Magnification

• At what point in their life cycle do most animals cell differentiate?


  early in their life cycle
• for how long do plant cells retain the ability to differentiate


  throughout their entire life cycle
• What is the purpose of cell division in mature animals?


  to repair and replace cells
• What changes does a cell go through as it differentiates?


  changes in gene expression and cell structure
• Define magnification?


  The number of times an image appears bigger compared to the size of the real object��
• Define resolution?


  The smallest distance between two objects that can be distinguished
• How does a light microscope work?


  passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed
• Advantages of a light microscope


  .inexpensive

  .easy to use

  .portable

  .observes both living and dead specimens
• Disadvantages of a light microscope?

  limited resolution
• How does an electron microscope work?


  It used a beam of electrons which are focused using magnets. The electron hit a fluorescent screen which emits visible light, producing an image
• Name 2 types of electron microscope


  Transmission electron microscope (TEM)

  Scanning electron microscope (SEM)
• Advantages of a electron microscope?


  Greater magnification and resolution than a light microscope
• Why do electron microscopes have a greater mag and resolution?


  they use a beam of electrons which has a shorter wavelength than photons of light
• How have electron microscopes enable scientists to develop understanding of cells?


  .allow small sub-cellular structures to be observed in detail

  .enable scientists to develop more accurate explanations about cell structure relates to function.
• Disadvantages of an electron microscope?


  .expensive

  .large so less portable

  .requires training to be used

  .only dead specimens can be observed
• Magnifications formula


  size of image/ size of real object