1. Evolution by Natural Selection

2. Evolution
What is it?
A change in heritable (able to be passed on from generation to generation) traits of biological populations over many generations.

3. Charles Darwin
One of many scientists that thought evolution occurred, first to publish the evidence to support it.
Wrote ‘On the Origin of Species: By means of Natural Selection’ in 1859
Alfred Russell Wallace, research in Australia, published paper with Darwin in 1858, doesn’t receive the same recognition.
Traveled around the world on the HMS Beagle and saw many different plant and animal species

4. Darwin
Hypothesized that present-day species are the descendants of ancient ancestors that they still resemble in some ways
Over millions and millions of years, present day species accumulated diverse adaptations that helped them to survive in their environment.
Finches, tortoises

5. Evidence
Fossils
are the imprints or remains of organisms that lived in the past
document differences between past and present organisms
reveal that many species have become extinct

6. Fossilization Process
Death decay burial/mineralization uplift/erosion discovery

7. Evidence The fossil record is incomplete because
many of Earth’s organisms did not live in areas that favor fossilization
fossils that did form were in rocks later distorted or destroyed by geologic processes
not all fossils that have been preserved are accessible to paleontologists

8. Evidence
Dating –
Relative – no exact year but deeper fossils = older, higher = younger
Absolute – can get close to the exact year, the older it is the less exact it becomes
Radioactive dating compares radioactive isotopes in a specimen
A few years – billions of years old depending on the element/isotope
Carbon 14, Uranium 238

9. Evidence What does the fossil record show?
Variety of life has constantly been changing
Organisms have become more complex over time
Very gradual changes over time
Extinctions are common – at least 5 mass extinctions

10. Evidence Comparative Anatomy – homologous structures
Similarities in anatomy between different organisms, similar structure but different function

11. Evidence
Embryology
Relationships between animals seen only before birth

12. Evidence Molecular biology Sequencing genomes of different organisms
The more similar the genomes are, the more likely they are to be related

13. Evidence Vestigial organs
An organ that is present but no longer serves a purpose
Tailbone and appendix in humans
Leg bones in whales
Parts of eyes in cave fish