Our world is a great incubator of life, however it likes to go through periods of change where only those ready to adapt will survive. Five times already, our planet has gone through periods of mass species extinction, forcing those who want to survive to adapt and overcome. We are now facing a sixth major extinction, one not caused by a force of nature, but caused by a single species. We will take a look into the first five major extinction and then delve into the one that is ongoing right now.
The first major mass extinction occurred approximately 440 mya, and is known as the Ordovician–Silurian extinction event. This event was triggered by rapid cooling, and the corollary effect of the lower sea level from glaciers forming. Laurentian brachiopods were hit the hardest by this event as they lived in shallower sections of the ocean leaving them the most exposed by the event. As most life at this time existed in the shallow waters it is, easy to see why this was the second largest of the five major mass extinctions.
The second mass extinction occurred approximately 370 mya and is commonly referred to as the Late Devonian extinction. 70 million years later, we have more complex life, which has moved out of the ocean making use of the land. The Late Devonian extinction is not a single event but a myriad of smaller scale extinctions such as the Kellwasser event, and the Hangenberg event that are combined to create the entirety of the major extinction event.
The third mass extinction happened approximately 245 mya and is referred to as the Permian–Triassic extinction event. “More than half of the families of living things died out, and as many as 90 to 96 percent of the planet's marine species were lost. At the same time, perhaps 70 percent of the land's reptile, amphibian, insect, and plants species went extinct” (evolution library, 2001). This makes it easy to see why this event is also called the “great Dying” as it is the most devastating of the five major extinction events. There are different schools of thought on how exactly this extinction event was triggered, however this time it was not cooling of the planet, but overheating that triggered the extinction.
The fourth major extinction happened approximately 210 mya and is referred to as the Triassic–Jurassic extinction event. It is this mass extinction that is thought to have allowed dinosaurs to become the dominant species on earth. This extinction was brought on by warmer annual temperatures, which...