Explain extinction of dinosaurs 65 million years ago and the subsequnt dominance of mammals.  Discuss in the light of Darwin's Principle of Natural Selection.

Expert Answers
enotechris eNotes educator| Certified Educator

Current theory has the mass extinction of 65 million years ago, otherwise known as the "Great Die-Off," caused by a massive meteor striking the Earth in what is now the Gulf of Mexico.  Scientists estimate 80% of species were destroyed. Earth's climate had been warmer than it is today, and the impact caused enough debris to be scattered into the atmosphere that the climate cooled relatively quickly.  (Part of the support for this theory is the uniform level of iridium found all around the world at the 65 million year level.  Meteors are rich in iridium.)  Thus the warm, stable climate that supported the dinosaurs altered abruptly, and the cooling climate favored creatures who could regulate body temperature (warm-blooded) like mammals.  Dinosaurs, being cold-blooded, or having body temperature altered by the climate, could no longer survive in a colder world.  Additionally, what warm-cultivated food supplies that existed were destroyed.  A massive ecosystem change occurred, which favored plants and animals that could survive the colder conditions.  Natural selection came into play by favoring those species that could survive the change and reproduce and pass on "cold living" characteristics; species that could not adapt to the cold died out. Since so much death occurred at once, species that remained could quickly develop and "fill in" the environments where dinosaurs had been supreme.

Access hundreds of thousands of answers with a free trial.

Start Free Trial
Ask a Question