The composition of the cerebrospinal fluid is similar to extracellular fluid with the exception of

Calcium

Calcium is known to be most abundant mineral present in the body  and they can be found in some foods and available in dietary supplements, resent in some medicine such as antacids. Also, calcium is required for muscle function,intracellular signaling, vascular contraction, hormonal secretion and nerve transmission.

•there must be variation for the particular trait within a population.

•the variation must be inheritable (that is, it must be capable of being passed on from the parents to their offspring).

•individuals with one version of the trait must produce more offspring than those with a different version of the trait.good

explanation:

yes it is weird but true