You are thinking of diffrent things. The big bang was a giant explosion that allowed all the dust and debris from that to come together to form earth. Billions of years later was the dinosaurs thing
an asteroid hitting the earth, drought, volcanoes, disease, or rising sea levels
About 65 million years ago a giant asteroid hit the Earth in today's Mexico. It caused many climate changes, which killed the dinosaurs.
Scientists usually refer to this as an asteroid, not a comet. It's the asteroid that caused the Chicxulub crater.
The dinosaurs all died out. A major catastrophe, probably an asteroid impact, caused their extinction.
Nobody really knows how dinosaurs got extinct.
A crater did not take out the dinosaurs..... But the crater caused by the asteroid that took out the dinosaurs is about 180 km (110 miles) in diameter.
Based on the popular theory that the dinosaurs went extinct due to the impact of a large asteroid, scientists think that the asteroid caused large amounts of debris to fly into the atmosphere, blocking out the sun. This caused global temperatures to drop, thus freezing the plants. In addition, without the sun the plants could not carry on photosynthesis, which caused them to die.
Based on the popular theory that the dinosaurs went extinct due to the impact of a large asteroid, scientists think that the asteroid caused large amounts of debris to fly into the atmosphere, blocking out the sun. This caused global temperatures to drop, thus freezing the plants. In addition, without the sun the plants could not carry on photosynthesis, which caused them to die.
Briefly, the theory is that the mass extinction which included the loss of the dinosaurs at the end of the Cretaceous period was caused by the impact of a large asteroid.
mexaco
Change can benefit an organism if the change gives it an advantage over other organisms. For example, the event that caused the dinosaurs to go extinct (probably an asteroid) affected mammals much less, allowing them to replace dinosaurs as the dominant type of animal on Earth.
Dinosaurs became extinct 65 million years ago, at the end of the Cretaceous period.