A.Skin color varies because of differences in ultraviolet radiation between different
regions of the world.
B.The amount of melanin in the skin affects the body’s production of vitamin D.
C.The amount of melanin in the skin affects the body’s ability to process lactose.
D.Light skin is a selective advantage outside the tropics, because it admits ultraviolet
radiation, which causes the body to manufacture vitamin D and thus prevents rickets
and osteoporosis.
E.Light skin is a selective disadvantage in the tropics, because it is more susceptible to
the destruction of the folate that is needed to produce folic acid to protect against neural
tube defects in human embryos.
In science, what is the relationship among explanations, associations, and theories?
A.An explanation must show how and why the thing to be understood is associated with
or related to something else. Theories require covariation: when one thing (a variable)
changes, the other one varies as well. Associations provide explanations for both
explanations and theories.
B.They mean the same thing.
C.An explanation must show how and why the thing to be understood is associated with
or related to something else. Associations require covariation: when one thing (a
variable) changes, the other one varies as well. Theories provide explanations for
associations.
D.Explanations and associations are explained by theories, which are observed
relationships between two or more variables.
E.An explanation must show how and why the thing to be understood is associated with
or related to something else. Thus, explanations and associations are the same thing. A
theory is a suggested but as yet unverified explanation.