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?

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

Which units would you choose best to fit these situations?

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

Work out the numerical values for these physical quantities.

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

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

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

How would you go about estimating populations of dolphins?

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

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