Final answer:
Fur in mammals serves multiple purposes including insulation, sensation, and communication. Composed of keratin, it traps air for thermal regulation and can be used by animals like cats for detecting vibrations and conveying social signals.
Step-by-step explanation:
Fur is a defining characteristic of mammals, playing several crucial roles such as insulation, communication, and protection. Fur is composed primarily of keratin, which is the same protein that makes up human hair. This material is arranged in such a way that it traps air in small pockets, utilizing the low conductivity of air to effectively insulate the mammal and retain body heat.
In addition to insulation, fur can be instrumental in sensing the environment. Cats are known for their vibrissae or whiskers, which are specialized hairs that connect to nerves and help these animals detect vibrations in their surroundings, which is particularly important for the nocturnal or burrowing species. Fur can also serve a social function; for instance, a cat may raise its fur to appear larger and more threatening to predators, a behavior that communicates a warning to potential threats.
The presence of fur is just one of the distinct traits of mammals, among other features like sweat glands, mammary glands, specialized teeth, and a neocortex region in the brain, responsible for higher-order functions such as seeing and hearing.