Equilibrium means that two forces are balanced. This is why some of the famous artwork doesn't usually have a bunch of, say, black on one side and then nothing on the other.
The answer is balance
They provide other organisms with food. got it from : https://quizlet.com/74022812/topic-test-science-flash-cards/#
The closer a planet is to the Sun, the stronger the Sun's gravitational pull on it, and the faster the planet moves. The farther it is from the Sun, the weaker the Sun's gravitational pull, and the slower it moves in its orbit.
What happens on Jane's elbow?
when a skin is scratched, the internal medium of the body enter directly in contact with the external environment, this could lead bacteria (saprophytic bacteria which lives on the skin, or bacteria from another source) it will provoke an inflammatory reaction to these pathogens and so, a pus will be formed (generally composed by dead neutrophils and purulent bacteria).
What happened on Sarah's knee?
The knee was just bruised, there's not skin scratching, it is still intact, so bacteria cannot go into the body through this injury. It just takes colors (red, blue, then yellow due to the rupture of capillaries which release blood, then will be degraded in bilirubin)