Transcript Spontaneous generation

How the Earth formed
• About 4.5 billion years ago
• From a cloud of gas and dust
(nebula) that also formed the
Sun and other planets and
comets and asteroids…
• “chunks” stuck together, which
attracted more chunks, which
stuck and attracted more
chunks…
How the Earth formed
• Kept getting hit with meteors
(bombardment), volcanic
eruptions
• Atmosphere not like today…CO2,
H2S
• First life may have formed 3.8
billion years ago…bacteria.
Spontaneous generation
• Theory stated that nonliving
things could turn into living
things
• We don’t believe that anymore
• Biogenesis: living things can only
come from living things.
• Took some proof…
Frencesco Redi
• 1600’s
• People believed meat turned into flies
• Had 2 jars with rotting meat, 1
uncovered and 1 covered with
screen
• Maggots only in the uncovered one
• Proved only that flies not from rotten
meat
Frencesco Redi
Vital force
• 1700’s
• Microscope had been discovered,
so the microbes they saw had
spontaneously generated due
to a “vital force” (life force) in
the air.
• Those microbes grew into bigger
forms of life
Larazzo Spallanzani
• 1700’s
• Believed microbes came from other
microbes.
• 2 flasks, boiled broth, 1 left open and
one sealed
• Open one became contaminated
• Supposedly the closed one had
killed off the “vital force” during
heating and seal wouldn’t let back
in
Larazzo
Spallanzani
Louis Pasteur
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Mid 1800’s
Swan-necked flasks
Boiled broth and left open to air
Curve in neck trapped microbes
Remained clear for up to a year!
If neck broke, contaminated within a
day
• Finally disproved spontaneous
generation
Louis Pasteur
How life formed…
• The scientific explanation
• Earth formed about 5 billion
years ago from cloud of gas and
dust that condensed.
• Early atmosphere contained
ammonia (NH3), hydrogen gas,
water vapor and methane
(CH4).
Oparin and Haldane:
• Proposed that these simple
molecules at high temperatures
(e.g. lightning) could form
amino acids and proteins
• Miller and Urey proved it could
happen
• Comets also have traces of amino
acids
First living things
• About 3 billion years ago
• Archaea: simple, one celled, autotrophic
(make own food), prokaryotes (no
nucleus)
• Chemosynthesis: use chemicals to
make energy
• Some species still around today, at bottom
of ocean by volcano vents.
• Took CO2 out of atmosphere and release O2.
• Responsible for our atmosphere today
Other “advances”
• Photosynthesis:
– First done by cyanobacteria (still alive
today…stromatolites)
• Eukaryotes:
– A large cell “swallowed” a small
prokaryote
– Over time, prokaryote multiplied inside of
eukaryote and became
mitochondria.
– Proof: own DNA, in a ring, multiply on its
own
Evolution
• Based on geological evidence, at
first
• Rocks form in layers
• Older ones at bottom
• Fossils in rocks similar closer together
• Farther apart fossils are, more
different
• Late 1700’s/early 1800’s
Fossils in rock strata
Catastrophism
• Georges Cuvier
• Noticed in rock layers that fossils
changed as go farther down
• Notice many sudden changes
• Said they were due to
catastrophes making species
extinct
Uniformitarianism
• Charles Lyell
• Said that the processes going on
today, geologically, were going
on back then, too
• So change not by catastrophe, but
slowly over long time
Jean Baptiste Lamarck
• Organisms change over time
• Believed in spontaneous
generation, and that simple
things could become more complex
in their life time
• Inheritance of acquired characteristics
• Parents’ traits change and they pass
that on to children
Jean Baptiste Lamarck
Charles Darwin
• And Alfred Russel Wallace
(Darwin published book first)
• Noticed differences between
species as traveled by ship
around the world (HMS Beagle)
• Descent with modification
– Traits passed on to children over
time
Charles Darwin
Comparing
Lamarck
and Darwin
4 Parts of the Theory
• Overproduction of offspring: nature
produces more offspring than can
survive. This leads to a
• Struggle to survive (need food, water, etc.).
Within a population there is
• Genetic variation that makes some creatures
better at surviving. These differences are
called adaptations.
• Differential reproduction: Creatures with
best adaptations survive to make more
like themselves.
4 Parts of the Theory
Proof for Evolution
• So over time, what a species looks
like can change
• Transitional species
– Fossils of species in between
modern and older set up a series
where can see changes
Transitional
species
Proof for Evolution
• Embryology:
– Creatures look very similar when
young
• Homologous structures
– Look alike between species (e.g. arm
bones)
• Vesitigial structures
– Seem to serve no function, but “left over”
from ancestor (e.g appendix, tail bone)
Structures
• Homlogous
• Analogous
Structures
• Vestigial
• Humans:
– Muscles that
move ears
– Appendix
– Tonsils
– Body hair
– Tail bone
– Wisdom teeth
Methods of Evolution
• Divergent evolution
– 1 ancestor gives rise to many
descendants that are different
– If fills up many ecological niches, called
adaptive radiation
• Convergent evolution
– Different ancestors’ descendents have
similar traits
– Called analogous structures (e.g wings)
Convergent
Evolution
Divergent Evolution
Divergent
Evolution
Adaptive
Radiation
• Evolve to fill
many niches,
e.g. live in
many places
or eat many
different
things
Adaptive Radiation