Paper 1

• What are the key microscopy techniques students should understand?

  • Development of microscopy techniques over time
  • Impact of electron microscopy on understanding sub-cellular structures
• How does electron microscopy differ from light microscopy?

  It has higher magnification and resolution
• What does higher magnification in electron microscopy allow biologists to do?

  Study cells in finer detail
• What is the formula for calculating magnification?

  magnification = size of image / size of real object
• How should answers be expressed if appropriate in calculations?

  In standard form
• How do bacteria multiply?

  By binary fission
• Under what conditions can bacteria multiply rapidly?

  If they have enough nutrients and suitable temperature
• What are two methods to grow bacteria?

  Nutrient broth solution and agar gel plate
• Why are uncontaminated cultures of microorganisms important?

  For investigating disinfectants and antibiotics
• How can the number of bacteria in a population be calculated?

  Using the mean division time
• What formula is used to calculate the cross-sectional area of colonies?

  Area = $\pi r^2$
• What are the aseptic techniques for preparing uncontaminated cultures?

  • Sterilize Petri dishes and culture media
  • Sterilize inoculating loops by flame
  • Secure Petri dish lid with adhesive tape
  • Store Petri dish upside down
  • Incubate cultures at 25°C
• What is the purpose of sterilizing Petri dishes and culture media?

  To prevent contamination
• Why should inoculating loops be sterilized before use?

  To eliminate unwanted microorganisms
• Why should the lid of the Petri dish be secured with adhesive tape?

  To prevent contamination
• At what temperature should cultures generally be incubated in school laboratories?

  25°C
• What is the importance of using estimations in biology?

  To judge relative size or area of structures
• What is the required practical activity for observing cells?

  • Use a light microscope
  • Observe, draw, and label plant and animal cells
  • Include a magnification scale
• How do different types of cells relate to their function?

  Structure of cells is specialized for function
• What types of specialized cells are found in animals?

  • Sperm cells
  • Nerve cells
  • Muscle cells
• What types of specialized cells are found in plants?

  • Root hair cells
  • Xylem cells
  • Phloem cells
• What is the importance of cell differentiation?

  It allows formation of different cell types
• When do most types of animal cells differentiate?

  At an early stage
• Do many types of plant cells retain the ability to differentiate throughout life?

  Yes
• What is the main purpose of cell division in mature animals?

  Repair and replacement of cells
• What do chromosomes contain?

  DNA molecules
• How are chromosomes typically found in body cells?

  In pairs
• What is the cell cycle?

  A series of stages for cell division
• What happens to genetic material during the cell cycle?

  It is doubled and then divided
• What must a cell do before it can divide?

  Grow and increase sub-cellular structures
• What occurs during mitosis?

  Chromosomes are pulled to each end of the cell
• What divides to form two identical cells at the end of mitosis?

  The cytoplasm and cell membranes
• What is a stem cell?

  An undifferentiated cell capable of differentiation
• What can stem cells give rise to?

  Many more cells of the same type
• Where are stem cells found in plants?

  In meristems
• What can stem cells from human embryos be made to differentiate into?

  Most different types of human cells
• What types of cells can stem cells from adult bone marrow form?

  Many types including blood cells
• What is the potential benefit of stem cell treatment?

  Help conditions like diabetes and paralysis
• What is therapeutic cloning?

  Producing an embryo with the same genes as the patient
• Why might stem cells from embryos not be rejected by a patient?

  They have the same genes as the patient