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COPYRIGHT 2005 Science Weekly, Inc.
Background
Hair is a unique feature of mammals, with most having thick coats of body hair that protects them from the weather, the sun, and predators. Unlike other mammals, most of our 5 million or so body hairs are on our scalp. Every hair is an outgrowth of part of our skin and each has two parts: The follicle, or root, is buried within our scalp; and the shaft, the part we see and feel, is above the scalp. Our hair consists mostly of keratin. It's the same protein as our toenails and fingernails, as are bird beaks, claws, feathers, porcupine quills, and hooves.
Three types of hair grow on the human body. While still in the womb, babies develop very fine hairs called lanugo. These hairs are shed about four weeks before the baby is born. Vellus hairs are the short, fine "peach fuzz" hairs that grow all over our bodies. In Caucasians, these hairs are usually colorless, or blond. Terminal hairs are the darker and more visible, like those on our scalp.
We never have a full head of hair. About 85% of it is growing, while the other 15% is resting or shedding. This is the hair cycle and it has 3 stages: Anagen, is the active growth period and its length varies from one person to another, lasting about 1,000 days or more; Catagen is the resting or intermediate period, lasting about 10 days; Telogen is the shedding period, lasting about 100 days.
Hair textures and colors are as varied as ethnic groups, from tight wiry curls to straight-as-a-ruler hair. The type of hair we inherited goes beyond our parents and grandparents to the part of the world where their ancestors originated. But why is hair straight, wavy, or curly? It depends on the shape of the hair shaft as seen in cross section under a powerful microscope.
Straight hair appears round; wavy hair has an oval shape; and curly hair has an elliptical or kidney-shaped appearance. African hair is the most fragile and grows the slowest; Asian hair is the strongest and grows the fastest; and Caucasian hair is somewhere in the middle.
Hair is like a mirror because it reflects much about our lifestyle. If one of our hair strands were examined under a powerful laboratory microscope, a forensic scientist could determine our ethnicity, whether we smoked, drank, or used drugs, among other things. Today, many employers use hair analysis to determine if a person is drug-free before hiring them. The DNA found in the cells of a single hair root left at a crime scene can help police identify, apprehend, and convict a criminal.
DID YOU KNOW??
Humans have about the same number of hair follicles as chimpanzees.
DID YOU KNOW??
Baldness is usually related to a person's genes. Environmental causes, such as radiation can also contribute to baldness
Level pre-A
Main Concepts: There are many different kinds of animals in the world. All have different colors and textures of hair or fur. Human beings are also animals.
Picture Activity
Ask where WHY FLY is visiting in this issue of Science Weekly. Answer: He is visiting a zoo filled with different kinds of animals, including some kids. Ask your students, "Which animals have the most hair?" and "Why do you think animals have hair?" Answer: Hair protects the animal's skin from cold and heat and the different colors of hair help them to hide from other animals that might eat them.
Explain to your students that hair and fur is the same thing. Introduce the new words to your students.
Vocabulary
Go over the pictures together first--hair, whale, chair, and chain. Show your students how to print in the first ha, and then ask them to fill in the remaining blank spaces with the same letters. Read the words aloud. Ask the students to make up a sentence using one of the words.
Weekly Lab
Explain to your students that our bodies are covered all over with hair, but some are so fine we hardly see them at all, like the hairs on our forearms. Most of our hair is on our scalp, but some parts of our body have no hair at all.
WHY FLY wants to know: "What would happen if you had hair growing on your lips, palms of your hands, and the soles of your feet?"
FLY-pothesis says: "I think ... we would have a hard time eating, holding things, and running because hair is slippery."
Math
Animals come in different shapes, sizes, and colors, just like humans. Ask your students to count the number of animals having stripes and spots, and animals having none. Have them print the numbers in the boxes and then add up all the numbers. Then, have them write the total in the last box. Ask your students to name the animals with stripes or spots, and why they think they have these markings. Ask them to name the animals without stripes or spots.
Storytelling
This activity is designed to...
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