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The preservation of embryos and juveniles is a rate occurrence in the fossil record. The tiny, delicate skeletons are usually scattered by scavengers or destroyed by weathering before they can be fossilized. Ichthyosaurs had a higher chance of being
In science, a theory is a reasonable explanation of observed events that are related. A theory often involves an imaginary model that helps scientists picture the way an observed event could be produced. A good example of this is found in the kinetic
Television has become the main source of informatio [00:03.84]and entertaiment for the average America [00:07.97]It is estimated that by the time a child reaches 1 [00:12.64]he or she has spent almost twice as much time watching TV as in the classroo
Have you ever considered sky divin [00:03.08]Thousands of people learn to sky dive each yea [00:06.82]The first major step to learn is proper touch down techniqu [00:11.57]That means learning how to fall properly,initially from a four-foot platfor [0
Franklin D Roosevelt was elected Presiden [00:16.12]in November 193 [00:26.98]When he took the presidential oat [00:38.14]the banking and credit system of the nati [00:54.33]was in a state of paralysi [01:05.49]The new preside [01:12.49]brought an ai
I remember just how it was that da [00:13.95]the first hint of spring floated across the rive [00:31.37]mixing with the coal smoke from the factorie [00:47.07]As I turned the corner on my way to wor [01:01.13]and came to the toy stor [01:11.31]I thou
Many people have criticized television programmin [00:18.39]They complain that it does not challenge the intellec [00:37.59]shows too much violenc [00:47.44]and appeals to the least educated of viewer [01:04.86]in order to get the largest audienc [01
The majority of fish live in shallow parts of the se [00:19.88]Fish are varied but they have certain common feature [00:40.46]Fins are special organs which help the fish to swim in wate [01:03.03]They can help the fish to stea [01:15.57]and steer its
Cells cannot remain alive outside certain limits of temperature and much narrower limits mark the boundaries of effective functioning. Enzyme systems of mammals and birds are most efficient only within a narrow range around 37C; a departure of a few
American black bears appear in a variety of colors despite their name. In the eastern part of their range, most of these brown, red, or even yellow coats. To the north, the black bear is actually gray or white in color. Even in the same litter, both
The invention of the incandescent light bulb by Thomas A. Edison in 1879 created a demand for a cheap, readily available fuel with which to generate large amounts of electric power. Coal seemed to fit the bill, and it fueled the earliest power statio
Atmospheric pressure can support a column of water up to 10 meters high. But plants can move water much higher; the sequoia tree can pump water to its very top more than 100 meters above the ground. Until the end of the nineteenth century, the moveme
The theory of plate tectonics describes the motions of the lithosphere, the comparatively rigid outer layer of the Earth that includes all the crust and part of the underlying mantle. The lithosphere(n.[ 地 ] 岩石圈 )is divided into a few dozen p
The increase in international business and in foreign investment has created a need for executives with knowledge of foreign languages and skills in cross-cultural communication. Americans, however, have not been well trained in either area and, cons
Accustomed though we are to speaking of the films made before 1927 as silent, the film has never been, in the full sense of the word, silent. From the very beginning, music was regarded as an indispensable accompaniment; when the Lumiere films were s
The ways of history are so intricate and the motivations of human actions so complex that it is always hazardous to attempt to represent events covering a number of years, a multiplicity of persons, and distant localities as the expression of one int
people appear to born to compute. The numerical skills of children develop so early and so inexorably that it is easy to imagine an internal clock of mathematical maturity guiding their growth. Not long after learning to walk and talk, they can set t
Before the 1850's, the United States had a number of small colleges, most of them dating from colonial days. They were small, church connected institutions whose primary concern was to shape the moral character of their students. Throughout Europe, i
When you first arrive in the U.S. [00:12.83]you will be given the name and telephone extension numb [00:30.38]of the officer who will be administering your programm [00:49.55]It will be helpful if you make a note in your dia [01:08.00]of this informa
The first true piece of sports equipment that man invente [00:21.71]was the bal [00:35.60]In ancient Egypt,as everywher [00:49.50]pitching stones was a favorite children's gam [01:05.59]But a badly thrown rock could hurt a child. [01:23.17]Looking fo