1. Lecture #3 Evidence of Evolution
Unit 6: Evolution

3. Evidence of Evolution Based on a large amount of evidence, most
scientists agree on the following three major
points
Earth is about 4.5 billion years old.
Organisms have inhabited the Earth for most of its history
All organisms living today evolved from earlier, simpler life forms.

4. There are 4 major areas of evidence that exist for evolution
1. Fossil Evidence
Fossils provide an actual record of Earth’s past life forms. Change over time (evolution) can be seen in the fossil record.
Fossils - Remains or traces of a once-living organism
Fossil specimens found in older rocks are different from those found in newer rocks.

5. Evidence for Evolution – The Fossil Record
Darwin and His Theory
Evidence for Evolution – The Fossil Record
9/22/2018
G. Podgorski, Biol. 1010

6. Darwin predicted that intermediate forms between the great groups of organisms would eventually be found.
Since Darwin’s time, many of these links have been found.
Ex: Archaeopteryx
links birds and
reptiles

7. The fossil record is far from complete. Finding fossils is no easy task. Not all organisms lived in areas where fossils form.
Paleontologists - scientists who study fossils.
They can determine the age of fossils using different techniques.

8. Radiometric dating is used to get an actual age (absolute age)
You can also compare a fossils position in the rock strata to the position of another fossil (relative age).

9. How does this help us? When fossils are organized from
oldest to youngest,
orderly patterns of
evolution can be
seen.
Example
Evolution of the horse

10. Evolution of the Whale

11. 2. Molecular Evidence (Comparative biochemistry)
Darwin could only study traits that could be
seen but molecular genetics supports his
theory
All living organisms have the same molecular code
Many organisms have homologous genes
Example: Hox gene directs growth of limbs; the
protein hemoglobin carries oxygen

12. Prediction: A species that descended from a common ancestor in the distant past should have more differences in the amino acid sequences of the same protein than do species that shared a common ancestor more recently. Common ancestor - species from which two or more species have diverged.

13. Comparing Proteins
This predication was tested by analyzing the amino acid sequences of hemoglobin in humans and several other species.
The data supported the prediction. Humans and gorillas have fewer differences than do humans and chickens.

14. Scientists can compare the # of nucleotide changes in a given gene as well. Closely related organisms = fewer base differences in the same gene
Comparing DNA
Phylogenetic tree

15. Phylogenetic tree- a branching diagram which shows how organisms are related through evolution. These provide strong evidence supporting evolution because they show the same relationships indicated by the fossil record.

16. Cladogram- a diagram used in which shows ancestral relations among organisms. It is based on shared characteristics.

17. Humans and Chimpanzees are 97% genetically identical.
This supports the claim that chimpanzees and humans have a common ancestor

18. 3. Homology
‘Same structure, different function’
Homologous Structures Structures found in organisms that share a common ancestry but have since evolved for different functions.
Example
The forelimbs of ALL vertebrates are made from the same
basic groups of bones, hooked up in the same way.

19. ‘Same function, different structure’
Analogous structures –
Similar features of
organisms that evolve
independently.
Example - Wings of a
fly and the wing of a
bird
‘Same function, different structure’

20. Vestigial Structures –
Structures that are reduced in size and function.
They are considered to be evidence of an organism’s evolutionary past.
These structures have no apparent function. (evolutionary leftovers)
Examples- human appendix, wisdom teeth, tailbone

21. Example- internal hind-leg bones in whales

22. 4. Early Embryological Evidence
Early on in development,
vertebrate embryos
are strikingly similar.
Each has
A tail
Pharyngeal pouches
(develop into gills in
amphibians and fish)
Buds that become limbs

23. Structures develop at different rates in different groups of vertebrates, and are called homologous structures when its all said and done.

24. Take 2 minutes to summarize what you have learned regarding the different sources of evidence of evolution that exist.