Transcript Overview of the Origin of Life

Overview of the Origin of
Life
Chapter 14
Biogenesis
vs
Spontaneous Generation
• Spontaneous generation- the thought
before the 17th century, living things could
come from non-living things
• Biogenesis=all living things come from
other living things
Redi’s Experiment
Italian Scientist
Flies
Meat
Eggs
Maggots
No Maggots
John Needham
Spallanzani Experiment
Italian Scientist #2
Pasteur’s Experiment
History of Earth
Formation of Earth
• 5 billion years ago the solar system was a
swirling mass of gas and dust
• The planets are thought to have formed
from violent collisions of space debris.
• The age of earth is approx. 4 billion years
old
• It is based on studying the layers of
sediment in the earth’s crust
Radioactive Dating
• Establishes the age of material
• All atoms of the same element have the
same atomic number
• However, they can differ in the number of
neutrons?
• (What is that called?)
Radioactive Dating Cont.
• Answer: Isotope
• Mass # = proton and neutrons in the nucleus
• Ex: Mass of carbon is 12, 6 protons and 6
neutrons
• Most elements have isotopes
• Isotopes are designated by their mass #- eg.
Carbon-12 = mass of 12
How about Carbon -14?
Isotopes
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Isotopes have unstable nuclei
They undergo radioactive decay
This are called radioactive isotopes
The length of time it takes for half of an
isotope to decay is referred to as: Half Life
• The age of the material can be determined
by measuring the particular radioactive
isotope it contains
Example of Carbon Dating
Alexander Oparin
• Thought the earth was once very different
and contained ammonia NH3, hydrogen
gas, and water vapor.
• Thought these elements formed organic
compounds of amino acids.
• Complex chemical reactions might have
occurred to bring about macromolecules
essential for life. (Name some?)
Harold Urey and Stanley Miller
• Ideas from Oparin
• Experiment: contained a chamber of gas,
as gas circulated electric sparks, (acting
as lightening) supplied the energy to drive
the chemical reaction
• Other experiments branched off from this
one including how ATP and DNA were
formed. 
Molecules to Cell-like Structures
Microspheres: organic molecules that
spontaneously form, spherical in shape and contain
protein-organized in a membrane
Coacervates
•
COACERVATES, polymer-rich colloidal droplets, have been studied in the
Moscow laboratory of A. I. Oparin because of their conjectural resemblance to
prebiological entities. These coacervates are droplets formed in an aqueous
solution of protamine and polyadenylic acid. Oparin has found that droplets
survive longer if they can carry out polymerization reactions.
Making Coacervates
Our Lab Experiment
First Life Forms
• 3.5 billion year old fossils found near the north
pole (unicellular organisms)
• Why is RNA necessary and DNA must have
RNA to carry out life functions?
• What does RNA have that DNA doesn’t (besides
Uracil)?
What was the Role of RNA?
• Thomas Cech- unicellular eukaryotes had
RNA that was able to act as an enzymeribozymes
• Life is thought to have started with self
replicating RNA
• Competition between RNA molecules may
have occurred- What does that remind you
of today that contains RNA?
The 1st Prokaryotes
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Very little oxygen
Must have been anaerobic
Very small in size
Most likely heterotrophic-taking organic
molecules from the environment
• As the resources for the heterotrophs
became limited autotrophs are thought to
have evolved.
Archeabacteria
• Kingdom of Unicellular organism that thrive in
harsh environments
• Most are autotrophic
• Obtain energy by chemosynthesis and not
photosynthesis
• Chemosynthesis- Carbon dioxide is the carbon
source, producing carbohydrates from
inorganic sources instead of from light.
• Energy is obtained from inorganic molecules
(sulfur)
Cyanobacteria
• One of the 1st photosynthetic microorganisms
• Able to withstand the change from carbon
dioxide to oxygen
• The ozone formed and even though toxic to
plants and humans helps to prevent UV
radiation on earth.
CYANOBACTERIA
OZONE
FIRST EUKARYOTES
• Began 2-1.5 billion years ago
• Small eukaryotes are thought to have developed inside
larger prokaryotes that were anaerobic
• Lynn Margulis-proposed they lived in an endosymbiotic
relationship- mutually beneficial relationship
• Aerobic prokaryotes are thought to have produced the 1st
mitochondria
• Later invaders thought to have given rise to chloroplasts
• Both chloroplasts and mitochondria contain some
genetic material (single stranded circular DNA) so they
are able to reproduce independently.
http://cosmology.com/Cosmology2.html
• http://hegel.lewiscenter.org/users/mhuffine
/subprojects/Instructor/IPBIO%20Main%20
Page/ppt/Attributes%20of%20life_files/v3_
document.htm