Evidence of Evolution

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)

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

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

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.

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)

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

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

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

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

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

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