Melanin is a dark skin pigment produced in animals in response to
environmental conditions. Its production is increased when melanocyte cells
in the skin are stimulated by melanocyte stimulating hormone (MSH), a
hormone produced by the pituitary. The graph below shows the production of
MSH 24 hours after no exposure (control), after ultraviolet light exposure
(UV), and after ultraviolet light exposure with sunscreen covering of skin.
Error bars indicate the range of replicate results.
A species of animal that can produce melanin lives in both southern and
northern latitudes. If the southern latitudes get more sun exposure for longer
hours per day than northern latitudes, predict the effects on the animals living
in the two locations.
% of
control
500-
400-
300-
200-
100-
control UV
UV +
sunscreen
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A. Animals with fur will have the same color skin regardless of
latitude, since the fur will act like a sunscreen.
B. Animals living in southern latitudes will express less melanin than
animals of the same species living in northern latitudes.
C. Animals with the same melanin genotype will have the same
expression of melanin and the same skin color regardless of
latitude.
D. Animals living in northern latitudes will have lighter skin color than
animals of the same species living in southern latitudes.