Running head: MAJOR EXTINCTION EVENTS AND BIODIVERSITY1Major Extinction Events and BiodiversityTisha JonesSouth University OnlineBiology II | BIO1021 S01Week 1, Assignment 3Professor EverettNovember 22, 2016
MAJOR EXTINCTION EVENTS AND BIODIVERSITY 2Major Extinction Events and BiodiversityDescribe the common pattern of alternating extinctions and radiations.“Biologists suspect we’re living through the sixth major mass extinction. Earth has witnessed five, when more than 75% of species disappeared. Palaeontologists spot them when species go missing from the global fossil record, including the iconic specimens shown here. “We don’t always know what caused them but most had something to do with rapid climate change”, says Melbourne Museum palaeontologist Rolf Schmidt.” (Richter, Murcia, Clark, Taylor, & Schmidt, 2015)In the first mass extinction, Ordovician, the graptolites were eighty-six percent dead. Most of them were sea creatures. They died over a million years. It was caused by an ice age thatwas short yet very severe. The sea levels were depressed and caused by the elevation of the Appalachians which in turn caused new silicate rock to be uncovered. This new rock drained carbon dioxide out of the atmosphere causing the Earth to get a lot colder.In the second mass extinction, Devonian, the Trilobites were seventy-five percent dead. The Trilobites were very diverse and plentiful that emerged after the Cambrian explosion. The armor and special eyes that they had helped them survive the Cambrian explosion. They were safe in the first mass extinction, but not for the second mass explosion. Land plants were the reason for the mass extinction. The land plants had deep roots that moved the soil and rocks around which caused nutrients to release into the ocean. The new nutrients caused the algal blooms to emerge thus in turn caused the oxygen to be drained from the ocean. Without the oxygen, the trilobites suffocated to death.