Hair on Mammals Can Be Used for All but Which of the Following?
Fur, Wool, Hair: What'south the Difference?
One of the features shared by well-nigh every mammal species on Earth — from antelopes to zebras, and fifty-fifty humans — is that their bodies are covered in structures known individually as "hairs" and collectively as "fur."
Fur can be dense or sparse; soft or coarse; colorful or drab; monochromatic or patterned. However, regardless of what information technology looks or feels similar, fur is an evolutionary characteristic that defines the mammalian lineage.
But what makes a panthera leo's mane different from a polar bear'south coat, a boar's bristles or a ram's fleece — or even the hair on our ain heads? [The World'due south 5 Smallest Mammals]
According to Kamal Khidas, curator of the vertebrate drove at the Canadian Museum of Nature, there are three types of hair in mammals that make up their fur: vibrissae, which are sensitive tactile receptors, such equally whiskers, used for sensing the environment; baby-sit hairs, the most conspicuous hairs, which serve as protection; and underhairs, whose primary purpose is insulation.
The length, thickness and density of these pilus types contribute to the incredible diversity nosotros come across in mammals' hirsuite pelts.
"Pilus is the basic unit of measurement," Khidas told Alive Science. Hair is made of keratinized filament — the same substance that makes upwardly our fingernails — and can vary in length from simply a fraction of an inch to about 3.3 anxiety (1 meter).
What is commonly called "fur" is typically recognized as "the relatively short hair with definitive growth that grows densely over the body," Khidas said. The type of fur known as wool is a kind of underhair — soft, thin, curly, flexible hair that never stops growing.
Human being hair is less differentiated than the hairs on other mammals, having characteristics of both guard hairs and undercoat hairs, co-ordinate to a manual on pilus microscopy published in 2004 by the Federal Bureau of Investigation (FBI).
But to brainstorm to understand how fur diverged into the diversity grown by animals alive today, we first demand to take a pace back in fourth dimension, to well-nigh 310 1000000 to 330 1000000 years ago, to an era when something akin to fur is thought to take first appeared.
A scaly commencement
The first type of "hair" to emerge in mammalian ancestors was perhaps a modification of scales, "or some sort of difficult, nonhair epidermal structures," Khidas told Alive Science in an electronic mail.
"What seemed to have happened was that some sort of dormant genes that already existed in mammal ancestors subsequently played a role in hair germination," Khidas said.
A need for insulation likely drove fur'due south evolution in early mammals, every bit information technology adult alongside another trait that differentiated them from reptiles: a consistently loftier body temperature that had to be maintained, using a process known equally thermoregulation. [In Photos: Mammals Through Fourth dimension]
Rob Voss, a curator in the mammalogy department at the American Museum of Natural History in New York City, told Live Science that fur's about important role for mammals is to help with thermoregulation, preserving their internal temperature regardless of external conditions.
In especially cold environments, terrestrial mammals such as the musk oxes, arctic foxes and polar bears rely on their thick coats to stay alive in frigid temperatures; dense fur traps a layer of air shut to their skin, which helps to proceed them warm. Semiaquatic mammals, such as fur seals and otters, also have a thick covering of fur, with sea otters sporting upwardly to 1 1000000 hairs per square inch of skin — more than any other mammal.
Slick-skinned marine mammals such equally whales, dolphins and elephant seals lost their hirsuite coverings long ago merely replaced the fur's insulation with a thick layer of blubber that shields them from the cold, Voss explained.
But in warmer climates, larger mammal species tend to have sparser coverings of hair, as large animals are generally able to maintain their core body temperatures without much insulation, Voss said. Smaller animals with college metabolic rates tend to have trunk temperatures that fluctuate more than dramatically, and are therefore more reliant on furry insulation to protect them from dips in external temperatures, he added.
More than just warmth
However, a mammal's fur can serve many purposes in addition to insulation. In some species, Voss told Live Science, baby-sit hairs evolved into highly specialized protective structures — like the porcupine's and hedgehog's quills, or the pangolin'due south armor, where hairs fuse together to form tough plates.
Fur can also be a source of camouflage. For instance, Voss said, small mammals' coats generally match the color of the soil in their environment so they'll blend in with the clay. Fur coloration can exist used for sexual selection, or to serve as a alarm to predators that an fauna carries toxic chemic weapons — equally is the case with the skunk.
"Rodents that have odors or toxic chemicals in [their] skin tend to be marked in black and white," Voss said. "Most of them are nocturnal, so colors like black and white stripes stand out."
And a recent study of zebras' distinctive striping suggested that their patterns might accept evolved to deter biting tsetse flies.
Because that mammals are so reliant on their fur, information technology's no wonder that they also work hard to keep it in good condition. Grooming isn't a loftier-maintenance luxury — it can be a matter of life and death, Voss noted.
"Most mammals invest an enormous amount of time in maintaining their fur, to preserve quality, function and insulation, and to weed out ectoparasites," Voss said.
The dull, muddy or disordered fur also sends a warning bespeak to prospective mammal mates, he added. "Hair is a good indicator of health in most mammals," he said. "Potent, good for you mammals accept glossy coats, while sick mammals have shabby-looking coats."
And what nearly humans? Our own pilus — fifty-fifty though we don't phone call it "fur" — is an intrinsic part of our mammalian heritage, though perhaps we have less of information technology overall than some of our fuzzy friends.
And while one aspect of our cranial hair is, in fact, rare among mammals — it grows continuously and isn't shed seasonally as well-nigh mammal fur is — when it comes to sexual selection, a sleeky, healthy caput of hair may be just equally important to u.s.a. every bit it is to our mammalian relatives.
"Most of the things we notice beautiful are markers of youth and health," Voss said. "This could be ane of the cues that humans apply unconsciously to assess youth."
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Mindy Weisberger is a Live Scientific discipline senior writer covering a general beat that includes climatic change, paleontology, weird creature behavior, and space. Mindy holds an Chiliad.F.A. in Motion picture from Columbia University; prior to Live Science she produced, wrote and directed media for the American Museum of Natural History in New York City. Her videos about dinosaurs, astrophysics, biodiversity and evolution appear in museums and science centers worldwide, earning awards such equally the Cine Aureate Hawkeye and the Communicator Honor of Excellence. Her writing has too appeared in Scientific American, The Washington Mail and How It Works Magazine.
Source: https://www.livescience.com/54701-fur-hair-wool-whats-the-difference.html