Transcript Evidence for Evolution - Hatboro

Scientific Evidence for
Evolution
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”)
Types of Fossils
Amber- Solidified sap
Types of Fossils
Ice Fossils
Types of Fossils
Tar pits- Le Brea Pits in LA
Types of Fossils
Mold and cast- which is a copy of the original
organism.
When impressions
are made in mud,
such as animal
footprints, they are
called imprints.
Age of Fossils
Law of Superposition- highest are youngest
Age of Fossils
Over millions of years, the shifting of the
earth’s crust has raised some regions that
one were under the seas and the layers are
visible. The Grand Canyon is an example.
Age of Fossils
What can you conclude about the age of these
organisms in the layers of sedimentary rock?
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)
Transitional forms
(species) in
whale evolution
Did you ever wonder why
we have wisdom teeth?
Vestigial Structures
- Vestigial is a scientific word for “leftover.”
- These structures are usually reduced in
size and serve little or no function.
Other examples…
Vestigial Structures
In the human body there are
more than 100 vestigial
structures!
-Tailbone
-Appendix
-Ear muscles
Vestigial Structures
What do you notice about this whale and
snake skeleton ?
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.
Anatomical Similarities
HOMOLOGOUS STRUCTURES- same
structure different function
Evidence for Divergent evolution
ANALAGOUS STRUCTURES- same function
different structure
Evidence for Convergent evolution
Anatomical Similarities
Two of these embryos are human,
one is the embryo of a pig. Can
you pick out the pig embryo?
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.
And now on to the last
piece of major evidence for
evolution….
Biochemical Comparisons
All forms of life have DNA. There are leftover
sections of DNA that are called junk DNA
because they don’t have a purpose. Maybe they
did at one time?
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.
Biochemical Comparisons
For example, chimp DNA and human
DNA are 98.2% similar!
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?
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.
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.