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Dinosaurs An era- extinct
What are dinosaurs? • Dinosaurs were the dominant vertebrateanimals of terrestrial ecosystem for over 160million years. The dinosaurs evolved from a group of early reptiles known as thecodonts, which arose during the Permian period (290-250 million years ago) and were dominant throughout the Triassic (250-208 million years ago.
Two major groups of dinosaurs evolved from the thecodonts The ornithischian (bird hips) dinosaurs The saurischian (lizard hips) dinosaurs
Commonalities of 2 groups Both of these dinosaur lineages originated at about the same time. Both evolved into many species that were ecologically important and persisted until about 66 million years ago.
Difference between the two dinosaur groups. "Bird-Hipped" dinosaurs" Lizard-Hipped" dinosaurs • They had beak-like bone in the lower jaw in front of the teeth, called a predentary. • Narrow palebral (the bone that crosses the outside of the eye socket) • Bony (ossified) tendons above the sacral area of the vertebrae • Opening below the nostrils (called the subnarial foramen) • An elongation some neck vertebrae (resulting in long necks) • A big thumb, • An extra, wedge-shaped ankle bone (the astragalus)
How did the dinosaurs die? This is one of the greatest mysteries of all times, and still waiting to be solved. All scientists agree that the last dinosaur died out for some reason about 65 million years ago
Different theories of dinosaur extinction: Greenhouse effect Asteroid ozone Giant meteor
Greenhouse effect: The phenomenon where the earth's atmosphere traps solar radiation, caused by the presence in the atmosphere of gases such as carbon dioxide, water vapour, and methane that allow incoming sunlight to pass through but absorb heat radiated back from the earth's surface.
Asteroid There is proof that an asteroid Over 9 miles wide stuck the earth on the tip of the Yucatan peninsula, in the Gulf of Mexico. Asteroids happen every now and then today, but a big one would be the size of a basket ball nowadays. A 9 mile long asteroid would change atmosphere all over the world. Massive forest fires would spread through countries, severe storms all over the world, poor air quality, ocean to ocean tidal waves, and probably the worst thing ever: It would eliminate ALL sunlight for longer than 6 months. This would surely kill 70% of all life forms. The only that would survive would be smaller animals hiding out through this destruction. :
Ozone layer The ozone layer is like a protective shield against these rays. It blocks most of the harmful energy that the sun sends to the surface of the earth.
Giant meteor If a huge meteor hit the earth The force of the impact would probably rise millions of tons of dust into the air. It might also shake the earth enough to start eruptions from many volcanoes. The dense clouds of smoke and dust in the air would keep sunlight from reaching the surface of the earth. And for this reason most of the planets would die.
To understand the ozone theory,lets discuss ……… Ultraviolet rays Volcanic eruptions Ozone layer- definition and dynamics Effect on living organisms (especially dinosaurs)
Ultraviolet rays The sun is the natural source to all life. Without it there cannot be life. But the sun is so powerful that it does create dangerous substances such as the most common ultraviolet rays. Ultraviolet rays create a small amount of radiation which is harmful to all living organisms. It also is known to cause cancer as well, which is fatal. This is where the ozone layer comes into effect to fend off these hazardous and dangerous rays. The ozone layer is like a protective shield against these rays. It blocks most of the harmful energy that the sun sends to the surface of the earth.
Volcanic eruptions It is assumed that during the Cretaceous period there were many outbreaks of volcano's. When a volcano erupted it not only sprays millions of gallons of hot lava, but also a mass of a certain chemical called Hydrochloric acid. This poisonous gas can deface the ozone layer. One volcano would do much harm but scientists know that during the Cretaceous period there was not only one, but mass amounts of aggressive behaviour by volcanoes around the world.
Ozone layer- definition and dynamics Definition Ozone : The ozone layer is like a protective shield against these rays. It blocks most of the harmful energy that the sun sends to the surface of the earth.
Ozone layer dynamics The ozone layer is roughly 1 ½ miles high in the atmosphere and is transparent to the naked eye. This ozone layer can be damaged by pollution and it's common to hear from scientists that automobiles and big industries are causing damage to the ozone layer. Of course there weren’t cars in the Triassic, Jurassic, and Cretaceous period so ozone should've been in perfect condition during these huge reptiles roamed the earth. Actually there is one natural disaster that can damage the ozone layer really bad. Volcanos.
Effect on living organisms (especially dinosaurs) Most Dinosaurs did not have fur, and many were known not to be like crocodiles laying in water all of the time. This is proven by the way that their bodies are shaped. So we know that they ran around land and if the ozone layer broke apart then cancer is free to spread throughout the world • This would be the beginning of dinosaurs dying off.
Scientific Evidence Dinosaur extinction theories you'd realize that many are linked to volcano's because of the proof of that timeline and the loads of volcano rock material found at the same ground level as the latest found dinosaur fossils Dinosaur diggers have found that when they dig up dinosaur fossils that are dated from the Cretaceous period they also find a lot of volcano rock in the same area.
North American fossils: At present the most informative sequence of dinosaur-bearing rocks in the world from the K–T boundary is found in western North America, particularly the late maastrichtian-age hell creek formation of Montana, USA. In addition to rich dinosaur fossils, there are also plant fossils that illustrate the reduction in plant species across the K-T boundary
Marine fossils The mass extinction of marine plankton appears to have been abrupt and right a Further analysis shows that several processes were in progress in the late Cretaceous seas and partially overlapped in time, then ended with the abrupt mass extinction.
The K-T Boundary and Iridium The Cretaceous–Tertiary extinction event, which occurred approximately 65.6 million years ago (ma), was a large-scale mass extinction of animal and plant species in a geologically short period of time. Widely known as the K–T extinction event, it is associated with a geological signature known as the K-T boundary, usually a thin band of sedimentation found in various parts of the world. Non-avian dinosaur fossils are only found below the K–T boundary, indicating that dinosaurs became extinct immediately before or during the event.
K-T Boundery continued… Scientists theories that the K–T extinctions were caused by one or more catastrophic events such as massive asteroid impacts the cxichulub impact or increased volcanic activities. Several impact crater and massive volcanic activity in the Deccan traps have been dated to the approximate time of the extinction event. These geological events may have reduced sunlight and hindered photosynthesis, leading to a massive disruption in Earth's ecology.
Multiple Effect In a review article, J. David Archibald and David E. Fastovsky discussed a scenario combining three major postulated causes: volcanism, marine regression, and extraterrestrial impact. In this scenario, terrestrial and marine communities were stressed by the changes in and loss of habitats. Dinosaurs, as the largest vertebrates, were the first to be affected by environmental changes, and their diversity declined. At the same time, particular materials from volcanism cooled and dried areas of the globe. Then, an impact event occurred, causing collapses in photosynthesis-based food chains, both in the already-stressed terrestrial food chains and in the marine food chains.
Evidence that discredits Ozone Theory Multiple v/s Single cause effect The major difference between this hypothesis and the single-cause hypotheses is that its proponents view the suggested single causes as either not sufficient in strength to cause the extinctions or not likely to produce the taxonomic pattern of the extinction.
Bibliography http://pubs.usgs.gov/gip/dinosaurs/ http://www.waoy.org/26.html http://en.wikipedia.org/wiki/Dinosaur http://www.pbs.org/wgbh/evolution/extinction/dinosaurs/asteroid.html Thunder Through the Prehistoric land of Dinosaurs’, 2004, John BonnettWexo (Wexo.J), Wildlife education. Abc: web references Abc: book references
Tyrannosaurus rex, Brontosaurus, triceratops… … But how did they get their names? Why are they so hard to say? In 1842 more than 150 years ago, a scientist named Sir Richard Owen made up the name “dinosaur”. Well actual he called them deinos sauros. Those two words are Greek words. Deinos means terrible, sauros means lizard. So the word dinosaur really means terrible lizard. Dinosaur names all come from either Greek or Latin words. So part of each dinosaur name has either a Latin or Greek word in it some where .Perhaps that’s why they are so hard to say!!!!
Here is how it works. • Triceratops is the three horned dinosaur. In Greek the word tri means three, cerat means horn and ops means face- three horned face. Do you see how it works? Tyrannosaurus rex is the fierce meat eater. Tyranno means tyrant, sauros means lizard, rex means king. So what do you think that means??????? Tyrant lizard king
Thank you ……… Shreyas Gangwani 9HUU
