History of life on earth

1. A History of Life on Earth
Chapter 5
Presented by
Amith Reddy

2. Before Life Began
• How old is the Earth ?
4.5 billion years
• Big Bang - gravity causes dust particles to condense
• Meteors for millions of years- how hot would the earth be?
• Earth has to cool down - steam escapes and rain allows
collection of water - earth now has……
• Atmosphere of Ammonia, Methane, water vapor,
Co2, and Nitrogen
• what is missing?

3. WHAT EVIDENCE DO SCIENTISTS USE?
• Fossils!
– trace
– mold
– cast
– amber
– imprint
– petrified
Images courtesy of the UC Museum of Paleontology Understanding Evolution: http://evolution.berkeley.edu."
Life Sciences-HHMI Outreach.
Copyright 2006 President and
Fellows of Harvard College.

4. Outline
Before Life Began
The Emergence of Life
Precambrian Life
Paleozoic Life: The Cambrian Explosion
Paleozoic Life: Ordovician to Devonian
Mesozoic Life
Marine life
Marine life
Terrestrial life
Terrestrial plants and arthropods
Vertebrates
Paleozoic Life: Carboniferous and Permian
The Cenozoic Era
Terrestrial life
Terrestrial life
Aquatic life
Aquatic life
The adaptive radiation of mammals
Pleistocene events

6. The Emergence of Life
Early evolution of life on Earth

7. Endosymbiosis

10. Evolution of cell types

11. Precambrian Life
• What do scientists think was alive way back then??
• Bacteria
• This era lasted for billions of years until more living
organisms evolved
Dr Tom Tregenza © Tom Tregenza
Dr Gordon Beakes © University of Newcastle upon
Tynelicensed
IMAGES for use through the Centre for Bioscience
ImageBank,http://www.bioscience.heacademy.ac.uk/imagebank/"
Life Sciences-HHMI Outreach.
Copyright 2006 President and
Fellows of Harvard College.

14. Stomatolites : Complex communities of (mostly) cyanobacteria produce all the atmospheric oxygen.

19. Paleozoic Era
540 Million years ago!!
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Now the earth is getting larger life!
First part of paleozoic is called cambrian
Protists!
Sea plants!
Sea animals!
Land plants!
Land animals!
what ended the paleozoic era??
Mass extinction!
Dr. Thomas W. Kammer

20. Cretaceous – Tertiary Extension
65.5 mill years ago
Permian – Triassic Extension
(Great Dying)
251.4 mill years ago
Ordovician – Silurian Extension
443.7 mill years ago

21. Species Extension in various periods of History

22. WHY DO WE HAVE DIFFERENT ERA’S?
Image courtesy of the UC Museum of Paleontology Understanding Evolution: http://evolution.berkeley.edu."

23. Why Mass extinction ? How did they survive???

24. Which life, Marine or Terrestrial has faster
growth or extinction ???

25. How did trees survive without roots ?

27. Formation of Earth

28. Why land moved or changed in Mesozoic life ??
Why they separate at different rate ? Why not all at once ??
What was the climate of the earth at this time ?

29. How/Why did only Gymnosperms first appeared
than Angiosperms ???

30. How are they different ???

32. Mesozoic era
245 Million years ago!!
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Dinosaurs
Reptiles
Small mammals appear
Birds evolve
Plate tectonics
what ended the mesozoic era?
mass extinction!
Meterorite ???

33. Image courtesy of the UC Museum of Paleontology Understanding Evolution: http://evolution.berkeley.edu."

34. Cenozoic Era
66 Million years ago!
• Mammals flourish
• Primates about 30 million years ago
• Modern human species – about 200,000 years ago

35. licensed for use through the Centre for Bioscience ImageBank,http://www.bioscience.heacademy.ac.uk/imagebank/"

40. • Where are fossils usually found?
• Who studies these?
• How do scientists determine the age of something billions of
years old?
– Relative dating
– Radiometric dating
Life Sciences-HHMI Outreach.
Copyright 2006 President and
Fellows of Harvard College.
Understanding Evolution: http://evolution.berkeley.edu."

43. Evolution of life on land
Q. Were animals or plants first?
• Animals were first! Land-plants (not algae) only appeared about 450
million years ago.
Q. When did the first flowering plants appear?
• Only about 120 million years ago! Before that, ferns, mosses, and
algae (incl. kelps etc.)
Q. When did mammals appear first?
• Before dinosaurs! ~220 million years ago.

44. Questions

45. Thank You