68K views · 364 reactions | What happens when you lose a keystone species, like sea otters or kelp? Find out in "Extinction: The Facts,” now streaming on the PBS Video app. | PBS | Facebook

In the middle of the Cambrian, life on land was about to get a little more crowded. And those newcomers would end up changing the world. The arrival of plants on land would make the world colder, drain much of the oxygen out of the oceans and eventually, it would help cause a massive extinction event. For more videos like this, check out our Youtube channel: youtube.com/eons | Eons • PBS