The Triassic-Jurassic Extinction

In the two essays being discussed we learn that science has a vast range of definitions. Science is the effort to understand (or to understand better), the history of the natural world and how the natural world works with observable physical evidence as the base of understanding. Science is about how the hypothesis is developed and how well it is defended.

The main dinosaurs that died off were Sauropod dinosaurs, long necked, four legged dinosaurs, and stegosauridae, class holding Stegosaurus. Other species that died include ammonites, similar to the living animals called nautilus, many marine reptiles, and bivalves, relatable to modern mollusca. Not much is known about this extinction. It is mainly linked to climate change. So far, no connection to volcanic activity or an asteroid has been made. This extinction gave way to the Cretaceous Period.

The Cretaceous mass extinction is the most well-known case of meteorite impact on the earth, but it certainly is not the only one. It is merely the most well-known. Due to the impact, debris entered earth's atmosphere and caused the plant life of the time to die off due to the lack of sunlight to survive. This made food much more scarce for the species that were dominant at the time. The competition was simply too much for them, and as the plant life died out, so did the herbivores and then the carnivores died out as well. Not only the land was impacted, however, the sea life was affected heavily by this impact as well. The lack of sunlight caused the oceans to become colder, causing the habitats of many marine animals to be drastically altered

The Cretaceous-Tertiary extinction or K-T extinction, which marks the Late Cretaceous, is a massive and large-scale extinction of animal and plant species that occurred over a short period of time 66 million years ago.

Four and a half billion years ago, the debris and dust left from the formation of the sun coalesced to form our home planet. 3.5 billion years ago, the first living organisms appeared on Earth. About 230 million years ago, Dinosaurs diverged from their Archosaurs ancestors during the middle to late Triassic period. For 160 million years they have dominated our planet. They are dubbed the most successful species to have lived on Earth. However, 65 million years ago, the most recent mass extinction seemed to have caused all of them to die-off. What caused the demise of the dinosaurs and 60% of life on Earth at the time? How did it affect life on Earth afterwards? Are all of the Dinosaurs dead? Will this happen to humans in the near future?

The age of the planet Earth is estimated to be about four point six billion years old. Life on Earth is estimated to have started one billion years later. Evolution has taken place since then. Evolving life from simple forms into more complex forms through the course of time. It all began with single celled organisms, prokaryotes. Later evolving in a period of two hundred million years, cyanobacteria began to produce photosynthesis. And life went on, evolving, adapting to its home. However through this course of time, mass extinctions have taken place on planet Earth. One of the most recent mass extinctions, has as a matter of fact left various amounts of evidence of the creatures which roamed the Earth at that time. Such magnificent creatures which varied from a very small size to giant sizes. Creatures which are now known to humanity as dinosaurs. The name of this extinction was the Cretaceous-Tertiary Mass Extinction. This extinction took place roughly sixty five million years ago. It has not been too long since this incident compared to the life span of the Earth. And yet it is still unclear how this extinction occurred. Paleontologists to this day, debate on how this extinction occurred. A major factor on what caused this extinction to occur was an impact of an asteroid. Another theory such as sea level regression is considered to be the blame for the extinction. Sea level regression is the drop of sea levels which aids to explain the marine mass extinction, however

The Cretaceous mass extinction had two theories on how and why it happened through the impact hypothesis. The first one was suggested that an asteroid collided with Earth 65 million years ago. Luis Alvarez and his son, Walter Alvarez found “high levels of the rare metal iridium” in the layers of the Earth during the periods of the Cretaceous and Tertiary located in Italy. Their proof is that it was the cause of extinction by an asteroid the size of 10 kilometers. The second impact hypothesis was from a crater that was found buried off the coast of Yucatan, Mexico. Due to the material that was thrown from the crater into the air, plant life could not receive sunlight to survive. The same goes for animals as the atmosphere was filled with dangerous

There are many theories explaining the extinction of the dinosaur. The Most probable theories are: a massive meteor hit the earth causing the extinction. B. A chain of volcano’s erupted and caused acid rain, shortage of sunlight and any other number of atmospheric problems that brought about the extinction of dinosaurs. C. Rapid Climate Change in a short period of time would have brought the dinosaurs to extinction because of an inability to evolve to the new environment. All these theories are possible but it is clear that it was a combination of all three theories working together that produced a worldwide extinction event.

There have been 5 mass extinctions in Earth’s existence. The names of these are (from most recent to least recent): Cretaceous–Paleogene, Triassic–Jurassic, Permian–Triassic, Late Devonian, and Ordovician–Silurian. The most well known mass extinction, Cretaceous-Paleogene, was theorized to have occurred through a massive comet or asteroid impact. A cold winter created by the impacting object forbid any plants and plankton to carry out photosynthesis. During this time, about three quarters of all life went extinct. This happened approximately 66 million years ago. Most life forms went extinct, with some ectothermic species and tetrapods weighing less than 25 pounds. Although everything seemed to look hopeless, adaptive radiation caused evolution

Fusulinid foraminifera disappeared completely, although other foram groups suffered much lower levels of extinction. Palaeozoic corals (Rugosa and Tabulata) also vanished. Stenolaemate bryozoans and articulate brachiopods suffered near-complete extinction. The extant echinoderm groups all experienced severe bottlenecks at this time: only two lineages of crinoids and echinoids made it into the Mesozoic. Several echinoderm groups (e.g. Blastoidea) suffered complete extinction.

We know that there is evidence that dinosaurs once roamed the earth. The only thing dinosaurs left behind is their bones that has helped us learn more about them like what they might have looked like, what they ate, and where they lived but the biggest mystery that still has not been explained is, what exactly caused this mass extinction of dinosaurs to be wiped off the face of the earth?Dinosaurs lived for 165 millions years until 66 million years ago when they went extinct. In this mass extinction 70 percent of species including dinosaurs, plants, and ocean animals were hit the hardest and caused them to die. In the ocean organisms like foraminifera that are single celled protists with shells, echinodermata marine invertebrate known as starfish

Another theory that some proposed as the cause of the Triassic-Jurassic mass extinction is high levels of toxic compounds released from volcanic activity. Directly around volcanic activity in the rift zone, there perhaps would have been high levels of Fluorine and Chlorine, both of which could have directly poisoned organisms. These large ejections of Chlorine and Fluorine could have led to ozone depletion and acid rain (McHone 2003). However, due to the fact that high levels of either of these compounds would have caused extinction without prejudice, the actual role that toxic compounds played during the Triassic-Jurassic extinction is hard to predict and study (Hautmann 2012).

Dinosaur extinction: An analysis of events and theories that possibly led to the dinosaurs' demise.

Over 98% of all organisms that have lived on Earth are now extinct. A mass extinction event occurs when a large number of species die out within a small time frame (relative to the age of Earth). Mass extinctions are intensively studied for both cause and effect, as there is usually room for debate regarding catalysts that precede the extinction and the massive influx of new biological species that follows. There have been five major mass extinctions, dubbed the “Big Five,” that have wiped out at least 50% of the species living at those times. The most well known mass extinction of the Big Five, with the decimation of every species of non-avian dinosaur, is the Cretaceous-Paleogene

They say as mammals continued to evolve, they drove the dinosaurs into extinction (“What Killed the Dinosaurs”). “Not only did mammals likely compete with dinosaurs for resources, many species survived the end-Cretaceous extinction and subsequently came to dominate Earth.” (“What Killed the Dinosaurs?”). This is primarily because the early mammals were a lot smaller than the mammals that exist today. “Some of the world's earliest mammals were the multituberculates, a group of small rodent like animals that first emerged on Earth about 165 million years ago.” (Welsh, Jennifer). Scientists predict that any mass extinction event that caused animals to go extinct affected larger animals than it did the smaller animals, such as mammals ("Dinosaurs Became Extinct 'due to Laying Eggs'"). Mammals remained small for almost 100 million years, while they out competed small and baby dinosaurs for food, shelter and resources until they were extinct. Once the dinosaurs were out of the way mammals were able to evolve and grow large in size like the mammals that exist today today (LiveScience). Fossil evidence sheds some light on this theory as well. Fossils of mammals believed to date back to about eighty five million years ago show that mammals began to change rapidly and grow. “This matches up with other mammal groups, including recently discovered species from the Late Cretaceous (between 100 million and 65 million years ago) showing highly specialized