The universe formed 14 billion years ago from an explosion referred to as the Big Bang • The universe is constantly expanding • http://www.brainpop.com/science/space/bigbang/zoom.weml
How did our solar system form? • Our solar system formed when the Big Bang explosion cooled.
How did Earth form? • Earth formed when dust, gases, and ice particles from the Big Bang collided, 4.6 billion years ago (4,600 million years ago). • http://www.teachersdomain.org/ext/ess05_img_walloftime/index.html
What keeps Earth from being bombarded with space debris? • Earth’s atmosphere and magnetic field protects it from being bombarded by space debris.
When did humans appear on Earth? • Humans appeared on Earth very, very recently; about 100,000 years ago.
How do we know what life existed on Earth before humans? • Fossils tell us what life forms existed before humans.
What is a fossil? • http://www.brainpop.com/science/diversityoflife/fossils/quiz/
A fossil is… • Body fossil- • Trace fossil- • Mold- • Cast- • Petrified fossil-
A fossil is the preserved remains or traces of an organism that lived in the past.
Body fossil- part of original organism that has been preserved; ex: bug in amber, mammoth in ice; saber-toothed tiger in tar pit
Trace fossil- footprints, nests, bite marks, poop (what an animal could leave behind)
How are fossils formed? • http://www.teachersdomain.org/folder/view/3748/
How can we find out how old a fossil is? • http://www.teachersdomain.org/resource/tdc02.sci.phys.matter.radiodating/
What are some things that you want to understand better about fossils and changes in life through time?