Introduction Chapter 1 Working scientifically x

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1 Contents Introduction v Chapter 1 Working scientifically x Thinking about x 1.1 Being a scientist Working safely Let s experiment Measuring and recording Let s investigate 22 Chapter review 26 Chapter 2 Understanding matter 28 Thinking about Matter The particle model of matter Changing states Heating up solids, liquids and gases 51 Chapter review 56 Chapter 3 Mixing and separating 58 Thinking about Pure substances and mixtures Colloids Separating mixtures Separating complex mixtures 83 Chapter review 88 Chapter 4 Electric circuits 90 Thinking about Switched on Series and parallel circuits Conductors and insulators Producing and using electricity 116 Chapter review 124 Chapter 5 Mysterious attraction 126 Thinking about Where s the attraction? Magnetic fields Static electricity Letting the sparks fly! 148 Chapter review 154 Chapter 6 Our place in space 156 Thinking about Finding out about the solar system Touring the planets How does Earth move in space? The mysterious Moon Effects of the Moon on the Earth 178 Chapter review 182 introduction Science Links 1 iii

2 Chapter 7 Cells of life 184 Thinking about Discovering cells A closer look at cells Cell specialisation From cell to organism 205 Chapter review 210 Chapter 8 Classification 212 Thinking about Classifying things Kingdoms we know best: plants and animals Other kingdoms: fungi, protista and monera 234 Chapter review 242 Chapter 9 New generations 244 Thinking about The reproductive organs Puberty Making more people Reproductive technology 264 Chapter review 274 Chapter 10 Skills link Fair tests Experimenting Scientific reports Measuring Investigating Cells Personal learning Collaborative learning 289 Index 292 About the authors iv Jacinta Devlin has taught general science, mathematics and VCE Physics over her ten years at Kilbreda College, Mentone. She co-authored the first edition of Heinemann Science Links 1 and 2, and was a contributing author to Heinemann Physics 12 2nd edition. Helen Cochrane is a general science, maths, biology and information technology teacher with over 20 years of experience. She now works as a science writer and consultant, with a special interest in research into human learning. Rhonda Coffey has taught science for 25 years in the Geelong region. She has always been keen to introduce ICT and investigative practices into the science curriculum, working in the three areas of science, ICT and library in schools. She has been a Science in Schools Professional Development Leader and currently works as a science writer. Contributing authors Esther Anderson, Rosetta Batsakis, David Coffey, Naomi Coghlan, Trish Kirley, Katrina Markwick, Julie Radford, Yvonne Sanders, Mira Starek, Lyn Tounson. Expert teacher review panel John Roberts (VELS Consultant), Brett Barber, Brian Harrison, Shameem Hashmi, John Maher, Paul Naughtin, Victoria Stats. Heinemann e n Science c Links 1

3 7. 1 Discovering cells One of the things that you did in the Thinking about was to write down how many times each specimen that you looked at had been magnified. Did you look at slides under a microscope? Microscopes and other magnifiers contain lenses that allow light to pass through them, but bend the light rays so that we can see things more clearly. Figure 7.2 Cork cells seen with a microscope by Robert Hooke in Figure 7.3 Cork cells under a light microscope stained with a fluorescent stain (2005). chapter cells of life 07 Figure 7.4 Different types of lenses carry out different functions. Microscopes and magnifi cation The magnification of a microscope tells you how much bigger the image is than the real object. If the microscope has a magnification of 400, then the image that you are looking at is 400 times bigger than the actual object. (The symbol in this case stands for magnified by ). To work out the magnification you must look at both the eyepiece (occular) lens and the objective lens of the microscope. Each has a number on it, such as 10 or 20. Multiplying these numbers together gives you the total magnification of the microscope. Ocular lens 10 Figure 7.5 Optical Microscope MagniÞcation = 400 Objective lens 40 Calculating the total magnification. 187

4 SCIENCE work Getting to know your microscope Light microscopes come in a variety of shapes and sizes; however, all of them have the same basic parts. Activity 7.2 What to do 1. With a partner, collect a microscope. Make sure you carry it with two hands, one around the arm and the other under the base; your teacher will show you how. Place your microscope on the bench away from the edge. You will also need your diagram of a microscope with labels and questions from Science@Work Look closely at your microscope and use figure 7.16 to find each of the labelled parts. Can you decide what each part is used for? 3. Table 7.2 contains a description and a function for each part of the microscope but they are all mixed up. Unscramble the information and write the corrected table into your book. 4. Compare your table with another group and discuss any differences. Table 7. 2 Parts of a microscope Name of part Description Function Figure A standard light microscope. Microscopes that are used in schools may look a little different from those used in laboratories, but they essentially work the same way. eyepiece (ocular) lens objective lens focus knob base mirror stage Flat bottom surface. Flat surface to sit slides on, has hole in its centre, may have clips. Iris like aperture which can be adjusted to allow light through. Knob that can be turned to move the lenses. The adjustable tube between the eyepiece and objective lenses. Lenses of different lengths which can be positioned above the slide. Holds the slide in place, letting light pass through it. Adjusts the position of the lenses so that the object can be seen clearly: can be coarse or fine. Light travels through it to the eyepiece lens. Controls the amount of light passing through the object. Supports the microscope. Reflects light up through the slide into the lenses. diaphragm Round with a shiny surface. Used to locate specimen, then get different magnifications. microscope tube Single lens closest to the eye. Enables you to see magnified specimen. 192 Heinemann e n Science c Links 1

5 SCIENCE work Using a microscope Aim To become familiar with the use of a microscope. EXPERIMENT 7.3! Materials light microscope tissue mini grid (optional) microscope lamp with filter newspaper slides and cover slips tweezers cotton wool hair clear plastic ruler fabric Part A: How big is it really? Method 1. Collect a microscope and carry it with both hands to the workbench, placing it well away from the edge. 2. Work out the magnification of your microscope when using the low and high power lenses. 3. Adjust your mirror so that an appropriate amount of light passes through the hole in the stage. 4. Place a clear plastic ruler on the stage of your microscope so that you can focus on the millimetre scale. Once you have focused your microscope, the area that you can see is called the field of view. It should appear as a round circle of light. 5. Using your low power objective lens, measure the width of your field of view. Note this down in your book. 6. Using your high power objective lens, measure the width of your field of view. Note this down in your book. How does it compare with your field of view using the low power objective lens? Extension Your teacher may have a mini grid that you can use to estimate the size of what you see under the microscope. Learn how to use the mini grid and then estimate the width of a strand of your hair. If you don t have a mini grid, remember the width of your field of view measured above and use this to estimate the width of the hair. Compare your hair with other people s hair is it thicker or thinner? Is blonde, red or dark hair thickest? Compare curly and straight hair is there a difference in the thickness? Part B: Upside down and back-to-front Method 1. Cut out a 1 cm square piece of newspaper. Make certain that it contains the letter e. 2. Place the print onto a microscope slide. Place a cover slip over the top of this. 3. Use the low power objective lens. While watching from the side, use the coarse adjustment to lower the objective lens until it is just above the stage. Note: Pressing it down too far may shatter the slide. 4. While looking through the eyepiece, carefully turn the coarse adjustment until the specimen can be clearly seen. 5. Carefully use the fine adjustment so that you can see the details of your specimen as clearly as possible. 6. Carefully move the slide until you have an e in focus. 7. Pencil a sketch of what you see. Is it right side up, upside down or back-to-front? How much of the field of view is covered by the e at this magnification? 194 Heinemann e n Science c Links 1

6 8. In which direction did the paper under the microscope move when you moved the slide to the left? What about when you moved it towards you? 9. Record the magnification that you are using. Evaluation What difficulties did you encounter while using the microscope? How could you improve your microscope technique? Extension Look at some other specimens, such as tissue, cotton wool, coloured paper and fabric. Sketch what you see and label the diagrams clearly. Remember to write down the magnification that you are using. questions Why are scientists who study the structure and function of cells called microbiologists? 2. List and describe ten things that scientists have found out using microscopes. 3. Create a T-chart covering the two main types of microscope and list the main similarities and differences between them. 4. Why was the invention of the electron microscope so important? List its advantages and disadvantages. 5. If you wanted a very detailed image of a cell, which microscope would you use? 6. List three ways in which an image seen under a microscope can differ from the original specimen placed onto the stage. 7. Outline the steps you would follow to obtain a clear focus using a light microscope on low and high power. 8. How many micrometres are there in one millimetre? If a cell is 50 µm in diameter, how big is it in millimetres? Would we be able to see this cell without a microscope? 9. What is the field of view of a microscope? How can it be used to estimate the actual size of objects placed under the microscope? 10. If our eyes can see things as small as 0.1 µm, and one cell is one-tenth of this size, what is the size of the cell in micrometres? 11. Create a poster or multimedia presentation covering the types of microscopes, when they were invented and by whom. chapter cells of life A closer look at cells scifile There is no typical cell shape. If we look at cells in the human body we fi nd column cells lining the stomach; balloon-shaped cells lining the bladder; red blood cells shaped like doughnuts in the blood stream; and fl at cells shaped like pancakes on the surface of the skin. Some bacteria cells are shaped like rods and spirals. Guard cells in the leaves of plants are shaped like small sausages. As microscopes developed over the years, scientists began to observe plants and animals in detail. Everywhere they looked they found cells. After careful observation and reading the work of other scientists, two German scientists, Matthias Schleiden and Theodor Schwann, developed the first two principles of the cell theory. Cell theory 1. All living things are made up of cells. 2. Cells are the basic units of structure and function in living things. Further work by Rudolf Virchow lead to the third principle. 3. All cells arise from pre-existing cells. 195

7 science science in action viruses are they ALIVe? Viruses are able to infect us and take over our cell functions so that they can trick us into making more of them. Apart from getting sick, we can't tell that they're in our bodies without complex technology. Viruses don t have cells like other organisms. This means that they don t have a nucleus, cell membrane or cytoplasm. However, they do have some chemicals found only in living cells. Viruses consist of a protein box that contains a strand of nucleic acid. This strand contains the instructions for making new viruses. When they get into living cells, viruses behave as though they are alive. When they are outside cells they don t display the characteristics of living things. Viruses are therefore not described as living, because they can t function independently. A virus may lie dormant for many years until it comes into contact with a living cell. Then it invades the cell and tricks it into making many, many new viruses. This eventually kills the host cell as it bursts open to release millions of new viruses into the body. Human diseases caused by viruses include influenza, acquired immune deficiency syndrome (AIDS), chickenpox and measles. protein capsule DNA inside Figure 7.22 This is the shape of a common virus. Did you know that they are measured in nanometres (nm)? A nanometre is equivalent to a millionth of a millimetre. legs to grip host cells are they alive? questions 1. How do viruses differ from animals and plants? 2. Are all viruses the same shape and size? 3. What features do viruses have in common with living things? 4. Do you think that viruses are living or non-living? Give reasons for your answer. 5. Create a poster or a PowerPoint presentation about one of the viruses mentioned above and its effect on humans. Include information about the shape of the virus, the symptoms of the disease, what can be done to prevent it and the treatments used. 199

8 SCIENCE work Making your own animal and plant cell Once you have collected the worksheets from your teacher, cut out the cell parts. Colour the cell parts so they will be easier to see. Paste the parts on the cell templates provided. Label the animal cell, the plant cell, and all of the organelles in each. Activity 7.7 questions Explain the cell theory using a poem, rhyme or role play. 2. What do all living things have in common? 3. What is an organelle? Name five organelles and state their function. 4. Where are the proteins made in a cell? 5. What is cytoplasm and where is it found? 6. What is the function of the cell membrane? What do you think would happen to a cell if its membrane burst? 7. What does a nucleus do? What would happen if it were damaged? 8. Write a short story or cartoon called Journey to the centre of the cell. You should describe what you see and how you move. 9. A biologist was studying the parts of a cell. She removed the nucleus from a skin cell with a very fine pipette, and found that the cell died within a few hours. What does this tell you about the importance of a nucleus? Present your answer as a journal entry Cell specialisation scifile Red blood cells do not have a nucleus! They lose this just before being released into the bloodstream so that they can be packed with oxygen-carrying haemoglobin. This means that they only live for about four or fi ve months and then die at a rate of two million per second! In a healthy body, new red blood cells are made at the same rate. Most plants and animals are made up of many different types of cells. They have different shapes and sizes because they have different jobs to do. Skin cells, for example, are a flattened pancakelike shape, whereas the cells lining your stomach are like house bricks standing on their ends. Cells are quite complex things, and they can perform a wide range of tasks including: ü taking in nutrients and carrying out chemical reactions ü producing waste products ü making useful substances such as bone ü reproducing by dividing in two ü moving, for example, some special cells such as muscle cells can contract, while sperm cells can swim ü exchanging gases with their surroundings ü capturing light energy from the sun, which is used to convert carbon dioxide and water to sugar. Does this list sound familiar? It should! Anything an organism can do is a result of its cells. 200 Heinemann e n Science c Links 1

9 KEY TERMS 07 cell division cell membrane cells cell theory cell wall chlorophyll chloroplast cilia cytoplasm magnification microscope nucleus organ organelles photosynthesis stomata system tissue vacuole Chapter review key ideas P O P Y G J H F W O X Z F C V U Z E M M A G N I F I C A T I O N C M M H K I X O I E L R E V Y J R Y H Q P C F T X I W T P S L U W O A P L N R E X O R G A N A Q L K B L S O O U B L M C R Y Y R Q T T E I T F L R C W L N H I G J Q U D H I Y P J S O L V M G O V C A Q L C E L L V U L P E C E T N M R J N B D O C Y T O P L A S M Z D I C C J I J R Y S M Q R A R Y B G R C M Y C H S Y D Y Z F H S M I R D I R I B O S O M E S S B J T E D A T O O F H H Q X O Z T L W O L M Z N X N S W N U H K D S E I S X L B J E H W C H R O M O S O M E S U D R Y H M G O Z E E H N U C L E U S U A Z C S E P I Z S L A W N B J I Q U N N T Y C E L L W A L L V A C U O L E O L Use the list of clues, the key terms and table 7.4 to help you find the words in the puzzle. Some ideas or rules about cells. A very thin boundary around the nucleus of the cell. A storage area of the cell that is full of fluid. The basic building blocks of all living things Many cells working together to do the same job. Many tissues working together to do the same job. Many organs working together to do the same job. All the systems together. A tool that helps us to see small things, such as cells, that we cannot see with our eyes. How many times bigger the object looks than it really is. Strong microscopes magnify objects many times. A living, jelly-like material that makes up the inside of cells. It has lots of chemicals and cell parts in it. The control centre of the cell. It is a bit like the brain of the cell. Small parts of the cell that make the energy for the cell to work. A thin boundary around the cell that keeps things in cells and lets some things that are needed into the cells. Little round parts of cells that make chemicals called proteins. Proteins are needed so that we can survive and grow. Chemicals in the nucleus of the cell that carry all the information we get from our parents. A boundary around the cell that gives the plant cells a definite shape. Plant cell walls help to give plants shape because plants do not have bones or skeletons like many animals. Green parts of plant cells that carry out the chemical reaction called photosynthesis. Photosynthesis turns light energy from the sun into chemical energy (carbohydrates) that animals can use for energy to survive when plants are eaten. 210 Heinemann e n Science c Links 1

10 review questions 1. Copy and complete the following table: Cell feature Plant cells Animal cells cell wall cytoplasm cell membrane large vacuole nucleus chloroplasts 2. A student was using a light microscope to observe some cells. She was using a 5 ocular and a 40 objective lens. How many times is the cell magnified? If she changed to a 100 objective, would she see fewer or more cells? Explain your answer. 3. If a cell is 50 µm wide, how many cells would be needed to span a distance of 4 cm? 4. Choose the correct word to complete the following sentences. (a) The part that controls what a cell does is the cytoplasm/membrane/nucleus/vacuole. (b) The process that takes place in a chloroplast is called growth/photosynthesis/cell reproduction/ movement. 5. Decide if the following statements are true or false. Rewrite the false statements to make them true. (a) Animal cells have cell walls. (b) A virus can only be seen with an electron microscope. (c) The average cell is 1 mm across. (d) Cells reproduce by dividing in two. (e) Light microscopes can magnify 3000 times. reflection cells 6. Match each of the following cell names with one of the diagrams below. Make a concept map covering their purposes in the human body. goblet cell, motor nerve cell, muscle cell, white blood cell, brain cell, egg cell 7. How could a microscope be used to help solve a crime? Present your answer as a news report or poster. 8. Why would there be many mitochondria in nerve and muscle cells? What is their purpose? 9. What are guard cells? What do they do? What are their two main stages? Draw diagrams to represent these stages. 10. Some scientists (called cytologists) study life processes by growing and observing cells in a laboratory. Find out how cell cultures are maintained and what scientists can learn by studying them. Present your answer in a format of your choice. complete 1. Complete the Mission that you began at the start of this chapter and present it to the class. Ask the class for feedback on your model. Make any improvements suggested by the class. 2. Imagine that you are one of the following: a skin cell on someone s face a red blood cell a muscle cell in a leg a motor nerve cell in the spinal cord a photosynthesising cell in a leaf a guard cell in a leaf a transport cell in a plant stem. Find out about your chosen cell, and then write an illustrated story, role play or diary entry about a day in your life. 211