The End of the World

Have anybody ever thought what the end of the world will be like? Do every live things just died off completely, or the Earth just exploded to count as the end of the world. When do religions mean when they say the world will end? Is it just mean that the human will all died off. If this was the case, what will happen to the animal that is living on this planet. Because as long as there is living thing on this planet, it will never be consider as the end of the world. Think about it.