Fossils are fundamental to discovering information about the past inhabitants of Earth over the course of its 4.5 billion year history. Along with learning about the geological time of the Earth, students also learned about the different types of fossils and how they give us insight into the past. We briefly explored the various types of fossils that can be found, including body fossils (cast, petrified wood, or whole body) that tell us what organisms looked like, and trace fossils (footprints, and coprolites) that tell us how an organism lived.
Students discovered that geologic time – the time period encompassing Earth’s formation til the present day- is divided into 2 major time spans: Precambrian time and Phanerozoic Eon– each of which were distinguished by the different forms of life and atmospheric conditions. For instance, students learned that during Precambrian time (4.5 billion years ago to 600 million years ago) Earth’s atmosphere consisted of very inhospitable conditions – toxic gases and constant bombardment by space debris. Students also learned that in spite of these conditions, Earth’s atmosphere changed to allow for special bacteria (cyanobacteria) to inhabit the earth. These bacteria left behind stromatolites -the first and oldest fossils on the planet. At the end of this time, students learned that oxygen becomes a predominant gas in Earth’s atmosphere, allowing for the emergence of even more complex single celled life forms.
Following this discussion of the early life on Earth, we discussed how more complex living things began to inhabit the earth during the Phanerozoic Eon (600 million years ago to present day). As a group, students noted that this eon was marked by the age of the dinosaurs and large land mammals (ancestors of common animals we are familiar with today), and finally,the evolution of humans (2 million years ago).
To continue with the exploration of the past, students were then turned into paleontologists! They were able to excavate their own dinosaur bone fossils from a rock using tools and techniques similar to those employed by paleontologists and reassemble their dinosaur skeletons.