Transcript Why is life on Earth so diverse???

Where
did all
this
diversity
come
from?!
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Why do these organisms look so similar?
 What has shaped their appearance over time?
► Why
are all these animals white?
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Why are Lemurs found only on Madagascar?
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How does something like THIS come about?!!
The Facts….
► 99%
of everything that has ever lived no longer exists
on the Earth – it is extinct
► Some modern organisms look very similar to other
unrelated organisms (ex. Ant-eaters & Echidnas)
► Some modern organisms look very similar to ancient
organisms that are now extinct (ex. fossils)
► For centuries, people looked at these fossils and tried
to EXPLAIN what they are, and what they mean
 What hypotheses could you propose for the diversity of life?
 What evidence could you gather?
 What do you ALREADY KNOW about inheritance?
“EVOLUTION” – what’s all the
fuss about?!
= “a scientific explanation of natural
phenomena, based on empirical evidence”
► Theory
 A theory brings together all the research into a single
cohesive, testable explanation
► Evolution
= “change over time”
 A scientific explanation for the origin, diversity and continued
change observed within living things
 Defined more specifically in Biology as “descent with
modification” (ie. The things alive today are modified
versions of their ancestors…just like you and me!)
 Physical traits are passed-on to offspring
 Some traits are beneficial, others aren’t
 The beneficial traits remain in the population, and become
more common over time – THIS IS “EVOLUTION”…
Let’s back up: “In The Beginning…”
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ALEXANDER OPARIN - FORMATION OF MACROMOLECULES WITHOUT
OXYGEN
STANLEY MILLER AND HAROLD UREY EXPERIMENT
 “Created” amino acids from simulated early Earth conditions…
http://en.wikipedia.org/wiki/Image:Miller-Urey_experiment_en.png creative commons copyright
THE FIRST CELLS!!!
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FIRST SIMPLE BACTERIA APPEARED AROUND 3.5
BILLION YEARS AGO
SOME ARE CYANOBACTERIA - THESE ARE
PHOTOSYNTHETIC BACTERIA (Stromatolites…)
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WHAT GAS DID THESE BACTERIA PRODUCE?
ATMOS. WAS ALMOST 10% O2 ABOUT 2.5 BILLION YEARS AGO
WHAT TYPE OF CELLS ARE BACTERIA?
WHAT TYPE OF CELLS ARE ALL OTHER ORGANISMS?
WHERE DID EUKARYOTIC CELLS COME FROM?
ENDOSYMBIOSIS…
Dr Gordon Beakes © University of Newcastle upon Tynelicensed for use through the Centre for Bioscience ImageBank,http://www.bioscience.heacademy.ac.uk/imagebank/"
ENDOSYMBIONT THEORY
THE BEGINNING OF THE EUKARYOTIC CELLS
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EVIDENCE FOR ENDOSYMBIOSIS
 DNA & structural similarities
evolution.berkeley.edu/evolibrary/article/0_0_0/endosymbiosis_03
Summary of Darwin’s
Theory of Evolution
1. Individual organisms in nature differ
from one another
2. Organisms produce more offspring than can
survive.
Turtle eggs
Insect eggs
Lobster eggs
Frog eggs
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3. Members of each species must
compete for limited resources.
4. Each organism has different
advantages and disadvantages for
the struggle of existence.
5. Individuals best-suited to
their environment survive and
reproduce. Those not suited will
be less likely to breed
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Survival of the fittest!
Nature (the environment) will
determine which organism is the
fittest to Survive
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6. Species change over time, by passing
on their useful (and harmful) traits to
their offspring
7. All species alive
today have
therefore
descended with
modifications from
ancient ancestors
Fossil
record
of the
camel
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8. Ultimately, ALL organisms on Earth
are united into a single tree of life…
Darwin’s original sketchbook drawing
Darwin’s Theory is supported by….
ARTIFICIAL SELECTION
► Nature
provides
variation but humans
decide what traits are
selected and passed
on.
► Hybridization brings
about new variations
Descent with Modification
Darwin proposed that
after long periods of
time, offspring of ancient
organisms spread out
through the environment,
and natural selection
then results in organisms
with traits that are very
different from their
ancestor
•Different structures
•Different niches
•Different habitats
We call this Adaptive
Radiation
Evidence of Evolution
►
Fossil Records-
fossils being
discovered were
evidence that
the world was
much older that
once thought.
Some fossils were very similar
to modern day creatures
99% of species that once
lived are now extinct!!!!!!
Fossils show history of life on Earth
Relative Dating
-The layering
of rock can
show which
fossils are
older.
Fossils show history of life on Earth
Radioactive Dating -using the half-life of radioactive
elements scientists can tell approx. how old a fossil is…
What Does The Fossil Record Tell Us
About Evolution?
► Sedimentary
rocks can be dated by studying the
decay of radioactive isotopes they contain.
► In some cases, successive layers of rocks of
different ages are so well-preserved that families
of similar fossils can be traced through the layers,
over several million years of history
► This apparent transition suggests a pattern of
development, and allows scientists to infer
changes from one form to another and construct a
diagram called a Phylogenetic Tree…
Trilobite Evolution
Phylogenetic
trees show the
evolutionary
ancestry of
organisms, based
on their inferred
relationships to
ancestral species
The History Of Life
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The fossil record has
allowed scientists to locate
the “first appearance” of
different organisms within
rocks of a specific age
The pattern of change &
progression suggests that
recent organisms might be
modified forms of ancient
organisms that previously
existed
The Geological Timescale
Based ONLY on the fossil
evidence, it appears that the
nature and diversity of life on
our planet has changed
dramatically throughout
Earth’s history
• But HOW have these
changes occurred?