Observing Living Things

Transcription

1 Observing Living Things Textbook pages 8 21 Before You Read Section 1.1 Summary This section describes the signs that scientists look for to help them decide if something is living or non-living. On the lines below, list two living things and then list two non-living things. Mark the Text Identify Details As you skim the section, use one colour to highlight the text or labels that talk about parts of a microscope. Use another colour to highlight facts about microscopes. Reading Check 1. What are two things that a microscope does? How can you tell if something is living or non-living? All living things have certain characteristics in common. Something is living if it has all of these characteristics: responds to its environment needs energy grows reproduces gets rid of wastes that build up in its body Another name for a living thing is organism. All organisms are made up of cells. A cell is the smallest living part of a living thing. Single-celled organisms are called unicellular. Organisms made of many cells are called multicellular. How can you see cells? Most cells are too small to see with just your eyes. You need a microscope to see them. At school you use a compound light microscope. It is a compound microscope because it combines two lenses. It is a light microscope because it uses light to view an object. A compound light microscope is shown on the next page. A microscope helps you focus two objects or details that are close together. This is called resolving power. A microscope also makes an object seem larger than it is. This is called magnification power. When you look into a microscope, the object you see is magnified, reversed, and turned upside down (inverted). 2 MHR Observing Living Things 2006 McGraw-Hill Ryerson Limited

2 A. eyepiece: has a lens you look through to magnify the image made by an objective lens B. objective lenses: lenses with different magnification power to magnify the object C. stage: a platform for the object you view D. light source: shines light through the object you view E. arm: supports the eyepiece F. coarse focus knob: focusses an object at low or medium power G. fine focus knob: focusses an object at high power Section 1.1 Summary continued The eyepiece lens often has a magnification power of 10. This means that an object seems ten times larger when you look at it with the lens. Each objective lens has its own power of magnification. The low-power lens is 4. The mediumpower lens is 10. The high-power lens is 40. How large does an object look when you combine the eyepiece lens with each objective lens? Use the table below to find out. Power of objective lens Power of eyepiece lens Calculation (power of objective lens multiplied by power of eyepiece lens) low power: = medium power: = high power: = Total magnification of the lens combination Reading Check 2. How large will an object look if you use a 4 eyepiece lens with a low-power objective lens? Are there stronger types of microscopes? A light microscope can magnify an object up to An electron microscope is much stronger. An electron microscope uses electrons instead of light to make an object look larger. One type of electron microscope is called a scanning electron microscope. It can magnify an object up to A camera or a monitor can be hooked up to an electron microscope. The picture that appears on the camera film or on the screen is called an electron micrograph. Many of the pictures in Chapter 1 of BC Science 8 are electron micrographs McGraw-Hill Ryerson Limited Observing Living Things MHR 3

3 Analyzing Information Use with textbook page 11. Characteristics of living things List five characteristics of living things. Give an example for each characteristic. Characteristic of living things Example MHR Observing Living Things 2006 McGraw-Hill Ryerson Limited

4 Interpreting Illustrations Use with textbook page 12. The compound light microscope Identify the following parts of a compound light microscope McGraw-Hill Ryerson Limited Observing Living Things MHR 5

5 Use with textbook pages Microscopes Vocabulary coarse focus knob compound light microscope electron micrograph eyepiece fine focus knob light source magnification power objective lenses resolving power reversed right side up upside down Cloze Activity Use the terms in the vocabulary box to fill in the blanks. Use each term only once. You will not need to use all the terms. 1. The _ is the microscope usually used in science classes and medical laboratories. 2. The _ is used for viewing and contains a lens that magnifies. 3. The _ brings an object into focus at low or medium power. 4. The _ brings an object into focus at high power. 5. The _ have different magnification power to magnify the object. 6. The _ supplies the light needed to view the slide. 7. The ability to distinguish between objects that are very close together is called _. 8. When you look through a microscope, you will observe an image that is magnified,, and. 9. A(n) _ is a picture taken by a camera hooked up to an electron microscope. 6 MHR Observing Living Things 2006 McGraw-Hill Ryerson Limited

6 Assessment Use with textbook pages Observing living things Match each Term on the left with the best Descriptor on the right. Each Descriptor may be used only once. Term 1. compound light microscope 2. objective lenses 3. eyepiece 4. stage 5. arm 6. total magnification 7. resolving power Descriptor A. power of the objective lens multiplied by the power of the eyepiece B. has two sets of lenses C. used for viewing and magnifying the image D. ability to distinguish between two objects that are very close to each other E. supports the eyepiece F. have different magnification powers to magnify the object G. supports the slide Circle the letter of the best answer. 8. Which of the following is not a characteristic of living things? A. needs energy B. hunts for food C. grows D. reproduces 9. What is the difference between a unicellular and a multicellular organism? A. size of cells B. structure of cells C. shape of cells D. number of cells 10. Which of the following is not a use of a microscope? A. magnifies distant objects B. magnifies objects that are close together C. magnifies unicellular organisms D. magnifies cells 11. Which of the following best describes an electron micrograph? A. a type of electron microscope B. a camera hooked up to an electron microscope C. a picture shown on a screen hooked up to an electron microscope D. a scanning electron microscope 12. If the objective lens is 40 and the eyepiece lens is 10, what is the total magnification? A. 400 B. 40 C. 10 D If the objective lens is 10 and the eyepiece lens is 10, what is the total magnification? A. 10 B. 100 C D McGraw-Hill Ryerson Limited Observing Living Things MHR 7