For the answer to the question above, I think the answer is simply because <span>four legs characteristic is not special to mammals but the hair that is something more important and special characteristic of the mammals, that's why. I hope this helps
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<span>The thymus.The thymus plays an important role in the development of T-lymphocytes which is an important type of white blood cell. It reaches maximum development at puberty and then the thymus begins to get atrophied (the shrinking of the thymus with age) and then the thymic stroma is replaced by fat tissue. Loss of thymic function is thought to contribute to weaker immune system of the elderly, increasing instances of diseases such as cancers and other infections.</span>
Emperor penguins have the ability to 'recycle' their own body heat. The arteries and veins lie close together so that blood is pre-cooled on the way to a penguin's feet, wings and bill and warmed on the way back to the heart. Emperors' feet are adapted to the icy conditions
Our bodies produce an enzyme called lactase. This enzyme helps our bodies digest lactose (a sugar found in milk). As we age, the amount of lactase our bodies produce decreases. Some people don’t produce as much as others. If you are lactose intolerant, it means your body doesn’t produce a lot of lactase. One option is to drink milk with lactase added to it.
Example: Lactaid
