How will life end on Earth?

Yet life's 4-billion year rule on this planet hasn't come uncontested. Evolution can't keep pace with rapid environmental change or protect us from certain extraordinary events. At least five separate extinction episodes have threatened life on Earth, destruction brought on by both cosmic bombardments and the planet's own internal turmoil. read more

When that happens, it'll flare up, become a red giant and engulf the inner planets and end any life remaining on Earth. Long before that, in fact, life have become uncomfortable on Earth because the sun is getting brighter all the time. read more

The other answers for this question are lacking a few important details. While it is true that Sol will turn into a red giant in about 5 billion years, probably destroying Earth in the process, life on Earth will likely be terminated long before that. read more