Life on Earth
1. ANALYSIS OF THE OLDEST
SEDIMENTARY ROCKS PROVIDES
EVIDENCE FOR THE ORIGIN OF LIFE
Questions
  What were the conditions on early Earth?
  What are the two scientific theories relating to the
evolution of the chemicals of life?
  What are some of the changes in technology that
have assisted in increasing our understanding of the
origin of life?
Technology
  Dot Point – Identify changes in technology that
have assisted in the development of an increased
understanding about the origin of life and the
evolution of living thing
Technology
Technologies enabled the testing of hypotheses being
proposed by scientists:
Early Technologies:
•  Swan-necked flasks designed by Louis Pasteur – showed
that air alone could not trigger spontaneous generation of
microorganisms
• The light microscope 1676 – Microorganisms discovered
using the light microscope
More Recent Technologies:
•  Radiometric dating e.g. radiocarbon dating – allowed
scientists to assign absolute dates to the sequence of life on
Earth – used to establish geological timescales and thus
fossils and rates of evolutionary change
•  Study of meteorites and volcanoes
•  Study of plate tectonics through rock dating – Continental
drift and sea floor spreading
• Simulation of conditions of early Earth
Organic chemicals essential for life
  There is evidence that life existed on Earth 3.8
billion years ago, and this was only possible because
of the presence of water.
  Essential elements necessary for life to form include
hydrogen, oxygen, carbon, nitrogen, phosphorous,
and sulfur.
  Living organisms use energy from sunlight or from
chemical reactions to combine these in various ways
to form their organic molecules – carbohydrates,
proteins, lipids (fats) and nucleic acids.
The Primitive atmosphere
  It is very difficult to recreate the conditions that would
have been present on the Earth at the time of its
formation.
  Scientists have tried, through experiments, to create the
conditions that prevailed at the time.
  There are currently two main views on where life
developed on the early Earth:
  Chemosynthetic – living matter is produced from nonliving matter
  Panspermia- organic molecules
carried to earth via meteorite
•  Scientists still argue about
the source of life.
Haldane and Oparin
  In the 1920s, John Haldane, a scottish biochemist and
Alexander Oparin, a Russian scientist independently
hypothesised that organic molecules would be spontaneously
produced when an energy source, such as UV light or
lightening, interacted with the (non-living) elements essential
to life.
The Experiments of Urey and Miller
The Experiments of Urey and Miller
  1953 – Stanley Miller and Harold Urey tested Oparin and
Haldane’s hypotheses.
  They set up glass apparatus as shown in the previous
slide.
 To simulate the Earth’s atmosphere, the gases of
water vapour, methane, hydrogen and ammonia were
mixed and exposed constantly to an electric spark,
which mimicked lightening.
 During this time a flask of water that represented the
ocean was heated, water vapour was given off and
later passed through a condenser as recycled liquid
water (rain).
The Experiments of Urey and Miller
  http://www.youtube.com/watch?v=iahBQolXQH8
The Experiments of Urey and Miller
  After one week of treatment the liquid in the flask
was red and cloudy.
  When tested, it was found to contain amino acids –
the basic unit of proteins – which are made up of
carbon, oxygen, hydrogen and nitrogen, as well as
other organic molecules.
  Amino acids are one common need of all living
things – they are the building blocks of proteins
Research Activity
  Dot Point – Gather information from secondary sources to describe the
experiments of Urey and Miller and use the available evidence to
analyse the:
  Reason for their experiments
  Result of their experiments
  Importance of their experiments in illustrating the nature and
practice of science
  Contribution to hypotheses about the origin of life
*Analyse - Identify components and the
relationship between them; draw out and relate
implications*
Research Activity
  Visit the Urey and Miller Experiment class wiki at:
https://ureyandmillerexperiment.wikispaces.com/
home
Work in pairs with someone you wouldn’t normally work
with. Upload your information to share with the class –
do not copy and paste slabs of information. Make concise
summaries of your research to share with the class
2.  Present your findings to the class
1. 
Further experiments
  More recent experiments have tested a range of
atmospheres and used different energy sources that
could have existed on Earth.
  The successful production of all of Earth’s 20 amino
acids from these experiments, and also of lipids,
sugars and nucleic acids indicate that the organic
molecules necessary for life could have been built
under primitive anoxic conditions, consistent with
that of early Earth, with the aid of an available
energy source such as volcanic heat, solar radiation,
UV light or electricity.
Significance of the experiments
  Why are the experiments of Urey and Miller
significant in the debate on the composition of the
primitive atmosphere?
Significance of the experiments
  Dot Point – discuss the significance of the Urey and Miller
experiments in the debate on the composition of the primitive
atmosphere
  The experiment is of tremendous importance in the quest for the
truth about the origin of life because it demonstrated that
organic molecules could be manufactured from inorganic
molecules under conditions thought to mirror those 3.8 billion
years ago.
  Effectively, Urey and Miller’s experiment supported Oparin and
Haldane’s hypothesis that life originated on Earth due to the
presence of local inorganic chemicals and an energy source.
  Some scientists saw this as debunking the outer space theory,
while others still pursue the outer space theory today.