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.
In the Arctic and Antarctic circles there is at least one day a year when the Sun does not rise and one day when the Sun does not set. This is because of their close location to Earth’s poles.
The Sun does not set on the summer solstice (June 21 in the north and December 21 in the south) and does not rise on the winter solstice (December 21 for the north and June 21 for the south). For this reason, the Arctic and Antarctic are called the “lands of midnight Sun” in the summer and “lands of noon darkness” 12 in the winter.
Yes. In 1997 a team of scientists at the Roslin Institute in Edinburgh, Scotland, announced the birth of Dolly the sheep, the first clone (identical copy) of an adult mammal. The process used to create Dolly, called somatic cell nuclear transfer, began with an egg cell from one sheep. The scientists destroyed that egg cell’s nucleus and then injected the nucleus from the cell of another sheep into the egg cell. With a little encouragement from electronic stimulation, the donated nucleus fused with the egg cell, and the new cell began to divide.
The cluster of cells was then implanted into the uterus of the sheep that had provided the egg cell, and five months later Dolly was born—an exact replica not of the sheep that had carried her in the womb but of the sheep that had supplied the nucleus. While cloning mammals is very controversial, some scientists argue that cloning farm animals has advantages to livestock farmers, who could use the technology to breed only highquality animals that produce the most milk or the finest wool.
In 1907 Miss Anna Jarvis of West Virginia asked guests to wear a white carnation to the church service on the anniversary of her mother’s death. But Mother’s Day became increasingly commercial, and Miss Jarvis spent the rest of her life trying to restore its simplicity.
The strain of her efforts to stop Mother’s Day and what it had become led her to an insane asylum, where she died alone in 1948.
The lizard is a reptile, a cold-blooded animal that is unable to internally control its own body temperature. In order to warm up or cool down, lizards and other reptiles—such as snakes, turtles, and crocodiles—move to different areas of their environment. They also use certain other behavioral traits to keep their body temperatures constant. For instance, if a lizard is starting to feel the intensity of the tropical sun, it might head into the shade or take a dip in a pool of water. The same lizard might also bask in the sun to warm up. Frilled dragons and collared lizards run on their hind legs in the heat of the day, making an artificial breeze to help cool themselves off. And another reptile, the crocodile, holds its jaws open to cool down on hot days.
The blood vessels in its mouth are close to the skin surface, and help transfer heat. Lying quietly is another technique the crocodile uses to warm its body and help digest its food. Because they are cold-blooded, reptiles can survive on much less food, compared to warm-blooded small mammals and birds, which burn much of their food to keep warm.
Wars have taken place since the beginning of recorded history, and they surely occurred before that as well. A war begins when one group of people (the aggressors) tries to force its will on another group of people, and those people fight back. War frequently springs from the differences between people, or from the desire of one group to increase its power or wealth by taking control of another group’s land. Often the aggressors feel that they are superior to the group they want to dominate: they believe that their religion, culture, or even race is better than that of the people they wish to defeat. This sense of superiority makes them feel that it is acceptable to fight to take the land, possessions, and even lives of the “inferior” group, or to force their ways on the dominated people.
Because countries can be very different from one another in government, religion, customs, and ideology (ways of thinking), it is not surprising that nations disagree on many things. But great efforts are usually made to settle the disagreements through discussion and negotiation—a process called diplomacy—before they result in anything as destructive as a war. War usually occurs when diplomacy fails. Because science and technology have allowed us to create such powerful and destructive weapons that can result in such devastating wars, we now have international organizations that work all the time to try to keep peace among nations.
The practice of using laurels to symbolize victory came from the ancient Greeks. After winning on the battlefield, great warriors were crowned with a wreath of laurels, or bay leaves, to signify their supreme status during a victory parade.
Because the first Olympics consisted largely of war games, the champions were honoured in the same manner: with a laurel, a crown of leaves. To “rest on your laurels” means to quit while you’re ahead.
A cobweb is an old, abandoned spider web that has collected dirt and dust. Sometimes the cobwebs you see in ceiling crevices and along floorboards are several draglines that spiders no longer use.
The common house spider—which feeds on many insects daily—often abandons webs that do not yield prey, and then constructs new ones until it finds a productive site. It’s best to sweep these old cobwebs away, and let your house spiders spin new webs, preferably outdoors!
The town meeting is one aspect of local government that still exists today, although it was created in the early years of the republic. At least once a year the registered voters of the town meet in open session to elect officers, debate local issues, and pass laws for operating a government. As a group, or body, they decide on road construction and repair, construction of public buildings and facilities (such as libraries and parks), tax rates, and the town budget.
Having existed for more than two centuries, the town meeting is often called the purest form of direct democracy because governmental power is not delegated, but rather exercised directly by the people. However, town meetings cannot be found in every area of the United States. They are mostly conducted in the small towns of New England, where the first colonies were established.
America’s founders did debate a bit as to whether or not to force children to attend schools, and they decided to leave such decisions to individual families and local and state governments. The words “education” and “school” do not appear in any of our founding documents, such as the Declaration of Independence, the Constitution, or the Bill of Rights.
Some of our most famous inventors, writers, and politicians were self-taught, learning through mentoring or apprenticeships, conversation, and reading. In 1850, Massachusetts became the first state to institute a compulsory schooling law.