Why were the dinosaurs so big?

Question

I need to know why the dinosaurs got so big to settle a dispute between my brothers

Answer 1

because that is the way that evolution sometimes work.

Answer 2

There is no good answer. My paleontologist pals are still scratching their heads. One theory, is that it is thought that perhaps the herbivorous dinosaurs grew big as a defensive mechanism. (Today, there are no predators that will take on a healthy adult elephant). In response to this, many of the predators grew bigger so that they could take on the large herbivores. A positive feedback loop developed. Possibly, the larger dinosaurs were able to out compete the smaller ones in their quest for survival. So, the genes that would produce yet larger animals were propagated producing larger and larger dinosaurs. That's one theory. It's also possible that there was simply so much large food around for the herbivores, and just the perfect amount of heat and atmospheric gases, that everyone just grew larger. It has also been stated that they grew large because of a difference in lifestyles. The significant difference between growth in reptiles and that in mammals is that a reptile has the potential of growing throughout its entire life, where a puny mammal such as ourselves, reaches our "terminal size" (cool scientific term) and stops growing, even though most of us continue to live for many years. That's why you see no 82 year old basketball stars. To continue with another thought, the size of the dinosaurs is possibly a simple consequence of how they fed. Vegetation is a tough diet for all animals and the sauropods were high browsers relying on the particularly tough leaves of conifers. Their teeth were simple and designed for nipping or raking foliage from trees, rather than for chewing (somewhat like a modern giraffe). They had stone laden gizzards (just like vultures) which they used to grind up the tough leaves, but breaking down the plant cells could only be achieved by using the stomach as a huge fermentation tank. Sauropods had to be big because they had to contain a huge stomach. Being big is a useful adaptation in itself. It gives some protection against predators - unless they too evolve bigger. It also gives more insulation, either to prevent overheating in the sun, or to avoid heat loss when it gets cold. In the end, the simple answer is, "because that was the perfect body-form for the time." All dinosaurs were not huge. But a few modern large animals - mammals - such as elephants and whales have grown that way just because evolution made them that way. Sort of a cop-out answer, I know, but the fact is, I have paleontologist friends, but I'm not a paleontologist - and they don't know anyway. But your question is a very popular question.

Answer 3

Simple, the time of the largest dinosaurs, the earth was proven to be basically a tropical planet and formed one land mass near the equator, baically where the tropical forest sit now. The whole world had tons of nurishing food for plant and fruit eating species which, along with an oxygen rich planet from all the vegitation, created larger species. So now meat eating species also had rich oxygen and an abudant meat supply. You can see it in evolution today - species that have a good and nurishing food supply will grow larger than a species that is malnurished.

Answer 4

Prior to 1846, dinosaures were called dragons. The translation of the word dinosaur, however, means terrible lizard. Dinosaurs were just really big lizards. Reptiles grow throughout the span of there life.
Before Noah's flood, the world was a much different place than it is today. The world that we live in today, as beautiful as it is, is a junkyard compared to what it was before the flood.
When God created the world it was a paridise made for living in. Today 70% of the world is water, 30% is land and only 3% of that land is inhabitable for human beings.
An 80 foot tall Apathosaurus has nostriles the same size as a horse. Resently, "scientist" have been saying that maybe dinosaurs died from a lack of oxygen. Their lungs and nostriles are both to small to breath the air that we breath today.
In amber (pertified tree sap) sometimes they find air bubbles that contains more oxygen than the air we breath today. And, it is believed that before Noah's flood there was a canopy of water above the earth (liquid, vapor, or ice), the had a green house effect on the earth that would have also increased the air pressure.
If the oxygen content was richer, and the air presure was increased, the Apathosaurus would have no problem breathing.
Back in Adam's day, people lived to be over 900 years old.
You won't find them in your public school textbooks, but, there are human fossiles found all around the world that are 9-13 feet tall.
I am not saying that humans grew throughout their life spans, just that everything grew really big in those times. Dragonflies with a 3 foot wing span. Grasshoppers 2 feet long. 18 foot tall rino. Hugh plants and trees.
So, put a lizard in the Garden of Eden, with oxygen rich air and increased air presure, let it live 900 years, and you have got yourself a terrible lizard.
Get "Evolution, Dinosaurs, and the Bible", 7 video seiminar by Dr. Kent Hovind @ drdino.com
see for yourself.

Answer 5

Vegetarian dinosaurs such as the sauropods needed to have big stomachs to digest what was pretty poor food- conifers and such that were difficult to digest without fermentation. A big stomach needs a big body to support it. Because the vegetarian dinosaurs were big the carnivorous dinosaurs needed to be big to attack them. But not all dinosaurs were big anyway.

Answer 6

Because they were. Its not a good idea to be big because you have a lot of body to keep fed. On the other hand, physical size does take you off the shopping list for smaller preditors.

There were a lot of smaller animals about at the time as well.

Answer 7

To be bigger was an advantage against many predators.
Also, less skin versus volume ratio helped keeping their body temperature, as they were basically reptiles without the automatic body temperature control that birds and mammals have.
Most of them were vegetarian and there was enough food for them until a drastic colder climate change caused their extinction.

Answer 8

not all dinosaurs were big, some were exteremley small
the bigger dinosaurs were probably that size because it was needed for survival.

Answer 9

Because, the earth gravity was lesser in that time.

Answer 10

They had a lot of land to fertilize.