The coco de mer tree, a palm that only grows today on two islands in the Seychelles, produces both the largest seed (each weighs about 44 pounds [20 kilograms]) and the largest nut in the world. The nut, which takes six to seven years to mature and another two years to germinate, is sometimes called the sea coconut or Seychelles nut. When early explorers first discovered the nut, they thought it came from a mythical tree at the bottom of the sea.
Sixteenth-century European nobles decorated the nut with jewels as collectibles for their private galleries. Today, the coco de mer is a rare protected species.
Once seeds are fully developed, they need a good place to grow. If they just fell to the ground beneath their parent plant, they would struggle, competing against each other for sunlight, water, and minerals. Most seeds need to travel—by wind, water, or with the help of insects and other animals—to better places to germinate, or start to grow into new plants. Some seeds, like those from conifer and maple trees, have wings attached. Others, like those of dandelions, have parachutes made of tiny hairs. Both features allow the seeds to be carried great distances by the wind, and they sometimes land in spots that are good for germination. Water carries other seeds to good growing places; the hard, watertight shell of a coconut, for instance, allows it to travel many miles at sea before finding a beach where conditions are suitable for growth.
Seeds sometimes have to wait a long time before they find good places to grow, places where the sun, moisture, and temperature are right. Most seeds are designed for the wait, protected by a hard outer pod (except those of conifers). Some seeds wait years to germinate, and some just never do. But inside each seed pod is a baby plant, or embryo, and endosperm, a supply of starchy food that will be used for early growth if germination takes place. Then a tiny root will reach down into the soil, and a tiny green shoot will reach up, toward the light.
Indeed, it does. A Venus flytrap is a carnivorous plant that attracts, captures, and kills insects and digests and absorbs their nutrients. The leaves of the Venus flytrap, Which can open wide, have short, stiff hairs called trigger hairs. When anything touches these hairs enough to bend them, the two lobes of the leaves snap shut, trapping whatever is inside. The “trap” will shut in less than a second, capturing flies and other insects.
When the trap closes over its prey, finger-like projections called cilia keep larger insects inside. In a few minutes the trap shuts tightly and forms an air-tight seal in order to keep its digestive fluids inside. These fluids help the plant digest prey. At the end of the digestive process, which takes from 5 to 12 days, the trap reabsorbs the digestive fluid and reopens. The leftover parts of the insect blow away in the wind or are washed away by rain.
Frogs are able to make their croaking noises because they have simple vocal cords that have two slits in the bottom of the mouth. These slits open into what is called a vocal pouch. When air passes from the lungs through the vocal cords, a sound is produced. The inflating and deflating vocal pouch makes the sound louder or quieter.
That sound changes depending on the kind of frog there are as many different kinds of croaks as there are frogs! Frogs croak for the same reasons that many animals make noises: to track down and then select a mate, and to protect their territory from other male frogs.
Dams, which are structures that hold back water, have been built since ancient times. They are usually made of earth, rock, brick, or concrete—or a combination of these things. They are constructed to control the flow of water in a river, and they are built for a number of reasons. One reason is to prevent flooding. Heavy rains in high country may cause water levels in a river to rise. As the river flows downhill, it may overflow its banks, flooding communities located downstream. A dam can prevent this by stopping or slowing rushing water, allowing it to be released at a controlled rate. Dams are also frequently used to store water for general use and farming. When a river’s flow is restricted by a dam, water often spreads out behind the dam to form a lake or reservoir in the river valley. That water can then be used as needed, preventing water shortages and crop damage during long periods of dry weather.
A great number of dams today are used to make electricity. Such hydroelectric dams are built very tall, to create a great difference in the height of the water level behind and in front of it. High water behind a dam passes through gates in the dam wall that allow it to fall to the river far below. As the water falls, it flows past huge blades called turbines; the turbines run generators that make electricity. One of the world’s largest and most productive hydroelectric dams is the Hoover Dam, located on the Colorado River between Nevada and Arizona. Built in the 1930s, it is 726 feet (221 meters) high and 1,244 feet (379 meters) long. Its reservoir (Lake Mead)—the world’s largest— supplies water to several states, allowing huge regions of naturally dry terrain in southern California, Arizona, and Mexico to flourish. Many modern dams are used for all three purposes: flood control, water storage, and hydroelectric power.
Birds migrate—or move regularly from one place to another—for several reasons, including warmth and the availability of food and water. Many species of birds mate and nest in specific areas of the world. Most of these areas are only comfortable during the warmer months of the year, so when the cold weather arrives birds migrate to warmer climates. These trips can be as long as thousands of miles. For example, the American golden plover breeds north of Canada and Alaska during the Northern Hemisphere’s spring and summer.
In the Northern Hemisphere’s fall, the plovers travel to southeastern South America to spend the “winter”—which is the summer season in the Southern Hemisphere—allowing the birds to find plenty of food. When spring arrives again in the Northern Hemisphere, the trip is reversed, and the plovers migrate back to the northern nesting grounds to breed.
The red carpet treatment dates back to the 1930s, when a carpet of that colour led passengers to a luxurious train, the Twentieth Century Limited, which ran between New York and Chicago.
The Twentieth Century was the most famous in America and was totally first class with accommodation and dining car menus that were considered the height of luxury. Walking the red carpet to the train meant you were about to be treated like royalty.
People can use the Internet to send electronic mail, known as e-mail, to one another in just a few seconds. Once you type a message into your computer to send to your cousin, let’s say, who lives miles from you across the country, it travels through the wires of your phone line as a series of electrical signals (or, for some people, the signals travel through the same cables that bring them cable television). These signals travel to a station run by your service provider, where a big computer sends them to an Internet routing center. Located all over the world, routing centers, which are linked to organizations and Internet providers, send the countless computer communications that come to them each second along the quickest possible routes to their destinations.
A giant computer there reads the address on your e-mail and sends it farther: depending on the distance it must travel, it may continue along phone lines, be changed into light signals that can travel with great speed along thin glass strands called fiber-optic cables, or be converted into equally speedy invisible bands of energy known as radio waves and transmitted to a communications satellite that will bounce it back to Earth, to a ground station located close to where your cousin lives. Once your message reaches the routing center nearest your cousin, it will be sent to the station of his or her service provider. From there it will be sent along regular phone lines to his or her computer. And all of this happens in a matter of moments.
During the last decade of the nineteenth century, the electric vehicle became especially popular in cities across America. People had grown familiar with electric trolleys and railways, and technology had produced motors and batteries in a wide variety of sizes. The Edison Cell, a nickel-iron battery, became the leader in electric vehicle use. By 1900, electric vehicles were the most popular car. In that year, 4,200 automobiles were sold in the United States. Of these, 38 percent were powered by electricity, 22 percent by gasoline, and 40 percent by steam. By 1911, the automobile starter motor did away with handcranking gasoline cars, and Henry Ford had just begun to mass-produce his Model T’s. By 1924, not a single electric vehicle was exhibited at the National Automobile Show, and the Stanley Steamer was scrapped that year. Because of “Clean Air” legislation, the energy crises of the 1970s, and concern for the well-being of the environment, car manufacturers have again marketed several all-electric cars and “hybrid” vehicles.
Hybrid cars use two or more different power sources to propel them, such as a gasoline engine and an electric motor. General Motors sold the Impact, an electric vehicle. And Honda offered people two hybrids, the Insight and a Civic sedan. The Toyota Prius is a hybrid that first went on sale in Japan in 1997, making it the first mass-produced hybrid vehicle. According to the United States Environmental Protection Agency, the 2008 Prius is the most fuel-efficient car sold in the United States. Because of this, electric cars and hybrid vehicles may be the new cars of the future, eventually replacing all-gasoline-powered cars.