Transcript File - Ms. G`s Classroom

Evidences of Evolution
Evolution
The Fossil Record
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skeleton of an oviraptor
The fossil record
contains many welldocumented examples
of the transition from
one species into
another, as well as the
origin of new physical
features.
Evidence from the
fossil record is unique,
because it provides a
time perspective for
understanding the
evolution of life on
Earth.
Preserved Hard Parts
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Most common types of
fossils.
La Brea Tar Pits, Los
Angeles, Ca. - full skeletons
of organisms such as the
saber-toothed tiger and the
wooly mammoth.
Wooly Mammoth
Saber-toothed Tiger
Preservation of Soft Parts
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Preservation of an
organism’s soft parts is
rare because organic
matter is subject to
decay.
In Siberia some 50
specimens of woolly
mammoths and a longhorned rhinoceros were
found preserved in ice
with even the skin and
flesh intact.
Preservation in Amber
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Amber is a tree resin that
has hardened and been
preserved in the Earth’s
crust for millions of years.
This tree resin was
generally secreted as a
protective mechanism
against disease and
insect infestation.
Often regarded as a
gem, amber is actually
an organic substance
whose structure has
changed very little over
time.
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Petrification
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Molecule by molecule, woods is
replaced by stable inorganic materials.
This occurs when logs are buried and
the organic matter is replaced by silica
(quartz) slowly as the groundwater
seeps through the wood.
Imprints
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An imprint fossil forms when an object is pressed into
mud, such as a leaf or insect. As it slowly dissolves, the
mud surrounding it can harden and a space is left. A mold
of the original object is formed, which fills with sediment
and becomes a fossil.
The imprint pictured is
an ammonite, a extinct
mollusk characterized
by its flat, coiled,
chambers shell.
Molds and Casts
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Molds or casts may be
left if shell material
dissolves before the mud
that the shells were
encased in.
Molds are hollows in the
shape of the shell left
after the shell has
dissolved.
Casts are the mud left
from the inside of the
shell after the shell has
dissolved.
Mold of a fossilized shell
Sedimentary Rocks

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Older fossils of simpler
life forms are found in the
older layers.
the upper strata generally
contains fossils of
younger, more complex
organisms.
Comparative Anatomy
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Organisms that have similar structures are related to each
other and share a common ancestor.
Vestigial Structures – structures that are no longer used by an
organism but provide evidence that certain organisms were
related and shared a common ancestor.
Coccyx bone, tonsils, appendix, nictitating membrane humans
Chicken nictitating membrane
Homologous Structures
 Anatomical parts that are similar in origin and structure,

but have different functions.
Provide evidence of common ancestry.
Analogous Structures

Structures that have
similar function but not
similar underlying
structure and form.

The similarity is
superficial and reflects an
adaptation of different
organisms to a similar
environment.
Comparative Cytology
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The cell is the unifying structure for all living organisms.
Organelles such as the cell membrane, mitochondria, and
ribosomes are structurally and functionally similar in the most
divergent organisms.
Comparative Biochemistry

Many diverse organisms have similar
DNA and protein structures, suggesting
evolutionary relationship and common
ancestry.
Comparison of Mouse and Human DNA nucleotides
Comparative Embryology
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Comparison of early embryonic development of among
groups of organisms evidences similarities in structure
and form, suggesting common ancestry.
Biogeography
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Continental Drift
--Pangea: about 200 million years ago, the continents were
locked together in a single supercontinent
--During the next 150 million years the supercontinent slowly
separated into 7 continents.
--Study of fossil locations confirms the theory that marsupials
migrated by land from South
America across Antarctica to
Australia before those two became
separate continents about 55
million years ago.
--Today, most of the world’s
marsupials are isolated in Australia.