Everyone has heard about the dinosaurs. No doubt one of the reasons why is because of their size, another being the fact that they ruled the Earth just like humans do now. In the grand scheme of things, dinosaurs represented a major turn in the evolutionary development of organisms on Earth.

Dinosaurs, the Greek word meaning terrible lizard, were the most advanced reptiles of all time; due to the fact they were allowed to occupy as many ecological niches as they could without much competition in any form. Literally, the sky was the limit. Although the sky was the limit, it is thought that the original dinosaurs were of very similar nature to that of the early reptiles mentioned on the previous page. Over time, these organisms slowly moved away from moving with 4 feet to 2 feet, essentially bipedal motion.

The first distinct dinosaurs occurred within the beginning of the Triassic Period, named after this occurrence. Two distinct types of dinosaurs had evolved, some that were bird-like and some that were reptile-like. Within these two categories, dinosaurs further diversified to become carnivores, herbivores or indeed omnivores. The main fact to heed is that the dinosaurs evolved and diversified at an amazing and effective rate, to the extent that they 'ruled the world'.

The most notable thing about these organisms is their size; they were huge compared to any other organism that had preceded them. This had obvious selective advantage, particular in the form of sheer bulk and power. The herbivores were also tall enough to graze on the top of trees, which were rarely taken advantage of as a source of food by organisms of the time, purely because they could not reach the top of trees.

Essentially, the dinosaurs continued to evolve, and in some cases became bigger and stronger, such as Tyrannosaurus Rex, the largest carnivore on Earth at the time. The Jurassic period also witnessed the emergence of the pterodactyl, a pendactyl digitate organism that ruled the skies. A balanced relationship would have occurred between the dinosaur herbivores and carnivores. The relationship between them, their relationship between other organisms, their relationship with the environment and the movement into new environments would all be under the influence of natural selection in the long run. While the dinosaurs ruled the Earth, a competitor was emerging, the Mammalian classification of species, of which, man belongs to.