Tissues, Organs, and Systems of Living Things PDF

Summary

This textbook chapter introduces tissues, organs, and systems of living things. It covers cell structures, the cell cycle, specialized cells in plants and animals, and how organs and systems work together. It also discusses the impact of medical imaging and public health strategies on individuals and society.

Full Transcript

ist10_ch01.qxd 7/22/09 3:23 PM Page 2 UNIT Tissues, Organs, A and Systems of Living Things Scanning electron micrograph of red and white blood cells flowing through a ve...

ist10_ch01.qxd 7/22/09 3:23 PM Page 2 UNIT Tissues, Organs, A and Systems of Living Things Scanning electron micrograph of red and white blood cells flowing through a vein in a human leg (magnification 4000⫻) 2 ist10_ch01.qxd 7/22/09 3:23 PM Page 3 Contents Cells are the basic unit of life and often 1 combine with other cells to form tissues. 1.1 Plant and Animal Cells 1.2 The Cell Cycle and Mitosis DI 1.3 Specialized Plant and Animal Cells An organ consists of groups of tissues and 2 works with other organs to form organ systems. 2.1 Organs in Animals and Plants DI 2.2 Organ Systems in Animals and Plants 2.3 Interdependent Organ Systems Advances in biological technologies have an 3 impact on individuals and society. 3.1 Medical Imaging Technologies DI 3.2 Public Health Strategies to Prevent Disease 3.3 Social and Ethical Issues in Systems Biology Unit Task Advancements in systems biology have affected society both in good ways and in bad ways. Your task is to present an opinion on how these advances have affected society. You may also discuss the controversies surrounding the advancements as well as the next step in development that may occur. Your presentation should be in the form of a collage, comic, video, PowerPoint presentation, monologue, written report, or brochure. Essential Question How have advancements in systems biology affected individuals and society? 3 ist10_ch01.qxd 7/22/09 3:23 PM Page 4 Exploring To protect themselves from the Spanish flu pandemic, people were encouraged to wear cloth masks. Reviving a Killer In 1918, one of the deadliest diseases was unleashed on the world. In early March of that year, medical authorities in the United States reported the first case of a deadly influenza. The symptoms — the skin turned blue, the feet turned black, and the lungs filled with blood — were unlike any symptoms previously seen. Victims, who were mostly young men and women, became ill and died within hours. At a time when hundreds of young adults were being killed while fighting in a world war, thousands more were being killed at home by the influenza virus. Within months of the first case, there were reports of widespread outbreaks in many parts of the world. Because the influenza infected people around the world, it was known as a pandemic. This influenza became known as the Spanish flu Between 25 million because it was first widely reported in Spanish newspapers. During the and 50 million people first six months of this pandemic, millions of people died. The Spanish flu died from the Spanish was responsible for the deaths of between 25 million and 50 million people flu. died from the Spanish flu. At the time, doctors believed that the spread of influenza could be controlled by limiting contact with the source of disease. People were told to wear masks when they were out in public, to cover the nose and mouth when coughing, and not to shake hands. Some people were put in quarantine, a situation in which an ill person or a suspected ill person was kept away from other people. 4 UNIT A Tissues, Organs, and Systems of Living Things ist10_ch01.qxd 7/22/09 3:23 PM Page 5 Lessons Learned Scientists learned valuable lessons from the 1918–1919 Spanish flu pandemic and were better prepared for the Asian influenza pandemic that occurred in 1957–1958 and the Hong Kong influenza pandemic in 1968. Governments and organizations, such as the World Health Organization, developed plans to handle future influenza pandemics. One strategy involved studying and researching the Spanish flu virus itself. In 1997, a team of researchers led by Canadian Dr. Kirsty Duncan dug up bodies of 1918 influenza victims buried in a Norwegian cemetery and attempted to “revive” the virus. Although researchers believed that the virus would still be capable of reproducing, this was not true. However, in 2005, American researchers were able to restore the virus using pieces of the virus obtained from various sources. A scientist works with the resurrected Researchers in Canada and the U.S. are currently working with the 1918 influenza virus in a special restored virus to understand what made it so deadly. airflow cabinet. Air is sucked into the cabinet and filtered before it is In 2008, scientists gained permission to study the corpse of a recirculated in a sealed laboratory. 39-year-old British diplomat who had died in 1918 from influenza. Because the body is in a lead-lined casket, researchers believe the body will be very well preserved and they will be able to obtain samples that will reveal information about the virus. By reviving and studying a killer virus, scientists hope to prevent future deaths from the virus. A1 STSE Science, Technology, Society, and the Environment Questions about Quarantine During the Spanish flu pandemic, health officials 2. Work with a partner and think about the attempted to prevent the spread of the disease by implications of living in your house under an placing sick people in quarantine. Quarantine imposed quarantine for two weeks. restricted the actions of individuals who appeared to 3. Repeat step 2, but assume that you are in need have the illness and kept them away from healthy of medical care and that the local hospital is people. An individual would be kept in quarantine under quarantine. until symptoms of the illness were gone. In some 4. Should governments have the right to impose a situations, signs would be posted on the front door of quarantine on individuals? Explain your answer. houses to indicate the presence of a quarantine. Today, public health officials may impose quarantine 5. What economic problems could be associated to stop the spread of disease. with the imposition of quarantine ? You will consider some of the political, economic, 6. Explain some of the social problems that could be social, and ethical issues associated with using associated with the imposition of quarantine. quarantine to prevent the spread of infectious 7. Explain some of the ethical issues associated with diseases. the imposition of quarantine. 1. As a class, discuss the term “quarantine” and 8. Do you think that placing sick people in quarantine give examples of the use of quarantine in society. prevents the spread of disease? Explain your answer. Exploring 5 ist10_ch01.qxd 7/22/09 3:23 PM Page 6 1 Cells are the basic unit of life and often combine with other cells to form tissues. 6 UNIT A Tissues, Organs, and Systems of Living Things ist10_ch01.qxd 7/22/09 3:23 PM Page 7 Skills You Will Use In this chapter, you will: Astrocytes (light green) are star-shaped cells in the examine cells under a microscope to identify the various brain and spinal cord. stages of mitosis in plants and animals examine different plant and animal cells under a microscope, and draw labelled biological diagrams to show how the cells’ organelles differ investigate, using a microscope, specialized cells in the human body or in plants, focussing on different types of cells, and draw labelled biological diagrams to show the cells’ structural differences investigate the rate of cell division in cancerous and non-cancerous cells using pictures or images, and predict the impact of this rate of cell division on an organism Concepts You Will Learn In this chapter, you will: describe the cell cycle in plants and animals, and explain the importance of mitosis for the growth of cells and repair of tissues explain the importance of cell division and cell specialization in generating new tissues explain the links between specialized cells and tissues in plants and animals Why It Is Important An important step in understanding how your body works is understanding the cell. Your body is made of trillions of cells. Before Reading Set a Goal to Understand New Vocabulary To understand the content of this chapter, you will need to understand many new terms. How many words in the following list of key terms do you recognize? Preview section 1.1, and note the terms in bold print. Make a two-column chart, recording new terms in the first column. Add definitions or explanations in the second column as you read. Key Terms anaphase cell concentration differentiation diffusion meristematic cells meristematic tissue mesophyll mitosis organelle phloem prophase red blood cells regeneration stomate tissue xylem Cells are the basic unit of life and often combine with other cells to form tissues. 7 ist10_ch01.qxd 7/22/09 3:23 PM Page 8 1.1 Plant and Animal Cells Here is a summary of what you will learn in this section: Cells have special structures that enable them to perform important life functions. Scientists use technology, such as the microscope, to understand the cell. Figure 1.1 A piece of moss, as seen through a microscope, shows many cells filled with chloroplasts, an organelle involved in photosynthesis. The cells are shown at a magnification of 500⫻. The Discovery of the Cell When the microscope was invented in the mid-1600s, it became possible for scientists to look at the previously invisible world of the cell. Imagine the strange and beautiful structures that appeared before the eyes of these scientists. Today, we use sophisticated electron microscopes that allow us to not only see the cell in detail but also to get a glimpse of some amazing sights (Figure 1.1). Robert Hooke was the first to describe cells in 1663 (Figure 1.2). He thought that the cells were the passages for fluids in a plant. Today, we understand that a cell is the basic building block of life. Every living organism is made of cells. A cell takes in nutrients from its environment and releases waste products into its environment. A cell Figure 1.2 Robert Hooke’s drawing can also divide to make copies of itself. A cell contains everything that of cork cells, as seen under a it needs to live and grow. microscope. He used the term “cells” based on what he saw. Using Technology to Study the Cell In the early days of cell biology, scientists used simple light microscopes to view sliced sections of living cells. These microscopes helped scientists see and study the external structure of a cell but revealed few details about the tiny specialized working parts within the cell. 8 UNIT A Tissues, Organs, and Systems of Living Things ist10_ch01.qxd 7/22/09 3:23 PM Page 9 Advances in technology, such as the development of the electron microscope (Figure 1.3), have allowed biologists to learn detailed information about different cell parts and their functions. Technology has also made the process of learning about the cell easier. For example, the electron microscope can produce images that are 1000 times more detailed than the light microscope (Figure 1.4). The discovery of the cell is an example of how scientific knowledge depends on technology. As our technology continues to improve, our knowledge and understanding of the cell will continue to expand. Figure 1.3 The world’s most powerful electron microscope, the Titan 80-300 Cubed, was installed at McMaster University in Hamilton, Ontario, in October 2008. Figure 1.4 Red blood cells viewed through a scanning electron microscope (magnification 3700⫻) A2 Quick Lab What We Remember about the Cell Cells come in a variety of shapes and sizes. However, Questions there are some structures that are common to cells. 4. Sometimes, we remember things better if we can There are also some differences. This activity will give visualize an example or illustration. What type of you an opportunity to review the information that you cell did you visualize when you were know about the cell. brainstorming about the cell? Purpose 5. There are many parts in a cell. Sometimes, it is To create a graphic organizer that shows what you easier to remember the functions of the different remember about the cell cell parts by using analogies to everyday things. For example, we may say that the cell has a part Procedure that acts like a brain. Use an analogy to describe one specific part of the cell that you placed in 1. Work in a small group of 2–4 students. your graphic organizer. 2. Brainstorm for two minutes with your group about 6. Did your group find that it was easier to what you remember about the cell. You may wish remember the parts of the cell, functions of the to use words, pictures, or phrases. Think about cell, or examples of cells? Explain. the different parts of the cell, the functions of these parts, or different examples of cells. 3. Create a graphic organizer using the words, pictures, or phrases that you came up with in step 2. Cells are the basic unit of life and often combine with other cells to form tissues. 9 ist10_ch01.qxd 7/22/09 3:23 PM Page 10 W O R D S M AT T E R Cell Parts and Their Functions The word “cell” is derived from the Latin word cellula, meaning small All living things are made of cells. Our bodies are made up of between compartment. The word “cyto,” as in 10 trillion (1013) and 100 trillion (1014) cells. A cell is the basic unit of life. cytoplasm, is from the Greek root meaning cell. Each cell contains smaller parts called organelles. These organelles have special functions that maintain all the life processes of the cell, including: intake of nutrients exchange of gases movement waste removal growth reproduction response to stimuli There are two types of cells: plant cells and animal cells (Figures 1.5 and 1.6). nucleus nucleolus chromatin rough endoplasmic reticulum smooth endoplasmic reticulum ribosomes (small brown dots) central vacuole Golgi apparatus cytoskeleton cytoplasm mitochondrion chloroplast cell membrane cell wall wall of adjacent cell Figure 1.5 A plant cell 10 UNIT A Tissues, Organs, and Systems of Living Things ist10_ch01.qxd 7/22/09 3:23 PM Page 11 nucleus rough endoplasmic smooth endoplasmic reticulum reticulum nucleolus chromatin cell membrane cytoskeleton ribosomes (small brown dots) vacuole Golgi apparatus cytoplasm mitochondrion lysosome Figure 1.6 An animal cell Structures and Organelles in Cells A cell contains structures and organelles that carry out various functions. Although all cells must perform the tasks that maintain life, not all cells are identical. Therefore, some structures and organelles are the same in both plant and animal cells while other structures and organelles differ between plant and animal cells. Cells are the basic unit of life and often combine with other cells to form tissues. 11 ist10_ch01.qxd 7/22/09 3:23 PM Page 12 Cell Membrane cell Every cell has a cell membrane that forms a protective membrane barrier around the cell (Figure 1.7). The cell membrane is made of a double layer of lipids. A lipid is a fat-like molecule that does not dissolve in water. The cell nucleus membrane is designed to allow different substances to move through it. One process for moving substances across the cell membrane is called diffusion. Diffusion depends on the concentration of the substance on both sides of membrane. cytoplasm The amount of dissolved particles, called solutes, in a solution is the concentration. When a substance is present in different concentrations on either side of the cell Figure 1.7 A cell showing the cell membrane, membrane, the particles will diffuse, or move, from an area cytoplasm, and large nucleus (magnification 6000⫻) of high concentration to an area of lower concentration (Figure 1.8). substances area of high concentration movement of substances cell membrane area of low concentration (a) (b) (c ) Figure 1.8 (a) There is a higher concentration of substances on one side of the cell membrane. (b) The substances move to the side that has a lower concentration until a balanced state, called equilibrium, is attained. (c) When equilibrium is reached, the substances diffuse across the cell membrane in both directions. Cytoplasm All cells contain cytoplasm, a jelly-like substance that fills the cell and surrounds the organelles (Figure 1.7). Cytoplasm contains the nutrients required by the cell to carry on its life processes. The organelles are suspended in the cytoplasm. The physical nature of the cytoplasm allows the nutrients and organelles to move within the cell. Nucleus The nucleus is the control centre organelle of the cell (Figure 1.7). It controls all the activities in a cell, including growth and reproduction. The nucleus is surrounded by the nuclear envelope, which contains pores to allow the transport of materials. Most nuclei also contain a small dense area called the nucleolus. 12 UNIT A Tissues, Organs, and Systems of Living Things ist10_ch01.qxd 7/22/09 3:23 PM Page 13 The nucleus contains nearly all of the cell’s DNA. DNA stands for deoxyribonucleic acid. Most of the time, the DNA is bound to proteins and appears as a granular substance known as chromatin (Figure 1.9). However, when a cell divides, the chromatin condenses to form chromosomes. DNA is very important to the cell because it contains the coded information for making proteins and other molecules. Proteins serve many purposes and are found in various locations in the cell. Vacuoles and Vesicles Vacuoles and vesicles are membrane-bound organelles that store nutrients, wastes, and other substances used by the cell (Figure 1.10). In plant cells, the central vacuole stores water for the cell. When water enters the cell, the central vacuole swells, causing the plant cell to Figure 1.9 The nucleolus and become firm. Vesicles transport substances throughout the cell. chromatin in a human cell, as seen through an electron microscope nucleus vacuole Figure 1.10 A leaf cell showing a large Figure 1.11 A mitochondrion, as vacuole (pale green) and nucleus (orange) seen through an electron microscope (magnification 11 000⫻) (magnification 80 000⫻) Mitochondria All cells require a source of energy: the organelles known as mitochondria supply that energy. Mitochondria are the powerhouses of the cell. Reactions occur in these organelles to convert the chemical energy in sugar into energy that the cell can use. Figure 1.11 shows a single mitochondrion. Lysosomes Lysosomes are organelles where digestion takes place. They are small organelles that are filled with enzymes. An enzyme is a protein that can speed up chemical reactions in the cell. Lysosomes also break down invading bacteria and damaged cell organelles. Essentially, they work as the Figure 1.12 Lysosomes (purple) in a white blood cell. The clean-up system in the cell. Figure 1.12 shows a lysosome. cell’s nucleus is light brown. Cells are the basic unit of life and often combine with other cells to form tissues. 13 ist10_ch01.qxd 7/22/09 3:23 PM Page 14 Golgi Apparatus The Golgi apparatus receives proteins from the endoplasmic reticulum. The function of the Golgi apparatus is to modify, sort, and package these proteins for delivery throughout the cell or outside of the cell. The Golgi apparatus looks like a stack of flattened membranes (Figure 1.13). Endoplasmic Reticulum The endoplasmic reticulum is an organelle that is made of a series of interconnected small tubes that carry materials through the cell. Rough endoplasmic reticulum is associated with making proteins (Figure 1.14). Ribosomes are small, dense-looking organelles that may be attached to the rough Figure 1.13 The Golgi apparatus is named after endoplasmic reticulum or free in the cytoplasm. Ribosomes are Camilio Golgi, who first identified it in 1898. the sites where proteins are assembled. Smooth endoplasmic reticulum is associated with the production of fats and oils (Figure 1.15). Smooth endoplasmic reticulum does not have ribosomes. Figure 1.14 Rough endoplasmic reticulum and ribosomes Figure 1.15 Smooth endoplasmic reticulum Cytoskeleton All cells have an internal network of fibres, called the cytoskeleton. The cytoskeleton is made up of protein filaments. It helps maintain the cell’s shape. Organelles in Plant Cells Some organelles are found only in plant cells. Cell Wall Only plant cells, bacteria, fungi, and some algae have a cell wall. The cell wall is a rigid frame around the cell that provides strength, protection, and support (Figure 1.16). 14 UNIT A Tissues, Organs, and Systems of Living Things ist10_ch01.qxd 7/22/09 3:23 PM Page 15 cell wall chloroplasts Figure 1.16 A leaf cell showing the cell wall and many chloroplasts (magnification 1000⫻) Chloroplasts Chloroplasts are found only in plant cells and some algae. These organelles contain a green substance called chlorophyll. Chlorophyll uses energy from the Sun to convert carbon dioxide and water into sugar and oxygen in a process called photosynthesis. Figure 1.17 shows the internal structure of a chloroplast. The chloroplast is made up of little sacs known as thylakoids. Thylakoids are stacked together in a way that resembles a stack of coins. They are surrounded by a thick fluid called stroma. A stack of thylakoids is called a granum; chloroplasts may have many grana. You can think of the thylakoids as being “solar collectors.” They collect light energy from the Sun, which is used during the process of photosynthesis to produce carbohydrates. The During Reading carbohydrates are used for the growth of the plant. One Word Connects to Another Word In the passage on chloroplasts, note the way in which each term stroma is connected to another term. Create a concept map to show the connections. Begin with a top bubble with the term “chloroplast,” and then connect granum chloroplast the other terms as you read the paragraph. Try this strategy with thylakoids another paragraph that contains new terms. Figure 1.17 Photosynthesis takes place in the chloroplast in a plant cell. Cells are the basic unit of life and often combine with other cells to form tissues. 15 ist10_ch01.qxd 7/22/09 3:23 PM Page 16 Suggested Activities Differences between Plant and Animal Cells A6 Inquiry Activity on page 24 A3 Quick Lab on page 21 Cell walls and chloroplasts are only found in plant cells. However, there A4 Quick Lab on page 21 are other differences between plant and animal cells: Plant cells contain a specialized chemical compound called chlorophyll, a pigment that makes photosynthesis possible. Plant cells have a large central vacuole. Vacuoles in animal cells tend to be small. Some plant cells store energy in the form of starch or oils, such as cornstarch and canola oil. Animal cells store energy in the form of glycogen, a carbohydrate, or as lipids in the form of fats. Some animal cells have specialized compounds: for example, hemoglobin in red blood cells and cholesterol in other cells. Animal cells have centrioles, which are paired structures that are involved in cell division. Plant cells do not have centrioles. Learning Checkpoint 1. What is an organelle? 2. What is the function of vacuoles and vesicles? 3. Describe the relationship between the functions of the endoplasmic reticulum and the Golgi apparatus. 4. Explain the role of the thylakoids in the process of photosynthesis. 5. State two similarities and two differences between plant and animal cells. The Microscope as a Tool for Cell Research The cell is very small — too small to be seen with the unaided eye. Once the microscope was developed, scientists were able to see and study the cell. Today, biologists use different types of microscopes to explore cell structure and function. This knowledge is useful in assessing our health because cells can be viewed under a microscope to look for abnormalities. Compound Light Microscope A compound light microscope uses light focussed through different lenses to form a magnified image of a specimen or object. Figure 1.18 shows a compound light microscope. 16 UNIT A Tissues, Organs, and Systems of Living Things ist10_ch01.qxd 7/22/09 3:23 PM Page 17 Table 1.1 Parts of a Microscope Part Function 1. Tube Separates the ocular lens from the objective lens 2. Revolving nosepiece Holds the objective lenses 3. Objective lenses Magnify specimen; three lenses are usually 4⫻, 10⫻, and 40⫻ 4. Stage Supports the slide for observation 5. Diaphragm Allows light to pass through the specimen 6. Condenser lens Focusses light onto the specimen 7. Lamp Supplies the light that passes through the specimen 8. Base Provides a stable platform for the microscope 13 9. Fine adjustment Sharpens an image 1 knob 10. Coarse adjustment Moves the stage up or knob down to focus on the 12 specimen 11. Stage clips Hold the slide in position on the stage 3 2 12. Arm Holds the tube in place and is used to carry the microscope 4 13. Eyepiece or ocular Magnifies the specimen, lens usually by 10⫻; single lens 11 5 10 6 9 7 8 Figure 1.18 This compound light microscope is commonly found in science classrooms. Cells are the basic unit of life and often combine with other cells to form tissues. 17 ist10_ch01.qxd 7/22/09 3:23 PM Page 18 Magnification The first microscope had a magnification of 20⫻, which meant that it produced an image that was enlarged by about 20 times. A compound light microscope has a series of lenses, which permits a higher level of magnification. For example, the compound light microscope has a maximum magnification of 1000⫻ to 2000⫻; this means that the image is 1000 to 2000 times bigger than the actual object. To find the total magnification, you multiply the power of the objective lens by the power of the ocular lens (eyepiece). A photo taken through a microscope is called a micrograph. A micrograph shows the magnified image of a specimen. To produce a Suggested Activity micrograph, either a camera is attached to a microscope in place of the A5 Inquiry Activity on page 22 eyepiece or a special microscope that has a camera and an eyepiece is used. Example Problem 1.1 Practice Problems Determine the total magnification of a microscope if the magnification of the objective lens is 10⫻ and the magnification of 1. Determine the total the ocular lens is 10⫻. magnification of a microscope with an Given objective lens of 100⫻ and Magnification of objective lens = 10⫻ an ocular lens of 10⫻. Magnification of ocular lens = 10⫻ 2. Determine the total Required magnification of a Total magnification = ? microscope with an objective lens of 4⫻ and Analysis and Solution an ocular lens of 10⫻. Multiply the magnification of the objective lens by the magnification of the ocular lens to get the total magnification. 3. Determine the total (10⫻)(10⫻) = 100⫻ magnification of a microscope with an Paraphrase objective lens of 40⫻ and Therefore, the total magnification is 100⫻. an ocular lens of 10⫻. Resolution Regardless of the magnification, being able to see clear detail in an image depends on the resolution, or resolving power, of the microscope. Resolution is the ability to distinguish between two objects that are very close together. For example, look at Figure 1.19. You may be able to see the individual dots in A and B, but it is hard to see the dots in D. This is because most people can only see dots that are 0.1 mm or larger. Using a compound light microscope, we can see individual objects that are closer together than 0.1 mm. 18 UNIT A Tissues, Organs, and Systems of Living Things ist10_ch01.qxd 7/22/09 3:23 PM Page 19 A B C D Figure 1.19 Can you see the individual dots that make up the circles in A, B, C, and D? Contrast It can be difficult to see the cell parts because both the cell and its background may be pale or transparent. Scientists use stains to improve the contrast between a cell’s structures and the background and to produce better images. Two common stains are methylene blue and iodine. In fluorescence microscopy, fluorescent substances are added to the cells. When the cells are placed in ultraviolet light, the fluorescent substances glow (Figure 1.20). Figure 1.20 A micrograph showing nerve cells that have been stained with a fluorescent stain. Cells are the basic unit of life and often combine with other cells to form tissues. 19 ist10_ch01.qxd 7/22/09 3:23 PM Page 20 Electron Microscopes An electron microscope uses a beam of electrons instead of light. The transmission electron microscope (TEM) is capable of magnifications of up to 1 500 000⫻ (Figure 1.21). Since a beam of electrons can pass through thin slices, only thin sections of cells can be examined. This means that an electron microscope cannot be used to look at living cells — only dead cells can be observed. A scanning electron microscope (SEM) provides information about the surface features of a specimen (Figure 1.22). The SEM operates up to a magnification of 300 000⫻ and produces three-dimensional images Take It Further of cells. Take a closer look at either the A photograph taken through either a TEM or an SEM is called an mitochondrion or the lysosome. electron micrograph. An electron micrograph provides detailed Briefly describe the function of the organelle. Find out how the information about the surface and texture of a cell, the shape and size of electron microscope has improved the particles in the cell, and the arrangement of the materials in a cell. the understanding of the structure As a result of new technology, research on cells has led to major and function of this organelle. Use breakthroughs in medicine and industry. For example, the scanning a graphic organizer to record your thoughts and your sources. Begin tunnelling microscope (STM) and the atomic force microscope (AFM) your research at ScienceSource. produce images of molecules within cells, which help scientists understand the structure and function of molecules within the cell. Figure 1.21 In a transmission electron microscope, the electrons Figure 1.22 A researcher using a scanning electron microscope travel down the microscope column and pass through the specimen. An image forms on a fluorescent screen at the bottom of the column. UNIT A Tissues, Organs, and Systems of Living Things 20 ist10_ch01.qxd 7/22/09 3:23 PM Page 21 A3 Quick Lab Cells on Display Purpose 2. You will work in partners. Decide which of the cell To create a model of a plant or an animal cell parts you will include in your model. For each cell part, decide on the shape, size, and texture. Materials & Equipment 3. Create your model using the modelling clay, and share it with the class. coloured modelling clay Questions Procedure 4. How do you think that the shape and structure of a specific cell part relates to its function? Explain 1. Select the type of cell — plant or animal — that your answer. you will model. 5. In this activity, you created a scientific model of the cell. What are some limitations of your model? A4 Quick Lab Practice Makes Perfect! It is useful to record your observations when using a Materials & Equipment microscope. A sketch is a basic drawing that provides LCD projector pen and/or pencil little detail but is accurate in scale and in proportion (Figure 1.23). prepared slides transparent ruler paper Purpose To practise drawing sketches of cells Procedure 1. Your teacher will display a prepared slide on an LCD projector. Study the cell carefully. 2. Draw a sketch of the cell showing the external structures. Make sure that your sketch reflects accurate scale and proportion. 3. Repeat step 2 for the other slides. Be sure to include a title for each sketch. Questions 4. What aspects of sketching did you find easy? What aspects did you find difficult? 5. What could you do to improve your sketches? Figure 1.23 A labelled sketch of an amoeba Cells are the basic unit of life and often combine with other cells to form tissues. 21 ist10_ch01.qxd 7/22/09 3:23 PM Page 22 SKILLS YOU WILL USE A5 Inquiry Activity Skills References 2, 6, 10 Using equipment, materials, and technology accurately and safely Communicating ideas, procedures, and results in a Creating Biological Diagrams of Plant and Animal Cells variety of forms A compound light microscope magnifies the image of Table 1.2 Microscope Magnification and Field a specimen. The magnification depends on the Diameter combination of lenses used. While it is interesting and Field Field informative to view objects under a microscope, it is Diameter Diameter difficult to know the actual size of the object being Field Magnification (mm) (µm) observed. To learn how to estimate the size of an low power object, you will compare it with something you already high power know — the diameter of the field of view, which is the entire area that you see when you look through the 3. Set up your ocular lens. You will then estimate the size of plant microscope and place and animal cells. You will record your observations in a transparent metric the form of a labelled biological diagram. ruler on the stage, so that it covers about Question half of the stage, as How can a compound light microscope be used to shown in Figure 1.24. estimate the size of a plant or animal cell? 4. Observe the ruler under low power. Move the ruler so that Materials & Equipment you are measuring the diameter (width) of the compound light transparent metric low-power field of view microscope ruler from left to right. Set Figure 1.24 Set-up for pen and/or pencil prepared slides of one of the millimetre measuring the diameter of plant and animal cells the field of view paper divisions at the edge of the field of view, as CAUTION: Practise proper techniques in handling the shown in Figure 1.25. microscope and slides. Procedure Part 1 — Determining the Size of the Field of View 1. Review the proper handling and use of the microscope in Skills Reference 10. 2. Copy Table 1.2 in your notebook. Record the magnification for each power. Figure 1.25 Move the ruler so that you can measure the diameter of the field of view. Line up a millimetre mark at the edge of the circle. 22 UNIT A Tissues, Organs, and Systems of Living Things ist10_ch01.qxd 7/22/09 3:23 PM Page 23 A5 Inquiry Activity (continued) 5. Measure the diameter of the low-power field of 10. Examine a prepared slide of an animal cell view to the nearest tenth of a millimetre. Record through the low- and high-power objective lenses. this measurement in your table. Convert the Repeat steps 8 and 9. diameter from millimetres to micrometres, and 11. Clean up your work area. Make sure to follow your record the measurement in your table. Remember teacher’s directions for safe disposal of materials. that 1 mm = 1000 µm. Wash your hands thoroughly. 6. You cannot measure the diameter of the high- power (HP) field of view because it is less than Analyzing and Interpreting 1 mm. However, you can use the following ratio to 12. How many times is the magnification increased calculate the field diameter under high power. when you change from the low-power to the high- power lens? high-power field diameter low-power magnification = low-power field diameter high-power magnification 13. State two observable characteristics that you can use to distinguish an animal cell from a plant cell Show your work. Record the high-power field based on what you saw using the compound light diameter both in millimetres and micrometres in microscope. your table. Skill Practice Part 2 — Estimating Cell Size 14. When using a microscope to view living cells, it is 7. Examine a prepared slide of a plant cell through sometimes difficult to obtain a good image of the the low- and high-power objective lenses. object. What two things can you do to ensure 8. Draw what you see in the field of view on low optimal viewing of the image? power. Calculate the scale of your drawing by comparing the diameter of the circle in your Forming Conclusions drawing with the field diameter that you obtained 15. How can you use a compound light microscope to in step 5. For example, if the field diameter of the estimate the size of a plant or animal cell? low-power objective was 3 mm and the diameter 16. If an object under low power had an actual cell of the circle on your drawing was 3 cm (30 mm), length of 30 µm, what would the cell length be the scale of the drawing would be 10:1. under high power? 9. Estimate the size of the cells that you view under 17. When you changed from low to high power, the the microscope by comparing them with the image also changed. State three ways in which diameter of the field of view. For example, a cell the image changed as the magnification was 1 that takes up 5 of a field of view that is 500 µm increased. 1 has a size of about of 500 µm, or 100 µm, 18. How would you estimate the size of an object 5 1 while a cell that takes up of a field of view that viewed under the high-power objective lens (40×) 2 is 500 µm in diameter has a size of about 1 of if you were given the size of the field diameter 2 500 µm, or 250 µm. when using the low-power objective lens (4×)? Cells are the basic unit of life and often combine with other cells to form tissues. 23 ist10_ch01.qxd 7/22/09 3:23 PM Page 24 SKILLS YOU WILL USE A6 Inquiry Activity Skills References 2, 6, 10 Conducting inquiries safely Observing, and recording observations Examining Plant and Animal Cells There are some similarities and some differences toward the paper towel. When all of the cells are between plant cells and animal cells that can be seen stained, remove the paper towel. using a compound light microscope. You will look at 6. Place the slide on the microscope, and observe cells from the human body and from an onion to see the cells. the similarities and the differences. 7. Create a labelled diagram of your skin cells. Question Include the magnification and scale. What similarities and differences between plant and Part 2 — Examining Plant Cells animal cells can be seen using a microscope? 8. Obtain a small section of onion. Use the tweezers to pull off a thin transparent layer of cells. 9. Prepare a wet mount of the onion cells. Add a Materials & Equipment drop of iodine stain, and follow the staining clear adhesive tape onion epidermis procedure in step 5. compound light iodine stain 10. Place the slide on the microscope, and observe microscope paper the cells. methylene blue stain paper towel 11. Create a labelled diagram of the onion cells. microscope slides and pen and/or pencil Include the magnification and scale. cover slips tweezers 12. Clean up your work area. Make sure to follow your teacher’s directions for safe disposal of materials. CAUTION: Practise proper techniques in handling the Wash your hands thoroughly. microscope and slides. Use care when staining. Cover your staining work area with a paper towel. Analyzing and Interpreting 13. Both the plant and animal cells used in this Procedure activity are specialized cells that form the outer layer of the organism. Describe how the Part 1 — Examining Animal Cells appearance and shape of the cells enable them to 1. Review the proper handling and use of the accomplish their task of covering and protection. microscope in Skills Reference 10. Set up your 14. Explain how the cells appeared to be different microscope. when viewed at different magnifications. 2. Take a small piece of clear adhesive tape, and 15. Explain why it is necessary to use onion stick it on the inside of your wrist. Remove the membrane that is only one cell in thickness. tape, and place it sticky side up on the slide. 3. Verify that cells are present by looking at your Skill Practice slide at low power and medium power. 16. Explain how the use of contrast (light levels and 4. Make a wet mount of your cells. Add a drop of use of stain) improved your understanding of the methylene blue stain to the slide at one edge of cells that you were viewing. the cover slip. Forming Conclusions 5. Place a piece of torn paper towel against the edge of the cover slip on the side opposite that of the 17. Describe the similarities and differences that you stain. The stain should move under the cover slip observed between the plant and animal cells. 24 UNIT A Tissues, Organs, and Systems of Living Things ist10_ch01.qxd 7/22/09 3:23 PM Page 25 1.1 CHECK and REFLECT Key Concept Review 15. Think about the function of the mitochondria. You have been asked to view 1. What five life processes do cells perform? cells taken from the leg muscle of an athlete 2. List the five organelles that are common to and cells taken from the skin of an elderly plant and animal cells. What are their individual. What differences in the number of functions? mitochondria would you see in the two samples? Explain your thinking. 3. What are three differences between plant and animal cells? 16. Explain how a microscope may be used to assess human health. 4. Why can the granum and thylakoid structures be described as “solar collectors”? 17. Write a short paragraph that compares and contrasts plant and animal cells by 5. Prepare a table that summarizes the considering structures, presence of organelles and structures found in plant and specialized compounds, and forms of energy animal cells. storage. 6. Explain how fluorescence microscopy works. 18. The scientist shown below is looking at cells through a fluorescent microscope. How has 7. Name two types of electron microscopes that the development of technology aided our are used by cell biologists. understanding of cells? 8. What is the name of the image created by an electron microscope? 9. Explain why the cell can be considered to be the “building block” of life. 10. Explain the importance of contrast in microscopy. 11. What two things can you do to create contrast when you use a compound light microscope to study a specimen? Connect Your Understanding 12. Explain why a cell biologist would choose to use an electron microscope rather than a light microscope. When would a light microscope be preferred? 13. What details of a microscope would you need Question 18 to know to determine the total magnification of the system? Reflection 14. Explain why you would expect the cells of a 19. Describe three things about plant and animal desert plant, such as a cactus, to have cells that you did not know before you started thickened cell walls. working on this section. For more questions, go to ScienceSource. Cells are the basic unit of life and often combine with other cells to form tissues. 25 ist10_ch01.qxd 7/22/09 3:23 PM Page 26 1.2 The Cell Cycle and Mitosis Here is a summary of what you will learn in this section: The life cycle of a cell has four phases. Growth and repair of cells is accomplished by mitosis. Cancer cells have an abnormal rate of cell division. Figure 1.26 An electron micrograph of the skin shows the different layers of cells. The Life and Death of Skin Cells Stare at your face in the mirror. Your eyes are bright and alive, and your skin looks... dead? Actually, when we look at our skin, we are viewing dead cells. You lose about 30 000 to 40 000 skin cells every minute. If you collected all the dead cells that you shed over a day, you would collect 0.5 g of dead cells. If you collected those cells over a year, you would have about 3 kg of skin cells. Since we lose so many skin cells every day, it is surprising that our skin does not simply wear away. However, our skin is made of different layers of cells (Figure 1.26). Skin cells are produced in the deeper layers of the skin and, in young people, mature over a period of about four weeks. During this time, the cells travel to the surface, where they are eventually sloughed off, leaving younger cells behind. The cells on the surface are old, dead cells that have become toughened and flattened. This change in structure enables them to form a good protective layer for your body. These surface cells are continuously being replaced by cells from the layer below. The time taken for the process of cell renewal changes as individuals age, or with changes in hormone or vitamin levels. For example, in older people, surface cells are held in the skin for up to 75 days, resulting in skin that is thicker and duller in appearance. 26 UNIT A Tissues, Organs, and Systems of Living Things ist10_ch01.qxd 7/22/09 3:23 PM Page 27 People apply products to their skin to keep it healthy, attractive, and young looking (Figure 1.27). The best way to keep skin healthy is to stay out of the Sun. Exposure to the Sun is responsible for damaging skin cells. Much of the damage is associated with premature skin aging, including the appearance of wrinkles and discoloured areas. Excessive exposure to the ultraviolet (UV) radiation in sunlight can also cause skin cancer: each year, about 30 000 Ontarians are diagnosed with skin cancer. The UV radiation changes the genetic information that is coded in the skin cells’ DNA. This affects the functions of the cell, including the ability to reproduce and to repair itself. You can protect your skin from UV damage by wearing protective clothing (long-sleeved shirts and hats) and sunglasses, limiting your time in the Sun, and applying sunscreen to exposed skin. Figure 1.27 People use skin creams to keep their skin looking healthy. A7 STSE Quick Lab Taking Protective Actions The Sun is necessary for all life on Earth, but it is also 4. Use the number of positive responses and the the source of ultraviolet (UV) radiation, which is total number of students surveyed to calculate harmful to skin cells. There are things that you can do the percentage of students who practise Sun to protect your skin. protection behaviours during the summertime. Purpose Questions To survey your class about Sun protection behaviours 5. Do your data suggest that youth are practising and to compare the class data with national data Sun protection behaviours? Procedure 6. How do your class data compare with the data in Table 1.3? 1. Think about your typical Sun protection behaviours during the summer. Table 1.3 National Sun Survey 2006 2. Create a table in your notebook in which to 16–24 years old Percent of Canadians who: record the results of your survey. Your table Male Female should indicate the total number of students spent at least 2 h in the Sun 47% 32% responding to the survey and the total number of daily “yes” and “no” responses. practised Sun protection 42% 58% 3. Participate in a survey of three questions of your behaviours class members. acquired a tan from the Sun 28% 49% Do you regularly practise Sun protection behaviours in the summer? Have you suffered at least one major 7. What is one action that you could take to sunburn in the summer? encourage your friends and family to practise Sun How many hours per day do you spend in protection behaviours? the Sun during the summer? 8. What Sun protection behaviours should people who work outside every day practise? Cells are the basic unit of life and often combine with other cells to form tissues. 27 ist10_ch01.qxd 7/22/09 3:23 PM Page 28 The Cell Cycle Every hour, about one billion (109) cells die and one billion cells are made in your body. Through careful observation, scientists have identified a repeating cycle of events in the life of a cell. This cycle of events is called the cell cycle. During much of the cell cycle, the cell grows and prepares for cell division. In fact, although the main goal of the cell cycle is division, the cell spends most of its time preparing for division. The cell is in interphase when it is preparing for cell division. Cell division involves packaging the genetic information in the nucleus into two equal portions; this process is called mitosis. Then, the cytoplasm is split into two portions so that the original parent cell divides to form two new “daughter cells.” Cells use mitosis in the processes of growth and repair. We can visualize the cell cycle by considering Figure 1.28. There are four phases in the cell cycle: first growth phase (G1), synthesis phase (S), second growth phase (G2), and mitosis (M). cell growth G1 phase cyt oki nes is telop hase anaphase M phase cell metaphase division mitosis ase rph ase S phase proph nte tion i plica A re DN G2 phase pre p ati ar o nf or mi t o s is Figure 1.28 The cell cycle has four phases. During most of the cell cycle, the cell is growing, replicating its DNA, and preparing for cell division. Chromosomes Every cell contains chromosomes. Each chromosome is a long piece of coiled DNA and proteins. The number of chromosomes in each cell differs between organisms. For example, a horse has 64 chromosomes, while a hermit crab has 254 chromosomes. The typical human cell has 46 chromosomes — 23 matching pairs of chromosomes. 28 UNIT A Tissues, Organs, and Systems of Living Things ist10_ch01.qxd 7/22/09 3:23 PM Page 29 Chromosomes are visible only when the cell is dividing. When the cell is not dividing, the DNA and centromere proteins that make up the chromosomes are spread throughout the cell in the form of chromatin. At the beginning of cell division, the chromosomes condense sister into visible structures. Before cell division can occur, chromatids each chromosome is copied. As shown in Figure 1.29, the chromosome consists of two identical copies, called sister chromatids. When the cell divides, one chromatid goes to each of the new cells. A Closer Look at Interphase A cell spends about 90 percent of its time in interphase. During interphase, the cell is growing. However, there is a limit to how big a cell can become. As a cell increases Figure 1.29 Each chromosome consists of two identical sister chromatids (shown magnified 8,300⫻). in size, the relationship of the surface area of the cell membrane to the amount of volume of cytoplasm changes. The volume of a cell’s cytoplasm increases faster than the surface area of a cell’s membrane. This affects how well a cell can absorb substances from its environment or expel wastes into its environment. When a cell reaches a certain size, it is healthier for the cell to undergo division. On average, the cells of an adult human are the same size as the cells in a child — however, there are more cells in an adult. During interphase, the cell takes in nutrients, grows, and conducts other normal cell functions. There are three phases of interphase. First Growth Phase (G1) This phase is a period of growth for the cell. During this phase, the cell also produces new proteins and organelles. If the cell is healthy and conditions are favourable, the cell moves into the next phase. Synthesis Phase (S) During this phase, the cell makes (synthesizes) an entire copy of the DNA of the cell. Key proteins that are associated with chromosomes are also produced during this phase. Second Growth Phase (G2) Once the DNA has been copied, the cell moves into the second growth phase. During this phase, the cell produces the organelles and structures needed for cell division. This phase is the shortest of the phases of interphase. Cells are the basic unit of life and often combine with other cells to form tissues. 29 ist10_ch01.qxd 7/22/09 3:23 PM Page 30 interphase early prophase late prophase chromatin mitotic centrioles fragments centrioles (duplicated) spindle of nuclear centromere envelope nucleus cell membrane chromosome, consisting of two sister chromatids DNA has been duplicated in the S phase The chromatin condenses to form

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