History of Current Life on Earth

1
History of Current Life on Earth

• Theories and Ideas on What Has Happened Since
  Life Began

2
Modern Life
3
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

4
Ordovician-Silurian Extinction
5
Ordovician-Sulurian Extinction

• Occurred 450 mya
• Caused by glaciation
• Dominant animals were marine
• More than 25 of marine families went extinct

6
Late Devonian Extinction
7
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

8
Permian-Triassic Extinction
9
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

10
End Triassic Extinction
11
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

12
Cretaceous-Tertiary Extinction
13
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

14
Fossil Record
15
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

16
Lucy
17
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)

18
Human Evolution
19
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