Practise your skills of proportional reasoning with this interactive haemocytometer.

Estimate these curious quantities sufficiently accurately that you can rank them in order of size

Examine these estimates. Do they sound about right?

Work with numbers big and small to estimate and calulate various quantities in biological contexts.

Work out the numerical values for these physical quantities.

Work with numbers big and small to estimate and calculate various quantities in biological contexts.

Which units would you choose best to fit these situations?

How many generations would link an evolutionist to a very distant ancestor?

When you change the units, do the numbers get bigger or smaller?

Work with numbers big and small to estimate and calculate various quantities in physical contexts.

Could nanotechnology be used to see if an artery is blocked? Or is this just science fiction?

How would you go about estimating populations of dolphins?

Can you rank these sets of quantities in order, from smallest to largest? Can you provide convincing evidence for your rankings?