Lesson Notes By Weeks and Term v4 - SHS 1
BIOLOGY AS THE SCIENCE OF LIFE
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BIOLOGY AS THE SCIENCE OF LIFE
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Subject: Biology
Class: SHS 1
Term: 1st Term
Week: 5
Grade code: 1.1.1.LI.2
Strand code: 1
Sub-strand code: 1
Content standard code: 1.1.1.CS.4
Indicator code: 1.1.1.LI.2
Theme: EXPLORING BIOLOGY IN SOCIETY
Subtheme: BIOLOGY AS THE SCIENCE OF LIFE
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Biology is the study of life, but much of life is too small for our naked eyes to see. The bacteria that can make us sick, the tiny organisms in a drop of water from the Densu River, and the very cells that make up a leaf of a cassava plant are all part of this invisible world. To study life properly, we need a tool to make these things visible. That tool is the microscope. In Ghana, doctors at Korle-Bu use microscopes to diagnose diseases like malaria by looking for parasites in blood. Scientists at the Cocoa Research Institute (CRIG) use them to study diseases affecting our precious cocoa pods.
A. What is a Microscope? A microscope is a scientific instrument that uses lenses to make very small objects appear larger, allowing us to see their details. The type we will use in our lab is the compound light microscope, which uses a combination of lenses and a light source to magnify an object. B. Parts of the Compound Light Microscope Let's break down the microscope into its main parts. It's like learning the parts of a car before you can drive it.
(i) Optical Parts (The parts for seeing) Eyepiece (or Ocular Lens): This is the lens you look through at the top of the microscope. It usually has a magnification of 10x or 15x. Objective Lenses: These are the lenses closest to the specimen. They are mounted on a rotating turret called the Revolving Nosepiece. Most school microscopes have three: Scanning Power (shortest): Usually 4x magnification. Low Power (medium): Usually 10x magnification. High Power (longest): Usually 40x magnification.
(ii) Mechanical Parts (The support and movement system) Body Tube: Connects the eyepiece to the objective lenses. Arm: The part that connects the head of the microscope to the base. You hold this part when carrying the microscope. Base: The bottom of the microscope, used for support. You place one hand under the base when carrying it. Stage: The flat platform where you place the slide for observation. Stage Clips: Metal clips that hold the slide securely in place on the stage. Revolving Nosepiece: A rotating turret that holds the objective lenses. You turn it to switch between different magnifications. Coarse Adjustment Knob: The large knob used for focusing the image under low power. NEVER use it on high power, as you can crash the lens into the slide and break them both. Fine Adjustment Knob: The smaller knob used for sharp, precise focusing, especially on high power.
(iii) Illumination System (The parts for lighting) Diaphragm (or Iris): A rotating disc under the stage that controls the amount of light reaching the specimen. You might need less light for a transparent specimen and more for a darker one. Light Source (Illuminator): Either a mirror that reflects ambient light up through the specimen, or a built-in electric lamp. C. Important Concepts: Magnification and Resolution Magnification: This is how much larger the microscope makes an object appear. To find the Total Magnification, you multiply the power of the eyepiece lens by the power of the objective lens you are using.