11) When did plants, animals, and fungi start colonizing land? Why did they do this, and why was it important? 12) What events resulted in what we call fossil fuels? What type of organisms are responsible for fossil fuels? 13) What is a mass extinction event? Why is it hard to determine the cause(s) for mass extinction events? 14) Why are extinction events often followed by the evolution of new groups of organisms? 15) What is a niche? 16) Did mammals exist at the same time as dinosaurs? 17) What is coevolution and how is it relevant to understanding the history of life on earth? 18) Why did the dinosaur extinction lead to mammals becoming dominant on land? 19) Not in the video: What is the Anthropocene? How are humans currently effecting life on earth? .