| Front | the arctic fox is brown in summer and white in winter while a rabbit reared at low temperature grows black hair on areas like the nose ears and feet but white hair on the body. explain both situations |
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| Back | fox grows summer coat in spring in response to UV exposure producing more MSH so more melanin which darkens the hair; in late summer it starts to grow the white winter coat because, although lots of MSH being produced, there are no MSH receptors on the melanocyte cells at this point so no melanin is made, resulting in a white coat areas of rabbit like the feet are cold so tyrosinase (enzyme involved in the production of melanin) is active but in hotter areas like the body the tyrosinase denatures so becomes inactive so melanin cannot be made, resulting in white hair |
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