Magnify-cent Biology!!
IB Biology
Topic 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
Now try the Magnification Revision
poster as a group!
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.
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.
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