Transcript Document

History of Current Life
on Earth
Theories and Ideas on What Has
Happened Since Life Began
Slide 1
Modern Life
Slide 2
Modern Life
• Cambrian Explosion
– ~ 500 mya
– All modern animal phyla appear in fossil
record
– First records of modern animal life
• Five catastrophes = Five mass extinctions
Slide 3
Ordovician-Silurian Extinction
Slide 4
Ordovician-Sulurian Extinction
• Occurred ~450 mya
• Caused by glaciation
• Dominant animals were marine
– More than 25% of marine families went
extinct
Slide 5
Late Devonian Extinction
Slide 6
Late Devonian Extinction
• ~380 mya
• Caused by cooling temperatures and a
possible meteorite impact
• Prior to extinction the dominant
animals were reef builders.
– About 22% of marine families perished
Slide 7
Permian-Triassic Extinction
Slide 8
Permian-Triassic Extinction
• ~250 mya
• Worst mass extinction
– Up to 95% of all species on Earth
suddenly became extinct
– Reason unknown, believed that the
ocean levels may have dropped
Slide 9
End Triassic Extinction
Slide 10
End Triassic Extinction
• ~200 mya
– Most likely caused by massive floods of
lava erupting from the central Atlantic
– Up to 22% of marine families
– Vertebrate deaths unknown
Slide 11
Cretaceous-Tertiary Extinction
Slide 12
Cretaceous-Tertiary Extinction
• ~65 mya
• Cretaceous period lasted 150 million
years
• Extinction mostly likely caused by
giant asteroid hit off of Mexico
– 16% of marine families went extinct
– 18% of vertebrates went extinct
Slide 13
Fossil Record
Slide 14
Fossil Record
• Fossil record
– Remains of a once living organism
– Bones, molds, casts, footprints
• Can be dated
– Relative Dating
• Estimates the age of events and fossils using
basic stratigraphic rules
• Provides a sequence of age
– Absolute Dating
• Based on the physical or chemical properties
of the materials artifacts and fossils
• Provides a numerical age
Slide 15
Lucy
Slide 16
Lucy
• Discovered by a team working in
Ethiopia with Donald Johanson
• 40% of a skeleton of a member of
Australopithecus afarensis
• About 3.2 million years old
• Small brain capacity (like apes) but
walked bipedal (like hominids)
Slide 17
Human Evolution
Slide 18
Human Evolution
• One current model looking at human
evolution and where it occurred
• Homo refers to human
• Different species existed and were
relations to each other, but did not
necessarily give direct rise to each
other
• Many other hominines exist and most
likely were common ancestors of
those in the genus Homo
Slide 19