Differences in what? Organically, it could be differences in DNA, differences in evolutionary history, or differences in environment, among many others. Inorganically, differences could be the result of a chemical property, object structure, or a plethora of hundred upon thousands of other things. Please be more specific next time if you would like a more specific answer.
All currents are caused by differences in pressure.
No. Some can be caused are caused by nurture: health - including diet and diseases.
The movement of material due to differences in density caused by differences in temperature is called convection.
Its caused ok differences in air pressure
the Bahamas
Wind
deep
land breezes r caused in the night.
church differences
Density Current
wind
Human nature. And, differences of opinions.