The Theory of Evolution

1. The Theory of Evolution

2. Just a Theory??? • Evolution is as solidly established as any scientific fact. (It is more than a just a Theory) • Natural Selection, one of the mechanisms for evolution is Theory, however….

3. In science, the term "Theory" does not express doubt. • In science, the term Theory is used to represent ideas and explanations that have been confirmed through many tests and observations made by many in the scientific community.

4. Evolution Defined!! • Change in the genetic makeup of a species. • Over many generations a species can evolve into something quite different. • Changes are caused by genetic mutations.

5. What is Evolution??? Life on earth evolved gradually beginning with one primitive species-perhaps a self-replication molecule-that lived more than 3.5 bya; it branched out over time, throwing off many new and diverse species; and the mechanism for most (but not all) of evolutionary change is natural selection.

6. Some thought that you would gain or lose features if you overused or didn't use them, and you could pass these new traits onto your offspring. A giraffe stretched its neck to reach higher leaves, and this stretched neck would be a trait inherited by its offspring Early Ideas of EvolutionLamarck; 18th Century

7. Traits gained during life are not passed on to children. Why? Logically it doesn't work. Imagine if you were in a car accident and had a leg amputated. This does not mean that your children will only have one leg. However, Lamarck was one of the first scientists to suggest that species do not stay the same forever. WRONG!!!

8. Geologists who concluded that the Earth is really old and that processes that changed Earth in the past are the same that change the Earth today! Called Uniformitarianism! Darwin observed that if the earth has evolved over time, then life must have done the same. Hutton and LyellLate 1700s and Early 1800s

9. Reasoned that if human population grew unchecked, then there would not be enough food or space for everyone…. Darwin realized that most organisms do not survive and reproduce; he wanted to know why some organisms did go on to reproduce…. Malthus 1798

10. Evidence for Evolution

11. Biogeography: The study of where organisms live now and where their ancestors lived in the past Patterns in the distribution of living and fossil species tell us how modern organisms evolved from their ancestors.

12. Fossils • Radioactive dating to establish the age of certain rocks and fossils show that the earth is 4.5 byo! • Recent fossil finds help scientists document stages and gaps in evolution. • Tiktaalik • “Scientists have discovered fossils of a 375 million-year-old fish, a large scaly creature not seen before, that they say is a long-sought "missing link" in the evolution of some fishes from water to a life walking on four limbs on land.”

13. Molecular Biology and DNA • All living organisms use DNA and RNA to carry information from one generation to the next. Homologous molecules Ex) same type of protein found in almost all living organisms EX) Hox genes: growth of front and hind limbs

14. Observations of Natural Selection • Darwin’s finches had all descended from a common ancestor. • Several finch species had different beak sizes and shapes. Darwin suggested that these shapes were adaptations based on the food that the birds ate.

15. Populations of finches- why are there so many similar species of finches occupying the same habitat? Competition- Individuals compete for limited resources. Darwin’s Observations

16. Why do so many different animals have the same structures, like the arm bones in a human are the same bones as a flipper in a whale? Homologous Structures: Structures likes bones or wings that are embryologically similar, but have different functions. Evidence of Common Descent and Evolution

17. Structures or organs that seem to serve no useful function Organisms that have vestigial structures probably share a common ancestry with organisms in which the homologous structure is functional Some cave-dwelling salamanders have eyes even though members of the species are completely blind. Vestigial Structures or Organs

18. More examples of vestigial structures Wings on flightless birds Hind leg bones on whales Human appendix Sexual organs of dandelions Human tailbone

19. Such physical similarities indicate that there are geneticsimilarities (DNA) between the organisms. These similarities can be considered evidence that the organisms shown probably descended from a common ancestor. Why do the embryos of animals look very similar at an early stage?