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Darwin’s Voyage of Discovery Darwin’s Voyage of Discovery As a child Darwin loved collecting organisms….did not like school or medicine (unlike his father/grandfather) Asked at age 22 to voyage to S. America as a naturalist (from a former professor) Set sail in 1831 on the HMS Beagle Voyage lasted 5 years! Darwin’s Voyage of Discovery Cpt Fitzroy was surveying and mapping waters for the British Navy. Hoped that Darwin would discover evidence to support Biblical creation Darwin was to observe, record (journals) and collect rocks, minerals, plants and animals He collected thousands of specimens and shipped them back to England Darwin’s Voyage of Discovery In S. America, Darwin discovered species, fossils and began making observations Darwin’s Voyage of Discovery Not only were they similar in appearance but both modern and extinct animals shared the same pattern of distribution Galapagos Islands Galapagos Islands A series of volcanic islands where species were similar (to those on S.A.) yet had unique traits Did not discover until much later that each island supported unique species of plants and animals Darwin had believed the “immutable” nature of species before he had left England… Upon returning in 1836 he spent much time analyzing his findings. His conclusions have made him a most famous scientist What did he observe? Darwin wondered why continents separated by large distances would have entirely different species occupying similar niches What is a niche? Niche The place where an organism lives and the roles that an organism has in its habitat. Geographic Distribution His observations and analysis of geographic distribution of organisms provided a foundation for the later scientific study of biogeography Biogeography The careful observation and analysis of the geographic distribution of organisms Single ancestry gave rise to similar new species in different locations Darwin’s birds… Of the 26 birds he found on the Galapagos islands, 25 were different species (ornithologist Gould). Primarily finches and mockingbirds Gould suggested that a single ancestral species transported from a nearby land might give rise to a # of similar but distinct new species (especially when isolated) Darwin’s birds… Darwin also observed that remote islands were populated by flying organisms and land animals such as lizards, turtles (no mammals) Why? Darwin Committed his life to analyzing his discoveries Homologous and Analogous Features Darwin was also curious about comparing species that were very different in outward appearance Found that body parts of organisms with entirely different functions were similar in structure Can you think of any? Homologous features Structures that share a common origin but may serve different functions in modern species Homologous features Darwin wrote; “What can be more curious than that the hand of a man, formed for grasping, that of a mole for digging, the leg of a horse, the paddle of the porpoise, and the wing of the bat, should all be constructed on the same pattern, and should include the same bones, in the same relative positions?” Analogous Features Structures similar in function but not in origin or anatomical structure Conclusion… Organisms with homologous features likely shared a more recent common ancestor, while those with analogous features did not. Embryonic Development Homologous features can also appear during embryonic development Such features serve no function as the organisms grow Human tail Anteater teeth Vestigial Features and Anatomical Oddities Vestigial features are rudimentary and nonfunctioning structures that are homologous to fully functioning structures in closely related species Dogs have a vestigial toe (as do pigs) Vestigial structures in humans BODY HAIR: Brows help keep sweat from the eyes, and male facial hair may play a role in sexual selection, but apparently most of the hair left on the human body serves no function. THIRTEENTH RIB: Our closest cousins, chimpanzees and gorillas, have an extra set of ribs. Most of us have 12, but 8 percent of adults have the extras. MALE UTERUS: A remnant of an undeveloped female reproductive organ hangs off the male prostate gland. FEMALE VAS DEFERENS: What might become sperm ducts in males become the epoophoron in females, a cluster of useless dead-end tubules near the ovaries APPENDIX: This narrow, muscular tube attached to the large intestine served as a special area to digest cellulose when the human diet consisted more of plant matter than animal protein. It also produces some white blood cells. Annually, more than 300,000 Americans have an appendectomy. WISDOM TEETH: Early humans had to chew a lot of plants to get enough calories to survive, making another row of molars helpful, but unless you chew a lot of branches, these will eventually come out in a painful procedure. Only about 5 percent of the population has a healthy set of these third molars. Anatomical Oddities Geese with webbed feet who never enter water (frigate bird) Whales with hipbones Artificial Selection Darwin knew there was some mechanism of inheritance that was key to the evolutionary process….but what was it? He reasoned that if humans could alter the appearance and behaviour of species through artificial selection (crops, dog breeds), then the env’t could have a similar selective effect on wild species Artificial Selection If the Earth was as old as scientists were predicting and if the fossil evidence supported a comparable age for organic life, there could be time for even small changes in species to accumulate over many thousands of generations The Struggle for Survival Darwin was convinced of the evidence of biogeography and comparative anatomy which supported evolution He also supported the idea of artificial selection…but how did nature chose individuals with particular desirable variables for reproduction? Malthus Postulated that in nature both plants and animals produce more offspring than are able to survive Darwin realized that there must be competition among individuals of the same species to survive (most do not survive to reproduce) Practice questions Complete the “Try this activity” on p.527 Complete Q 3, 5-7, 9, 10 on p.528 Theory of Evolution by Natural Selection Wallace a young naturalist had arrived at the same theory as Darwin for Evolution (it had taken him 2 yrs vs. Darwin’s 20 yrs) They presented their findings in 1858 Darwin knew it would be controversial He published his Origin of Species in 1859 Natural Selection The means of preserving favourable genetic variations and rejecting injurious variations Individuals pass on inherent variations to their offspring. The ones with favourable variations survive. (selection) Survival is NOT random,but mutation is. The process by which favourable variations become more common The Theory of Evolution by Natural Selection Observation 1 Individuals w/in a species vary in many ways Observation 2 Some of this variability can be inherited Observation 3 Every generation produces more offspring than can survive (pass on variations) Observation 4 Pop. Of species tend to remain stable in size Inference 1 Members of the same species compete with each other for survival Inference 2 Individuals with more favourable variations are more likely to survive and pass them on. Survival is not random Inference 3 As these individuals contribute proportionately more offspring to succeeding generations, the favourable variations will become more common (This is natural selection) Survival of the Fittest Only those organisms best adapted to existing conditions are able to survive and reproduce. NATURAL SELECTION At the opposite end scale, natural selection is sometimes interpreted as a random process. This is also a misconception. The genetic variation that occurs in a population because of mutation is random-but selection acts on that variation in a very non-random way: genetic variants that aid survival and reproduction are much more likely to become common than variants that don't. Natural selection is NOT random! Unanswered questions… For Natural Selection to result in the formation of a new species….time was needed…and lots of it! Not everyone agreed that the Earth was many millions of years old. Also, the fossil record did not show transitional forms of organisms Unanswered questions… Today we have radiometric dating (giving us absolute age) and have unearthed fossils that show intermediate species of vertebrates Unanswered questions… Over time, the role of environmental change became more evident-peppered moth Unanswered questions… But what about the mechanism for variation? The answer became clearer when Mendel came onto the scene 6 years later. This paved the way for the revelation in molecular genetics that mutation and recombination provide the source for new inheritable variations Practice Questions Complete the “Try This Activity” on p.532 Complete Questions 1, 5, 7 on p.533 Quiz-Tuesday, December 8th-Chp. 11 Unit Test-Wednesday, December 16th