Evolution in the U.
General overview The evidence for evolution Darwin and other 19th-century biologists found compelling evidence for biological evolution in the comparative study of living organisms, in their geographic distribution, and in the fossil remains of extinct organisms. The amount of information about evolutionary history stored in the DNA and proteins of living things is virtually unlimited; scientists can reconstruct any detail of the evolutionary history of life by investing sufficient time and laboratory resources.
Darwin, CharlesOverview of Charles Darwin's life, with a focus on his work involving evolution. The following sections identify the most productive of these sources and illustrate the types of information they have provided.
The fossil record Paleontologists have recovered and studied the fossil remains of many thousands of organisms that lived in the past. This fossil record shows that many kinds of extinct organisms were very different in form from any now living. It also shows successions of organisms through time see faunal succession, law of ; geochronology: Determining the relationships of fossils with rock stratamanifesting their transition from one form to another.
When an organism dies, it is usually destroyed by other forms of life and by weathering processes. On rare occasions some body parts—particularly hard ones such as shells, teeth, or bones—are preserved by being buried in mud or protected in some other way from predators and weather.
Eventually, they may become petrified and preserved indefinitely with the rocks in which they are embedded. Methods such as radiometric dating —measuring the amounts of natural radioactive atoms that remain in certain minerals to determine the elapsed time since they were constituted—make it possible to estimate the time period when the rocks, and the fossils associated with them, were formed.
Radiometric dating indicates that Earth was formed about 4. The earliest fossils resemble microorganisms such as bacteria and cyanobacteria blue-green algae ; the oldest of these fossils appear in rocks 3.
The oldest known animal fossils, about million years old, come from the so-called Ediacara faunasmall wormlike creatures with soft bodies. Numerous fossils belonging to many living phyla and exhibiting mineralized skeletons appear in rocks about million years old. These organisms are different from organisms living now and from those living at intervening times.
Some are so radically different that paleontologists have created new phyla in order to classify them. The first vertebrate s, animals with backbones, appeared about million years ago; the first mammal s, less than million years ago. The history of life recorded by fossils presents compelling evidence of evolution.
The fossil record is incomplete. Of the small proportion of organisms preserved as fossils, only a tiny fraction have been recovered and studied by paleontologists.
In some cases the succession of forms over time has been reconstructed in detail. One example is the evolution of the horse. The horse can be traced to an animal the size of a dog having several toes on each foot and teeth appropriate for browsing; this animal, called the dawn horse genus Hyracotheriumlived more than 50 million years ago.
The most recent form, the modern horse Equusis much larger in size, is one-toed, and has teeth appropriate for grazing.
The transitional forms are well preserved as fossils, as are many other kinds of extinct horses that evolved in different directions and left no living descendants.
The present-day Przewalski's horse is believed to be the only remaining example of a wild horse—i. Numbered bones in the forefoot illustrations trace the gradual transition from a four-toed to a one-toed animal.
Using recovered fossils, paleontologists have reconstructed examples of radical evolutionary transitions in form and function. For example, the lower jaw of reptiles contains several bones, but that of mammals only one. The other bones in the reptile jaw unmistakably evolved into bones now found in the mammalian ear.
At first, such a transition would seem unlikely—it is hard to imagine what function such bones could have had during their intermediate stages.African American parents and white teachers clash in the Ocean Hill-Brownsville area of New York City, over the issue of community control of the schools.
Teachers go on strike, and the community organizes freedom schools while the public schools are closed. Milliken v.
Bradley. Liberty and Learning: The Evolution of American Education [Larry P. Arnn] on caninariojana.com *FREE* shipping on qualifying offers. Larry P. Arnn, the President of Hillsdale College, traces the history of education from the founding of the U.S.
Office of Education (based on the Prussian system) in to the Higher Education Act of and its subsequent reauthorizations.
- Howard University is established in Washington D.C. to provide education for African American youth "in the liberal arts and sciences.” Early financial support is provided by the Freedmen's Bureau.
Diane Ravitch-former assistant secretary of education and a leader in the drive to create a national curriculum-examines her career in education reform and . The most comprehensive evolutionary science resource on the Internet. In this article, the historical evolution of higher education refers to higher learning in the United States from the colonial era to the present day.
A radically pluralistic system of public, private, and for-profit two- and four-year training institutes and colleges and professional and graduate.