Would a lower oxygen level affect dinosaurs?

Yes, with a lower oxygen level, the dinosaurs could have experienced extreme respiratory stress. This is similar to what humans encounter when living or working at extremely high altitudes without supplemental oxygen.

Todays atmospheric oxygen level is 21 percent, but modern animals have the proper physiology to live in this atmosphere. Dinosaurs first evolved when the atmosphere was oxygen rich, and they had the right physiology for this situation. Studies of an Apatosaurus skeleton show a limited capacity to breath, with relatively small nostrils and probably no diaphragm. This was fine as long as the atmosphere was rich in oxygen, but it was inadequate when the oxygen levels fell.

Under this scenario, dinosaurs may have experienced three different events leading their gradual extinction. First was a cooling climate toward the end of the Cretaceous period. Second, the oxygen levels might have fallen, making it extremely difficult to breath. This probably led to a reduction in dinosaur diversity, shrinking the number of genera from 35 about 10 million years before the end of the Cretaceous period to only 12 at the end. At that point, a third and final catastrophic event may have occurred: An asteroid impact or impacts, and/or volcanic activity, which finally pushed the remaining dinosaurs to extinction.

Amber, which is fossilized tree sap, has been found to sometimes preserve fossil evidence, such as ancient insects, and even bubbles of oxygen, which may be analyzed for clues about the prehistoric atmosphere (iStock).

What is the theory concerning radiation killing off the dinosaurs?

According to recent findings, dinosaurs and other animals may have gone extinct because of epidemics of cancer. And although highly debated, some scientists believe these epidemics may have been caused by a massive burst of neutrinos or weakly interacting elementary particles from a star with no electric charge and apparently no effective mass from dying stars in our galaxy.

What could have caused lower oxygen levels at the end of the Cretaceous period?

The reduction in oxygen levels in Earths atmosphere toward the end of the Cretaceous period may have been caused by volcanic activity. Volcanic activity could have increased, modifying the relative amounts of atmospheric gases, such as carbon dioxide and oxygen. In turn, this would influence the evolution of life on the planet.

This is known as the Pele hypothesis, after the Polynesian goddess of volcanoes.

Many people today are concerned that global warming evidenced by such phenomena as melting ice caps will lead to species extinctions, including, possibly, our own. Scientists speculate that environmental changes may have also led to the dinosaurs extinction (iStock).

What is the mammal theory of dinosaur extinction?

The mammal theory of dinosaur extinction (which falls under the theory of gradualism) states that dinosaurs were slowly wiped out by mammals, animals that only appeared around the end of the Mesozoic era (the end of the Cretaceous period). The mammals could have eaten many of the dinosaurs eggs (thus, the dinosaurs had difficulty reproducing); or the mammals could have taken over territory from the dinosaurs. On a smaller scale, such events happen today, especially when an introduced species takes over another species by eating the native organisms young, or by taking over the territory and eating the available food supply.

What is the climate theory of dinosaur extinction?

The climate theory of dinosaur extinction is one that many scientists believe is more feasible than most other theories. One of the theories of gradualism is that the movement of continents over millions of years brought about changes in Earths climate, including the changing of oceanic currents; spreading of deserts; drying up of inland seas; shifts in Earths axis, orbit, or magnetic field; spreading of polar ice caps; and the increase in volcanic eruptions. The resulting slow climate changes (from either one, several, or all of the above events) caused the gradual decline of the dinosaurs. They could not evolve quickly enough to compensate for the changes.

What is the poison plant theory of dinosaur extinction?

The poison plant theory of dinosaur extinction involves the development of angiosperms (flowering plants), a new type of plant that first flourished during the Cretaceous period. Some of the plants were no doubt poisonous to dinosaurs, and the plants probably developed protective toxins to prevent being eaten. The more prolific plant-eating dinosaurs may have died out as the plants became more toxic to these animals; in turn, the carnivores had fewer plant-eating dinosaurs to eat.

But this theory is too simplistic. There were many plants in the world, including varieties that were non-poisonous. In addition, the idea does not explain the mass extinction of marine organisms animals that had nothing to do with flowering plants on land at the end of the Cretaceous period.

Did dinosaurs get blown away by hurricanes?

No one really knows, but several researchers think this may have been possible.

These scientists studied huge hurricanes called hypercanes, monster storms that grow much larger than modern hurricanes, especially if the ocean water is greatly warmed. They believe a large impacting meteorite struck or a major volcano erupted in shallow ocean waters, causing the ocean water temperatures to rise, doubling the temperatures we currently find in the tropics. This increase in water temperature could have created immense hypercanes. In turn, the storms could have carried water vapor, ice crystals, and dust high into the atmosphere, blocking sunlight and destroying the protective ozone layer that shields animals from the ultraviolet radiation of the Sun. The effect could have devastated the dinosaurs. Scientists acknowledge the idea is a little far-fetched, but not impossible.

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