Melanin a substance or pigment that gives the normal color for skin , hair , eye iris , feathers and scales. In humans, those with darker skin have higher amounts of melanin. By contrast, those with less pigment have lighter or more fair skin coloring. Melanin, sometimes referred to as a chemical, is formed as part of the process of metabolizing an amino acid called tyrosine. In the skin, melanin is formed by cells called melanocytes. Certain medical conditions, such as albinism, are associated with the lack of melanin. Albinism is a condition marked by the absence of a normal amount of pigment in the body. Animals, humans, and even plants can have albinism. Albinism exists in a number of variations. Depending on the type of albinism, the skin, hair, and eyes may all be affected. In fact, ocular albinism affects not only the color of the eyes, hair, and skin, but also results in poor vision. Additionally, some types of melanin deficiency are associated with increased mortality rates. Melanin provides many benefits to human beings. One of the most recognized benefits involves ultraviolet rays of the sun. Melanin provides a natural protection against the harmful effects of these rays. However, it does not provide complete protection from the sun, and individuals with darker skin tones are still at risk from the sun's damaging rays. Generally, those with darker skin tones and more melanin are able to tolerate exposure to the sun for hours without getting sunburn. By contrast, a person with lighter skin may get sunburn after spending only minutes in the midday sun. Skin cancer is directly related to exposure to the sun and the presence of less than optimal amounts of pigment. Sun exposure has even been linked with cataracts. Melanin is also a mechanism for absorbing heat from the sun. This purposes is of particular importance to cold-blooded animals. Snakes, lizards, certain types of fish, and a wide range of other animals depend on their surroundings, including the rays of the sun, to establish and maintain their body temperatures. Also important for sharpness of vision, melanin serves to minimize the number of light beams that enter the eye. It also provides for the absorption of scattered light within the eye. In this way, pigmentation allows for more keen sight. Source
