Magnify-cent Biology!!

IB Biology Topic 2

Learning OutcomesEveryone 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 cellCalculate the magnification factorThe line 5 m is 20 mm long. So 20 000 m = 5 mMagnification is 20 000/5 = x 4 000. Calculate the length of structure GLength of G is 12 mm = 12 000 m Magnification is x 4 000Real size is 12 000/4000 = 3 m Calculate the diameter of structure BDiameter is 8 mm = 8 000 m Magnification is x 4 000Real size is 8 000/ 4 000 = 2m Calculate the diameter of the nucleusDiameter is 36 mm = 36 000 mMagnification is x 4 000so real size is 36 000/4 000 = 9 m Calculate the diameter of the cell at its widest point109 mm = 109 000 m = 109 000/4 000 = 27–25 mFor all the answers above there is a tolerance limit of + or – 0.5mm, so + or – 0.1 – 0.2 mThere 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 longTherefore, 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 625Actual 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 625Actual length is 120 000/625 = 192 m Calculate the length of structure C.29 mm = 29 000 m magnification is x 625Actual length is 29 000/625 = 46.4 m Calculate the length of the vacuole.80 mm = 80 000 m magnification is x 625Actual length is 80 000/625 = 128 m.

Learning OutcomesEveryone 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