What do reindeer eat in the winter?

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In winter reindeer rely on high-carbohydrate lichens called reindeer moss, which they reach by digging craters in the snow. The calf follows its mother and shares this food. The reindeer survive on this low-protein diet by recycling urea (normally a waste product) within the digestive system and making use of its nitrogen.

What are the basic functional systems of animals?

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Animals’ basic functional systems include a musculoskeletal system, for supporting and moving the body; a nervous system, for receiving and processing sensory information and for carrying signals to control muscle and hormone activity; an endocrine system, for secreting hormones to chemically control bodily functions; a digestive system, for receiving and processing food; a circulatory system, for carrying nutrients and oxygen to cells and carrying away their wastes; and a reproductive system, for producing offspring to ensure species survival.