1. Magnify-cent Biology!! IB Biology Topic 2

2. Learning Outcomes Everyone should: Compare relative sizes of biological molecules, viruses, cells and bacteria using appropritate SI units Most will: Calculate magnification from a scale bar Some might Calculate magnification and actual size of biological drawings and specimens

17. Now try the Magnification Revision poster as a group!

18. Answers for the animal cell Calculate the magnification factor The line 5  m is 20 mm long. So 20 000  m = 5  m Magnification is 20 000/5 = x 4 000. Calculate the length of structure G Length of G is 12 mm = 12 000  m Magnification is x 4 000 Real size is 12 000/4000 = 3  m Calculate the diameter of structure B Diameter is 8 mm = 8 000  m Magnification is x 4 000 Real size is 8 000/ 4 000 = 2  m Calculate the diameter of the nucleus Diameter is 36 mm = 36 000  m Magnification is x 4 000 so real size is 36 000/4 000 = 9  m Calculate the diameter of the cell at its widest point 109 mm = 109 000  m = 109 000/4 000 = 27–25  m For all the answers above there is a tolerance limit of + or – 0.5mm, so + or – 0.1 – 0.2  m There are other perfectly correct ways of doing the calculation, so if your method is different, but arrives at the correct answer, then that is fine.

19. Answers for the plant cell Calculate the magnification factor. The line representing 40  m is 25 mm or 25 000  m long Therefore, magnification factor is 25 000/40 = x 625. Calculate the thickness of the cellulose cell wall. Wall is 3.0 mm = 3 000  m Magnification is x 625 Actual thickness of wall is 3 000/625 = 4.8  m Calculate the length of the cell. 120 mm = 120 000  m magnification factor is x 625 Actual length is 120 000/625 = 192  m Calculate the length of structure C. 29 mm = 29 000  m magnification is x 625 Actual length is 29 000/625 = 46.4  m Calculate the length of the vacuole. 80 mm = 80 000  m magnification is x 625 Actual length is 80 000/625 = 128  m.

20. Learning Outcomes Everyone should: Compare relative sizes of biological molecules, viruses, cells and bacteria using appropriate SI units Most will: Calculate magnification from a scale bar Some might Calculate magnification and actual size of biological drawings and specimens