Survival or Extinction Plain Ole Luck

Currently, many scientists think survival is a combination of a great deal of adaptability and a healthy dose of plain ole good luck.

Natural selection happens very slowly and gradually. This means only a few species die out every million years or so. Even

CASE STUDY: COLD BLOODED VERSUS WARM BLOODED

Some scientists have wondered if body temperature has anything to do with surviving the K-T mass extinction. Reptiles like crocodiles and alligators are cold-blooded animals.They need direct sunlight shining on them to stay warm. If it is cold and rainy, their bodies become very cold. Mammals are warm-blooded animals.Their bodies stay warm whether it is sunny outside or not. For example, humans maintain a constant body temperature of 98.6°F (37°C). Warm-blooded animals need to eat all the time to maintain their body temperature.

During the K-T mass extinction, we are sure of one thing:The temperature changed in extreme ways. We do not know if the world became extremely hot or extremely cold. Perhaps the warm-blooded mammals adapted more easily to these shifts in temperature. Scientists theorize this could be one of the reasons mammals survived.

However, cold-blooded animals survived as well—crocodiles, turtles, alligators, and lizards, to name a few. Some say cold-blooded animals had an advantage.They could slow their bodily processes down and not eat for long time spans. This allowed them to wait out the disaster until the temperatures went back to normal.

Both cold-blooded reptiles and warm-blooded mammals survived the K-T mass extinction. Research suggests that some dinosaur species were warm blooded and others were cold blooded. However, there were no surviving dinosaurs. At this point, scientists cannot say if survival is linked to body temperature.

The great auk was a flightless bird last seen around 1844. Several factors predicted its extinction: it did not breed until it was several years old, laid only a few eggs at a time, and did not have many safe places to raise its young. Still, humans, who killed thousands of auks for their feathers, oil, and meat, are the main reason for their extinction.

so, after intense investigations of the evidence over many years, it seems that no one can predict exactly what will make one species more adaptable than another. The very traits that will allow one species to adapt and survive are unknown. These specialized survival traits only emerge when a species is confronted by a new situation. We have all heard heroic stories about people finding incredible strength, for example, to pull a car off another person. This shows us how we never really know what hidden strengths we have until we need them.

As we have seen, these rules of survival—adapt or die—are doubly true during a mass extinction. Most species cannot adapt quickly enough in these extreme circumstances and die off. Yet, a few do survive even these most challenging circumstances. If a species' size does not matter, what traits help some survive while others become extinct?

Random luck. Fossil records show that the very traits that helped species adapt and survive during ordinary times have nothing to do with living through a mass extinction. In fact, scientists hypothesize that those exact same traits could even be the cause of their extinction. Those species that do endure a mass extinction just happen to have some surprising special trait that allows them to survive. Therefore, many evolutionary scientists conclude that it is impossible to predict exactly who will outlive a mass extinction.

To sum it up, life is unpredictable. Who would have bet that dinosaurs would become extinct and mammals would thrive? Either way, perhaps humans should just thank their lucky stars it turned out this way!

CHAPTER SIX

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