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EVOLUTION: Geological Time Scale
a. The age of the earth is 4.5 billion years old.
b. Geological history of the earth is divided
into eras, periods, and epochs.
c. Fossil record provides relative dating of
rock layers; top layers of rock are younger
than lower layers.
EVOLUTION: Geological Time Scale
d. Absolute dating method uses radioactive
isotopes.
(1). Isotopes each have a particular half-life
or time it takes for half of the isotope to
decay and become nonradioactive.
(2). Carbon-14 is used to date organic
matter; half decays to Nitrogen-14 each
5,770 years.
EVOLUTION: Geological Time Scale
Absolute dating continued:
(3). Half of potassium-40 decays to argon40 each 1.3 billion years; it is used to
estimate the age of younger rocks.
(4). Half of Uranium-238 decays to lead 206
every 4.5 billion years; it is used to
estimate the age of older rocks.
EVOLUTION: Fossil Evidence
a. Fossils are remains, traces or other direct
evidence of past life forms.
b. Most fossils form from burial of plants and
animals in sediment; soft parts are more
often consumed or decomposed but may
leave imprints if buried rapidly.
c. Most fossils are embedded in sedimentary
rock . Which are weathered particles that
provide strata from lower older layers to
upper newer layers.
EVOLUTION: Fossil Evidence
d. Paleontologists study the fossil record
based on boundaries between strata, where
one mix of fossils gives way to another.
e. Transitional links are intermediate
between major groups.
Example: Archeopteryx has features
intermediate between primitive reptiles and
birds.
Archeopteryx fossil
Archeopteryx drawing
EVOLUTION: Anatomical Evidence
a. Many organisms share a unity of plan;
for example, vertebrate forelimbs contain
the same sets of bones used for different
functions in bat wings, whale fins, etc.
b. The simplest explanation is having a
common ancestor whose basic forelimb
plan was modified in succeeding groups as
each continued along its own evolutionary
pathway.
EVOLUTION: Anatomical Evidence
c. Homologous structures are similar
structures derived through descent from a
common ancestor.
d. Analogous structures have similar functions
but differ in anatomy and did not derive from
the same ancestral structure; for instance,
an insect wing and a bird wing.
EVOLUTION: Anatomical Evidence
EVOLUTION: Anatomical Evidence
e. Vestigial structures are reduced and
functionless anatomical features that are
fully developed and functional in other
ancestral groups.
Vestigial structures are evidence of an
organism's evolutionary history.
(1). Flightless birds have vestigial wings.
(2). Snakes have remnants of a pelvic
girdle.
(3). Humans have a tail bone but no tail.