It means that the fit and well adjusted ones thrive and "make it", and the weak ones that can't adapt die.
Answer:
Well unless you have your testicales removed but I don't really know
3rd: Every action has an equal and opposite reaction. So the third law basically says that if you shoot out stuff in one direction you will move in the other direction. This is howrockets work in a vacuum. They have a source of fuel which is heated up so that it expands and is pushed out of the rocket.
Hope this helps a little... ^^
They can determine the liquid layers and solid layers by seismic waves
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