People who have darker skin have more melanin which is a black or dark brown pigment in the skin. When we are out in the sun our skin produces more melanin, which helps our skin be more resistant in the sun. This is why we tan.
Answer:
D. 3:1
Explanation:
Gregor Mendel, in one of his numerous studies, performed a cross between purebred dominant (TT) pea plants and purebred recessive (tt) pea plants. All the offsprings of this cross appeared heterozygous tall (Tt) in the F1 generation.
However, when he self-crossed the F1 generation i.e. Tt × Tt, Mendel obtained a phenotypic ratio of 3 tall plants (dominant traits) : 1 short plant (recessive). This showed that the masked gene (recessive) was still present.
Because blue pigment in nature
The nervous system communicates through electrical impulses and the communication is very fast. It works in a relay fashion, from point to point comparable to the way the old telephones systems used to work.
The endocrine system communicates by chemical signals via the bloodstream. Hormones are secreted into the blood and extra cellular fluids, then transported to target cells, which must bear a receptor to be able to bind to a specific hormone, and respond.
Hormones are chemical messengers secreted into blood or extracellular fluid that affect the function of other cells.
Endocrine communication is not quite as fast as the nervous system communication
