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The Evolutionary History of Life “Of course, long before you mature, most of you will be eaten.” “The picture’s pretty bleak, gentlemen. The earth’s climate is changing, the mammals are taking over, and we all have brains the size of a walnut.” “Now this end is called the thagomizer, after the late Thag Simmons.” “Evolution’s been good to you, Sid.” Top Ten Myths About Evolution 1. Humans and great apes had a common ancestor about 5 million years ago Humans and monkeys had a common ancestor about 50 million years ago 2. “Theory” does not mean “hypothesis” or “guess” Music Theory Stress Theory Quantum Theory Number Theory “Theory” means an organized set of related ideas. 3. If you find your room trashed and your TV and stereo missing, will you hesitate to call the police because nobody saw it happen? 4. Maybe not. But once the origin happens, everything after that is history. And historical evidence is preserved in the physical record. 5. “Survival of the Fittest” “The winner of the Super Bowl is the team with the most points.” What does “fittest” mean? 6. 7. Darwin suggested birds had evolved from reptiles in 1859; Archaeopteryx was discovered in 1862. Piltdown Man Famous Early Fossil Man Hoax Controversial from the start because it didn’t match evolutionary expectations. 8. Are you a vegetable or mineral? Humans have hair and nurse young just like all other mammals Traits like nurturing, cooperation and monogamy are often favored by evolution because they enhance survival of species 9. Is the following number sequence random: 592653589793238462643383279? It not only looks random: it is random. But lacking in meaning? No. These are the digits of pi beginning with the fourth decimal place. Random does not mean “meaningless” The Scientific Meaning of Random Something cannot be predicted with better accuracy than that predicted by statistics. The phenomenon is its own simplest description Randomness and Evolution Biological systems are far too complex to describe or predict mathematically We have incomplete information Significant events like climate change or asteroid impact are unpredictable. 10. The Second Law of Thermodynamics is often paraphrased as: ”Things always go from bad to worse” ”Disorder in the Universe is always increasing" The Second Law of Thermodynamics The Second Law is about entropy ________ = (Heat Absorbed)/Temperature Entropy can decrease locally if it increases elsewhere Intuitive notions of “_______” are of no relevance whatsoever Chemical Reactions are not Random Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Na Cl Channeled Scablands, Washington Scabland Terrain, Oregon The Geologic Record Physical evidence records mostly smallscale, Fossils show a gradual increase in complexity with time Fossil forms ________ between major groups are well documented Over most of its history, life on Earth was _______ Were the Dinosaurs Failures? Human History = Dinosaurs = Dinosaurs had: years for every year of human history years for every day hours for every second Prebiotic Evolution The basic molecules of organic chemistry are easily made The first self-replicating molecule was almost certainly DNA assembles from simpler materials all the time DNA Total length of human DNA in a single cell is about 2 meters A human body contains about The total length of DNA in a human body is thus __________, or twenty billion kilometers, the circumference of the orbit of Pluto. Plants and Animals CO2 + H2O + Energy = Sugars, Starches, etc. + O2 (toxic waste). O2 is actually toxic (even to us!) Idea: Take the sugars and starches (from somebody else) combine it with the waste O2, and get energy Amazing Events in Life History “Invention of Sex” We are a team The Great Freeze Mass Extinctions Dinosaurs = Permian extinction Selection Deliberate selection for desirable traits by humans (only since ca. 1700) Unsystematic selection for desirable traits by humans (domesticated animals and plants) Unconscious and unintentional selection by humans (self-domestication of animals) Natural selection with no human intervention at all Lessons from Selection Artificial selection has produced organisms radically different from their natural state Natural selection has resulted in dramatic changes in natural populations with and without human intervention Microorganisms and viruses change with dazzling speed (mutation of flu viruses, resistance to antibiotics, move to new hosts) This Descended from Wolves? Evolution By Natural Selection Charles Darwin and Alfred Russell Wallace, 1859 Organisms are adapted to their environments Individuals vary More organisms are born than can possibly survive Variations best suited to the environment tend to survive and be passed on. Mutations Change in “If you fix it often enough, you’ll break it” Most organisms already adapted Chance of random Many mutations are Radical changes Mutations may be useful Convergent Evolution Unrelated organisms may develop similar features Often dictated by physical constraints Shark, tuna, dolphin, seal, squid, penguin, ichthyosaur Deer, pronghorn, impala Albatross, pterosaur Exaptation Modification of existing structure to serve new function Fin – paw – wing – hand Scale – feather There are no half-formed organisms What Good is Half an Eye? What Does a Bug See? What Does a Bug See? What Good Is Half An Eye? A “partially-developed” eye can be very useful Selection will favor: More Receptors (Sharper Image) Wider Angular Spread (Better direction discrimination) Better Image Processing What Good is Half a Wing? Gliders Powered Flight Pterosaurs? Fish Snakes Lizards Physics of Gliding Terminal Velocity Air Resistance = Gravitational Acceleration 200 km/hr for a human 20 km/hr for a mouse Selection favors duration and control Two Bumblebee Myths Theoretically, bumblebees should not be able to fly. Bumblebees can’t glide well. Neither can many aircraft A bumblebee can carry more than its own weight, something no airplane can do. C-5A empty 238,000 lb., maximum takeoff weight 840,000 lb. Classification of Dogs and Humans Kingdom Phylum Class Order Family Genus Species Animalia Chordata Mammalia Carnivora (Dogs) Canidae Canis familiaris Primates (Humans) Hominidae Homo sapiens “Actually, I considered this an extreme honor. Besides, I knew no one was going to write and ask to name a new species of swan after me. You have to grab these opportunities when they come along.” Below Species Ideally, species is a genetic group capable of breeding As used for humans, has little scientific meaning The Five Kingdom System Protista (one-celled organisms) Bacteria* Ediacaran Fossils? (ca. 700 m.y. ago) Above a Kingdom Bacteria differ from all other kingdoms in lacking a cell nucleus We need a bigger box Superkingdoms or Need electron microscopes and molecular biology to see differences Moral of the Story Isolation creates variation which leads to speciation Objectives 1. Be able to define species in terms of population___________________. 2. Explain under what circumstances species will, and will not, change. Objectives 3. Describe the process of speciation, with reference to allopatric, parapatric, and sympatric modes. 4. Distinguish the various types of isolating mechanisms that can lead to speciation. The Case of the Road-Killed Snails A. Sometimes it is easy to see how an animal that flies long distances would be able to take its genes from one place to another, but what about the slow-moving snail? B. Yet even snails confined to relatively small areas show genetic variation that could possibly lead to eventual speciation many years hence. On the Road to Speciation A. What is a Species? 1. The morphological species concept express the following: a. Species, ____________________. b. Attempting to determine whether similar, yet different, animals are the same species by appearance (__________) is not reliable due to the subtle variations that are displayed. 2. The Biological Species concept relies on reproduction to define relatedness of species. a. Ernst Mayer says, “Species are groups of interbreeding natural populations that are reproductively isolated from other such groups”. b. As good as it is, this definition is troublesome for organisms that are nonsexually reproducing and those___________________ _______. 3. __________ is the attainment of reproductive isolation, but genetic changes between populations of the same species can be countered by gene flow. 4. __________is the process whereby local units of a population become reproductively isolated from other units and thus experience changes in gene frequencies between them. B. Reproductive Isolating Mechanisms 1. Reproductive isolating mechanisms are any heritable features ___________________ _________ ________ that _________ interbreeding between genetically divergent populations. 2. Prezygotic mechanisms take effect before or ____________ fertilization. a. ___________: patterns of courtship may be altered to the extent that sexual union is not achieved (for example: albatross courtship rituals). b. ____________: different groups may not be reproductively mature at the same season, month or year (example: periodical cicadas). c. ___________: two populations are mechanically isolated when differences in reproductive organs prevent successful interbreeding (example: floral arrangements in sage plants discriminate between different bee pollinators). d. ____________: potential mates may be in the same general area by not in the same habitat where they are likely to meet ( example: different species of manzanita shrubs live at different altitudes and habitats). e. _____________: incompatibilities between egg and sperm prevent fertilization (example: signals to pollen grains to begin growing toward the egg). Isolation creates variation which leads to speciation 3. Postzygotic mechanisms take effect ________ fertilization. a. Sometimes fertilization does occur between ______________, but the hybrid embryo is weak and dies. b. In some instances the _________ are vigorous but __________ (example: mule produced by a male donkey and a female horse). Speciation in Geographically isolated Populations A. _________________Defined 1. In this model some physical barrier arises and prevents gene flow between populations. 2. Allopratic refers to the “ _________” the two species occupy. 3. Reproductive isolating mechanisms evolve in the genetically diverging populations and will result in complete speciation when the two species can no longer interbreed. B. The Pace of Geographic Isolation 1. Isolation may be _________ as in an ____________ that results in separation of species. 2. ___________, on the other hand, may produce conditions that yield separate over _____________. 3. Studies of enzymes from fishes on the Atlantic and Pacific sides of the Isthums of Panama reveal molecular differences. C. Allopatric Speciation on Archipelagos 1. An archipelago is an island chain some distance away from a continent. 2. The finches of the Galapagos Islands are evidently ancestors of mainland finches that invaded first a few islands and then spread to others, diverging as time progressed. Models for Other Speciation Routes A. Sympatric Speciation 1. In this model, species may ___________________ _____________, in the absence of a physical barrier. 2. Literally means “____________________ _________________”. 3. In two crater lakes of East Africa exist small fish called Cichlids. a. The species in each lake are alike in their mitochondrial DNA and unlike the species in neighboring lakes and streams. b. The lakes are small so the fish must live in sympatry. 4. Polyploidy is the inheritance of three or more of each type of chromosomes due to improper separation of chromosomes during meiosis or mitosis. a. Speciation is instantaneous for __________ that are polyploid. b. Polyploid animals are _________ because of dosage compensation which regulates the level of gene expression in chromosomes. B. _______________ 1. Daughter species form from a small proportion of individuals along a common border between two populations. 2. Literally means “__________________”. 3. Interbreeding individuals produce hybrid offspring in this region called a ___________. Isolation creates variation which leads to speciation Patterns of Speciation A. Branching and Unbranched Evolution 1. Cladogenesis applies to populations that become isolated from one another and subsequently _____________________. 2. Anagenesis is a pattern of descent in which species form within a single, ____________________. B. Evolutionary Trees and Rates of Change 1. ________________summarize information about the continuity of relationships among species. 2. The ______________of speciation is represented by tree diagrams with branches at slight angles to each other to show slow change over time. 3. The _______________of speciation is drawn with short, horizontal branches that represent abrupt periods of speciation followed by stable periods. C. Adaptive Radiations 1. An ____________is a burst of microevolutionary activity that results in the formation of ______________ _____________. 2. The presence of adaptive zones presents Isolation creates variation which leads to speciation D. Extinctions- End of the Line 1. Extinction is the rather inevitable loss of species as local conditions change over periods (usually long) of time. 2. Mass extinctions are abrupt disappearances due to catastrophic, global events. Why Some Biologists Prefer Intelligent Design Over Evolution “It is absolutely safe to say that if you meet somebody who claims not to believe in evolution, that person is ignorant, stupid or insane.” - Professor Richard Dawkins Evolutionary Biologist A Scientific Dissent From Darwinism 761 scientists listed by doctoral degree or current position. Evan Pugh Prof. of Chemistry, Pennsylvania State University Member of the National Academy of Sciences Lyle H. Jensen Eugene Buff Ph.D. Genetics Institute of Developmental Biology, Russian Academy of Sciences Henry Schaefer Paul Ashby Alan Linton Professor Emeritus, Dept. of Biochemistry University of Washington Director, Center for Computational Quantum Chemistry University of Georgia Ph.D. Chemistry Harvard University Emeritus Professor of Bacteriology University of Bristol (UK) Dean Kenyon Emeritus Professor of Biology San Francisco State University David W. Forslund Robert W. Bass Ph.D. Astrophysics, Princeton University Fellow of American Physical Society Ph.D. Mathematics, Rhodes Scholar, Johns Hopkins University Daniel W. Heinze Ph.D. Geophysics Texas A&M University “We are skeptical of claims for the ability of random mutation and natural selection to account for the complexity of life. Careful examination of the evidence for Darwinian theory should be encouraged.” 1) Difficulty Forming the First Cell 2) Logical Evidence of Design Difficulty Forming First Cell Can very simple elements of a world come together and create a complex organism? AIR WATER EARTH Modern Cells-complex How Did the First Cell Evolve? “A particularly remarkable molecule was formed by accident, a molecule that had the ability to reproduce itself. “ Similar molecules clustered together. They wrapped a protective membrane around themselves as a barrier. - Professor Richard Dawkins Hypothetical First Cell Requirements for First Cell: 1. 2. 3. 4. Problem 1 The first cell required two types of complex molecules. Non-living Molecules Organic Molecules Water Carbon dioxide Methane Phosphate Ammonia DNA A single DNA molecule stretched to its full length extends more than SIX feet. Problem 2 Where to find a membrane? Cell Membranes Composed of complex ___________ molecules. Phospholipid Chemical Structure Problem 3 How did the self-replicating molecule wrap the membrane around itself? Problem 4 How do food and waste get in and out? Modern Cell Membranes Protein Channel in Membrane Side View Front View What is the chance of even one simple protein molecule forming at random? Evolutionists estimate it to be only 1 in 10113. That’s a 1 with 113 0’s after it!!! Any event that has 1 chance in 1050 is dismissed by mathematicians as never happening. 10113 is larger than the total number of all the atoms in the universe! Without a membrane embedded with protein channels, the first cell could not have functioned. “It was my science that drove me to the conclusion that the world is much more complicated than can It is only through the supernatural that I can understand the mystery of existence.” be explained by science. - Professor Allan Sandage worked with Edwin Hubble at Mount Wilson Observatory Cell Membrane Animation Cause and Effect Random Forces Forces vs. Directed by Intelligence Product of Random Force Product of Directed Force Product of Undirected Force Product of Directed Force Product of Random Force Product of Design Bacterial Flagellum Macroevolution The Fossil Record The Fossil Record Gaps in the Fossil Record Gaps exist because: History of Life on Earth Three main events: Origin of Cellular Organisms Beginning of Multicellular Life Colonization of Land Colonization of Land Continental Drift Continental Drift Isolation creates variation which leads to speciation Movement of the Continents Over Time The Five Mass Extinctions Radiation Example: loss of flight or sight Adaptive Radiation Origin of Mammals Origin of Mammals Differences from reptiles: From Reptile to Mammal From Reptile to Mammal Mammalian jaw is more advanced Overview