What my cause individuals to have versions of traits that are different from others in the same species

How many variables are altered in a good experiment? a.1 b.0 c.2 d.3

How is the male reproductive system different from other body systems? it isn’t necessary to vital signs. it monitors other body systems, and adjusts if necessary. it transports items from one system to another. it is the only system that produces hormones in the male.

Explain how fossils scientists make discoveries about the lives of organisms and about how environments have changed over time. plz hurry up it time