Identify the force that caused stars and planets in the universe to become layered according to density differences in their compositions

The answer is gravity.  According to general relativity by Einstein, the bending of space-time is dependent on the nature of the matter of the object, or energy, momentum, and radiation. The heavier the object, the bigger the curvature of space-time it causes, that is felt as gravity. Heavier objects with a bigger gravity pull, pull other objects (with lesser gravity pull) more towards them than vice versa.

the father in the first generation probably had the recessive colorblind trait in his x chromosome. if he and his wife both had the colorblind trait, even if she had 1 recessive and 1 dominant, then that trait would be passed on to their kids.

(since you didn't attach the family tree this is just an assumption)

the element that provides strength to the exoskeletons of clams and oysters is phosphorus.

this is so because calcium carbonate is the main component in the shells. calcium carbonate is strengthened by phosphorus.

explanation: