1. Chapter 22~ Evolutionary Thought

3. Evolution Evolution: change over time Natural selection: –populations of organisms can evolve if individuals having certain heritable traits leave more offspring than others (differential reproductive success) Evolutionary adaptations: –inherited characteristics that enhance organisms’ survival and/or reproduction November 24, 1859

4. The Origin of Species Focused biologists’ attention on the great diversity of organisms Marine Iguanas of the Galàpagos Islands

5. Darwin made two major points in his book –He presented evidence that the many species of organisms presently inhabiting the Earth are descendants of ancestral species –He proposed a mechanism for the evolutionary process, natural selection

6. The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species In order to understand why Darwin’s ideas were revolutionary –We need to examine his views in the context of other Western ideas about Earth and its life

7. Evolutionary history Linnaeus: biology, taxonomy Hutton: geology, gradualism Lamarck: biology, evolution Malthus: economics, populations Cuvier: paleontology, catastrophism Lyell: geology, uniformity Darwin: natural selection Mendel: inheritance Wallace: natural selection

8. Evolutionary history

9. Science Before Darwin The Great Chain of Being – Scala Naturae (Aristotle) People thought that each species was a divine creation (The Old Testament) Carolus Linnaeus (1700’s) –Interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose –Was a founder of taxonomy, classifying life’s diversity “for the greater glory of God”

10. Questions Loom Large Fields of research investigating living things around the planet –Biogeography- Distribution of organisms around the world –Comparative Morphology- Study of similarities and differences in the body plans of major groups (phyla)

11. Fossils The study of fossils –Helped to lay the groundwork for Darwin’s ideas Fossils are remains or traces of organisms from the past –Usually found in sedimentary rock, which appears in layers (strata) 9 million years of erosion caused by the Colorado River = Grand Canyon

12. Cuvier and Catastrophism Paleontology, the study of fossils –Was largely developed by French scientist Georges Cuvier Cuvier opposed the idea of gradual evolutionary change –And instead advocated catastrophism, speculating that each boundary between strata represents a catastrophe

13. Gradualism –Is the idea that profound change can take place through the cumulative effect of slow but continuous processes Geologists Hutton and Lyell (theory of uniformity) –Perceived that changes in Earth’s surface can result from slow continuous actions still operating today –Exerted a strong influence on Darwin’s thinking

14. Science Before Darwin Lamarck (1744 - 1829) proposed that evolution occurs through the use & disuse of physical features –“Inheritance of Acquired Characteristics”

15. Darwin’s Voyage and Research As a boy and into adulthood, Charles Darwin –Had a consuming interest in nature Soon after Darwin received his bachelor’s degree in theology –He was accepted on board the HMS Beagle as the ship’s “naturalist”

16. The Voyage of the Beagle During his travels on the Beagle –Darwin observed and collected many specimens of South American plants and animals Darwin observed various adaptations of plants and animals –That inhabited many diverse environments

17. Darwin’s interest in the geographic distribution of species –Was heightened by the Beagle’s stop at the Galápagos Islands near the equator west of South America England EUROPE NORTH AMERICA Galápagos Islands Darwin in 1840, after his return SOUTH AMERICA Cape of Good Hope Cape Horn Tierra del Fuego AFRICA HMS Beagle in port AUSTRALIA Tasmania New Zealand PACIFIC OCEAN Andes ATLANTIC OCEAN

18. Darwin’s Voyage (1831-1836) Saw fossils of extinct armadillos that looked similar but not identical to living ones Finches on Galapagos islands resembled finches on the main land

19. Competition Keeps Populations in check Malthus wrote that the human population would cover the Earth if it went unchecked. Disease, war, and famine keep it from going out of control. Population: all the individuals of a species living in a specific location Adaptation: the changing of a species that makes them better suited to its environment

20. In 1844, Darwin wrote a long essay on the origin of species and natural selection –But he was reluctant to introduce his theory publicly, anticipating the uproar it would cause In June 1858 Darwin received a manuscript from Alfred Russell Wallace –Who had developed a theory of natural selection similar to Darwin’s Darwin quickly finished The Origin of Species –And published it the next year

21. Theory of Evolution by Natural Selection 1859 Darwin published his theory Three major findings –There is genetic variation in a population or species –Some individuals are better suited to the environment and survive to have more offspring (fitness) –Traits that are adaptive will spread in a population

22. Descent with Modification Darwin never used the word evolution in the first edition of The Origin of Species The phrase descent with modification summarized Darwin’s perception of the unity of life The phrase refers to the view that all organisms are related through descent from an ancestor that lived in the remote past Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

23. In the Darwinian view, the history of life is like a tree with branches representing life’s diversity Darwin’s theory meshed well with the hierarchy of Linnaeus Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

24. Fig. 22-7

25. Darwin’s Journey of Enlightenment 4 major observations: –Exponential fertility –Limited resources –Individuals vary –Variation is heritable

26. Descent with Modification 2 Inferences: Non-random survival Natural selection (differential success in reproduction)

27. Further Evidence used by Darwin In the process of artificial selection –Humans have modified other species over many generations by selecting and breeding individuals that possess desired traits Terminal bud Lateral buds Brussels sprouts Cabbage Flower cluster Leaves Cauliflower Flower and stems Broccoli Wild mustard Kohlrabi Stem Kale

28. “Absence of evidence is not evidence of absence.”

29. 22.3: Overwhelming Evidence

30. Macroevolutionary changes zMacroevolutionary change yIs the cumulative change during thousands of small speciation episodes zThis section looks at the evidence yDirect evidence xObservation xComparative Molecular Evidence: yFossils: yMorphology: zThen we will learn how to classify organisms based on the evidence

31. Fig. 22-13 Predator: Killifish; preys mainly on juvenile guppies (which do not express the color genes) Guppies: Adult males have brighter colors than those in “pike-cichlid pools” Experimental transplant of guppies Pools with killifish, but no guppies prior to transplant Predator: Pike-cichlid; preys mainly on adult guppies Guppies: Adult males are more drab in color than those in “killifish pools” Source population Transplanted population Source population Transplanted population Number of colored spots Area of colored spots (mm 2 ) 12 10 88 66 4 4 2 2 0 0 RESULTS EXPERIMENT

32. The Evolution of Drug-Resistant HIV The use of drugs to combat HIV selects for viruses resistant to these drugs HIV uses the enzyme reverse transcriptase to make a DNA version of its own RNA genome The drug 3TC is designed to interfere and cause errors in the manufacture of DNA from the virus Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

33. Some individual HIV viruses have a variation that allows them to produce DNA without errors These viruses have a greater reproductive success and increase in number relative to the susceptible viruses The population of HIV viruses has therefore developed resistance to 3TC The ability of bacteria and viruses to evolve rapidly poses a challenge to our society Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

34. Fig. 22-14 Weeks Patient No. 3 Patient No. 2 Patient No. 1 Percent of HIV resistant to 3TC 0 0 25 50 75 100 2 4681012

35. Natural selection does not create new traits, but edits or selects for traits already present in the population The local environment determines which traits will be selected for or selected against in any specific population Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

36. Phylogeny: the evolutionary history of a species zSystematics: the study of biological diversity in an evolutionary context yLineages- lines of descent that connect ancestral and derived organisms zThe fossil record: the ordered array of fossils, within strata (layers) of rock

37. Evolution evidence: Comparative Anatomy zHomologous structures (homology) zDescent from a common ancestor zVestigial organ ywhale/snake hindlimbs; wings on flightless birds

38. Anatomy & Development zVestigial structures: structures that either have no use or are reduced in size because they are not needed. zHomologous structures: structures that share a common ancestry. zMorphological Divergence: structural differences accumulate between lineages zMorphological Convergence: structural similarities accumulate between lineages (analogies form)

40. zSorting homology vs. analogy... zHomology: likeness attributed to common ancestry zAnalogy: likeness attributed to similar ecological roles and natural selection zConvergent evolution: species from different evolutionary branches that resemble one another due to similar ecological roles