Evidence for Evolution Isn’t Evolution just a Theory?

4 Categories of Evidence: Draw into Notebook Category of evidence Explanation/ Notes Examples 1. Fossil Record 2. Embryology 3. Comparative Anatomy 4. Molecular Biology Fossil Geographic Structural Developmental Molecular

Life on Earth has changed Fossils tell a story… the Earth is old Life is old Life on Earth has changed

1. Fossil Record Fossils are located in sedimentary rock new layers cover older ones, which creates a record over time fossils also show that organisms have lived on Earth over a long period of time

Age of fossils Relative dating – Age determined by which layer the fossils are found in- older usually below, younger above Absolute dating- determined by radioactive dating- date in years

Why are fossils rare? The environment must be favorable. Trilobite 526 mya Cambrian The environment must be favorable. Organisms must 'fall' into conditions where decay does not occur (swamps, bogs, lakes, caves). Geological processes and human activity also destroy the sedimentary rocks which contain fossils. Prehistoric fish 145 mya Cretaceous Bryozoan 450 mya Ordovician

Evolution of birds Fossil of Archaeopteryx lived about 150 mya (Jurasic) links reptiles & birds The avian nature of the brain and inner ear of Archaeopteryx (Alonso et al. 2004) - Archaeopteryx, the earliest known flying bird from the Late Jurassic period, exhibits many shared primitive characters with more basal coelurosaurian dinosaurs (the clade including all theropods more bird-like than Allosaurus), such as teeth, a long bony tail and pinnate feathers. However, Archaeopteryx possessed asymmetrical flight feathers on its wings and tail, together with a wing feather arrangement shared with modern birds. This suggests some degree of powered flight capability but, until now, little was understood about the extent to which its brain and special senses were adapted for flight. Alonso et al. (2004) investigated this problem by computed tomography scanning and three-dimensional reconstruction of the braincase of the London specimen of Archaeopteryx. A reconstruction of the braincase and endocasts of the brain and inner ear suggest that Archaeopteryx closely resembled modern birds in the dominance of the sense of vision and in the possession of expanded auditory and spatial sensory perception in the ear. Alonso et al. (2004) concluded that Archaeopteryx had acquired the derived neurological and structural adaptations necessary for flight. An enlarged forebrain suggests that it had also developed enhanced somatosensory integration with these special senses demanded by a lifestyle involving flying ability.

? ? ? ? Where are the intermediate fossils? Whales and the Fossil Record Land Mammal ? Complete series of transitional fossils ? Where are the intermediate fossils? ? ? There are innumerable intermediate & transitional forms Whales as land creatures returning to the water…. Where are the intermediate forms of whale ancestors? Cartoon making fun of this idea. The cartoons disappeared 10-12 years ago when this fossil was found. Ambilocetic natans = “Walking whale who likes to swim” 4-5 intermediate forms all found in last 2 decades Indus River valley in between India & Pakistan. How do we know Evolution happens Ocean Mammal

Who was Lucy? (Australopithecus afarensis) 3.2 myo fossil found in Ethiopia in 1974 she was 3’6”, 62 lbs. A. afarensis skull found in 1992 – suggests that the species did not change for 900,000 years Becoming a Fossil

2. Embryology Study of fetal development Scientists looks at different embryos of different species and compare them with one another

Embryo’s and our Common Ancestor Example: embryos of fish, salamander, tortoise, chick, rabbit, and human are similar! This shows evidence of a common ancestor Embryo’s and our Common Ancestor

3. Comparative Anatomy Comparing body parts between species

Compare the bones…

Homologous structures Structures that come from the same origin but perform different functions Example: Forelimbs of human, cats, whales, & bats are homologous – evidence of a common ancestor

Analogous structures Different anatomies, but same function No evolutionary relationship

Vestigial structures Have no use or serve a less important function, often reduced in size Show evidence of a shared ancestry

Wisdom Teeth human ancestors had larger jaws with more teeth, to help chew down plants to compensate for a lack of ability to efficiently digest cellulose As human diet changed, a smaller jaw was selected by evolution, yet the third molars, or "wisdom teeth", still commonly develop in human mouths

Appendix vestige of the cecum, located on right side of body an organ that would have been used to digest cellulose by herbivorous ancestors

Darwin’s Tubercle Present in 10.4% of the population First described by Darwin as evidence of a vestigial structure indicating common ancestry among primates

Coccyx “tailbone”, remnant of a lost tail All mammals have a tail at one point in their development In humans, it is present for a period of 4 weeks (week 14-22)

Nictitating membrane “third eyelid” small fold of tissue on the inside corner of the eye. present in birds, reptiles, fish, amphibians. Owl Toad Toad Owl Shark

4. Molecular Biology Comparing DNA and proteins between species That fact that we actually share specific genes and proteins, is powerful evidence of our common ancestry

Comparing genes (DNA) for eye control Example: DNA for the eye gene between a fly, shark, squid, and flatworm is very similar!

Comparing aa sequences for hemoglobin The less differences between species, the more closely related they are Species Amino Acid Differences from Human Hemoglobin Gorilla 1 Rhesus Monkey 8 Mouse 27 Chicken 45 Frog 67 Lamprey (jawless fish) 125

Molecular evidence allows scientists to build “family” trees