Natural selection is the process by which an organism uses its traits to survive and reproduce. In this mechanism of evolution, organisms have favorable traits for survival and reproduction. The more adapted an organism is to its environment, the more likely it is to have heritable traits that are passed down to new coming offsprings, and really, this also applies for the likeliness of the organism to survive and reproduce in general. The more these heritable traits are passed down and used with offspring, the more common the favorable traits are in the community.
In all of the above!
The water cycle describes how water travels from the oceans, evaporating into the atmosphere and back to Earth in the form of rain, and during this process the water is stored in all those places.
The greater amount of eumelanin in darker skin protects folate from being broken down by UV radiation and thus increases fitness among populations in high-intensity UV areas. ... However, it does not explain why there is variation in human skin color.
