Calculating the size of an organism using a scale bar

How do you know the size of a microorganism? You will notice that many pictures of microorganisms have a scale bar. A scale bar is a very useful tool that allows us to calculate the actual size of objects. Follow the instructions below to figure out the length of this Oxytricha trifallax protist.

INSTRUCTIONS:

a) Measure the length of Oxytricha trifallax using your ruler. (Express your answer in mm.)

b) Measure the length of the scale bar with your ruler. (Express your answer in mm.)

c) To find the actual size of the organisms, take your answer and multiply it by the number on the scale bar. The units on the scale bar are in μm and so your answer must be in μm. How big is Oxytricha trifallax?

d) How many μm are there in a mm?

e) How many Oxytricha trifallax could lie end to end in 1 mm?