The notion is referred to as the latitudinal diversity gradient, and this means that as you get further from the equator towards the poles, there is less diversity. The temperature begins to decrease, and the days become shorter.
By shifting heat from the equator toward the poles, ocean currents play an essential role in regulating the climate. Ocean currents are extremely important to sea life. When you move toward the poles, due to the earth's arch, solar insulation arrives at an incline to the earth's surface, the angle from the vertical becoming greater the closer you get to the poles, and the sun goes down in the sky.
Ocean currents transport warm water to the poles, while the cold water goes from the poles back to the tropics.