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