Geologic Timeline Individual Reflection

In this activity, I found that three major events that changed the course of Earth's history are the Cambrian explosion, the Triassic period, and the Quaternary period. The Cambrian explosion followed the Precambrian era, during which organisms capable of undergoing photosynthesis developed, increasing the amount of oxygen in the atmosphere to be high enough to support life. The Cambrian explosion is noted by a sudden appearance in the fossil record when many organisms suddenly began to exist. This is a major event in the history of Earth because all life originated from this one geological event. The Triassic period is a pivotal period because it was during the early times of dinosaurs and the origin of mammals. Dinosaurs eventually evolved into the birds and reptiles of our current time period, making it significant in being the birthplace of many species that we know and love today. The creation of mammals was extremely significant because it was also the birth of the unique characteristics of hair, warm-blood, milk producing females, live births, and much more complex brains. This event set the stage for the population of intelligent species, humans, which drastically changed the history of Earth. Leading up to the third major event in the history of Earth: the quaternary period. This period consists of the first fossils of homeosapiens and our present day. The quaternary period significantly altered Earth's history because we quickly and immensely populated the planet, causing crucial events such as global warming. The mark on the planet that we are making now will cause future generations to look back at our accomplishments and consider them a drastic turning point in the geological timeline.

It was surprising to me that the majority of Earth's history consists of the Precambrian period, before life even existed. I was also astonished at the millimeter of space our species takes up on our 10 meter timeline. Before this activity it never really hit me how insignificant we are in the history of our planet. It's hard to wrap your head around the fact that our lives are so short and our impact on Earth is so microscopic.

I still want to know why marine life developed before land creatures?

<https://commons.wikimedia.org/wiki/File:Timeline_evolution_of_life.svg>