evolution

1. Evidence of Evolution

2. Evidence of Evolution
 EVOLUTION - genetic change in a
population of organisms over time
 4 Types of Evidence that scientists have
gathered in support of evolution
 Fossils
 Comparative Anatomy & Structures
 Embryology
 Biochemistry (Proteins & DNA)

3. Fossils
 What is a FOSSIL?
 The preserved remains or traces of an organism that is
no longer living
 Usually found in
sedimentary rocks

4. What can fossils show?
 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
 Reveals ancient climate & environmental conditions
 Indicates development of life from simple to complex
 Indicates life began in water

5. Fossils
 Types of Fossils:
 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.

6. How can fossil age be determined?
 Depth of fossils help to determine their age
 Lower layers are older than those in upper layers
 Radioactive Isotope Dating
 Carbon-14, Uranium-238,
Potassium-40
 Measure the proportion of an
isotope relative to its more
stable form (half life)

7. Why is the fossil record incomplete?
 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

8. Comparative Anatomy
 Study of anatomical structures to find similarities
and differences
 HOMOLOGOUS STRUCTURES – parts with similar
basic structure (derived from same structures in
embryo—same common descent), but may vary in
function

9. Comparative Anatomy
 ANALOGOUS STRUCTURES – structures
that have the same function (may look
somewhat alike), but have different
structures and DO NOT have a common
descent
 Example: wings have developed
independently in insects, reptiles, birds, and
bats

10. Comparative Anatomy
 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
 Examples:
 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

11. Embryology
 Patterns of
embryological
development can
indicate a common
ancestry
 Fish, birds, mammals
& reptiles all have gills;
only fish retain theirs
 Fish, birds, humans &
reptiles all have tails;
ALL but humans retain
theirs

12. Biochemical Similarities
 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