Evidence of Evolution
Evidence of Evolution
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EVOLUTION - genetic change in a
population of organisms over time
4 Types of Evidence that scientists have
gathered in support of evolution
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Fossils
Comparative Anatomy & Structures
Embryology
Biochemistry (Proteins & DNA)
Fossils
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What is a FOSSIL?
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The preserved remains or traces of an organism that is
no longer living
Usually found in
sedimentary rocks
What can fossils show?
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Organisms have appeared and disappeared, and have
changed over time
Extinction of species
Transitional forms reveal links between groups:
Archaeopteryx: between reptiles & birds
Eustheopteron: amphibious fish
Seymouria: reptile-like amphibian
Also, mammal-like reptiles & whales with hind limbs
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Reveals ancient climate & environmental conditions
Indicates development of life from simple to complex
Indicates life began in water
Fossils
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Types of Fossils:
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1. IMPRINT – thin, soft object (leaf, feather) is
buried and sediments later harden
2. MOLD – Buried organism disappears and
leaves an empty space
3. CAST – mold filled by
minerals (replica of organism)
4. PETRIFICATION – minerals
replace hard parts (bones, teeth, etc.) of
organism
5. AMBER – entire organism fossilized in tree sap
6. FROZEN – entire organism frozen in ice
7. TRACE – footprints, trails, etc.
How can fossil age be determined?
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Depth of fossils help to determine their age
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Lower layers are older than those in upper layers
Radioactive Isotope Dating
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Carbon-14, Uranium-238,
Potassium-40
Measure the proportion of an
isotope relative to its more
stable form (half life)
Why is the fossil record incomplete?
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1. Soft tissue rarely preserved
2. Movement of the earth’s crust has
obliterated or covered many fossils
3. Fossilization takes place only in certain
types of habitats and under favorable
conditions
4. Paleontologists have not dug up every
place on earth
Comparative Anatomy
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Study of anatomical structures to find similarities
and differences
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HOMOLOGOUS STRUCTURES – parts with similar
basic structure (derived from same structures in
embryo—same common descent), but may vary in
function
Comparative Anatomy
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ANALOGOUS STRUCTURES – structures
that have the same function (may look
somewhat alike), but have different
structures and DO NOT have a common
descent
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Example: wings have developed
independently in insects, reptiles, birds, and
bats
Comparative Anatomy
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VESTIGAL STRUCTURES – reduced body parts (in
comparison to the same complex structure in other
organisms) that have little to no function; remnant of an
ancestor
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Examples:
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Human appendix (other mammals
it is necessary to aid in digestion)
Human external ear muscle
(useless, but still there)
Human tailbone (coccyx)
Human wisdom teeth
Bird wings – Penguins adapted for
swimming, ostrich wings for
balance and courtship
Embryology
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Patterns of
embryological
development can
indicate a common
ancestry
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Fish, birds, mammals
& reptiles all have gills;
only fish retain theirs
Fish, birds, humans &
reptiles all have tails;
ALL but humans retain
theirs
Biochemical Similarities
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Similarity of proteins, RNA & DNA molecules
The more closely related organisms are, the
more similar is the biochemical makeup
Indicates common ancestor
Universality of genetic code – supports evolution
Similar chemistry & structure of chromosomes
among Eukaryotes
Chlorophyll is the same basic molecule in all
photosynthetic organisms