1. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings PowerPoint ® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Chapter 22 Descent with Modification: A Darwinian View of Life

2. Overview: Endless Forms Most Beautiful A new era of biology began in 1859 when Charles Darwin published The Origin of Species The Origin of Species focused biologists’ attention on the great diversity of organisms Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

3. Darwin noted that current species are descendants of ancestral species Evolution can be defined by Darwin’s phrase descent with modification Evolution can be viewed as both a pattern and a process Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings survivorship at extreme conditions

4. To understand why Darwin’s ideas were revolutionary, we must examine them in relation to other Western ideas about Earth and its life Concept 22.1: The Darwinian revolution challenged traditional views of a young Earth inhabited by unchanging species Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

5. Scala Naturae and Classification of Species The Greek philosopher Aristotle (384-322 B.C.) viewed species as fixed and arranged them on a scala naturae The Old Testament holds that species were individually designed by God and therefore perfect Carolus Linnaeus (1707-1778) saw the adaptations as evidence that God had designed each species for a specific purpose. He created taxonomy. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

6. Ideas About Change over Time 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 or strata Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings www.wired.com the lower the strata the older the sample

7. Georges Cuvier developed Paleontology, he advocated catastrophism, speculating that each boundary between strata represents a catastrophe Geologists James Hutton and Charles Lyell perceived that changes in Earth’s surface can result from slow continuous actions still operating today Lyell’s principle of uniformitarianism states that the mechanisms of change are constant over time This view strongly influenced Darwin’s thinking Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

8. Lamarck’s Hypothesis of Evolution Lamarck hypothesized that species evolve through use and disuse of body parts and the inheritance of acquired characteristics The mechanisms he proposed are unsupported by evidence Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Bonsai trees are "trained" to be dwarf, a seen will produce a normal sized tree

9. As the 19th century dawned, it was generally believed that species had remained unchanged since their creation However, a few doubts about the permanence of species were beginning to arise Concept 22.2: Descent with Modifications by Natural Selection explains adaptations of organisms and the unity and diversity of life Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

10. Darwin’s Research Charles Darwin had a consuming interest in nature through out his life After graduating, he took an unpaid position as naturalist and companion to Captain Robert FitzRoy for a 5-year around the world voyage on the Beagle Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

11. The Voyage of the Beagle During his travels on the Beagle, Darwin collected specimens of South American plants and animals He observed adaptations of plants and animals that inhabited many diverse environments Darwin was influenced by Lyell’s Principles of Geology and thought that the earth was more than 6000 years old His interest in geographic distribution of species was kindled by a stop at the Galápagos Islands near the equator west of South America Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

12. Fig. 22-5 NORTH AMERICA EUROPE AFRICA AUSTRALIA GREAT BRITAIN SOUTH AMERICA ATLANTIC OCEAN PACIFIC OCEAN Cape of Good Hope Tierra del Fuego Cape Horn Tasmania New Zealand Andes Equator The Galápagos Islands Pinta Marchena Genovesa Santiago Daphne Islands Pinzón Fernandina Isabela San Cristobal Santa Fe Santa Cruz Florenza Española

13. Fig. 22-5b The Galápagos Islands Pinta Marchena Genovesa Santiago Daphne Islands Pinzón Fernandina Isabela San Cristobal Santa Fe Santa Cruz Florenza Española

14. Darwin’s Focus on Adaptation In reassessing his observations, Darwin perceived adaptation to the environment and the origin of new species as closely related processes From studies made years after Darwin’s voyage, biologists have concluded that this is indeed what happened to the Galápagos finches Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

15. Fig. 22-6 (a) Cactus-eater(c) Seed-eater (b) Insect-eater

16. The Origin of Species Darwin developed two main ideas: – Descent with modification explains life’s unity and diversity – Natural selection is a cause of adaptive evolution Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

17. 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

18. 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

19. Fig. 22-8 Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) Moeritherium Barytherium Deinotherium Mammut Elephas maximus (Asia) Stegodon Mammuthus Loxodonta africana (Africa) Loxodonta cyclotis (Africa) 0 10 4 2 5.5 24 34 Millions of years ago Years ago Platybelodon

20. Artificial Selection, Natural Selection, and Adaptation Darwin noted that humans have modified other species by selecting and breeding individuals with desired traits, a process called artificial selection Darwin then described four observations of nature and from these drew two inferences Observation #1: Members of a population often vary greatly in their traits Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

21. Fig. 22-9 Kale Kohlrabi Brussels sprouts Leaves Stem Wild mustard Flowers and stems Broccoli Cauliflower Flower clusters Cabbage Terminal bud Lateral buds Brassica olerasia var. capitata var. gemmifera var. acephala var. botrytis var. italicavar. gogylodes

22. Observation #2: Traits are inherited from parents to offspring Observation #3: All species are capable of producing more offspring than the environment can support Observation #4: Owing to lack of food or other resources, many of these offspring do not survive Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

23. Inference #1: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals "The higher chances of survival, the more offspring they have" example: fishes, frogs, birds, insects Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

24. Inference #2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations "Those that survive will bring the favorable traits with them" Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

25. Note that individuals do not evolve; populations evolve over time Natural selection can only increase or decrease heritable traits in a population Adaptations vary with different environments Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

26. Concept 22.3: Evolution is supported by an overwhelming amount of scientific evidence New discoveries continue to fill the gaps identified by Darwin in The Origin of Species Direct Observations of Evolutionary Change – evolution of drug-resistant TB and MRSA – color change in moths, from light to dark due to pollution Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

27. 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

28. The Fossil Record The fossil record provides evidence of the extinction of species, the origin of new groups, and changes within groups over time Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

29. Fig. 22-15 Bristolia insolens Bristolia bristolensis Bristolia harringtoni Bristolia mohavensis Latham Shale dig site, San Bernardino County, California Depth (meters) 0 2 4 6 8 10 12 14 16 18 1 2 3 3 3 1 2 4 4

30. The Darwinian view of life predicts that evolutionary transitions should leave signs in the fossil record Paleontologists have discovered fossils of many such transitional forms Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

31. Fig. 22-16 (a) Pakicetus (terrestrial) (b) Rhodocetus (predominantly aquatic) (c) Dorudon (fully aquatic) Pelvis and hind limb Pelvis and hind limb (d) Balaena (recent whale ancestor)

32. Homology Homology is similarity resulting from common ancestry Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

33. Anatomical and Molecular Homologies Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Humerus Radius Ulna Carpals Metacarpals Phalanges HumanCatWhaleBat

34. Comparative embryology reveals anatomical homologies not visible in adult organisms Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Pharyngeal pouches Post-anal tail Chick embryo (LM)Human embryo

35. Vestigial structures are remnants of features that served important functions in the organism’s ancestors Examples of homologies at the molecular level are genes shared among organisms inherited from a common ancestor – tail in human embryo – teeth in birds Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

36. Homologies and “Tree Thinking” The Darwinian concept of an evolutionary tree of life can explain homologies Evolutionary trees are hypotheses about the relationships among different groups Evolutionary trees can be made using different types of data, for example, anatomical and DNA sequence data Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

37. Fig. 22-19 Hawks and other birds Ostriches Crocodiles Lizards and snakes Amphibians Mammals Lungfishes Tetrapod limbs Amnion Feathers Homologous characteristic Branch point (common ancestor) Tetrapods Amniotes Birds 6 5 4 3 2 1

38. Convergent Evolution Convergent evolution is the evolution of similar, or analogous, features in distantly related groups Analogous traits arise when groups independently adapt to similar environments in similar ways Convergent evolution does not provide information about ancestry Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

39. Fig. 22-20 Sugar glider Flying squirrel AUSTRALIA NORTH AMERICA

40. Biogeography Darwin’s observations of biogeography, the geographic distribution of species, formed an important part of his theory of evolution Islands have many endemic species that are often closely related to species on the nearest mainland or island Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

41. Earth’s continents were formerly united in a single large continent called Pangaea, but have since separated by continental drift An understanding of continent movement and modern distribution of species allows us to predict when and where different groups evolved Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

42. What Is Theoretical About Darwin’s View of Life? In science, a theory accounts for many observations and data and attempts to explain and integrate a great variety of phenomena Darwin’s theory of evolution by natural selection integrates diverse areas of biological study and stimulates many new research questions Ongoing research adds to our understanding of evolution Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

43. Fig. 22-UN1 Observations Over time, favorable traits accumulate in the population. Inferences and Individuals in a population vary in their heritable characteristics. Organisms produce more offspring than the environment can support. Individuals that are well suited to their environment tend to leave more offspring than other individuals The End