1 Evidence of Evolution Chapter 16Biology Concepts and Applications, Eight Edition, by Starr, Evers, Starr. Brooks/Cole, Cengage Learning 2011.

2 16.3 Evolution: Development of New TheoriesChange that occurs in a line of descent (lineage) 19th-century naturalists tried to reconcile traditional beliefs with evidence of evolution Georges Cuvier’s theory of catastrophism Now abandoned hypothesis that catastrophic geologic forces unlike those of the present day shaped Earth’s surface Lamarck’s theory of inheritance of acquired characteristics due to environmental factors Species gradually improved over generations to drive to perfection. Ex. Giraffe  long neck

3 Voyage of the Beagle Charles Darwin’s observations on a voyage around the world led to new ideas about species Theory of uniformity (gradual, repetitive change) Idea that gradual repetitive processes occurring over long time spans shaped Earth’s surface Theory challenged idea that Earth was 6,000 yrs old **However, must have taken longer to sculpt Earth’s surface

4 Voyage of the Beagle

5 16.4 Descent with ModificationDarwin compared the modern armadillo with the extinct glyptodont Glyptodont – Argentina Extinct but similar to Armadillo Armadillo – live only in Places the Glyptodont once lived

6 People who influenced DarwinHenslow – Botanist, friend and mentor. Introduced him to Capt. Fitzroy Malthus – Economist, Theory that overpopulation will drive humans extinct Lyell – Geologist, Theory that the earth was older than thought at that time. Found old rocks and fossils Emma – His wife, supporter and proofreader of all his manuscripts

7 Variations in Traits Darwin observed that variations in traits influence an individual’s ability to secure resources – to survive and reproduce

8 A Key Insight – Variation in TraitsAdaptation (adaptive trait) A heritable trait the enhances an individual’s fitness Artificial selection Selective breeding of animals by humans

9 Darwin, Wallace, and Natural SelectionIn 1858, Charles Darwin and Alfred Wallace independently proposed a new theory, that natural selection can bring about evolution

10 Key Concepts: A THEORY TAKES FORMEvidence of evolution, or changes in lines of descent, gradually accumulated Charles Darwin and Alfred Wallace independently developed a theory of natural selection to explain how heritable traits that define each species evolve

11 Theory of Natural SelectionProcess in which environmental pressures result in the differential survival and reproduction of individuals of a population who vary in the details of shared, heritable traits Can lead to increased fitness Fitness Degree of adaptation to an environment, as measured by an individual’s relative genetic contribution to future generations.

12 Main Premises of the Theory of Natural Selection1. A population tends to grow until it begins to exhaust the resources of its environment 2. Individuals must then compete for resources such as food and shelter from predators 3. Individuals with forms of traits that make them more competitive tend to produce more offspring

13 Inferences of the Theory of Natural SelectionEnvironmental factors acting on a range of traits in a population influence differential survival and reproduction of individuals (natural selection) Forms of heritable traits that impart greater fitness to an individual become more common in a population over generations

14 Comparative Morphological Evidence

15 Fossil Evidence Fossil  physical evidence Of an organism that livedIn the ancient past Mapping rock formation: Deeper layers hold Fossils of simple marine Life. Layers above held Similar but more intricate Fossils. Higher layers, Similar that belong to Modern species.

16 16.5 Fossil Evidence FossilsPhysical evidence of life in the distant past Found in stacked layers of sedimentary rock Younger fossils in more recently deposited layers Older fossils underneath, in older layers

17 Fossilization

18 Fossilization Begins when organisms become covered by sediments or volcanic ash. Water seeps into the remains, and metal ions and other organic compounds dissolved in water replace the minerals in the bones and hard tissues. Pressure and mineralization process transforms the remains into rock

19 Stratification Layers of sedimentary rock made from river silt, sand, volcanic ash, and other materials from land to sea

20 Interpreting the Fossil RecordThe fossil record is incomplete Have fossils for 250,000 known species Most times, remains are obliterated by decay because organic materials decompose in the presence of oxygen Material remains IF encased in air-excluding materials (sap, tar, ice, or mud) Favors species with hard parts, dense populations with wide distribution, and that persisted a long time

21 Dating Fossils Geologic time scale  Chronology of Earth’s HistoryBoundaries for major intervals determined by transitions in the fossil record Correlated with macroevolutionary events Includes dates obtained by radiometric dating

22 Macroevolution Major patterns, trends, and rates of change among lineages (Geologic time scale)

23 Radiometric Dating: Half-LifeRadioactive dating Method of estimating the age of a rock or fossil by measuring the content and proportions of a radioisotope and its daughter elements Oldest terrestrial rock (tiny zircon crystal) in Australia 4.404 billion years old Recent fossils that still contain carbon can by dated by measuring their carbon 14 content Complete decay of 14C occurs in 60,000 years

24 Parent isotope remaining (%)parent isotope in newly formed rock 100 75 after one half-life Parent isotope remaining (%) 50 after two half-lives 25 1 2 3 4 Time (half-life) for any radioisotope a A simple way to think about the decay of a radioisotope to a more stable isotope, as plotted against time. Fig a, p.248

25 Fig b-d, p.248

26 Key Concepts: EVIDENCE FROM BIOGEOGRAPHYCorrelating evolutionary theories with geologic history helps explain the distribution of species, past and present

27 Biogeography – evidence for evolutionAlfred Wallace  Biogeography Study of patterns in the geographic distribution of species and communities Looked at the natural forces that shape life Raised ? Isolated species look suspiciously similar to species living across vast expansions of open ocean, or on the other side of mountain ranges

28 Biogeography – evidence for evolutionRhea South America Ostrich Africa All flightless birds. Long, muscular legs. Inhabit flat, open grasslands about the same distance from the equator.*Common Ancestors! Emu Australia

29 16.7 Plate Tectonics TheoryMovements of Earth’s tectonic plates rafted land masses to new positions Pangea: First ancient supercontinent that formed about 237 million years ago and broke up about 152 million years ago Gondwana  supercontinent that existed before Pangae, more than 500 million years ago Include Southern Hemisphere and India and Arabia Most modern species live only in places that were once part of Gondwana

30 16.7 Plate Tectonics TheoryPlate Tectonics OR Continental drift Theory that Earth’s outer layer of rock is cracked into plates Slow movement of which rafts continents to new locations over geologic time Movements had profound impacts on the directions of life’s evolution Evidence of at least 5x since Earth’s outer layer solidified 4.55 billion years ago, a single supercontinent with one ocean lapping the coast line formed and then split up. 14 million years ago, that Earth and it’s continents mirror today

31 Evidence of Drifting ContinentsEvidence for plate tectonics theory Distribution of global land masses Global fossil distribution Magnetic rocks Seafloor spreading from mid-oceanic ridges In faults (fault lines) Volcanic island chains  form as a plate moves across an undersea hot spot (place where a narrow plume of molten rock wells up from deep inside Earth and ruptures a plate

32 Drifting Continents

33 a 420 mya b 237 mya c 152 mya d 66 mya e 14 mya Fig , p.251

34 Key Concepts: EVIDENCE FROM COMPARATIVE MORPHOLOGYSpecies of different lineages often have similar body parts that may be evidence of descent from a shared ancestor

35 Comparative Morphological EvidenceComparative Morphology Study of body parts and structures among groups of organisms Organisms outwardly similar but different internally Fish and porpoises  Very different Outwardly different but similar internally Human arm and porpoise flipper Elephant leg and bat wing Useless parts  leg bones in snakes or vestiges of tail in humans

36 16.8 Comparative MorphologyComparisons of body form and structure of major groups of organisms Reveals evolutionary connections among lineages

37 Morphological DivergenceHomologous structures: Similar body parts that became modified differently in different lineages Evidence of descent from a common ancestor Morphological divergence Evolutionary pattern in which a body part of an ancestor changes in its descendants

38 Homologous StructuresMorphological Divergence

39 1 2 3 4 stem reptile 5 Fig a, p.252

40 1 2 3 pterosaur 4 Fig b, p.252

41 1 2 chicken 3 Fig c, p.252

42 2 3 penguin Fig d, p.252

43 1 porpoise 4 2 5 3 Fig e, p.252

44 1 2 bat 3 4 5 Fig f, p.252

45 1 2 3 4 5 human Fig g, p.252

46 1 2 3 4 elephant 5 Fig h, p.252

47 Morphological ConvergenceAnalogous structures: Body parts in different lineages that look alike, but evolved separately after the lineages diverged Did not evolve in a common ancestor Morphological convergence Evolutionary pattern in which similar body parts evolve separately in different lineages

48 Analogous Structures

49 Morphological convergenceInsects Bats Humans Crocodiles Birds wings wings wings limbs with 5 digits Fig d, p.253

50 16.9 Changes in Patterns of DevelopmentSimilarities in patterns of embryonic development suggest shared ancestry Mutations in genes that affect development may cause morphological shifts in a lineage Gene duplications account for some differences between closely related lineages

51 Comparative Embryology: Vertebrate RelationshipsHuman Mouse Bat Chicken Alligator All vertebrate embryos have similar stages: - Stage with 4 limb buds, a tail, and divisions called somites along their back

52 Key Concepts: EVIDENCE FROM COMPARATIVE BIOCHEMISTRYMolecular comparisons help us discover and confirm relationships among species and lineages

53 DNA, RNA, and Proteins Comparisons of DNA, RNA, and proteins reveal and clarify evolutionary relationships