Why were prehistoric animals so large?

Answer 1

In the past reptiles were the dominant species, so could eat everything they wanted. Now there are warm blooded animals (mammals). Mammals can hunt at night and in cold environments so mostly reptiles do nolonger have the chance to grow large.

There is much debate on what caused the dinosaurs to die out, leaving this evolutionary window for mammals to take advantage of.

Answer 2

It's simple: survival of the fittest. If there were two animals of the same age and gender, but one was bigger, the bigger one would be more likely to survive; mainly because it would be stronger and weigh more. With more strength and weight, it could take down more prey in a shorter period of time, e.a. pinning its prey in a corner. As more animals became advanced, there was less need to constantly fight (either for food or survival), and, having smaller bodies would conserve heat and/or energy. The reason their bodies evolved was mainly because it became unnesacary to always be suited for battle, like to carry around a machine gun in New York City. It was simply not needed.

Actually a big body helped animals conserve heat when it heated up they were wearing a parka in an oven so to say

Answer 3

For the most part, they weren't. Many of the animals from various time periods were about the same size as those that fill their ecological niches today. However, the reason for large body size in animals is either to avoid predation or to avoid competition for food. Herbivores at the end of the Cretaceous period got so big to avoid predators, but as a result the predators got larger, too.

Relative animal size also has a lot to do with energy and water management. Arctic or hot-climate species are often larger to better manage their body heat. Surface (hence radiant) heat loss or gain is directly affected by dimensions, and rises with the "square" of body dimensional increases. Body mass, on the other hand, increases with the "cube" function, rising faster than surface area as the animal's size increases. Polar bears shed less heat per unit of body mass than does a smaller Asian sun bear or an American black bear living in the American south. African elephants can eat less to live because of good heat- or water-retention. They can also shed that heat effectively with those giant radiator ears.

And just FYI, the large baleen whales of today are the largest organisms that have EVER inhabited the earth. They are several times larger than the largest dinosaurs.

Answer 4

The larger an animal is, the less of its body mass is exposed to the elements. This is also why animals in a desert climate tend to be smaller.

Many animals cool off by increasing the surface area of their bodies. For example, crocodiles will open their jaws to release heat during the day's peak temperatures. The desert fox is famous for its large ears, which partially serve to regulate body temperature.

Answer 5

Oxygen causes.The oxygen in the atmosphere in prehistoric times were greatly higher.

Answer 6

because they had to adapt when the world started to have a larger population.