Answer: During sexual reproduction, the genetic material of two individuals is combined to produce genetically-diverse offspring that differ from their parents. The genetic diversity of sexually-produced offspring is thought to give species a better chance of surviving in an unpredictable or changing environment
THE DOPPLER EFFECT. Anyways, it would have a higher whistle as it approaches you, when it gets to you it only gets quieter because it leaves after. Think of a motorcycle going by, its loud coming to you then as it passes it gets quieter.
In a direct current, the electric charge, or current, only flows in one direction. In an alternating current, the electric charge changes periodically.