Evidence on prehistoric sharks essay

In casual encounters with the material universe, we rarely feel any difficulty here, since we usually deal with things that are clearly alive, such as a dog or a rattlesnake; or with things that are clearly nonalive, such as a brick or a typewriter. Nevertheless, the task of defining "life" is both difficult and subtle; something that at once becomes evident if we stop to think. Consider a caterpillar crawling over a rock. The caterpillar is alive, but the rock is not; as you guess at once, since the caterpillar is moving and the rock is not.

Evidence on prehistoric sharks essay

Paleontology and stratigraphy During the 17th century the guiding principles of paleontology and historical geology began to emerge in the work of a few individuals.

Nicolaus Stenoa Danish scientist and theologian, presented carefully reasoned arguments favouring the organic origin of what are now called fossils.

Also, he elucidated three principles that made possible the reconstruction of certain kinds of geologic events in a chronological order. This excursion into paleontology led Steno to confront a broader question. Steno cited evidence to show that when the hard parts of an organism are covered with sediment, it is they and not the aggregates of sediment that are firm.

Consolidation of the sediment into rock may come later, and, if so, the original solid fossil becomes encased in solid rock. He recognized that sediments settle from fluids layer by layer to form strata that are originally continuous and nearly horizontal.

Major Problems from the Start

His principle of superposition of strata states that in a sequence of strata, as originally laid down, any stratum is younger than the one on which it rests and older than the one that rests upon it. Steno's four laws of stratigraphy. Hooke argued for the organic nature of fossils.

Elevation of beds containing marine fossils to mountainous heights he attributed to the work of earthquakes. Streams attacking these elevated tracts wear down the hills, fill depressions with sediment, and thus level out irregularities of the landscape.

Earth history according to Werner and James Hutton The two major theories of the 18th century were the Neptunian and the Plutonian. The Neptunistsled by Werner and his students, maintained that the Earth was originally covered by a turbid ocean.

The first sediments deposited over the irregular floor of this universal ocean formed the granite and other crystalline rocks.

The Scottish scientist James Huttonleader of the Plutonists, viewed the Earth as a dynamic body that functions as a heat machine. Streams wear down the continents and deposit their waste in the sea.

Subterranean heat causes the outer part of the Earth to expand in places, uplifting the compacted marine sediments to form new continents.

Hutton recognized that granite is an intrusive igneous rock and not a primitive sediment as the Neptunists claimed.

Intrusive sills and dikes of igneous rock provide evidence for the driving force of subterranean heat. Hutton viewed great angular unconformities separating sedimentary sequences as evidence for past cycles of sedimentationupliftand erosion. His Theory of the Earthpublished as an essay inwas expanded to a two-volume work in John Playfaira professor of natural philosophy, defended Hutton against the counterattacks of the Neptunists, and his Illustrations of the Huttonian Theory is the clearest contemporary account of Plutonist theory.

Hydrologic sciences The idea that there is a circulatory system within the Earth, by which seawater is conveyed to mountaintops and there discharged, persisted until early in the 18th century.

Two questions left unresolved by this theory were acknowledged even by its advocates. How is seawater forced uphill? How is the salt lost in the process? To explain the rise of subterranean water beneath mountains, the chemist Robert Plot appealed to the pressure of airwhich forces water up the insides of mountains.

Evidence on prehistoric sharks essay

The French Huguenot Bernard Palissy maintained, to the contrary, that rainfall is the sole source of rivers and springs. In his Discours admirables ; Admirable Discourses he described how rainwater falling on mountains enters cracks in the ground and flows down along these until, diverted by some obstruction, it flows out on the surface as springs.

Palissy scorned the idea that seawater courses in veins to the tops of mountains. For this to be true, sea level would have to be higher than mountaintops—an impossibility.

In his Discours Palissy suggested that water would rise above the level at which it was first encountered in a well provided the source of the groundwater came from a place higher than the bottom of the well. This is an early reference to conditions essential to the occurrence of artesian water, a popular subject among Italian hydrologists of the 17th and 18th centuries.Devil In The Dark () The Horta was an example of Silicon life.; Now we are really sailing off into terra incognito.

"Here be dragons" and all that. But if you have starships, you almost have to have aliens (Isaac Asimov's Foundation trilogy being the most notable exception).The "science" is called Astrobiology, the famous "science in search of a subject". All About Sharks The Strange and Terrifying World of Prehistoric Sharks Since first appearing at least million years ago, sharks have undergone many strange and sometimes terrifying changes to evolve into the sharks we know today.

TOP TEN PREHISTORIC SHARKS. Sharks frequently appear as the subjects of horror stories which often depict them as cold merciless killers that live to kill.‭ ‬The truth of the matter is not so clear cut as worldwide sharks fill an important part in marine ecosystems that would be irreversibly changed if they disappeared.‭ ‬Today’s sharks however come .

Dear Twitpic Community - thank you for all the wonderful photos you have taken over the years. We have now placed Twitpic in an archived state. Megalodon was the largest prehistoric shark that has ever lived!

Thousands of teeth have been found worldwide, however only few bones. Below is an essay on "Megalodon" from Anti Essays, your source for research papers, essays, and term paper examples.

Megalodon’s as sharks, shed their tens of thousands times in a lifetime, so /5(1). Pib's Collection of Cryptozoology Resources. Have we found all the large animals still living in the world?

Probably not, since in the last decade some previously unknown species have surfaced in Southeast Asia, for example.

Living pterosaurs ("pterodactyls")? by Glen J. Kuban