Which factors affect the gravitational force between two objects?

The size of each object and the space between them.

When dealing with the force of gravity between two objects, there are only two things that are important – mass, and distance. The force of gravity depends directly upon the masses of the two objects, and inversely on the square of the distance between them.

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link:

organ system-an organ system is a group of organs that work together to perform one or more functions. each does a particular job in the body, and is made up of certain tissues.