Transcript Evidence for Evolution Part 1

Evidence for
Evolution Part 1
Fossil records, zoogeographical maps, DNA
sequences, homologous, analogous.
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Warm-up Questions:
• Which scientist coined the theory of
evolution while studying finches?
Charles Darwin
• ________________ is the term used for when
natural selection leads to the creation of a
new species.
Speciation
There are several places we can see
evidence of evolution/evolutionary
relationships:

-fossils,

-comparative anatomy,

- biochemistry/DNA,

-embryology,

- and biogeography.

Evidence of Change Over
Time

Fossils are evidence of organisms that lived long ago that
are preserved in Earth’s rocks.
TYPES OF FOSSILS
Fossils Types
Formation
Trace fossils
A trace fossil is any indirect evidence
left by an animal and may include a
footprint, a trail, or a burrow.
Casts
When minerals in rocks fill a space
left by a decayed organism, they make
a replica, or cast, of the organism.
Molds
A mold forms when an organism is
buried in sediment and then decays,
leaving an empty space.
Petrified
fossils
Petrified-minerals sometimes penetrate
and replace the hard parts of an organism
Amber-Preserved
At times, an entire organism was
quickly trapped in ice or tree sap that
hardened into amber.
or
frozen fossils
Paleontologist:

Scientists who study ancient life by using fossils to understand
events that happened long ago.
They use fossils to determine the kinds of organisms that
lived during the past and sometimes to learn about their
behavior.
Fossil Formation:

For fossils to form, organisms usually
have to be buried in mud, sand, or clay
soon after they die.

Fossils are not usually found in other
types of rock due to the ways those
rocks form.

Example: the conditions under which
metamorphic rocks form often destroy
any fossils that were in the original
sedimentary rock.
How fossils form

Few organisms become fossilized because, without burial,
bacteria and fungi immediately decompose their dead bodies.

Occasionally, however, organisms do become fossils in a
process that usually takes many years.
Fossil Formation Contd.
Relative Dating:

Scientist use several methods for determining the age of a
fossil.

This method indicates that the fossils found closer to the
surface, in an undisturbed ground, are younger, and the
fossils found in deeper strata are older.

This method only gives a relative age between the fossils and
not a specific age of the fossils.
Using this principle, scientists can determine relative age
and the order of appearance of the species that are
preserved as fossils in the layers.
Relative Dating Contd.
Anatomical Evidence:

There are two types, homologous and
analogous.
Homologous Structures:

Structural features with a common evolutionary origin

Science sees structural similarities as evidence that
organisms evolved from a common ancestor.

Homologous parts are similar in structure, but may be very
different in specific function.
Analogous Structures:

The body parts of organisms that do not have a common
evolutionary origin but are similar in function.

Analogous parts are very different in structure, but perform
similar functions.
Vestigial Structure:

A body structure in a present-day organism that no longer
serves its original purpose, but was probably useful to an
ancestor.
Video
Biochemical Relationships:

Scientists believe that the fact that ALL LIVING THINGS
have A,T,C, and G in their DNA and all use the same coding
for proteins means we are all related in some way.
Embryology:

The study of how similar embryos are for different
organisms (may be evidence of relation)
Embryology Contd.

Scientists believe the shared features in the young embryos
of different species suggest evolution from a distant,
common ancestor.
Pharyngeal
pouches
Pharyngeal
pouches
Tail
Fish
Tail
Reptile
Bird
Mammal
Chicken
Rat
Turtle