Sponges Ruled the World After Second-Largest Mass Extinction

Sponges may be simple creatures, but they basically ruled the world some 445 million years ago, after the Ordovician mass extinction, a new study finds. Roughly 85 percent of all species died in the Ordovician mass extinction, the first of the world's five known mass extinctions. "We think the sponges thrived because they can tolerate changes in temperature and low oxygen levels, while their food source (organic particles in the water) would have been increased enormously by the death and destru