Practise your skills of proportional reasoning with this interactive haemocytometer.

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

Examine these estimates. Do they sound about right?

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

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

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

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

Work out the numerical values for these physical quantities.

Which units would you choose best to fit these situations?

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?