Scientific Evidence for Evolution

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Scientific Evidence for Evolution
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Fossils

• Fossils are a strong piece of evidence to support
  the theory of evolution.
• Fossil preserved remains or marking left by
  organisms that lived in the past. (Latin
  fossilis means dug up)

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Types of Fossils

• Sometimes full organisms can be preserved in
  sticky amber that hardens. Amber is a resin that
  is produced by trees you should be familiar
  with this from Jurassic Park!

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Types of Fossils

• Organisms can be preserved for millions of years
  in very cold environments. An example of this is
  the woolly mammoth found recently in Russia.

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Types of Fossils
In addition, animals can be trapped in tar and
preserved like in the La Brea tar pits in LA.
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Types of Fossils
By far the greatest numbers of fossils form on
the bottoms of lakes and seas. Sometimes the
shape of an organism is preserved in rock as a
mold. Sometimes a mold fills with minerals and
forms a cast which is a copy of the original
organism.
When impressions are made in mud, such as animal
footprints, they are called imprints.
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Age of Fossils
Most fossils are found in sedimentary rock so
called because sediments from eroded rock on land
collect in rivers, seas and oceans and harden.
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Age of Fossils
Over millions of years, the shifting of the
earths crust has raised some regions that one
were under the seas and the layers are visible.
The Grand Canyon is an example.
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Age of Fossils
What can you conclude about the age of these
organisms in the layers of sedimentary rock?
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Why Fossils are Strong Evidence

• The sequence of fossils is consistent all over
  the Earth consistent evidence of change through
  time
• Many transitional forms of fossils have been
  found (fish to amphibian, amphibian to reptile)

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Transitional forms in whale evolution
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Did you ever wonder why we have wisdom teeth?
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Vestigial Structures
Scientists hypothesize that at one point, our
ancestors needed these extra teeth! They are an
example of a vestigial structure. Vestigial is a
scientific word for left-over. These
structures are usually reduced in size and serve
little or no function. Scientists use the
presence of vestigial structures as evidence that
evolution has occurred.
Other examples
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Vestigial Structures
In the human body there are more than 100
vestigial structures!
Take the tailbone, for instance. It is the
evolutionary remnant of a ancestral, reptilian
tail! No muscles attach to it, it has nothing to
do with balance or anything else. So then why do
we have it?
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Vestigial Structures
This is a picture of an appendix that is being
removed because it is infected.
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Vestigial Structures
Horses use their appendix to break down cellulose
plant cell walls. Ours has no function! Does
that mean ours lost its function as we evolved?
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Vestigial Structures
And why do we have muscles to move our ears when
they dont work? (Except for that friend of
yours that can wiggle their ears when they
concentrate ?)
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Vestigial Structures
What do you notice about this whale skeleton?
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Vestigial Structures
It has left-over hind leg bones!!! The tail
side of the snake below also has remnants of a
pelvis. What could this mean??
Scientists conclude that both whales and snakes
evolved from four-legged ancestors Why else
would they have these structures?
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Vestigial Structures

1. Fingernails on manatee fins which evolved from
   legs
2. Cave-dwelling organisms such as crayfish that
   have eyestalks but no eyes
3. Species of flightless beetles and birds that have
   wings.

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Okay, now that I have your attention
Do you remember what the study of structure is
called?
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Anatomical Similarities
If you said ANATOMY, you are right!
There are certain structural similarities among
living things that scientists point to as more
evidence for evolution. Lets take a look
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Anatomical Similarities
The structure of the arm and hand of a human, the
flipper of a whale, the limb of a cat, the wing
of a bat and the wing of a bird are quite
different in appearance because they are adapted
to perform different functions. Even with
these different functions though, inside the
structures are surprisingly similar
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Anatomical Similarities
Parts of different organisms that have similar
internal structures, but different forms and
functions are called HOMOLOGOUS STRUCTURES.
Homologous structures are regarded as evidence
that some species evolved from a common ancestor.
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Anatomical Similarities
Be careful though! Sometimes animals have
similar parts that are different in structure and
development. Look below
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Anatomical Similarities
Although insects and birds both have wings, they
are different in structure. An insect wing does
not have bones at all it is made of a tough
substance called chitin. Structures that have
similar external forms and functions but
different internal structures are called
ANALOGOUS STRUCTURES. These structures are NOT
used as evidence for evolution.
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Two of these embryos are human, one is the embryo
of a pig. Can you pick out the pig embryo?
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Comparing Embryos

• Its weird that you cant really tell! But the
  one on the right is the pig embryo
• Comparing the embryo development of different
  species can provide additional evidence of
  evolutionary relationships because embryos of
  closely related species show similar patterns of
  development.
• For example

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Comparing Embryos

• All vertebrate embryos have gill slits,
  two-chambered hearts and tails at some point in
  their development.
• These similarities support the idea that they
  have a common origin.

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And now on to the last piece of major evidence
for evolution.
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Biochemical Comparisons
All forms of life have DNA. There are leftover
sections of DNA that are called junk DNA because
they dont have a purpose. Maybe they did at one
time?
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Biochemical Comparisons
A wide range of organisms from fruit flies to
worms to mice to humans have very similar
sequences of genes that are active early in
development. Remember from the movie
scientists put mouse eye genes in an eyeless
fruit fly eyes developed! What can this
mean? These genes were present in a very early
common ancestor of all these groups.
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Biochemical Comparisons
On top of that Proteins in all organisms are
composed of the same set of 20 amino acids. And
hemoglobin is found in almost every multicellular
animal. The more closely related two organisms
are, the more similar their DNA code is.
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Biochemical Comparisons
For example, chimp DNA and human DNA are 98.2
similar!
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Well, what do you think?You must agree that the
observations themselves cannot be refuted.
However, do you agree with the interpretation
of these observations and their use to support
evolution?
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The particulars of the jump from nonliving to
living that occurred sometime in our planet's
early history is a profound enigma and will
likely remain that way for some time to come,
says Harvard's Andy Knoll. The hard part, and
the part that I think nobody has quite figured
out yet, is how you get them working together.
How do you go from some warm, little pond on a
primordial Earth that has amino acids, sugars,
fatty acids just sort of floating around in the
environment to something in which nucleic acids
are actually directing proteins to make the
membranes of the cell?
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In the early 1950s, Stanley Miller essentially
put methane (natural gas), ammonia, hydrogen gas,
and water vapor into a beaker. This was a view of
what the primordial atmosphere would have looked
like.He put an electric charge through that
mixture to simulate lightning going through an
early atmosphere.

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After sitting around for a couple of days, all of
a sudden there was this brown goo all over the
reaction vessel. When he analyzed what was in
the vessel, rather than only having methane and
ammonia, he actually had amino acids, which are
the building blocks of proteins. In fact, he had
them in just about the same proportions you would
find if you looked at organic matter in a
meteorite. So the chemistry that Miller was
discovering in this wonderful experiment was not
some improbable chemistry, but a chemistry that
is widely distributed throughout our solar system.