Why is white white and black black?

Answer 1

just because, just like pink is pink and purple is purple.

WRONG ANSWER. Not exactly. The coloring of the skin, hair, mucous membranes, and retina of the eye is known as pigmentation. Pigmentation is due to the deposition of melanin which is a coloring matter. The melanin is produced by specialized cells called chromatophores.

Chromatophores are pigment-containing and light-reflecting cells found in amphibians, fish, reptiles, crustaceans, andcephalopods. They are largely responsible for generating skin and eye colour in cold-blooded animals and are generated in the neural crest during embryonic development. Mature chromatophores are grouped into subclasses based on their colour (more properly "hue") under white light: xanthophores (yellow), erythrophores (red), iridophores (reflective /iridescent), leucophores (white), melanophores (black/brown) and cyanophores (blue). The term can also refer to coloured, membrane associated vesicles found in some forms of photosynthetic bacteria.

Some species can rapidly change colour through mechanisms that translocate pigment and reorient reflective plates within chromatophores. This process, often used as a type of camouflage, is called physiological colour change. Cephalopods such as octopus have complex chromatophore organs controlled by muscles to achieve this, while vertebrates such as chameleons generate a similar effect by cell signaling. Such signals can be hormones orneurotransmitters and may be initiated by changes in mood, temperature, stress or visible changes in local environment.

Unlike cold-blooded animals, mammals and birds have only one class of chromatophore-like cell type: the melanocyte. The cold-blooded equivalent, melanophores, are studied by scientists to understand human disease and used as a tool in drug discovery. In other words, it's a biological uniqueness.