A History of Life on Earth

Presented by

Amith Reddy

Chapter 5

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?

Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

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."

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

Outline

The Emergence of LifeEarly evolution of life on Earth

Endosymbiosis

Evolution of cell types

Life Sciences-HHMI Outreach. Copyright 2006 President and Fellows of Harvard College.

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 Gordon Beakes © University of Newcastle upon Tynelicensed

Dr Tom Tregenza © Tom Tregenza

IMAGES for use through the Centre for Bioscience

ImageBank,http://www.bioscience.heacademy.ac.uk/imagebank/"

Stomatolites : Complex communities of (mostly) cyanobacteria -

produce all the atmospheric oxygen.

Paleozoic Era540 Million years ago!!

• 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

Cretaceous – Tertiary Extension65.5 mill years ago

Permian – Triassic Extension (Great Dying)

251.4 mill years ago

Ordovician – Silurian Extension 443.7 mill years ago

Species Extension in various periods of History

WHY DO WE HAVE DIFFERENT ERA’S?

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

Why Mass extinction ? How did they survive???

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

How did trees survive without roots ?

Formation of Earth

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 ?

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

How are they different ???

Mesozoic era245 Million years ago!!

• Dinosaurs

• Reptiles

• Small mammals appear

• Birds evolve

• Plate tectonics

• what ended the mesozoic era?

• mass extinction!

• Meterorite ???

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

Cenozoic Era66 Million years ago!

• Mammals flourish

• Primates about 30 million years ago

• Modern human species – about 200,000 years ago

licensed 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.

• Where are fossils usually found?

• Who studies these?

• How do scientists determine the age of something billions of years old?– Relative dating

– Radiometric dating

Understanding Evolution: http://evolution.berkeley.edu."

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.

Questions

Thank You