Biology PDF

Biology i want to create a full and complete test for me using the material, i want ease multiple questions as dificult questions, make any question using all details from the material dont be afraid it can be very long if it will help me learn and memorize th...

Biology i want to create a full and complete test for me using the material, i want ease multiple questions as dificult questions, make any question using all details from the material dont be afraid it can be very long if it will help me learn and memorize the whole material (when sending i might also send some exercices so use it as well) "The Compound Microscope Most cells are too small to be seen with the unaided eye. Our knowledge of cells has been greatly improved by our ability to see them through the compound microscope. This microscope is commonly called the compound light microscope because it uses lenses and a light source to magnify the specimen. The compound light microscope is the most common and versatile type of microscope today (Figure 1). It is easy to use and relatively inexpensive. Visual description Figure 1 The parts of a compound microscope. Linking to Literacy Pause and ReflectAfter reading a graphic, it is a good idea to pause and think about what you have read. Ask yourself, “Do I know the parts of the compound microscope and how they work?” Magnification Microscopes, magnifying glasses, binoculars, and some curved mirrors enable us to magnify the appearance of specimens. Magnification refers to how much a specimen is enlarged in appearance. In microscopy, magnification of a specimen is achieved using a lens system. The amount by which a specimen is magnified can be expressed as a number. A magnifying glass with a magnification of 2× will make a specimen appear to be two times larger than its actual size. Compound microscopes use two lens systems to magnify a specimen—an ocular lens (eyepiece) and an objective lens. A compound microscope generally has three objective lenses, each with a different magnification. The eyepiece commonly magnifies 10 times (10×). The three objective lenses usually magnify the specimen 4× (low-power objective lens), 10× (medium-power objective lens), and 40× (high-power objective lens). The total magnification is determined by multiplying the magnification of the eyepiece by the magnification of the objective lens being used (Table 1). Biology 1  Table 1 Determining Total MagnificationEyepiece magnificationObjective lens magnificationTotal magnification(eyepiece magnification × objective lens magnification)10×4×(low-power objective)40×10×10×(medium-power objective)100×10×40×(high-power objective)400× Safety and the Compound Microscope The compound microscope is a delicate instrument that needs to be used safely. Some tips to keep in mind include the following: Always keep the microscope upright when handling it. Use two hands to carry the microscope—one under the base and one on the arm (Figure 2). Place the microscope near the centre of the desk or table where it will be used. Figure 2 The microscope should be carried with one hand under the base and one hand on the arm. Be careful when handling glass slides—they may shatter if dropped. When sunlight is used for illumination, ensure that the Sun cannot be focused directly through the microscope. When you are observing a specimen through the microscope, keep both eyes open to avoid straining your eyes. Always store the microscope with the lower-power objective lens in place and the stage lowered. This will prevent the objective lens from being accidentally scratched by the slide when you begin using the microscope. Only use the coarse-adjustment knob with low-power objective lenses. Use the fine-adjustment knob at higher powers. Use the microscope in a dry area. Your hands should also be dry when using a microscope. Remember to unplug the microscope from the electrical outlet by grasping and pulling the plug, not by pulling on the power cord. Coil the power cord neatly around the arm of the microscope when returning the microscope to its storage area. The Microscope’s Field of View When you look through the eyepiece of a microscope, you see a circular area in which the enlarged image of the specimen can be viewed. This is called the field of view. The diameter of the field decreases as you use more powerful lenses to view a specimen. The total magnification increases and the components of the specimen appear larger (magnified), but a smaller portion of the specimen is seen. Figure 3 shows two photos of human liver cells seen through a compound light microscope. In Figure 3(a), the cells were viewed under low power (50× total Biology 2  magnification), while in Figure 3(b), they were viewed under high power (600× total magnification). Can you see the difference in the two fields of view? Figure 3 (a) Human liver cells magnified 50x (b) Human liver cells magnified 600x Since a larger portion of a specimen is seen under low power, scientists use low power to scan a specimen. When they see an area they are interested in, they switch to higher powers to see more detail. Biological Drawings To accurately record observations, scientists draw a circle to represent the field of view. Next, they draw what they see through the microscope in the circle. They label the total magnification and use straight, horizontal lines to label any visible structures. Biological drawings are drawn with firm, short strokes and are usually two-dimensional. To keep the drawing simple, scientists use dots called “stipple” instead of shading (Figure 4). Figure 4 Scientists use lines and stipple for the details of their drawings. Try This: Modelling a Microscope’s Field of View Skills Menu: performing, observing, analyzing, communicating Skills Handbook: 2.B.6. In this activity, you will model a microscope’s field of view with your index finger and thumb. Equipment and Materials: pencil; paper; ruler On a sheet of paper, draw three circles, each 5 cm in diameter. Label the circles 1, 2, and 3. Choose an object in your classroom to observe that is at least 2 m away from you, and at your eye level. Form a finger circle with your index finger and thumb (Figure 5). Place your finger circle about 30 cm away from your right or left eye. Centre the distant object in your finger circle while looking through the circle with one eye. The visible portion of the object is the field of view. Draw what you see in the field of view in circle 1 on your sheet of paper. Move two paces closer to the object, keeping your finger circle the same distance from your eye. Draw what you see in the field of view in circle 2 on your sheet of paper. Carefully move four paces back from the object, again keeping your finger circle the same distance from your eye. Draw what you see in the field of view in circle 3 Biology 3  on your sheet of paper. What happened to the appearance of the object in the field of view as you moved closer to the object? What happened to the appearance of the object in the field of view as you moved away from the object? How do the steps in this activity relate to the changes in total magnification and field of view that occur when you observe a specimen through a microscope under different powers of magnification? Before the invention of the compound microscope, it was almost impossible to see any type of detail in cells. Viewing cells is important for understanding our health and that of the environment around us. In the next Learning Objects, you will learn how to use this powerful tool. Unit Task How can you apply your new knowledge of the microscope when completing the Unit Task? What important concepts in this Learning Object will be especially useful? Check Your Learning Look back at the image of skin in Cells. What are your thoughts as you look at this image? What questions do you have about this photo? A scientist will first focus on a specimen using the low-power objective lens, and then move to a higher magnification. Explain why. What is “field of view”? When observing a specimen under medium power, which adjustment knob should be used to focus the image? Why? In a well-written paragraph, describe how you would bring a microscope back to its storage area after using it. Create a biological drawing of the specimen shown in Figure 6. Assume that the photograph was taken through a microscope with a total magnification of 400×. Figure 5 Microscopes and Cells Credit Credit Try ThisA Scavenger Hunt for the Tiniest Things Caution! Safety Needed Environmental Protection Follow the instructions as well as other safety details your teacher provides. Your teacher will share rules of safe conduct with you before you start the Biology 4  scavenger hunt. Be sure you understand and follow all the safety rules provided by your teacher. Avoid inhaling small particles such as pollen, mould, or wood dust if you handle these materials. Some types of pollen and mould can cause allergic reactions. Wood dust is known to cause cancer and can have other toxic effects such as eye, nose, and throat irritation. Go on a scavenger hunt around the classroom, in the hallway, and perhaps around the school property. Search for three of the tiniest things around you. What is the smallest thing that you can examine with the unaided eye? List three things that you could not see with the unaided eye but that are probably present in and around the school. Create a visual scale to compare the relative size of the small things that you listed. Place the largest object on the left and the smallest object on the right. Under the scale, indicate whether the object can be observed with the unaided eye or with a microscope. Comparing Sizes of Small Objects Many living things around you are too small to observe. The human eye can only make out objects that are larger than 0.1 mm. Take out a ruler and observe the 1 mm marking. Now imagine one-tenth of 1 mm. That is the visual limit of the human eye. The term scale refers to comparing objects by their size or by their amount. In the diagram, pictures are used to give a sense of the kinds of objects that are visible at different segments of the scale. The three coloured bars under the number scale show the range of sizes that are visible to the unaided eye, with the light microscope, and with the much more powerful electron microscope. Get Instructions Visual description Credit Cells Are Tiny Units of Life When scientists talk about life or living things, they are referring to organisms. Organisms are able to take in and organize matter and energy from their surroundings to meet their needs. These needs include growing, moving, and responding to changes inside and outside their bodies. The bodies of organisms have structures that help them meet their needs. The smallest life-related unit of an organism is the cell. Plants, animals, and most other organisms are made up of millions of cells. Some organisms, such as bacteria and yeasts, are made up of just one cell. Biology 5  Try ThisGet to Know the Compound Light Microscope Most cells are too small to observe without tools. To observe cells and other microscopic objects, we need to use a microscope. A compound light microscope is the type of microscope that you will use to observe organisms and their cells. Compound Light Microscope Media player Play Restart Rewind Forward Volume Slower Faster Hide captions Show transcript Preferences Enter full screen 0:00 / 2:54Speed: 1xPaused Credit Use the video to get to know the parts of your microscope and what they do. Knowing the names and functions will help you use this technology safely and effectively to observe the wonders of the microverse. After the video, read and discuss "How to Handle and Care for Your Microscope." Your teacher may share additional information as well. How to Handle and Care for Your Microscope Use both hands to carry it. One hand holds the arm while the other supports the base. Keep the microscope in an upright position at all times. Keep the stage clean and dry. Use only lens paper to clean the lenses. Place the slide on the stage, and secure it with the stage clips. Focus with the low-power objective lens first. Use the coarse adjustment knob to do this. Use the coarse adjustment knob only when you use the low-power lens. Do not use it with other lenses. Focus by moving the lens upward from the slide. Biology 6  Remove the slide when it is not being used. When you put the microscope away, position the stage clips so they point forward, and make sure the low-power lens clicks into place below the eyepiece. Cover your microscope when it is not in use. At any time, tell your teacher if the lenses are dirty, if parts aren’t moving smoothly, or if anything else seems faulty. Student Check-In Choose the best answer. Which statement about cells and the microscopic world is true? Only organisms that can be seen with the unaided eye can take in and organize matter and energy from their surroundings to meet their needs. The cell is the smallest life-related unit of an organism. All organisms on Earth are made up of millions of cells. Most cells can be observed with the unaided eye. Check Answers How did you do? If you need to, now is a good time to go back and review any material. Checkpoint Rank these prefixes for measurement from smallest to largest: kilo, micro, nano, mega, milli. Describe how you would carry the microscope to your desk. List some things that you need to do before putting the microscope away. Microscopes like those you use at school have three lenses. An early, extremely powerful microscope used only a single lens. The Dutch person who invented it was an amateur, self-taught scientist. Investigate Antonie van Leeuwenhoek to find out how he was able to observe things in the late 1600s that scientists would not be able to observe for another 150 yWhat Is a Cell? What do you have in common with a stealthy shark, a stinky skunk, a slimy slug, a stunning sunflower, and a scrumptious strawberry? Based on the title above, you are probably guessing cells. But what exactly are cells, and in what ways are the cells of all life forms similar? In what ways are they different? After you watch this video, answer the following questions. What information presented in the video did you know already? What did you find out about cells that you didn’t know before? What did you find out about ways that animal cells and plant cells are similar and different? Biology 7  Why might it make sense for there to be these similarities and differences? In this video, cells are called “building blocks,” “tiny universal units of life,” and “small containers of chemicals and water.” Did you find using different descriptions for cells helpful? confusing? both? Explain your reactions. What would you like to learn more about? What are you still wondering about cells?thank you, do the same with this ''The Cell Theory Credit Try This Viewing Cells A few early microscopes had been invented and were being used around the middle of the 1600s in Europe. Imagine that you were living at that time and had a microscope to try. You decide to examine a thin strip of bark from a cork oak tree. Credit An oak tree, Quercus suber Credit Bark showing the cork Credit Drawings made by Hooke after viewing cork oak tree bark with an early microscope Examine the bark of the cork oak tree in the second photo. Make a drawing of the bark sample from the photograph. How would you describe the structures you observe? What do the structures remind you of? What might you call them? Examine Hooke's drawings of the tree bark in the third photo. Do you think Hooke did an adequate job in drawing the cork oak tree bark? Does your drawing look similar to Hooke's drawing? Explain. What questions would you have after looking at the bark? How might you try to answer these questions? Development of the Cell Theory Over 4000 years ago, Chinese scientists invented the water microscope. This microscope consisted of a lens at one end of a tube that was filled with water. It could magnify things by 150x. Centuries later, in the late 1500s, Dutch opticians Hans Jansen and his son Zacharias invented the first compound microscope. By the mid-1600s, improvements in lenses allowed English scientist Robert Hooke Biology 8  and Dutch scientist Antonie van Leeuwenhoek to use microscopes with higher magnifications to study cells. By the mid-1850s, scientists like Theodor Schwann, Matthias Schleiden, and Rudolph Virchow in Germany had recorded thousands of observations about the cells of plants, animals, and other living things. Based on their studies, scientists agreed on three important facts about cells and the basic characteristics of living things. Together, these facts are called the cell theory. Use the interactive to explore the three main ideas of the cell theory. Get Instructions The cell is the basic unit of life. This single-celled organism is called an amoeba. It is a complete life form that is able to take in nutrients, use energy, produce and remove wastes, react to its environment, grow, and reproduce. This amoeba is surrounding an algal cell to use for food and energy. All living things are made up of one or more cells. Unlike an amoeba, which is a complete organism unto itself, the skin that surrounds your body is made up of collections of cells of the same kind that work together. All new cells are produced from previously existing cells. Cells do not arise out of nothing and nowhere. They reproduce to form new cells. Credits Scientists consider the cell to be the basic functional unit of life. Cells have structures that enable them to carry out life processes. Life processes include all of the chemical reactions that help a living thing obtain and use energy, break down nutrients, build molecules, grow, copy its genetic material, and excrete wastes. All living things take in nutrients either by eating food or producing their own food using the Sun’s energy. Energy from food is used for many purposes, such as growth, responding to changes in the environment, movement, and even sleep. Credit The snowy owl visits southern parts of Ontario from the Arctic in late fall and Biology 9  winter, and returns to the Arctic to breed each spring. Mice are among its sources of food. Single-Celled and Multi-Celled Organisms Credits Whether an organism is one‐celled or many-celled, its cells carry out life processes. Paramecium is a single-celled organism. Animals like the turtle and black bear are multicellular organisms consisting of millions of cells that work together. All living things are made of one or more cells. Some living things are only one cell. These individual cells that are able to meet their needs for survival on their own are called single-celled organisms, or unicellular, organisms. Examples of unicellular organisms are bacteria and some protists such as Stentor and Paramecium. Many unicellular organisms play an important role in recycling nutrients. Many unicellular fungi and bacteria, for example, are decomposers. They break down dead plant and animal material, releasing usable nutrients and carbon dioxide back into the environment. Some bacteria are able to change nitrogen in the air into a material that acts as a plant fertilizer. Fungi and bacteria are also used in the food industry. Yeast, a fungus, is used to produce breads and pastries. Yogurt is produced by bacterial action on milk. Multi-celled, or multicellular, organisms are made up of many cells that work together to meet the survival needs of the whole organism. Plants, animals, and most fungi are examples of multicellular organisms. Even animals that are microscopic may be made up of hundreds or thousands of cells. Unicellular organisms grow by increasing in cell size, up to a certain point. Multicellular organisms grow by increasing the number of cells in their body. Living Things Come Only from Other Living Things Organisms reproduce in different ways. Many unicellular organisms, such as bacteria, reproduce by dividing into two cells. Each new cell is the same as the original cell, because it has the same genetic material. Other organisms must have a mate to reproduce. Each member of a mating partnership provides different genetic information, so their offspring are not identical to them. Student Check-In Complete the sentences based on what you have just learned about the basic functional unit of life and related life processes. Biology 10  Fill in the blanks. Over time, scientists came to agree on a theory based on three important facts about and the basic characteristics of living things. The cell theory states that all cells are produced from previously existing cells. A robin is an example of a organism. Check Answers How did you make out? If you need to, now is a good time to go back and review any material. Checkpoint List the key points of the cell theory. Why is the cell theory valuable to scientists? Why might the cell theory not be a useful concept for other cultures in describing life? Which point of the cell theory is related to reproduction—the process in which new organisms are produced? Briefly describe two ways in which previously existing cells produce new cells. What is the difference between a unicellular and a multicellular organism? Give an example of each Explain why a whale cannot exist as a single-celled organism.The Nature of Cells: The Cell Theory Scientists have been studying living things for over 400 years. At first, they made observations with their unaided eyes. Later, the development of the microscope allowed scientists to see cells for the first time. After observing many different living things under the microscope, scientists realized that all living things are made up of cells. This conclusion led scientists to develop the cell theory—an explanation that summarizes the basic characteristics of living things. The cell theory states the following: All living things are composed of one or more cells. The cell is the basic unit of life. All cells come from pre-existing cells. The cell theory is true for all living things, regardless of size or complexity. Since cells are common to all living things, studying cells can help us understand how Biology 11  living things work. Different living things carry out the characteristics of life in different ways. Plants, for example, respond to their environment differently than animals do. Figures 1 to 3 show cells from different living things. Studying cells has improved our knowledge of how different living things meet their needs. You will learn more about this in Organizing Cells. Figure 1 Two types of plant cells: the dark kidney bean–shaped cells are used for gas exchange and the puzzle piece–shaped cells are epithelial cells. Figure 2 Nerve cells allow animals, including humans, to respond to changes in their environment. Figure 3 Smooth muscle cells line the organs of the digestive system and help move food through the digestive tract. Linking to Literacy Summarizing the Main IdeaSummarizing is identifying the most important points in the text. As you read, look for the important details by asking yourself, “What are the basic principles or ideas of cell theory?” Unit Task The cell theory summarizes the basic characteristics of living things. How will you apply this theory to the Unit Task? Check Your Learning What does the cell theory state? Explain how scientists developed the cell theory. In this section, you saw photos of four different types of cells. Why do we study cells from different living things? Concept 1Scientists classify cells into two types based on the presence or absence of a nucleus. Activity: Asking Questions About Cells As a scientist, you observe the two cells shown in Figure 1.10. Record at least three observations you can make. What questions can you ask based on your observations? What hypothesis would you state based on your observations and questions? How would you test your hypothesis? As scientists have studied millions of cells, they have developed criteria that let them classify all cells into two main types. These two types—prokaryotic cells and eukaryotic cells—are compared in Figure 1.10. Prokaryotic Cell Eukaryotic Cell Visual description Figure 1.10 The two main types of cells. The top is a prokaryotic cell and the Biology 12  bottom is a eukaryotic cell. Select a red dot to reveal the name of the cell part. Prokaryotic Cells A prokaryotic cell does not have a separate nucleus. In fact, the word prokaryotic comes from the words pro-, which means before, and karyon, which means nucleus. In addition to lacking a nucleus, prokaryotic cells are simpler than the other type of cells. They have fewer internal structures. Eukaryotic Cells A eukaryotic cell has a nucleus, which contains the cell's genetic material. The nucleus is surrounded by a membrane. The eu- part of the word means proper, so a eukaryotic cell is one that has a proper or actual nucleus. Eukaryotic cells also contain other internal structures called organelles, which carry out cell processes. Eukaryotic cells are about 10 times as large as prokaryotic cells, and they are more complex. Table 1.2 compares these two types of cells. CharacteristicProkaryotic CellEukaryotic CellGenetic material contained in nucleus surrounded by a membranenoyesOrganelles surrounded by membranesnoyesSize and complexitysmaller and less complexabout 10 times as large and more complexCan carry out all processes needed to stay aliveyesyesExamplebacteriumliver cell of an animal Table 1.2 Comparison of Prokaryotic and Eukaryotic Cells Activity: Cell Models Build a model of an organism that either is or contains prokaryotic or eukaryotic cells. Use materials you bring from home, those provided by your teacher, or computer software to make your model. How can you connect the components of your model to the processes of life? Before you leave … Use a Venn diagram to compare and contrast prokaryotic and eukaryotic cells. Write three statements that are true of both prokaryotic and eukaryotic cells.it was to creat a test just like you did with first material, please use this and the one before to create a full test also use the questions i provided on the test''Cell Theory Interactive Activity Fill in the blanks. Identify the part of the cell theory that each statement belongs to. A bacterial cell reproduces by dividing into two equal halves that are identical to the original cell. The cell is the basic unit of life. All organisms are made of one or more cells. All new cells Biology 13  are produced from previously existing cells. Euglena is a unicellular organism that can carry out basic life functions. The cell is the basic unit of life. All organisms are made of one or more cells. All new cells are produced from previously existing cells. A cell can use energy and produce waste. The cell is the basic unit of life. All organisms are made of one or more cells. All new cells are produced from previously existing cells. Cells can produce energy for life processes. The cell is the basic unit of life. All organisms are made of one or more cells. All new cells are produced from previously existing cells. Heart muscle is made from sheets of cardiac muscle cells. The cell is the basic unit of life. All organisms are made of one or more cells. All new cells are produced from previously existing cells. An amoeba moves around and engulfs a Paramecium. The cell is the basic unit of life. All organisms are made of one or more cells. All new cells are produced from previously existing cells. Skin cells reproduce to make new skin cells. The cell is the basic unit of life. All organisms are made of one or more cells. All new cells are produced from previously existing cells. Yeast is a unicellular organism. The cell is the basic unit of life. All organisms are made of one or more cells. All new cells are produced from previously existing cells. Plants and animals are made of cells. The cell is the basic unit of life. All organisms are made of one or more cells. All new cells are produced from previously existing cells. A mushroom is a multicellular organism. The cell is the basic unit of life. All organisms are made of one or more cells. All new cells Biology 14  are produced from previously existing cells. All living organisms contain at least one cell. The cell is the basic unit of life. All organisms are made of one or more cells. All new cells are produced from previously existing cells. Check Answers Credits 2.1 Plant and Animal Cells Biology as a science is built on three simple but very important ideas. These three ideas form the cell theory. The cell theory states that: All living things are made up of one or more cells and their products. The cell is the simplest unit that can carry out all life processes. All cells come from other cells; they do not come from non-living matter. All living things are made up of cells, but these cells may be very simple or very complex. The simplest organisms are archaea and bacteria. These simple, single- celled life forms are called prokaryotes (Figure 1(a)). The cells do not have a nucleus. More complex cells can exist as single-celled organisms or multicellular organisms. The cells of these organisms, known as eukaryotes, have a more complex internal organization, including a nucleus. Eukaryotes include all protists, fungi, animals, and plants, from the tiniest Amoeba to the longest whale and the tallest tree (Figure 1(b) to (d)). The cells of eukaryotes are much larger than the cells of prokaryotes: tens to thousands of times larger. There are even some eukaryotes that are made up of one huge cell with very many nuclei. Visual description Figure 1 The relationship between prokaryotes and eukaryotes. The bacterium (a) is a prokaryote. The Amoeba (b), the whale (c), and the pine tree (d) are all eukaryotes. Cell Structure Your body is made up of many specialized organs that carry out all the processes needed to live. In the same way, a eukaryotic cell also has specialized parts, called organelles, that carry out specific functions necessary for life. Structures Common to Plants and Animal Cells All cells have to perform the same basic activities to stay alive: use energy, store materials, take materials from the environment, get rid of wastes, move substances to where they are needed, and reproduce. Each organelle has a specific function within the cell. Just as workers in a factory or a hospital coordinate their efforts to achieve a purpose, the various organelles of a cell work Biology 15  together to meet the needs of the cell—and the whole organism. Figure 2 shows the organelles in a typical plant cell and a typical animal cell. (a) This diagram shows a plant cell. Select a letter for an explanation of each organelle. (b) This diagram shows an animal cell. Select a letter for an explanation of each organelle. Visual description Figure 2 Plant and animal cells have many of the same organelles, but there are some differences. Cytoplasm All the organelles inside the cell are suspended in the cytoplasm. The cytoplasm is mostly water, but it also contains many other substances that the cell stores until they are needed. Many chemical reactions take place within the cytoplasm, which can change from jelly-like to liquid, allowing organelles to be moved around. Cell Membrane The cell is surrounded by a flexible double-layered cell membrane (Figure 3). The function of the cell membrane is both to support the cell and to allow some substances to enter while keeping others out. For example, water and oxygen molecules can easily pass through the cell membrane, but larger molecules, such as proteins, cannot. Because of this ability, the cell membrane is called a “semi- permeable membrane.” Figure 3 This TEM image of a cell highlights the cell membrane in green. A similar membrane also surrounds most organelles in a eukaryotic cell. Nucleus The nucleus is a roughly spherical structure within the cell (Figure 4). The nucleus contains genetic information that controls all cell activities. This genetic information is stored on chromosomes. Chromosomes contain DNA (deoxyribonucleic acid), the substance that carries the coded instructions for all cell activity. When a cell divides, the DNA is copied so that each new cell has a complete set of chromosmes. Figure 4 The large nucleus is easily visible inside this starfish cell. Mitochondria Cells contain many mitochondria (singular: mitochondrion) (Figure 5). Mitochondria are sometimes called the “power plants” of the cell because they make energy available to the cell. Active cells, such as muscle cells, have more mitochondria than less active cells, such as fat-storage cells. Cells store energy as Biology 16  a form of glucose (a sugar). The mitochondria contain enzymes that help to convert the stored energy into an easily usable form. This process is called cellular respiration and requires oxygen. The waste products of this reaction are carbon dioxide and water. glucose + oxygen → carbon dioxide + water + usable energy Cells in which cellular respiration has to happen very fast, such as muscle cells and cells in the liver, have many mitochondria. In contrast, cells that are fairly inactive—that do not have to respire quickly—tend to have very few mitochondria. Fat cells may have only one or two mitochondria. Figure 5 The mitochondrion (17 000 ×) is the large, reddish, oval structure in this TEM image. Endoplasmic Reticulum The endoplasmic reticulum is a three-dimensional network of branching tubes and pockets (Figure 6). It extends throughout the cytoplasm and is continuous from the nuclear membrane to the cell membrane. These fluid-filled tubes transport materials, such as proteins, through the cell. Figure 6 The endoplasmic reticulum (5 500x), coloured brown in this TEM, transports materials throughout the cell. Endoplasmic reticulum is important in many types of cells. In the brain it assists with the production and release of hormones. In the muscles the endoplasmic reticulum is involved with muscle contraction. Golgi Bodies Golgi bodies collect and process materials to be removed from the cell (Figure 7). They also make and secrete mucus. Cells that secrete a lot of mucus, such as cells lining the intestine, have many Golgi bodies. Figure 7 Golgi body (30 000×) Vacuoles A vacuole is a single layer of membrane enclosing fluid in a sac. The functions of vacuoles vary greatly, according to the type of cell. These functions include containing some substances, removing unwanted substances from the cell, and maintaining internal fluid pressure (turgor) within the cell. (The special role of plant vacuoles is explained below.) Animal cells may have many small vacuoles that are often not visible. Mature plant cells usually have one central vacuole that is visible under a light microscope. Some animal cells can change their shape to wrap around and surround smaller objects to bring them inside the cell. Amoeba do this to obtain food. Some white Biology 17  blood cells engulf bacteria to kill them. During the engulfing process, a portion of the cell membrane turns inside out and forms a vacuole inside the cell until the engulfed object is digested. Then any waste material is ejected from the cell as the vacuole again joins up with the cell membrane. Organelles in Plants Cells Only Plant cells and animal cells have many structures in common, but there are also some differences. Plant cells have some organelles that animal cells do not have (Figure 8). (a) (b) Figure 8 Plant cells (a) have a cell wall, large vacuoles, and chloroplasts (5 500×). Animal cells (b) do not (2 500×). Cell Wall The cell wall is found just outside the cell membrane of a plant cell. It is a rigid but porous structure made of cellulose. The cell wall provides support for the cell and protection from physical injury. The cellulose may hold together long after the plant has died. The paper in a book is composed mostly of cellulose from the cell walls of trees. Vacuole Plant cells usually have one large vacuole, which takes up most of the space inside the cell. When these are full of water, turgor pressure keeps the cells plump, which keeps the plant’s stems and leaves firm. If the water level drops, however, the vacuoles lose turgor pressure and the cells become soft. The plant stems and leaves become limp and droopy until the water is replaced. Chloroplasts Many plant cells that are exposed to light, such as the cells of leaves, have structures called chloroplasts (Figure 9). Chloroplasts contain chlorophyll and give leaves their green colour. More importantly, chloroplasts absorb light energy. This light energy is used in photosynthesis—the process of converting carbon dioxide and water into glucose and oxygen. carbon dioxide + water + energy (sunlight) → glucose + oxygen Figure 9 Chloroplasts in plant cells (250×) Photosynthesis allows plants to obtain their energy from the Sun so that they can make their own food. Plant cells rely on mitochondria to metabolize glucose, just as animal cells do. In Summary Biology 18  The cell theory states that all living things are made up of cells, the cell is the simplest unit that can carry out all life processes, and all cells are reproduced from other cells. The simplest single-celled organisms, including bacteria, are prokaryotes. More complex organisms, including multicellular organisms, are eukaryotes. Eukaryotic cells contain organelles that carry out specific life functions. The cell membrane, cytoplasm, nucleus, mitochondria, endoplasmic reticulum, Golgi bodies, and vacuoles occur in both plant and animal cells. Structures found only in plant cells are chloroplasts, a large vacuole, and the cell wall. Check Your Learning Summarize the cell theory in your own words. Are your cells prokaryotic or eukaryotic? Explain. What is the most obvious difference between prokaryotic and eukaryotic cells? How does the nucleus coordinate cell activities? When you exercise, you breathe harder and faster. Using your knowledge of organelles, explain why this happens. Not all plant cells contain chloroplasts. What is the most likely reason for this? Plant cells are surrounded by a cell wall. What is the function of this structure? Plant cells can make their own “food”—glucose. Why do plant ceUse the Opposite WordAntonyms An antonym is a word that means the opposite of another word. Knowing the antonyms for some of the words you use will help to increase your vocabulary. For example: I think this movie will entertain me. I think this movie will bore me. In the example, entertain and bore are antonyms. By using antonyms, you can make your writing clearer. Read each pair of words below. Select the pairs that are antonyms. sink / float give / donate accept / deny capture / free collect / distribute order / command Check Answers Complete the sentences below by choosing an antonym for each word in Biology 19  parentheses ( ). When we breathe in, our lungs fill with air and (shrink) expand get smaller. Exercise causes our heart rate to (decrease) go slower increase. A fever may cause our body temperature to (fall) rise drop. Washing your hands (allows) prevents permits germs from spreading. Check Answers Find an article online and make a list of at least six verbs that you find. Think of an antonym for each one and write it next to the verb.Photosynthesis and Cellular Respiration Balance Each Other Try ThisWhere Does It Come From? Trees begin as tiny seeds and many become towering giants. Where does their mass and matter come from? In the 1600s, a physician and chemist from Brussels named Jan Baptista van Helmont designed and carried out an experiment to answer this question.He placed a small willow tree of 2.2 kg in a pot with about 90 kg of dried soil. He covered the top of the pot with a metal plate that had one hole for the trunk and smaller holes for watering. The only substance added to the pot during the experiment was water. After five years, van Helmont removed the tree and measured its mass as well as the mass of the soil. The mass of the tree was almost 77 kg. The soil had lost only 57 g. In recording his conclusions, van Helmont stated that about 75 kg of “wood, barks, and roots arose out of water only.” Was van Helmont correct with his conclusion about water? What was the energy source for the tree? What substances other than water did the tree use for its growth? Credit The Sun is the ultimate source of energy for almost all living things on Earth. Green plants and plant‑like organisms use the Sun’s energy to make their own food. To do so, they carry out a biochemical process called photosynthesis. During this process, cells in the green leaves and stems of these plants transform light energy into chemical energy. The chemical energy is stored in energy‑rich food compounds such as glucose, which is a type of sugar. Living things need to release the stored chemical energy to live. Another Biology 20  biochemical process takes place in their cells to make this happen. In the cells, glucose is broken down and its components are rearranged. This process, called cellular respiration, releases the energy, which can then be used for life functions. The table summarizes and compares details about photosynthesis and cellular respiration. Comparing Photosynthesis and Cellular Respiration Intentionally empty Photosynthesis Cellular Respiration What is it? a series of chemical changes in which green plants capture the Sun’s light energy and transform it into chemical energy that is stored in energy rich food compounds such as sugars a series of chemical changes that let living things release the energy stored in energy rich food compounds such as sugars to fuel all life functions Which living things use it? only green plants and plant-like organisms nearly all living things on Earth, including plants How is energy changed? light energy changed to chemical energy chemical energy changed to other forms of energy such as kinetic (motion) energy and heat What substances does it use? carbon dioxidewater glucoseoxygen What substances does it produce? glucoseoxygen carbon dioxidewater How can it be represented? light energy + carbon dioxide + water → glucose + oxygen glucose + oxygen → carbon dioxide + water + usable energy Why is it important? Photosynthesis transforms the Sun’s energy into a form that living things can use to survive Biology 21  Photosynthesis produces the oxygen that most living things need to survive Cellular respiration releases the energy that living things use to survive Cellular respiration produces the carbon dioxide that green plants need to carry out photosynthesis Notice that photosynthesis and cellular respiration are complementary processes. This means that they balance each other. Photosynthesis stores energy. This is balanced by cellular respiration releasing the stored energy. Photosynthesis uses carbon dioxide and water, and it produces glucose and oxygen. This is balanced by cellular respiration using glucose and oxygen and producing carbon dioxide and water. Each process makes the raw materials that the other process needs to store energy or to release energy. In this way, each process sustains the other. Together, both processes sustain life. Try ThisPhotosynthesis and Cellular Respiration Balance Each Other View both video clips. What is the source of energy for the organisms shown? What substances are required, and what is produced? Compare and contrast the energy-related processes involved. How are they related? Media player Play Restart Rewind Forward Volume Slower Faster Hide captions Turn on descriptions Show transcript Preferences Enter full screen 0:00 / 0:12Speed: 1xPaused Credit Media player Play Restart Biology 22  Rewind Forward Volume Slower Faster Hide captions Turn on descriptions Show transcript Preferences Enter full screen 0:00 / 0:15Speed: 1xPaused Credit Student Check-In Choose the correct answer from the choices provided. Photosynthesis can be performed by animals plants fungi. Check Answers Choose the best answer. Cellular respiration is a very important process for organisms. Which one of the following is necessary for cellular respiration to take place? sunlight water oxygen carbon dioxide Check Answers How did you make out? If you need to, now is a good time to go back and review any material. Checkpoint What forms of energy are transformed during photosynthesis and cellular respiration? Which substances are used and produced by photosynthesis and by cellular respiration? Describe how you have recently been part of the complementary processes of photosynthesis and cellular respiration.InvestigateModel How Photosynthesis and Cellular Respiration Cycle Carbon and Oxygen Biology 23  Photosynthesis and cellular respiration play key roles in the one‑way flow of energy through ecosystems. These two processes also play key roles in the cycling of matter, such as carbon and oxygen, in ecosystems. Scan the image. The labels will help you understand how photosynthesis and cellular respiration are complementary processes for the cycling of carbon and oxygen. Because this is a cycle picture, you can start reading at any point and follow the arrows. Credit Photosynthesis and cellular respiration interact with each other as part of a cycle of matter that uses and re- Biology 24