Evolution Evidence and Theory

1. EvolutionEvidence and Theory Chapter 14 HonorsBiology

2. Early Biological Though • Heavily influenced by theology • All organisms were created simultaneously • Each distinct life-form was permanently fixed and did not change over time

3. Evolution- Is it true? • A genetic change within a population over time! • Population- interbreeding single-species group

4. Fossils- Documentation • Fossil - trace of a long-dead organism. • Sedimentary rock - formed by dust, sand, or mud deposited by wind or water over dead organism • Formed by hard body parts of an organism—shell, bones, teeth, or woody stems • Hard minerals replace the tissue of the organism leaving rocklike structures

5. Sedimentary Rock

6. Fossils • Mold– imprint in rock in the shape of an organism • limestone • Cast– forms when molds are filled with hard minerals Mold Cast

7. Limestone • Limestone – most abundant , non-classic sedimentary rocks. • Limestone is produced from the mineral calcite (calcium carbonate) and sediment. • Chalk is another type of limestone that is made up of very small single-celled organisms.

8. Robert Hooke 1635-1703 • He concluded that fossils are remains of plants and animals • He mostly studied “petrified wood” with the aid of the microscope • He hypothesized that living organisms had somehow been turned to rock

9. Petrified WoodWood that has turned to stone!

10. Non-evolutionary Explanations • Catastrophism • Georges Cuvier (1769-1832) • High numbers of species were created originally • Series of catastrophes produced rock layers • destroyed many species, preserving some as fossils • Modern day species are the survivors of these catastrophies

11. Uniformitarianism • James Hutton (1726-1797) and Charles Lyell (1797-1875) • Developed theory of uniformitarianism • Geologic change resulted from slow, continuous actions similar to those at work today

12. Distribution of Fossils • Nicolaus Steno (1638-1686) • “law of superpositon” – states that the top layers of stratum contain the youngest fossils while the lower ones are older • Determine the “relative age” of a fossil • “absolute age”- age in years determined by radiological evidence

13. Succession of Forms • Mass extinctions – brief periods during which large numbers of species disappears. • Resulted from drastic changes in the environment, volcanic activity or collisions with asteroids (may have blocked sunlight for long periods of time and decreased temp.)

14. Biogeography • Biogeography – is the study of the geographical distribution of fossils and of living organisms. • A comparison of fossil types with types of living organisms in the same geographic area • shows that new organisms arise in areas where similar forms already lived. • Ex: armadillos in North & South America where glyptodonts lived in the past.

15. Armadillos

16. Glyptodonts

17. ScaphognathuscrassirostrisLab Fossil

18. Theories of Evolution • I. Lamarck’s Explanation: • He hypothesized that acquired traits were passed on to offspring. • Proposed that similar species descended from a common ancestor (fossil records)

19. Acquired Trait • It’s not determined by genes! • Occurs during an organism’s lifetime • result of the organism’s experience or behavior. • Ex: 1. Muscles on a body builder • 2. Giraffe’s necks did not get longer by trying harder and harder to reach tall trees- Genetic

20. Beginning of Modern Evolutionary Theory • II. Charles Darwin (1809-1882) & Alfred Wallace (1823-1913) • Darwin & Wallace announced their hypotheses at the same time • Darwin’s name became more associated with evolution The Origin of Species published

21. Darwin’s Voyage on the Beagle • Sailed in 1831 for five years • Collected specimens and kept careful records of his observations • Sailed to South America (Galapagos Islands) and the South Pacific

22. Voyage of the Beagle

23. Darwin’s Findings • Collected 13 similar but separate species of finches. • Each finch species had a distinctive bill for specialized food source. • Implied that the finches shared a recent common ancestor

24. Darwin’s Finches

25. Darwin’s Findings

26. Darwin’s Theories • TWO THEORIES; • 1. DESCENT WITH MODIFICATION – The newer forms appearing in the fossil record are actually the modified descendants of older species • Organisms similar to each other- common ancestor • Organisms that are dissimilar -share a more remote ancestor

27. 2. Modification by Natural Selection • MODIFICATION BY NATURAL SELECTION – states HOW evolution occurs. • Organisms best suited to their environment reproduces more successfully than other organisms Leaf tailed gecko

28. Based on 4 postulates Postulate- something taken as self-evident  • 1. Individual members of a population differ • Variations arise purely by chance resulting from random mutations in DNA • 2. Variations are passed from parent to offspring • 3. Some individuals in a population survive and reproduce successfully but others do not • 4. Individuals with advantageous traits survive longest and leave the most offspring- natural selection

29. Adaptation- Adaptive advantage • A population of organisms adapt to their environment • # of genes for favorable traits increases • Fitness- a single genetic organism’s contribution to the next generation’s survival • A well adapted organism will reproduce successfully and have a high fitness

30. High Fitness? Low Fitness?

31. High Fitness? Low Fitness?

32. High Fitness? Low Fitness?

33. High Fitness? Low Fitness?