Scientific contributions to a theory of evolution

1. Scientific contributions to a theory of evolution SBI3U Section 8.1 Pg 326-330

2. The Science of Paleontology • Paleontology is the study of ancient life through the examination of fossils • A fossil is the preserved remains of a once living organism • Fossils can be preserved in amber (when organisms get stuck in the stick sap of a tree), permafrost, dry caves and as rock

3. Formation of Fossils • Fossils generally form when an organism falls into a body of water and is covered over time by layers of sediment • Subterranean waters rich in minerals seep into the decaying tissues and gradually replace the chemicals present in the tissues • The minerals eventually form into rock thus creating a fossil

4. Development of Evolutionary Theory and… Natural Selection and… Darwin’s voyages

5. Aristotle • 384-322 B.C. – Aristotle – wrote the ScalaNaturae, or ladder of life. • It described a Great Chain of Being which had a graduating complexity. • Humans were on top. • There was not mention of transformation, extinctions. Organisms were immutable.

6. Archbishop James Usher • 1650 – Archbishop James Usher of Armagh declared that the Earth was created on Sunday October 23 4004 B.C.

7. Carolus Linnaeus • 1700’s - Linnaeus wrote the Systema Naturae, thus developing taxonomy. • The classification system of Genus species was introduced.

8. Thomas Malthus • 1766-1834 – Thomas Malthus – An essay on the Principles of Populations • stated that reproductive increases are geometric(populations increase by a multiplicative factor) while availability of resources increase at a slower rate • Excess fertility creates more offspring than the environment can sustainand overpopulation will result in a lower quality of life and deaths due to lack of resources

9. Baron Georges Cuvier • 1769-1832 – Baron Georges Cuvier developed the theory of Catastrophism, which explained that catastrophes in the past caused the extinction of local species • Cuvier is the founder of palaeontology (Ross in Friends)

10. Sir Charles Lyell • 1798-1875 – Sir Charles Lyell, a geologist • Uniformitarianism • The geological processes we see today are the same that they have always been. • Slow, subtle processes could happen over a long period of time and still result in substantial changes

11. Jean Baptiste Lamarck • 1809 – Lamarck stated that organisms would become progressively better adapted to their environment over their life times • Eg. Giraffes necks grew longer through constantly stretching to get to food that was high up on trees • The adaptations that parents gained throughout their life times would be passed on to their children (Inheritance of acquired characteristics) • He also suggested that body parts that were not used would disappear ( use and disuse)

12. Sir Charles Darwin • At 16 was sent to medical school… he thought it was boring, and left • Enrolled at Christ College at Cambridge to become a clergyman (at this time, most prominent naturalists and scientists were clergymen) • Graduated in 1831 at age 21

13. Sir Charles Darwin • Reverend John Henslow, a professor of botany, introduced Darwin to Captain Robert FitzRoy (HMS Beagle), and gave Darwin Lyell’s book • Set out on the HMS Beagle for 6 years as the captains companion (unofficial naturalist) • Mission was to chart the South American coast • While the ship was on the coast, Darwin would go ashore and collect specimens of local animals and plants, as well as fossils of extinct animals I’m on a boat

14. Voyage of the Beagle

16. Darwin’s Finches • While on the Galapagos islands, Darwin collected samples from 13 similar but separate species of finches • Different beak shapes and sizes specialized for a particular food source Darwin hypothesized that the finches must have all had a common ancestor. He also found fossils of hippo sized rodents. The similarities of the fossils to modern day rodents led him to believe species changed over time.

17. Natural Selection • Organisms produce more offspring that can survive. Therefore , organisms compete for limited resources • Individuals of a population vary extensively and much of this variation is heritable • Individuals that are better suited to local conditions survive to produce more offspring • Processes for change are slow and gradual

18. Sources of evidence for evolution SBI3U Section 8.2 Pg 332-340

19. Evidence from the fossil Record • There have been fossils found in layers of rock that resemble species to day, with fossils found in layers closer to the surface(younger) having a closer resemblance to fossils found in deeper(older) layers • Fossils appear in chronological order in the rock layers meaning that the deeper that you dig a more primitive ancestor of a certain species can be found • Not all organisms appear in the fossil record at the same time for example fish have been shown to be the oldest vertebrates followed by amphibians, reptiles, mammals and birds thus indicating a direct line of evolution

21. Evidence from Transitional Fossils • A transitional fossil is a fossil that shows intermediary links between groups of organisms and shares characteristics common to two now separate groups • Eg. Archaeopteryx shows a transitional stage in the fossil record because it had characteristics of both reptiles and birds • It had both feathers like birds and teeth and claws like reptiles • These transitional fossils show two very different species can evolve from a common ancestor

22. Evidence from Biogeography • Biogeography is the study of the past and present geographical distribution of species populations • Darwin hypothesized that species evolve in one location and then spread out to other regions • It has be found that related species are found in regions that are closer to each other rather than regions that are similar in environment (e.g. cacti are found only in North and South American deserts but not in African, Asian or Australian deserts • Closely related species are almost never found in exactly the same location meaning that at one point an ancestral population migrated to another location and evolution took place

23. Evidence from Anatomy • All vertebrate forelimbs contain the same set of bones, organized in similar ways • The best explanation for this is that the basic vertebrate forelimb originated with a common ancestor

24. Homologous structures • Structure that have similar structural elements and origin but may have a different function • The limbs shown have similar structures like number of bones, muscles, ligaments, tendons and blood vessels

25. Analogous Features • Features that have a similar function, but have a different origin • Analogous structures evolve in species of different origin who live in similar ecological units

26. Evidence from Embryology • Embryology is the study of early, pre-birth stages of an organisms development • The embryos of different organisms exhibit similar stages of embryonic development • E.g. all vertebrates embryos have paired pouches, or out-pocketings of the throat

28. Evidence from DNA • Scientists can determine how closely related two organisms are by comparing their DNA • If two species have similar DNA sequences it means that they must have had a common ancestor • Through DNA analysis scientists have determined that dogs are related to bears and whales and dolphins are related to hoofed animas such as cows and deer