Final answer:
Type 6 skin on the Fitzpatrick scale is dark brown or black skin that tans very easily and rarely burns. The Fitzpatrick scale classifies skin types based on their reaction to UV light. Melanin production, which increases upon UV exposure, determines skin color.
Step-by-step explanation:
Type 6 skin on the Fitzpatrick scale refers to dark brown or black skin. This skin type rarely burns and tans very easily. The Fitzpatrick scale is a numerical classification scheme for the color of skin and its response to UV light. It ranges from type 1, which is very fair skin that burns and never tans, to type 6, which is deeply pigmented and tans without burning.
The color of skin is largely determined by the presence of the melanin pigment, which also determines the color of hair. When skin is exposed to UV light, the production of melanin increases, leading to a darker skin color. This process is a protective mechanism to prevent UV damage to the underlying skin cells.
Conditions such as Addison's disease can cause hyperpigmentation of the skin as well, which is a sign not related to UV exposure but to an underlying medical condition. Associated skin marks, like large brown spots or dark lesions on various parts of the body, can indicate other health issues requiring medical attention.