Numbers

• What is the focus of the study material?

  Biology Papers 1 & 2
• What is standard form in mathematics?

  • Two parts: a number between 1 and 10, and a power of 10
  • Example: $7.3 \times 10^4$
• How can standard form be used?

  To write very large or very small numbers
• What is the power of 10 for numbers greater than 1?

  Positive power of 10
• How is the number 920000 expressed in standard form?

  1. 2 x 10⁵
• What is the power of 10 for numbers less than 1?

  Negative power of 10
• How is the number 0.00703 expressed in standard form?

  1. 03 x 10^-3
• How do you convert between standard form and ordinary numbers?

  • Count decimal places
  • Example: $7900 =$$7.9 \times 10^3$ (4 jumps)
  • Example: $0.000035 =$$3.5 \times 10^{-5}$ (5 jumps)
• What should you be careful about when counting for standard form?

  Don't just count zeros to work out the power
• How do you convert 1 g to micrometres?

  1. Convert grams to metres: $1g =$$10^{-9}m$
  2. Write in standard form: $1 \times 10^{-9}m$
  3. Convert to micrometres: $10^{-9} \times 10^{6} =$$10^{-3}m$ or 0.001m
• What does "micro" mean in terms of powers of ten?

  10^-6
• What are the average sizes of the following structures in nanometres? (protein molecule, chloroplast, cell)

  • Protein molecule: 2 nanometres
  • Chloroplast: 10 nanometres
  • Cell: 0.1 millimetres
• How long is a hen's egg in standard form?

  6 cm = 6 x 10⁰ cm
• How long is a hen's egg in micrometres?

  60000 micrometres
• If a bacterial cell is 3μm long, how would you estimate its width?

  Estimate based on typical bacterial cell dimensions
• What is the procedure for using a light microscope?

  1. Start with the lowest magnification
  2. Clip the slide onto the stage
  3. Adjust the focus knobs to bring the image into view
• What is the first step when using a light microscope?

  Always start with the lowest magnification
• What should you do after clipping the slide onto the stage?

  Adjust the focus knobs to bring the image up through the eyepiece