1 Introduce. When Minutes Count... How Much Magnification? magnifying box, ruler Other Materials: penny. Lesson 1 Pages Science Background

Transcription

1 Lesson 1 Pages Objecti tives Make models of plant and animal cells. Explain the cell theory. Describe the functions of the various parts of plant and animal cells. How Do Plant and Animal Cells Differ? Transparency DI 4 How Much Magnification? magnifying box, ruler Other Materials: penny Tool Kit Review Skills: Measure, Observe, Compare What to Do Use a ruler to measure the diameter of a penny. Record the measurement. Place a penny in a magnifying box and observe it. Measure the diameter of the penny s magnified image. Divide the diameter of the magnified image by the diameter of the penny. The result is the magnifying power of the lens. How powerful is the lens in the magnifying box? How many times larger is the object? Life s Blood Blood cells travel through your body all the time. Red blood cells have hemoglobin that enables them to carry oxygen to the body and return carbon dioxide to the lungs. Blood cells are produced in bone marrow. In the Investigate, you will learn more about cells. 1 Introduce Build on Prior Knowledge Use the Fast Fact for a discussion starter about the lesson topic. How many kinds of cells can you see in the photograph? How do they differ in function? When Minutes Count... If time is short, consider these options. Conduct the Investigate as a whole-class demonstration. Use the Activity Video/DVD to model the Investigate. 30 CXENL07ASE6X_C01L1 30 2/18/05 6:11:24 PM Science Background The Development of the Cell Theory The similarities that exist among all living things are summarized by the cell theory. The cell theory states that: Cells are the basic units of life. All organisms are made up of cells. All new cells come from preexisting cells. Modern cell theory developed through many years of observation and research. Biologist Robert Hooke coined the term cell in the mid-sixteenth century. In the 1830s, Matthias Schleiden, a German botanist, was the first to state that all plants are made of cells. During that same period, Theodor Schwann, a German zoologist, said that all animals are composed of cells. Webliography Keyword cells 30 CHAPTER 1

2 CXENL07ALM6X_CH01.indd :43:29 PM Plant and Animal Cells Inquiry Skill Mini-Lesson Investigate Materials plastic mixing spoon 2 small plastic bags orange sections lemon gelatin powder plastic sandwich box grapes boiling water 2 plums 2 twist ties mixing bowl ice cubes Procedure 1 Make models to observe the differences between plant cells and animal cells. Use the spoon to mix the gelatin powder with boiling water and several ice cubes in a mixing bowl. Allow the liquid to cool. CAUTION: Boiling water can burn you! Use care when near it! 2 Place a plastic bag in the sandwich box. Pour in half of the cooled liquid. Add one plum, several orange sections, and several grapes. Tie the bag shut, and allow the mixture to set. 3 Fill the other plastic bag with the other half of the cooled liquid. Add orange sections and one plum. Tie the bag shut. Allow the mixture to set. 4 When both mixtures have set, remove them from the plastic bags. 5 Compare your model cells. Then compare them to the plant and animal cells shown here. Which of your cells is more like the unknown cell? What do you think it is? Draw Conclusions 1. What similarities and differences did you observe between your two models? Which looks like the plant cell photo and which like the animal cell? 2. Inquiry Skill One model cell has a kind of part that the other does not have. Based on what you know about plants and animals, infer what function that part might have. Plant Cell Animal Cell Unknown cell Investigate Further Investigate Further With classmates, try to fit several cells of each type together. What differences do you observe about how the cells of each type fit together? What can you infer about how each cell is protected? CXENL07BSE6X_C01L1 31 7/19/05 6:28:51 PM Infer Display the transparency. Have students study the diagram of the cell. Remind students that inferences are based on observation and on what they already know. Have students use inference to answer the questions on the transparency. Inquiry Skill practice is provided in Reading Support and Homework. 31 Transparency IS 4 2 Teach Time 30 minutes Grouping groups of 3 Alternative Materials C salad oil instead of gelatin Investigate Further Investigate Further lnvestigate C raisins, strawberries, or other fruits instead of oranges, plums, and grapes Lab Manual pages can be used to record results. Inquiry Skill Tips and Self- Assessment are also provided. Tips and Guided Inquiry Explain that, in a real cell, the material represented in the model by gelatin is more fluid, allowing some materials to move throughout the cell. Point out that models have limitations in that they do not duplicate nature exactly. What does the gelatin represent? cytoplasm What might the plum represent? the nucleus of the cell Expected Results Students should conclude that cells are made up of several smaller parts and that both plant and animal cells contain some of the same parts. Draw Conclusions 1. The plant cell has a definite shape; the animal cell does not. Students should be able to match each model with the correct photograph. 2. Students may be able to infer that plants make their own food but that animal cells do not. The extra parts probably help plants make food. Students can use this page in the Lab Manual for Independent Inquiry. With classmates, try to fit several cells of each type together. What differences do you observe about how each type fits together? What can you infer about how each cell is protected? Materials model cells made by you and your classmates Video Segment 6600 Lab Manual p. LM What will you determine in this investigation? Students will determine differences in how well the different types of cells fit together. 2. Describe your observations in the table below. Model plant cells How did the cells fit together? Model animal cells 3. What differences do you observe about how each cell type fits together? Based on this, infer how each cell is protected. Students should note that the plant cells have a definite rectangular shape and can easily fit together. The animal cells have no definite shape and cannot easily fit together. Students should infer that plant cells have a cell wall that gives them a firmer shape and protects them. LESSON 1 31

3 CXENL05ATR6_C01_L1_RS04 1 1/21/05 7:23:47 AM Reading in Science Reading in Science 2 Teach continued VOCABULARY chloroplasts p. 34 cell wall p. 34 nucleus p. 35 chromosomes p. 35 DNA p. 36 SCIENCE CONCEPTS C what the cell theory is C how the parts of the cell function READING FOCUS SKILL MAIN IDEA AND DETAILS Look for details about animal and plant cells. Main Idea VOCABULARY For Vocabulary Cards and activities, see Reading Support and Homework. SCIENCE CONCEPTS Have students read each concept and make a list of questions they have. List their questions on the board, and have students refer to them and revise them as they read through the lesson. READING FOCUS SKILL MAIN IDEA AND DETAILS Tell students that the information in this lesson is organized to help them recognize a main idea and the details that support it. 1 The Cell Theory If there were no pictures or books to tell you about cells, how would you know they existed? Before the microscope was invented, no one had any idea about such things as cells. In 1665, Robert Hooke built a microscope that magnified things 30 times. He looked through it at a thin piece of cork and realized that the cork was made up of very tiny boxlike sections. He named these sections cells, which means small compartments in Latin. The photo below shows what Hooke saw in the cork. 2 Microscopes Old & New Scientists today use electron microscopes to magnify items up to 1,000,000 times their actual size! 3 detail detail detail Ten years later, Anton van Leeuwenhoek (LAY vuhn hook) built a microscope that magnified objects 300 times (300X). With this new, more powerful microscope, Leeuwenhoek discovered a world of one-celled organisms in pond water. Almost 200 years went by after Hooke s discovery and Leeuwenhoek s studies of microscopic organisms before scientists began studying cells in detail. At first, they thought that only plants had cells. As better microscopes were developed, they noticed Key Science Concepts Review what students know about cells. Are all cells alike? Explain. No, there are many kinds of cells, even in a single organism. Different functions are performed by different cells. How do organisms grow? They grow larger by producing new cells. Critical Thinking How has the development of electron microscopes allowed scientists to better understand the structure and function of cell parts? These highpowered microscopes allow scientists to see smaller cell parts than they can see through traditional light microscopes. Critical Thinking Why did it take until the 1800s for scientists to propose the cell theory? Up until the time of Hooke and Leeuwenhoek, scientists had never observed a cell. It was not until better technology was developed that scientists were able to observe cells and their functions. 32 This is what Hooke saw through his microscope. He compared what he saw to rooms in a monastery. He gave them the same name cells. Reading Skill Mini-Lesson Under an electron microscope, a single grain of pollen can be seen very clearly. CXENL07BSE6X_C01L1 32 7/7/05 11:10:47 AM USE TYPOGRAPHIC CLUES Display the transparency. Explain that italics are often used in text to make important information stand out on a printed page. Have students locate the italicized words on pp and explain why these phrases or sentences are important. Transparency RS 4 Use Typographic Clues Italicized Text 1 cells are the building blocks of living things 2 all life processes take place in cells 3 new cells are produced from existing cells Why does this information appear in italicized text? Possible answers: it emphasizes the main idea of the text; it is important imformation. 32 CHAPTER 1

4 6 that every living organism they studied had cells. By the late 1800s, scientists had developed a three-part theory about cells. The first part states that cells are the building blocks of all living things. In other words, all living things are made up of cells. Some organisms have only one cell, while others have many. In addition, the parts of a living organism, such as its hair, skin, or leaves, are made of different kinds of cells with different functions. A human has hundreds of kinds of cells. The photographs on this page show some of the kinds of cells in plants and animals. The second part of the theory states that all life processes take place in cells. The energy in food is released in cells. Growth and reproduction take place in cells. The third part of the theory states that new cells are produced from existing cells. Living things begin life as a single cell. This single cell divides into two cells. Each new cell also divides into two cells. After a certain point, the cells begin to specialize and take on different functions. Cell division is what causes you or any other organism to grow. Your body constantly produces new cells to replace cells that die. Your skin, for example, produces new skin cells as the old cells die and fall away. MAIN IDEA AND DETAILS What are the three parts of the cell theory? Stentor Stentor is a single-celled organism found in fresh water. Microscopes enable researchers to observe a world of singlecelled organisms. Muscle cells like these help the human heart pump. Animal cells may have different purposes, but they all have similar structures inside. 5 4 Under the Microscope Muscle Cell Plant Cell Structures called chloroplasts inside this plant cell enable it to perform photosynthesis Interpret Visuals Remind students that some organisms, like the single-celled organism shown, are made up of only one cell. Other organisms are made up of millions of cells. How are the cells in the photos alike? They are all too small to be seen without the aid of a microscope. They all contain similar parts. In what ways are the cells different? They have different colors, shapes, and sizes. The plant cell has structures that enable it to make its own food. Inquiry Skills Use Models Ask students to think back to the Investigate in which they modeled plant and animal cells and then observe the photo of the plant cell. What cell structure might the grapes in your cell model represent? They most likely represent the structures inside plant cells that enable them to perform photosynthesis chloroplasts. Main Idea and Details Answer: Cells are the building blocks of life; all life processes take place in cells; and all new cells are produced from existing cells. 33 CXENL07BSE6X_C01L1 33 7/1/05 12:11:54 PM Reaching All Learners Intervention Reteach Intervention Reader Target: Struggling readers Intervention Strategy: The Intervention Reader presents the essential lesson content at the reading level A visual glossary and other text-style and comprehension aids increase student understanding of the content. Assess: The Intervention Reader Teacher Guide provides strategies for assessment and additional intervention. Cells, Reproduction, and Heredity CXENL07ARD06_LLR01_Cv.indd 3 2/17/05 8:07:19 AM LESSON 1 33

5 7 Develop Science Vocabulary chloroplasts Chloroplasts are located in leaf cells and in some stem cells. Chloroplasts contain chlorophyll, the green pigment that enables plants to carry out photosynthesis. Photosynthesis is the process in which plant cells convert water and carbon dioxide in the presence of sunlight to sugar and water, releasing oxygen. cell wall Explain that the cell wall is a rigid structure and does not change shape as the cell membrane does. 7 The Parts of a Cell You saw some similarities and differences in animal cells and plant cells during the 9 Investigate. Inside both types of cells are structures that perform specific functions. These structures are called organelles. Organelles help keep the cell alive and healthy. The organelles are surrounded by cytoplasm, a clear, jellylike substance that holds them in place. Animal and plant cells are similar, but there are differences between them. Only plant cells contain organelles called chloroplasts. The chloroplasts make the plant s food (sugar) by the process of photosynthesis. Chloroplasts are found mostly in the cells of a plant s leaves. A single leaf cell may have 40 to 50 chloroplasts. A plant cell also has a cell wall, a stiff outer layer that surrounds and protects the cell and gives it shape. Animal cells don t have cell walls, but both plant and animal cells have a cell membrane that holds the cell material inside. This membrane also controls what substances enter and leave the cell. Both plant and animal cells have organelles called vacuoles, which store nutrients and wastes. In animal cells, vacuoles are very small. In plants, one large vacuole takes up most of the cell. Vacuoles are bigger in plant B Inside the leaves of this plant are many cells that contain chloroplasts. 8 Interpret Visuals 9 Allow students time to study the illustrations and read the captions on this page. How are the illustrations on this page related to one another? The photos and diagrams show plant cells that relate to the picture of the plant. What two cell structures are found in plant cells but not in animal cells? chloroplasts and cell walls What is the function of the cell wall? It provides protection and shape for the plant cell. Critical Thinking What feature of plant cells allows plants, such as giant redwood trees, to grow tall? The cell wall it provides support and structure for the plant. 8 Cell Wall A Plant Cell Cytoplasm Nucleus This drawing shows the different organelles found in plant cells. Mitochondria Nuclear Membrane Vacuole Cell Membrane Chloroplast This cell came from a corn plant. The cell wall and several organelles are visible through a microscope. 34 CXENL07BSE6X_C01L1 34 7/7/05 11:10:57 AM Reaching All Learners ESL / ESOL Support Comprehensible Input Help students learn the parts of the cell. Beginning Have students make simple labeled sketches of plant and animal cells. Tell students to label the parts of each cell. Intermediate Students can keep a catalog of plant and animal cells. Students should include sketches or tracings of the different cells shown in the chapter as well as the names of the cell parts and their functions. Advanced Students can write two paragraphs describing the parts of the animal and plant cells that are alike and the parts that are different. For strategies and lesson support, see ESL Support pp CHAPTER 1

6 Chromosome An Animal Cell 10 Inquiry Skills Nuclear Membrane Mitochondria Nucleus 11 Compare Ask students to compare the animal and plant cells shown on these pages. What cell organelles are shared by both plant and animal cells? cell membrane, cytoplasm, mitochondria, vacuoles, nucleus, nuclear membrane Develop Science Vocabulary 10 Cytoplasm Vacuole How is this animal cell different from a plant cell? nucleus The nucleus directs the cell s activities from within the nuclear membrane. The nucleus is like the manager of the cell. chromosomes A chromosome is the structure that carries an organism s genetic information. It is made up of DNA and proteins. The DNA contains information about the characteristics of the plant or animal cell. It is often referred to as the cell s blueprint. A chromosome provides information to the nucleus about every function of life Cell Membrane cells because they are the storage places for the sugar, wastes, and water the plant produces. The nucleus is the cell s control center it directs all of the activities that take place inside the cell. The nucleus contains chromosomes, the structures that carry an organism s genetic information. They also control activities within the cell. The nuclear membrane surrounds the nucleus and holds it together. Cells also contain bean-shaped organelles called mitochondria (my toh KAHN dree uh). Food and oxygen combine in the mitochondria to release the food s energy, carbon dioxide (CO 2 ), and water (H 2 O). This process is known as respiration. The energy released during respiration enables a plant or animal to complete all its cell activities. MAIN IDEA AND DETAILS What are the functions of different organelles in plant and animal cells? A Chromosomes in its cells contain the information that determines how the horse looks. Organelles Make a detailed scientific diagram of an animal cell or a plant cell. Use the pictures in the textbook as a guide. Label all the organelles. Which part of the cell is the control center? 12 Main Idea and Details Answer: The nucleus holds chromosomes, mitochondria release energy from food, vacuoles store food and wastes, and chloroplasts manufacture food minutes CXENL07BSE6X_C01L1 35 7/7/05 11:11:14 AM Reaching All Learners Plant Cells vs. Animal Cells Intervention Reteach Target: Students who have trouble understanding the difference between plant and animal cell parts Intervention Strategy: Hands-On Activity Provide students with microscopes and prepared slides of plant and animal cells. Challenge students to make sketches of what they see and to label the cell parts. You may also want to have students make scrapings of skin cells under their fingernails for observation. Assess: Have students compare their sketches with the illustrations on these pages, identifying the correct cell parts. Organelles Materials: pencil and paper Students diagrams should contain all the cell organelles shown on these pages. (the nucleus) LESSON 1 35

7 Develop Science Vocabulary DNA DNA is the genetic material that is contained within the nucleus of each plant or animal cell. It is made up of a double strand, or helix, of substances called nucleic acids that help determine the function of the cell. Explain that DNA is an acronym, or a name derived from initials. Have students name other things or organizations, such as NASA or NOAA, whose names are acronyms. Interpret Visuals How are chromosomes and DNA related? Chromosomes contain DNA. What instructions might the nucleus send to other parts of the cells? It might instruct the various parts of the cell to perform a certain action, such as to release energy, or to collect waste products. Main Idea and Details Answer: The chromosomes in the nucleus have instructions for all cell activities. The Nucleus 13 The chromosomes in the nucleus contain instructions for all cell activities. It wasn t until the electron microscope was developed in the 1930s that scientists could study chromosomes in living cells and watch them divide. They found that before cells divide, the chromosomes are copied so that each new cell receives all the chromosomes it needs to 14 function. Chromosomes are made up of DNA 15 and proteins. DNA stands for deoxyribonucleic (dee AHKS ee ry boh noo KLAY ik) acid. This chemical provides detailed instructions to the cell about every function of life. For example, it directs the cell to divide to make more cells and to perform various other activities. DNA contains the codes that determine physical characteristics such as flower color in plants and hair color in humans. MAIN IDEA AND DETAILS Why is the nucleus considered the control center of a cell? The chromosomes in this image are magnified 10,000 times. Most of the time, chromosomes are not bunched together and look like a glob in the nucleus. These chromosomes are visible because they are dividing. Pores in the nuclear membrane let certain materials into and out of the nucleus. The nucleus has an enclosed structure, the nucleolus, in which some important cell parts are made. 36 CXENL07BSE6X_C01L1 36 7/1/05 12:12:02 PM History of Science: DNA The double helix structure of the DNA molecule was determined in 1953 by James Watson and Francis Crick after studying a copy of Rosalind Franklin s X-ray pattern of DNA samples and other data about the chemical properties of DNA. Have interested students find out more about the events leading to the development of the DNA model. Students can build DNA models to go along with their research. 36 CHAPTER 1

8 CXENL07BRS6X_ indd 5 7/21/05 2:58:39 PM CXENL07ARS6X_CH01.indd :19:35 AM 1. MAIN IDEA AND DETAILS Draw and complete this graphic organizer. Reading Review Reading Review 3 Assess and Extend 2. SUMMARIZE Summarize the similarities and differences between plant cells and animal cells. 3. DRAW CONCLUSIONS Compare what takes place in chloroplasts with what takes place in mitochondria. 4. VOCABULARY Use the words in the vocabulary list to order the parts of a plant cell from the inside out. Writing Math Social Studies Expository Writing Write a newsletter article for third graders in which you describe the cell theory. Tell about the scientists who discovered cells and about the development of microscopes, beginning with Hooke s. A Lesson Quick Study MICROSCOPE CELL THEORY B Test Prep Solve a Problem A typical animal cell has a diameter of mm. Find how many animal cells would fit across the diameter of a penny. A penny has a diameter of 2 cm. C 5. Critical Thinking Explain why a food that is claimed to make a person taller can t do this. 6. Which does the nucleus of a cell contain? A. chloroplasts B. chromosomes C. food D. oxygen Make a Time Line Research the contributions of Schleiden and Schwann to the cell theory. Then make a time line showing the events that led to the development of the theory. Start the time line at Links CXENL07BSE6X_C01L1 37 7/19/05 6:39:10 PM The Lesson Quick Study in Reading Support and Homework provides the opportunity for students to practice inquiry skills, review lesson vocabulary, apply reading skills, and use critical thinking and problem solving. Students can use the second page of the Lesson Quick Study to complete the graphic organizer from the Reading Review. The graphic organizer is also available on overhead and electronic transparencies. Harcourt Reading Support and Homework Lesson 1 - How Do Plant and Animal Cells Differ? 1. Inquiry Skills Practice Infer Using what you know about plants and animals, infer why plants have chloroplasts and animals do not. Plants have chloroplasts because they make their own food during the process of photosynthesis. Animals depend on plants and other animals for their food. 2. Use Vocabulary p. RS 5 p. RS 6 Match the clue on the left to the term on the right. D These contain an organism s A. chloroplasts genetic information B. cell wall B A stiff outer layer that surrounds the cell C. nucleus C The cell s control center D. chromosomes A Where food is made during photosynthesis 3. Reading Skill Practice Main Idea and Details Read the selection. Underline the main idea. List at least three details about the main idea. Plants and animals are made up of cells that have important jobs to do. But how does each cell know what its job is? The nucleus of the cell helps it determine its job. The nucleus controls all the activities of the cell. How does the nucleus tell the cell what to do? The nucleus has tiny openings in its membrane that let information in and out. The nucleus is the control center of the cell. The nucleus helps each cell determine its job. It controls all the activities of the cell. The nucleus lets information in and out of it through the tiny openings it has in its membrane. 4. Main Idea and Details 37 Use this space to complete the graphic organizer shown in the Reading Review of the Student Edition. A Cells are the building blocks of life. Microscope Cell Theory B All life processes take place in cells. 5. Critical Thinking and Problem Solving C All new cells come from existing cells. DNA contains codes that determine your physical characteristics. What are some of those characteristics that are found in your DNA? Answers will vary. Students should be able to describe their physical characteristics such as hair color, eye color, type of earlobe, tongue roll, and so on. Harcourt Graphic Organizer Transparency GO 4 1. A Cells are the building blocks of life. B All life processes take place in cells. C All new cells come from existing cells. 2. Similarities: Both kinds of cells have mitochondria, cell membranes, nuclei, nucleolus, chromosomes, and organelles. Differences: Only plant cells have chloroplasts and cell walls. 3. A plant makes food in the chloroplasts through photosynthesis. The mitochondria release energy in the food so cells can carry out life processes. 4. DNA, chromosome, nucleus, chloroplasts, cell wall 5. Each person s DNA determines how tall that person will be. As long as a person receives adequate nutrition, eating special foods will not help him or her become taller. 6. B, chromosomes Links Writing Student articles should detail the three parts of the cell theory discussed in this lesson. Students can consult the Writing Models in Teaching Resources as they complete the Link. Rubrics are also provided. Math 20,000 cells Social Studies Students time lines should begin with the invention of the microscope and include that both Schleiden and Schwann concluded that all plants and animals are made up of cells. LESSON 1 37 FLORIDA IMAGING PDF