How can fish breathe underwater?

Living creatures need oxygen to survive, and fish are no exception. Human beings 68 use their lungs to take in oxygen, and fish breathe using their gills. A fish’s gills are full of blood vessels that absorb the tiny particles of oxygen from the water.

The fish sucks the water in through its mouth and squirts it out through its gills; during this process, the gills take the oxygen from the water into the blood vessels. A fish’s gills are not constructed to take oxygen from the air, so they cannot breathe on dry land.

Why do tropical rain forests grow so many plants?

Rain forests—thick forests of trees and other plants found in the lowland areas of the Tropics around the world—exist in parts of Australia, Indochina, India, the Malay Peninsula, the East Indies, in central and western Africa, and in Central and South America. Unlike forests in many other parts of the world, which have been affected by global climate changes like the Ice Age, tropical rain forests have been growing uninterrupted in some places for millions of years. During that time an unimaginable number of different types of plants and animals have evolved to use every food source and live in every spot there. Tropical rain forests have more plant and animal species than the rest of the world combined, and scientists continue to discover new species. Because tropical rain forests are located near the equator, their climate is warm.

The name “rain forest” comes from the fact that they receive a lot of rain—between 160 and 400 inches (4 and 10 meters)—throughout the year. Plants grow very quickly under such ideal conditions. In order to get the sunlight that they need for photosynthesis (the process by which they and other green plants make their own food), rain forest trees grow very tall, up to 130 feet (40 meters) high. Their tops form a huge canopy that shades most of the ground, protecting plants on the ground from excessive sunshine as well as wind. Rain forest trees have very shallow roots, for the soil in which they grow is poor, having long been depleted of nutrients by the needs of thick plant life over millions of years. But the abundant life all around contributes organic matter (the decomposed remains of plants and animals) to the surface of the soil, which is enough to nourish these grand, ancient forests.

Why do people have different color skin?

Skin color—which ranges from light pink to dark brown—is determined by the amount and type of the pigment melanin there is in the skin. Melanin comes in two types: phaeomelanin (red to yellow) and eumelanin (dark brown to black).

Both amount and type are determined by four to six genes. One copy of each of those genes is inherited from your father and one from your mother. Each gene comes in several coding sequences, which results in a variety of skin colors around the world.

How many computers are there in the world?

According to statistics from technology research companies such as Gartner Inc., in April 2002 the billionth personal computer (PC) was shipped. The second billion mark (some being ordered as replacements for older PCs) was reportedly reached in 2007. With personal computers becoming more popular around the world, research companies estimate that there will be more than two billion PCs in active use by 2015.

In the United States, more than half of the people who use a computer are also connected to the Internet.

Why are crops sprayed with pesticides?

Farmers and state governments use chemical pesticides to protect their crops from insect pests, weeds, and fungal diseases while they are growing. They also spray their crops with pesticides to prevent rats, mice, and insects from contaminating foods while they are being stored.

While these actions are meant to benefit human health and bring a wide variety of fruits and vegetables to the supermarket, they can also harm people, wildlife, and the environment. This is why there are strict controls in place over their sale and use.

What is the difference between self-pollination and cross-pollination?

Since flowers possess both male and female parts, some flowers can fertilize themselves— or fertilize another flower on the same plant—which is called self-pollination. Or the ovules of one flower may be fertilized by the pollen of a different flowering plant of the same species, a method called cross-pollination.

The wind, water, insects, and other animals help to carry pollen from one flower to another. Crosspollination usually produces a better plant: the offspring of cross-pollination possesses the genetic traits of two parents, which may give it new characteristics that will help it survive in an always-changing environment. Cross-pollination is so desirable, in fact, that many flowering plants have developed different ways to keep selfpollination from happening. In the flowers of a spiderwort plant, for example, the stamens are ready to release pollen grains before the pistils are ready to accept them, so the pollen has to travel to other spiderwort plants in search of a ripe pistil.

What causes a rainbow?

A rainbow is an arc that shows all the colors, with their different wavelengths, that make up visible light. Seven colors make up a rainbow, and they always appear in the same order: red, with the longest wavelength, is on the top, followed by orange, yellow, green, blue, indigo (a deep reddish-blue that is often difficult to see), and violet, which has the shortest wavelength. A good way to remember the order of those colors is by taking the first letter of each to spell “ROYGBIV,” pronounced “roy-jee-biv.” A rainbow occurs when sunlight passes through water droplets and is refracted or bent by their rounded shape into separate wavelengths.

Rainbows can sometimes be spotted in the spray of lawn sprinklers, in the mist of waterfalls, and—most spectacularly—in the sky during a rain shower when the Sun is still shining. A rainbow appears in the part of the sky opposite the Sun. Because the Sun must also be low in the sky, near the horizon, late afternoon is the best time to look for a rainbow if the day has been sunny with a few short rain showers or thunderstorms.

How hot is the Sun?

The Sun is extremely hot. The surface of the Sun (or its outer visible layer, called the photosphere) is about 10,000 degrees Fahrenheit (5,537 degrees Celsius)— about 50 times the temperature required to boil water.

The core of the Sun, where solar energy is created, reaches 27 million degrees Fahrenheit (15 million degrees Celsius). It is so intense that nuclear reactions take place there.

Interesting facts about Hair

1.    On average, a man spends about five months of his life shaving.
2.    On average, a hair strand’s life span is five and a half years.
3.    On average redheads have 90,000 hairs. People with black hair have about 110,000 hairs.
4.    Next to bone marrow, hair is the fastest growing tissue in the human body.
5.    In a lifetime, an average man will shave 20,000 times.
6.    Humans have about the same number of hair follicles as a chimpanzee has.
7.    Hair will fall out faster on a person that is on a crash diet.
8.    The longest human beard on record is 17.5 feet, held by Hans N. Langseth who was born in Norway in 1846.
9.    The average human head weighs about eight pounds.
10.    The reason why some people get a cowlick is because the growth of their hair is in a spiral pattern, which causes the hair to either stand straight up, or goes to a certain angle.
11.    The reason why hair turns gray as we age is because the pigment cells in the hair follicle start to die, which is responsible for producing “melanin” which gives the hair colour.
12.    The fastest growing tissue in the human body is hair.

13.    A lifespan of an eyelash is approximately 150 days.
14.    A survey done by Clairol 10 years ago came up with 46% of men stating that it was okay to color their hair. Now 66% of men admit to coloring their hair.
15.    The big toe is the foot reflexology pressure point for the head.
16.    The average human scalp has 100,000 hairs.
17.    The first hair dryer was a vacuum cleaner that was used for drying hair.
18.    Ancient Egyptians used to think having facial hair was an indication of personal neglect.
19.    The loss of eyelashes is referred to as madarosis.
20.    Hair and fingernails are made from the same substance, keratin.
21.    Eyebrow hair lasts between 3-5 months before it sheds.
22.    A Russian man who wore a beard during the time of Peter the Great had to pay a special tax.
23.    Everyday approximately 35 meters of hair fiber is produced on the scalp of an adult.
24.    Hair is made from the same substance as fingernails.
25.    Brylcreem, which was created in 1929, was the first man’s hair product.

What is the Joshua tree?

The Joshua tree is a desert tree that grows in southwestern North America, in California, Arizona, Utah, and Nevada. A native of the Mojave Desert, these droughttolerant trees thrive in the open grasslands of California’s Joshua Tree National Park. The Mormon pioneers named this tree after the prophet Joshua, because its extended branches resembled the outstretched arm of Joshua as he pointed with his spear to the ancient city of Ai. The trees are twisted and spiky, with tough leaves, and look a little bit like a tree from a Dr. Seuss book. Joshua trees can grow from seed or from an underground rhizome of another Joshua tree. They grow very slowly, sometimes 3.9 to 7.8 inches (10 to 20 centimeters) in their first few years.

The tallest trees reach about 49 feet (15 meters) tall. The trunk of a Joshua tree is made of thousands of small fibers and does not have yearly growth rings, Which makes it hard for scientists to tell the tree’s age. Although the fragile tree has shallow roots, if it survives the harsh desert environment, it can live hundreds— even thousands—of years.