Scientific Notation
You should know how to correctly convert numbers to scientific notation and then multiply and divide them. Link below can help you out.
Unit Conversion (Dimensional Analysis)
Many times you will be given a measurement in one unit and be required to answer in another unit. Unit conversion will be necessary. Below is some more information on dimensional analysis.
Percentages
You should be able to calculate percentage increases and decreases.
Doubling Time
At what point with the population of X double? This is a common question that you will need to know how to answer. Add this to your toolbox.