vaccinations, autoimmune disorders, white blood cell count, and nerve damage. Additional Findings In a study, pupils who had not been taught about the nervous system and students that had been taught about the nervous system (at the same school) both denied the role of the brain in coughing, sleeping, and blinking. The curricular unit appeared to have no effect on the results. Some could quote the statement the brain controls voluntary and involuntary movement (which was taught in class), but only one child could apply this to examples. (Making Sense of Secondary Science, pp. 46 and 47) Students understanding of dynamic equilibrium must include comprehension of the various elements involved, as well as the ability to relate these processes to one another. For this reason, students often gain a partial understanding of the topic, but find it difficult to have a complete understanding. One preconception students may have is that homeostasis represents a particular number or fixed value. For example, they may feel that blood sugar must return to a specific value after eating, at which point the level has returned to homeostasis. Some students indicated that increases in heart and breathing rates during exercise are attributed to the exercise itself, while others responded that blood is needed to continue exercising or that blood itself requires the increase in oxygen. Homeostasis is a concept that 23

12 Biology, Quarter 2, Unit 2.3 Homeostasis (14 days) students are often expected to learn without the benefit of concrete experience. Student investigations through case studies or experiments can give students the opportunity to experience the concrete results of this abstract physiological phenomenon. (The Biology Teacher s Handbook, Fourth Edition, pp. 53 and 54) 24