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

16.1 Early Discoveries By the 19th century, advances in geology, biogeography, and comparative morphology resulted in awareness of change in lines of descent of species

Geological Evidence Asteroids: small planets size 1-1,500 kilometers Mile wide Barringer Crater in Arizona 300,000 ton asteroid, 50,000 years ago. Impact 150x greater than Hiroshima bomb

Geological Evidence Mass extinction Inferred from evidence  Permanent loss of major groups of organisms Occurred 65.5 million years ago Event marked by unusual, worldwide layer of rock called the K-T boundary layer Below layer  Dinosaur fossils Above layer  no Dinosaur fossils Impact crater off the coast of the Yucatan Peninsula dates about 65.5 million years ago Inferred from evidence  20 km or 12 mile wide asteroid wiped out the dinosaurs

16.2 Early Beliefs, Confounding Discoveries Aristotle  Naturalist Person who observes life from a scientific perspective Viewed nature as a continuum of organization, from lifeless matter through complex plants and animals “Great chain of being” From the lowest form (snakes) to humans and even spiritual beings Chain links = a species Each new species discovered was another link in the chain of being Chain = complete and continuous Once chain is complete  meaning of life would be revealed

Early Beliefs, Confounding Discoveries Alfred 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

Early Beliefs, Confounding Discoveries Rhea 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

Comparative Morphological Evidence Comparative 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

Comparative Morphological Evidence

Fossil Evidence Fossil  physical evidence Of an organism that lived In 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.

16.3 Evolution: Development of New Theories Change 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

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

Voyage of the Beagle

Key Concepts: EMERGENCE OF EVOLUTIONARY THOUGHT Long ago, Western scientists started to catalog previously unknown species and think about their global distribution They discovered similarities and differences among major groups, including those represented as fossils in layers of sedimentary rock

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

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

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

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

Theory of Natural Selection Process 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.

Main Premises of the Theory of Natural Selection 1. 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

Inferences of the Theory of Natural Selection Environmental 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

Key Concepts: A THEORY TAKES FORM Evidence 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

16.5 Fossil Evidence Fossils Physical 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

Fossilization

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

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

Interpreting the Fossil Record The 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

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

Geologic Time Scale

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

Radiometric Dating: Half-Life Characteristic time it takes for half of a quantity of a radioisotope to decay Ex. Uranium 238  thorium 234   lead 206 (takes 4.5 billion yrs) Predictable radioactive decay can be used to find the age of a volcanic rock

Radiometric Dating: Half-Life Radioactive 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

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. 16.11a, p.248

Fig. 16.11b-d, p.248

Key Concepts: EVIDENCE FROM FOSSILS The fossil record offers physical evidence of past changes in lines of descent

16.7 Plate Tectonics Theory Movements 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

16.7 Plate Tectonics Theory Plate 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

Evidence of Drifting Continents Evidence 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

Forces of Plate Tectonics

(solid layer of mantle) hot spot asthenosphere island arc oceanic crust oceanic ridge trench continental crust lithosphere (solid layer of mantle) hot spot asthenosphere (plastic layer of mantle) subducting plate Fig. 16.14b, p.250

Drifting Continents

a 420 mya b 237 mya c 152 mya d 66 mya e 14 mya Fig. 16.15, p.251

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

16.8 Comparative Morphology Comparisons of body form and structure of major groups of organisms Reveals evolutionary connections among lineages

Morphological Divergence Homologous 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

Homologous Structures Morphological Divergence

1 2 3 4 stem reptile 5 Fig. 16.16a, p.252

1 2 3 pterosaur 4 Fig. 16.16b, p.252

1 2 chicken 3 Fig. 16.16c, p.252

2 3 penguin Fig. 16.16d, p.252

1 porpoise 4 2 5 3 Fig. 16.16e, p.252

1 2 bat 3 4 5 Fig. 16.16f, p.252

1 2 3 4 5 human Fig. 16.16g, p.252

1 2 3 4 elephant 5 Fig. 16.16h, p.252

Morphological Convergence Analogous 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

Analogous Structures

Morphological convergence Insects Bats Humans Crocodiles Birds wings wings wings limbs with 5 digits Fig. 16.17d, p.253

16.9 Changes in Patterns of Development Similarities 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

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

Chimps and Humans: Genes That Control Growth Rate

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

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

Molecular Clock Neutral mutations accumulate in DNA at a predictable rate Help estimate when two lineages diverged Mitochondrial DNA (mtDNA) is inherited intact Closely related species share more nucleotide or amino acid sequences than less related ones

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

Constructing a Cladogram All organisms are related by descent Representing life’s history as a tree with branchings from ancestral stems clarifies relationships

Constructing a Cladogram

Fig. 16.27a, p.260

Fig. 16.27c, p.260

Fig. 16.27d, p.260

Life’s Evolutionary History

Key Concepts: ORGANIZING THE EVIDENCE Evolutionary tree diagrams are based on the premise that all species interconnect through shared ancestors—some remote, others recent

Animation: Comparative pelvic anatomy

Animation: Evolutionary tree diagrams

Animation: Finches of the Galapagos

Animation: Geologic forces

Animation: Interpreting a cladogram

Animation: Morphological divergence

Animation: Mutation and proportional changes

Animation: Plate margins

Animation: Radioisotope decay

Animation: Radiometric dating

Animation: The Galapagos Islands