生命起源

In the early Paleozoic, plants evolved to leave the water and invade the terrestrial landscape. Following this transition, vertebrates emerged into land-based ecosystems, and Carbon Dioxide concentrations increased in the atmosphere. The greenhouse warming of the Earth propelled the success of both prevascular and vascular plants, as well as the related terrestrial radiation of the three lineages of the reptiles. This week, you'll also learn about the Permian-Triassic mass extinction and later environmental changes that opened the door to the rise of the diapsids.

This week, you'll learn more about the Permian-Triassic extinction event, which caused more than 80% of life to go extinct. This opened vast swaths of ecological opportunity for radiation and diversification of life during the Mesozoic. You'll learn about symbiosis, which was widely utilized during this period, as well as the fascinating lineage of diapsid reptiles that rose to replace the synapsid predators of the late Paleozoic. We'll also discuss the rise of the dinosaurs, as well as the catastrophic meteor impact that drove the dinosaurs to extinction.

With the demise of the dinosaurs, mammals rapidly radiated and diversified during the Cenozoic. The combination of abundant food sources and significant fluctuations in global climate fostered extreme variations in morphology, body size, and interaction with the environment. You'll learn why mammals had a distinct advantage over previous groups, and you'll also have the opportunity to explore multiple theories on primate and hominoid evolution in the context of global conditions during this period.

No matter where you are or what you believe, sometime in your life you will look up into the sky and ask: What is out there? Where are we going? Is there life elsewhere in the universe?

This course is dedicated to searching for answers to these questions. The fundamental concepts of life and habitable environments, established upon the modern synthesis of the Tree of Life, will direct us in recognizing biospheres that might be quite different from our own. In the last week of this course, we will look in detail at what the future has in store for space exploration and the search for life in the cosmos.