Why are no dinosaurs on earth?

Answer 1

To keep its line going, every creature needs a niche, a part of the environment that allows it to obtain food, protect it from becoming food, and successfully raise its young (this may or may not involve it actually parenting them). Some animals are good are finding niches, such as people -- and cockroaches. They can live anywhere (or almost), eat all sorts of stuff and have good strategies for producing offspring. Others have precarious niches, like the great panda and the koala. They have special food sources and if anything happens to those, they're in big trouble. Dinosaurs had a whole planet, but its ecosystem was very interwoven; when part of it was severely damaged, other parts began to fail, rather like mountain climbers tied together and all falling when one of them does. Whatever happened (most folks think a collision with an asteroid or comet), it damaged so much most dinosaurs couldn't recover from it. Apart from birds.