Download Evidence of Evolution

Evidence of Evolution
Chapter 15-3
2008-2009
I. Darwin’s Evidence
• A. For millions of years living things
have been evolving
• B. 4 areas of evidence:
– 1. Fossil Record
– 2. Geographical Record Distribution of
living species
– 3. Homologous Structures
– 4. Similarities in Embryology
– 5. Molecular Biology
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II. Fossil Record
• A. Shows how different organisms &
species have changed over time
• B. Paleontologists study fossils
• C. Fossils are preserved remains of
dead organisms
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• D. Radioactive Dating
– 1. Its used to determine the absolute
age of fossils
– 2. Half-life = time it takes for ½ of the
radioactive isotopes to decay
• a) Isotope= an atom with an abnormal # of
protons or neutrons
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• E. Relative Dating
– 1. aging of fossils by comparing its
placement among other fossils in rock
layers.
– 2. Older rock layers are found under
younger rock layers
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Types of Fossils
The term fossil refers to any
parts or impressions of an
organism that may survive after
its death.
Trilobites
preserved in
sedimentary
rock
Fossils form best when
organisms are buried quickly
in conditions that slow the
process of decay.
A layer of shell
still covers the
stone interior
of this
ammonite
Fossils are most commonly
found in sedimentary rock.
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Bird bones
preserved in a tar
pit
Formation of
Sedimentary Rock
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III. Geographic Distribution Of Living
Species
• A. Different species lived in different
areas.
• B. Similar environments had species
with similar characteristics or
anatomies.
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Continental Drift
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Biogeography – distribution of species
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Biogeography
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• C. Darwin’s Theory: Decent with
Modification
– 1. Organisms are related to one another
through a common ancestor
– 2. Over time natural selection produces
organisms with different structures or
behaviors causing changes in species
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IV. Homologous Body Structures
• A. Structures that vary in form and
function but are constructed from the
same basic bones.
– 1. Ex: arms & legs of reptiles & mammals
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Comparative Anatomy –
Homologous Structures
Wings
Comparative Anatomy
– Analogous
Structures
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• B. Vestigial Structures
– 1. organs that have reduced in size
and are traces of homologous organs
in other species.
– 2. Ex: Hind legs in whales
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Vestigial Organs in Whales
Ex: Whales are the
descendants of
large, four-legged
land mammals that
existed some 60
million years ago.
Over many years,
the pelvis & femur
have become very
small & no longer
fulfill a locomotory
function.
Femur
Pelvis
Hindlimb
Forelimb
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• C. These provide strong evidence that
organisms have descended, with
modifications, from common
ancestors.
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V. Similarities in Embryology
• A. Early stages of embryos of many
animals are similar
• B. It is clear that the same groups of
embyronic cells develop in the same
order and in the same pattern.
• C. It is these similarities that give rise
to homologous structures.
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Comparative Embryology
Developmenta
l Stage
Amphibian
Bird
Monkey
Human
Fertilized
egg
Late
cleavage
Body
segment
s
Gill
slits
Limb
buds
Late fetal
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VI. Molecular Biology
• A. Closely related organism have very
similar DNA sequences
• B. Organisms that are not closely related
do not have similar DNA Sequences
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Molecular Biology
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Summary of Darwin’s Theory
• 1. Organisms produce more offspring
than can survive
• 2. Because more organisms are
produced than survive, there is
competition for resources
• 3. Individual organisms are different &
this variation is heritable
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• 4. “Unique” organisms have
advantages & disadvantages.
• 5. Those best suited for their
environment will survive and reproduce
most successfully.
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• 6. Species alive today are descendants
with modifications from relative
species that lived in the past.
• 7. All organisms trace back to a single
common ancestor organism.
• THIS IS EVOLUTION!
2008-2009