Chapter 15: Theory of Evolution • Who was Charles Darwin? • How did he come up with the theory of Natural Selection & evolution? How did Darwin’s visit to the Galapagos Islands (off the coast of South America) affect his thinking? http://www.geol.umd.edu/~jmerck/galsite/research/projects/fitz/currents.gif How are unique organisms, like this Galapagos Island Tortoise, adapted to their environment? http://www.probe.org/galapagos/web-ray_tortoise.jpg Harriet the Tortoise, carried to the Australian Zoo by Charles Darwin? • When Darwin’s ship, the Beagle, visited the Galapagos Islands in 1835, the crew collected dozens of the huge land tortoises. The adults were eaten but some small tortoises were taken on the ship around the world. • Harriet, mistakenly named “Harry” and thought to be male for over a century, was 330 lbs & a star at the Australian zoo. Many people believe she was one of Charles Darwin’s tortoises. • Harriet was at least 175 years old and recently died. http://www.conservationmagazine.org/2011/01/darwin%E2%80%99s-pet-tortoise/ Harriet with the “Crocodile Hunter”, who was one of many zoo keepers that cared for her over the years. msnbc.msn.com australiazoo.com.au Why are there so many kinds of finches on the Galapagos Islands? Why are their beaks different? http://images.google.com/imgres?imgurl=http://www.thisviewoflife.org/evolution/finch.jpg&imgrefurl=http://www.thisviewoflife.org/evolution/finch. html&usg=__SDMg5Nbog4zBDG3nIjndQrC8oss=&h=440&w=519&sz=204&hl=en&start=5&um=1&itbs=1&tbnid=JySKhMK-oM_O0M:&tbnh=11 1&tbnw=131&prev=/images%3Fq%3Devolution%2Bfinches%26um%3D1%26hl%3Den%26tbs%3Disch:1 Why are there so many kinds of beetles? What is Evolution? • Simply put: It is changes that occur in a population over time. http://softwarecreation.org/images/2008/evolution1.jpg Evolution: a process by which organisms become more sophisticated over time and in response to its environment. (especially to a more advanced or mature stage) http://www.paulhina.com/hinablog-archives/duh.jpg What Evolution is not: • Evolution does not & never did mean that man “descended from an ape”. • It means we are related to them. • Both man & apes had a common ancestor. http://www.cartoonstock.com/lowres/pha0127l.jpg • Individuals do not evolve -populations do - over timein response to the environment. Evolution • Is how scientists explain how all organisms, both living and extinct, are related. • Is considered a “cornerstone” theory of biology. • Consists of natural selection, microevolution & macroevolution. There exists some controversy- we will address that issue in this chapter too. http://www.evoyage.com/What-is-Evolutions-Voyage-2.gif Chapter 15 Definition of Evolution • Evolution is the process of change in the inherited characteristics within populations over generations such that new types of organisms develop from preexisting types. • Ideas of Darwin’s Time – Most people of the time believed species were permanent & unchanging. – Scientific understanding of evolution began to develop in the 17 and 1800s – geologists and naturalists compared geologic processes & living & fossil organisms around the world. Scientists began to study Rock layers & fossils “strata”- the layers of rock • Inferred that oldest rock were made first & would be found on the bottom • Oldest rock would have oldest fossils Ideas about Geology • Georges Cuvier –catastrophismsudden catastrophic events caused mass extinction • Charles Lyell –uniformitarianismsame mechanisms that shaped Earth’s surface in the past continue to work today. • Catastrophism • sudden catastrophic events caused mass extinctions Uniformitarianism • The same mechanisms that shaped Earth’s surface in the past continue to work today. evolution.berkeley.edu hweelin.tumblr.com Jean Baptista Lamarck -Theory of Evolution -proposed that individuals could develop traits during their lifetime, from experience or behavior -idea was: inheritance of acquired characteristics as a mechanism for evolution. Lamarck believed that the long necks of giraffes evolved as generations of giraffes reached for ever higher leaves. Lamarck also believed more simple life forms evolved into more complex life forms Darwin was not the first naturalist to propose that species changed over time into new species—that life evolves. Even his own grandfather had discussed the concept of evolution. Chapter 15 Darwin’s Voyage on the ship: HMS Beagle •Studied many things on the islands passed by boat. •he was so seasick he wanted to get off the boat. •The things he saw were the basis for his life work. Descent with Modification • BOOK: On the Origin of Species by Means of Natural Selection. – argued that descent with modification occurs – all species descended from common ancestors – natural selection is the mechanism for evolution. Darwin’s Evolutionary Theory (which he called “natural selection” not “evolution”) -over many generations, natural selection causes characteristics of populations to change. -natural selection is responsible for evolution. -organisms with the best adaptations are more likely to survive & reproduce. Natural Selection • The process by which individuals that are better adapted to their environment survive & reproduce more successfully than less well adapted individuals do. • A theory to explain the mechanism of evolution. • Individuals do not evolve -populations do - over timein response to the environment. Note the differences in evolution theory, Lamark vs Darwin. e-ducation.net What is survival of the fittest? • It is NOT- “King of the Jungle”with the meanest, biggest, most muscular animal killing all the smaller ones. • Example- 2 dogs- One is the perfect specimenshiny fur, wins shows, smart, etc. & the other is small, ugly, mangy, living in the alley. The ugly dog visits every female dog in the county and reproduces many times, but the perfect dog never has puppies- • which dog will pass on his traits? Ugly dog with lots of puppies = more successful than a beautiful dog with no offspring http://puppyintraining.com/wp-content/uploads/2008/12/howmany.jpg Chapter 15 Natural Selection Summary: 4 Main Parts of Darwin’s Reasoning • 1. Overproduction- more offspring are produced than can survive • 2. Genetic Variation- within a population, individuals have different traits • 3. Struggle to Survive- individuals must compete with each other to exist. • 4. Differential ReproductionOrganisms with the best adaptations to environment more likely to survive & reproduce. Chapter 15 II. Section 9-2 Evidence of Evolution • Evolutionary theories are supported when several kinds of evidence support similar conclusions. Evidence of evolution can be found by comparing several kinds of data: A. The fossil record B. Biogeography C. Anatomy and Development D. Biological molecules. Chapter 15 A. The Fossil Record 1. The Age of Fossils – Geologic evidence supports theories about the age and development of Earth. –Superposition- if rock layers have not been disturbed, lower strata is oldest. – Relative Age - compare to other fossils – Absolute Age - use radiometric dating 2. The Distribution of Fossils – Fossil record shows the types & distribution of organisms on Earth have changed over time. 3. Transitional Species – Fossils of transitional species show evidence of descent with modification. Evidence of Whale Evolution Skeletons show sequence of transitional species that support the hypothesis that whales evolved from 4 legged land-dwelling mammals. Note: tiny, non-functioning hip bones in modern whales. Chapter 15 B. Biogeography • Biogeography - the study of the locations of organisms around the world, provides evidence of descent with modification. • Example: Australia- The Marsupials there resemble rodents, wolves, cats, anteaters of other continents. May be evidence that these species evolved in isolation. Biogeography Marsupials in Australia • current findings support a simple paleobiogeographic hypothesis, that indicates only a single migration from South America to Australia gave rise to all the Australian marsupials. • (South America, Antarctica, and Australia were connected in the South Gondwanan continent) blogs.discovermagazine.com boardgamegeek.com Marsupials, a class of mammals with undeveloped young (live in mom’s pouch) • Of the 260 known marsupial species, just a couple live in the Americas, and the rest live in Australia and the Australasian islands that surround it. • There are no living marsupial species native to Europe, Asia, or Africa. Placental mammals out-competed with them millions of years ago. The only one in North America is the opossum! http://www.bigsiteofamazingfacts.com/how-many-marsupial-species-live-in-europe-asia-or-africabesides-native-australia-and-how-did-they-evolve Chapter 15 C. Anatomy and Physiology • Analogous structures -are similar in function but have different evolutionary origins. (Does not show evidence for evolution) • Homologous structures have a common evolutionary origin. (shows evidence of evolution) • Vestigial structure- structures that are reduced in size & function- but may have been complete & functional in an organism’s ancestor. (shows evidence of evolution) Chapter 15 Forelimbs of Vertebrates The organisms show Homologous partsAnatomical structures that have related structure, even if the function Is different. Shows a relatednessused to show a common ancestor. Homologous structures Comparing the structural features found in different organisms reveals a basic similarity. example is the forelimb of mammals - Although function is quite different, they are similar structurally. Analogous structures • We must look at structures that look & function the same but are not derived from the same embryonic tissue. • Analogous features do not show recent, related ancestry. Vestigial structures • Features which serve no useful function any longer in the organism. • Examples: the pelvis bone in the whale, tailbone & appendix in humans, pelvis & leg bones in some snakes, etc Organism may become more similar or more different over time. • Divergent Evolution- 2 species become more and more dissimilar. • Convergent Evolution- Species which have different ancestors, but have become more similar Divergent evolution: • example Sharks that had a common ancestor have become more different than each other over time. • Especially rays & sharks. elasmo-research.org D. Biological Molecules -Chromosomes & Macromolecules • Provide the most precise information about the evolution of life • (This is now the most important evidence! DNA!) • DNA, RNA & Proteins are Macromolecules that are compared between organisms. • Can indicate a common evolutionary history. • Example- the number of differences in amino acids is a clue to how long ago 2 species “Diverged” Hemoglobin Comparison Proteins indicate degree of relatedness. Differences - Amino Acids in Protein Cytochrome C Number of different amino acids found in human cytochrome C as opposed to selected organisms Organism # of amino acids different compared to humans Human 0 Self (Family Hominidae, Order Primates) Monkey 1 Different family (Pongidae), same order (Primates) Pig, bovine, sheep 10 Horse 12 Dog 11 Rabbit 9 Chicken, Turkey 13 Duck 11 Rattlesnake 14 Turtle 15 Tuna 21 Different class (Ostheichthys), same phylum (Chordata) poikilothermic Moth 31 Different phylum (Arthropoda), same Kingdom (Animalia) Candida fungus 51 Different Kingdom (Fungi) Different order (Carnivora), same class (Mammalia) Different class (Aves), same phylum (Chordata) homeothermic Different class (Reptilia), same phylum (Chordata) poikilothermic What is a Phylogenic Tree ? • A family tree that shows evolutionary relationships thought to exist among organisms. • Is a hypothesis about the relationships & is subject to change as more is learned. • A phylogenic tree of mammals: Branches show they are related to each other. Closer branches show closer cousins. Farther apart on the branches indicate more distant relationships. A Phylogenic Tree- shows how organisms are related! What is the common ancestor for all these animals? How are different animals related? Example: Evolutionary Relationships Between Whales & Hoofed Mammals In this phylogenic tree - which animals are most distantly related? -which animal here is most closely related to the horse? Still a Developing Theory (the theory of evolution is still evolving) • Modern scientists integrate Darwin’s theory with other advances in biological knowledge. • Theories and hypotheses about evolution continue to be proposed and investigated. Types of evolution: • Convergent evolution - organisms that are not closely related resemble each other – become more similar – because they have responded to similar environments. • Divergence and Radiation – In Divergent evolution, related populations become less similar as they respond to different environments. – Adaptive radiation is the divergent evolution of a single group of organisms in a new environment. How do Darwin’s Finches show “divergent evolution” More vocabulary: Artificial selection.- when a human breeder chooses individuals that will parent the next generation. (ex- dogs) Co-evolution – When 2 or more species have adapted to each other’s influence. (ex- flowering plants & pollen carrying insects An example of coevolution http://www.smithsonianmag.com/arts-culture/from-the-castle-200712.html (Explanation of the photo previous page) The Madagascar star orchid produces nectar at the bottom part of its slim, foot-long throat. After observing a specimen, Charles Darwin predicted the existence of a moth with a proboscis long enough to reach that nectar. Sure enough, decades later the giant hawk moth of Madagascar was discovered and named Xanthopan morganii praedicta in honor of Darwin's prescience. As the moth sucks up the nutrient-rich nectar from the orchid, packets of pollen stick to its body. When the moth visits other star orchids to feed again, the pollen rubs off and pollinates those orchids. The moth gets exclusive access to food and the orchids get a reliable pollinator • Read more: http://www.smithsonianmag.com/arts-culture/from-the-castle200712.html#ixzz1p14T1jZ0 Coevolution • The increasing occurrence of antibiotic resistance among bacteria is an example of coevolution in progress. Case Study: • Caribbean Anole Lizards • (p 308) text Natural Selection of Anole Lizard Species Question: The graph below shows the variation in average beak size in a group of finches in the Galápagos Islands over time. These finches eat mostly seeds. Use the graph to answer the question that follows. Beak size in these finches is correlated to the size of seeds they can eat. What can be inferred from the graph? 1. In wet years, the finches that survive are mostly those that can eat larger seeds. 2. In dry years, the finches that survive are mostly those that can eat larger seeds. 3. In all years, the finches that survive are mostly those that can eat larger seeds. 4. In all years, the finches that survive are mostly those that can eat smaller seeds. Answer- In dry years, the finches that survive are mostly those that can eat larger seeds. Question: The diagram below shows possible evolutionary relationships between some organisms. Use the diagram to answer the question that follows. What does the diagram imply about warbler finches and armadillos? Answer: They share a common ancestor. 1. They are unrelated. 2. They are equally related to glyptodonts. 3. They share a common ancestor. 4. They did not evolve from older forms of life.