What is extinction? What is an endemic species and why are such species vulnerable to extinction? Define and distinguish between the background extinction rate and a mass extinction. How many mass...

What is extinction? What is an endemic species and why are such species vulnerable to extinction? Define and distinguish between the background extinction rate and a mass extinction. How many mass extinctions has the earth experienced? What is one of the leading causes of the rising rate of extinction? Explain why the monarch butterfly is threatened with extinction.