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Biology

Biology. The Study of Life. Cell Theory: Before Microscopes. Before microscopes, most people believed in spontaneous generation (The belief that living things could arise from non-living matter). 1668: Francesco Redi attempts to disprove the spontaneous generation in maggots.

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Biology

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  1. Biology The Study of Life

  2. Cell Theory: Before Microscopes • Before microscopes, most people believed in spontaneous generation (The belief that living things could arise from non-living matter). 1668: Francesco Redi attempts to disprove the spontaneous generation in maggots. 1745: John Needham attempts to prove spontaneous generation. Attributes results to a “life force” Spontaneous generation was upheld until the mid-1800s.

  3. In 1859, Louis Pasteur finally disproved the theory of spontaneous generation.

  4. Used a swan-shaped flask to show that if no microbes could get into the broth, nothing would grow • What made his experiment good? Controlled Variables - Same broth, light, temp. Manipulated Variable - Whether or not microbes have access to broth Responding Variable - Whether or not microbes grew What impact do you think this had on medical practice.

  5. The Development of the Microscope • Explain the following statement: • “You may owe your life to the invention of the microscope.” • 1595: The Janssen Bros. invent the first microscope. • - It was compound (2 lenses)

  6. 1665: Robert Hooke improves on the design • - Observes first tiny units of life and calls them “cells”

  7. Antoni van Leeuwenhoek was the first person to see living cells.

  8. Cell Theory: Gets It’s Start … • 1839: M.J. Schleiden, Theodor Schwaan put forth a three part cell theory: 1)All living things are made up of one or more cells.

  9. 2) Cells are the smallest functional units of organisms (i.e. the organism’s needs are the cells’ needs). - Take in nutrients - Use energy to do work (life processes) - Get rid of wastes - Maintain certain temperatures and chemical conditions (e.g. acidity) Multi-cellular organisms are just cells working together to accomplish these basic tasks Cell Tissue Organ System Body

  10. 3)All cells come from pre-existing cells through the process of cell division. (not from spontaneous generation)

  11. Microscopes as Windows to Cells • The Compound Light Microscope • Light passes through the specimen • Lenses enlarge, or magnify, the image. • micrometres (μ)are used to measure very tiny objects. (1mm = 1000μm) (a) Light micrograph (LM) of a white blood cell (stained purple) surrounded by red blood cells

  12. Magnification • An increase in the specimen’s apparent size. • To calculate the magnification of the microscope – ocular x objective

  13. F.O.V. • Field of View (F.O.V.): The diameter of the circular region of the slide visible under the microscope • the higher the magnification, the smaller the field of view.

  14. Field of view can be used to estimate the actual size of objects

  15. The field of view under higher magnification can be less than 1mm. We can estimate by using the low magnification and F.O.V. in a formula. Determining the F.O.V. of Higher Magnifications

  16. Determining the F.O.V. of Higher Magnifications Example: High F.O.V. (HP) = Low F.O.V. (LP) x LP magnification ÷ HP magnification Example: HP magnification = 40X LP magnification = 4X LP F.O.V. = 4500µm HP F.O.V. = 4500µm x 4X ÷ 40X HP F.O.V. = 4500µm x 0.1 HP F.O.V. = 450µm

  17. Resolution • The ability to distinguish individual objects. • The greater the magnification, thesmaller the objects that can be resolved.

  18. Contrast • dark vs. bright • phase contrast microscopes enhance contrast.

  19. Nucleus is stained Fluorescent Stains Staining • used to increase contrast and to show specific parts of cells.

  20. It uses a beam of electrons • It has a higher resolving power than the light microscope • The Electron Microscope (EM)

  21. Human height Length of some nerve and muscle cells Chicken egg • The electron microscope can magnify up to 100,000X Unaided eye Frog eggs Plant and animal cells Nucleus • Such power reveals the diverse parts within a cell Light microscope Most bacteria Mitochondrion Electron microscope Smallest bacteria Viruses Proteins Small molecules Atoms

  22. SEM • The scanning electron microscope (SEM) is used to study the detailed architecture of the surface of a cell (b) Scanning electron micrograph (SEM) of cilia (above) And a white blood cell

  23. TEM • The transmission electron microscope (TEM) is useful for exploring the internal structure of a cell (c) Transmission electron micrograph (TEM) of a white blood cell & cilial

  24. Homework • Read page 510 of your textbook and complete the Instant Practice Problems • Using page 508 of your textbook, completely label the microscope picture.

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