Transcript Origin of Life

Origin of Life
From spontaneous generation
to biogenesis
Spontaneous Generation
• Spontaneous Generation-the long-held
belief that living things could suddenly
exist if the right combination of non-living
objects were brought together in one
place.
• Seemed to be supported by the religious
beliefs of the time.
• Before 1800’s
• Ex: wooden box + cloth + wheat = rats
Francesco Redi (1626-1697)
• Italian scientist who
documented the life cycle of
the fly.
• Challenged the belief that
flies spontaneously arose
from rotting meat.
• Hypothesis: If adult flies are
kept away from rotting meat
then new flies will not
develop because maggots
come from adult flies.
Redi’s Experiment
Experimental
Control
Maggots
No Maggots
Redi’s supported hypothesis
was a major blow to the
supporters of spontaneous
generation, but…
Lazzaro Spallanzani (1729-1799)
• The invention of the microscope lead to
speculation that a “vital force” caused
bacteria and protists to spontaneously
appear in liquids.
• Spallanzani- Italian scientist who designed
an experiment to test the hypothesis that
microorganisms come from existing
microorganisms and not a “vital force”.
• Hypothesis: If boiled meat broth is sealed to
keep out airborne microorganisms then new
microorganism will not develop and spoil the
broth because microbes in the air cannot
land in the broth.
Spallanzani’s Experiment
Control
Experimental
Spallanzani’s results supported his
hypothesis but.. supporters of spontaneous
generation objected that he had “destroyed” the vital
force of the air inside the flasks by boiling them.
Spontaneous generation continued to be the
preferred explanation for another 100 years.
Louis Pasteur (1822-1895)
• Paris Academy of Science offered a prize to
anyone who could conclusively clear-up the
spontaneous generation controversy. And
the winner is…
• Pasteur- French scientist who showed
organisms in the air lead to the spoilage of
food. Also described the process of
fermentation and invented the pasteurization
of milk.
• Hypothesis: If boiled meat broth is kept in a
container that is open to the air but traps
airborne particles then new microorganism
will not develop and spoil the broth because
microbes in the air cannot land in the broth.
Pasteur’s Experiment
Swan
neck
Control
Broth
boiled
Experimental
Broth cooled,
sits for 1
year
Broth spoils one
day after neck is
broken off
Out with Spontaneous
Generation… ..Hello Biogenesis
Spontaneous Generation:
Belief in the transformation of non-living to
living.
Biogenesis:
Supported theory that all living things are
derived from living things.
Origin of Life
How did life begin?
1. Creation
A. A divine supernatural being must have created life on
Earth because it is just too complicated to have happened
randomly.
B. A superior intellect (way smarter than us!) must have
created life on Earth because it is just too complicated to
have happened randomly.
2. Extraterrestrial Origin- life began on another planet
from an older planetary system and was transferred
to Earth on a meteorite.
3. Origin from simple inorganic compounds life arose
from inorganic compounds brought together by the
special conditions of the Early Earth
Formation of Earth
• Most planets have surfaces that
are either toxic, too hot, too cold,
or fluctuate too dramatically
between hot and cold.
• Our solar system is approximately
5 billion years old, with the first
400 million being the actual
formation of planets from
interstellar dust.
• When the earth first cooled,
volcanic activity caused high
amounts of hydrogen, methane,
and ammonia.
• Oldest fossils are almost 3.5
billion years old
Radioactive Dating
• Many elements have radioactive
Isotope Half-life (years)
isotope forms that can be
detected.
C14
5,730
• When rock solidified or the body
of an organism forms, a certain
Th230
75,000
amount of radioactive Carbon,
1,300,000,000
Thorium, Potassium, or Uranium K40
becomes trapped.
238
U
4,500,000,000
• All radioactive elements naturally
decay and turn into their nonradioactive forms (C14àC12)
•The time it takes for ½ of the radioactive isotope content of a
sample to decay is called the HALF-LIFE.
•By measuring how much of a certain radioactive isotope is left,
we can estimate the age of an object. The lower the amount of
radiation, the older it is.
Simulation Card Activity: First
Conditions on Earth
• Obtain a deck of cards for your group
• Deal three cards and try to make one of the
following combinations: NH2-CH2-COOH, CH3COOH, or CH3-CH2-COOH
• Record your results on the data sheet provided
for this activity. Repeat this 19 times.
• Count the number of molecules you were able to
form. Then, calculate the probability of forming a
molecule with each deal.
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Stanley Miller (1930& Harold C. Urey (1893-1981)
•Urey and his student Stanley Miller built an apparatus capable of
simulating the conditions of early Earth.
evaporating____________
ocean
•Warm water vapor that simulated__________
___________
was created by a flask of boiling water.
water
•The vapor then passed through a reaction chamber where a mixture of
hydrogen
methane
ammonia were combined with the
___________,
_____________,
and ___________
vapor.
•Electrodes then electrified the steamy mixture in the reaction vessel to
provide energy for the formation of new chemical _________.
bonds
gas
•The vapor next passed through a condenser to change the ________
to a
liquid.
•The liquid was then collected and analyzed.
•Complex biomolecules including: amino acids, ATP, and Nucleotides were
produced.
Jean Baptiste de Lamarck (1744-1829)
• One of the first to suggest that the species we have on
Earth today may have descended from a common
ancestor.
• Studied a collection of fossilized invertebrates and
observed that many of them shared common physical
traits.
• Hypothesized that acquired traits were passed on to
offspring from parents.
• Acquired Traits were believed to be the result of learned
behaviors or experiences and not by genes.
• Lamarck believed that the giraffe’s neck is longer
because the parent’s necks grew longer during a lifetime
of trying to reach high leaves and that this new feature
was passed to the next generation.
• By this logic, removing a person’s appendix should
result in…
Evolution by Natural
Selection
Alfred Wallace
(1823-1913)
Charles Darwin
(1809-1882)
• Wallace and Darwin independently proposed
the hypothesis that species are modified by
natural selection.
• Traits are not acquired but are selected for by
environmental conditions.
• Darwin most known because The Origin of
Species was published by Darwin shortly after
he and Wallace published their papers.
Charles Darwin
(1809-1882)
• First to realize that in the same way
humans use artificial selection to create
new breeds of dogs and other domestic
animals, nature must somehow be
selecting for the creation of new species in
the wild.
• Collected most of his data as a naturalist
studying the fossils and living specimens
from South America.
HMS Beagle
•5 year mapping and collection
voyage of the coast of South
America and the South Pacific
Darwin’s Theories
1. Descent with Modification
•
•
Newer organisms in the fossil record are
actually the descendents of older species.
All species alive today descended from one
or a few original types of life.
Galapagos Island Finches
Darwin’s Theories
2. Modification by Natural Selection
• All living things have the potential to
produce more offspring than the World
can support, but growth is controlled by
the “cruelty of nature”.
• Because no two organisms (resulting
from sexual reproduction) are identical,
environmental pressures will lead to
the survival of the few offspring that
happen to be born with slightly more
useful features.
Darwin’s Theories
• Therefore, Natural Selection is the
mechanism that drives the process of
evolution.
• It can take MANY generations for
evolutionary change to occur
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Evolutionary Example: Bacteria
You
Watch
At
this
have
So…
point
a bacterial
what
95%
happens
infection
of the
You
stop
after
bacteria
that
taking
is
taking
your
has
the
causing
been
first
antibiotics
killed
doses
you and
toof
youneed
your
feel so
medication
antibiotics
much
better
Your bacteria have
evolved!
Now
But the
you
are few
sick all
over
bacteria
again
and
that
the
remained
antibiotic
will
andnot
were
be
productive
resistant
this
starttime
to
reproduce
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Terms – Just to be clear!
• Evolution – the change of populations of
organisms over generations
• Natural Selection – the process by which
organisms with favorable characteristics
reproduce at higher rates than those
without them; the mechanism for evolution
• Artificial Selection – the breeding of
organisms by humans for specific
characteristics; often produces new breeds
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Terms
• Fitness: the ability of an individual organism
to produce fertile offspring
– An individual with high fitness is well adapted to its
environment and reproduces successfully
• Adaptations: favorable traits that give an
organism an advantage in its environment and
enhance its fitness
• Vestigial Structures: features that were
useful to an ancestor but not to the modern
organism that has them (ex – Dorudon) 27
Homologous Structures
• Homologous structures: similar features
that originated in a shared ancestor.
http://www.fsteeman.dds.nl/fossiel/tussenvormen.html
Ichthyostega 360-370 mya
Analogous Structures
• Analogous Structures: features with
identical functions and look similar, but
with no anatomical or embryological
similarity
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Similarities in Embryology
• In the early stages of development, all
vertebrate embryos are similar, but those
similarities fade as development proceeds.
Similarities in Genetics
• Scientists in the new field of genomics can
look at the entire genome of organisms
(their DNA in computer code) and see how
similar the nucleotides are from one
species to another.
Patterns of Evolution
• Coevolution – the change of two or more
species in close association with one another
– Ex – plant and pollinator
– Madagascar orchid and Madagascan sphinx moth
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Patterns of Evolution
• Convergent Evolution – when the
environment selects similar characteristics even
though the ancestral types were quite different
– Ex – Shark and Whale
Patterns of Evolution
• Divergent Evolution – two or more related
populations become more and more dissimilar,
usually in response to habitat change
– Ex – Galapagos Island Finches