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Chapter 1-6

Evolution Chapter 1-6

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University of Guelph
BIOL 2400
Cortland Griswold

Evolution Midterm Review Chapter 1: 1.1 Whales: Mammals Gone to Sea - Cetacean’s posses many traits only found in mammals. In The Origin of Species, Darwin proposed an explanation for these similarities and differences. Cetaceans descended from mammals that lived on land, and their lineage evolved into marine mammals through natural selection. In a process of convergent evolution the ancestors of whales lost their hindlimbs and front legs became flippers. - Whales still have some similar traits from mammalian ancestors. Mammary glands of whales and land mammals are examples of homology. - Numerous cetacean fossils were found and they knew this due to synapomorphies. - Dorudon Atrox is a 40 million year old fossil that had the same synapomorphies as cetaceans. It also has some features that aren’t seen today in cetaceans. Such as, different teeth shapes that were more like land mammals. This proved that the evolution of peg- like teeth and baleen occurred after cetaceans had become aquatic. - In 1979 Gingerich traveled to Pakistan to investigate geological formation from the Eocene period (rocks that formed from 56 million to 34 million years ago). They found one interesting fossil that was similar to cetaceans. Gingerich and colleagues named it Pakicetus, which means “whale of Pakistan” in Latin. - Pakicetus was a big discovery since it was the oldest fossil of a cetacean found (50 million years) up to that point. Second reason was due to where it lived, on land. - Gingerich’s student, Thewissen traveled to Pakistan later and found a large mammalian fossil. It had cetacean synapomorphies too and thus concluded that it was a whale that could walk. So he named it Ambulocetus “walking whale”. - Research in the future concluded those cetaceans are most closely related to a group of mammals called artiodactyls, more specifically hippos. - Darwin argued that life evolved like a branching tree with new lineages from old ones. To reconstruct this phylogeny scientists can analyze morphology and genes. I.e. you could tell if ancestors were terrestrial or aquatic by looking at whether they drank freshwater or salt water since both contain oxygen atoms but the oxygen atoms are slightly different. Sea water has more oxygen atoms with 10 neutrons. Therefore whales and dolphins have larger percent of oxygen in bones. - When dolphin embryos are growing they have the same leg-building genes as humans however, it stops growing and dies back. - Natural selection favoured dolphins with large brains for processing social inforamtion Lineage A chain of ancestors and their descendants Natural Selection A mechanism that can lead to evolution, whereby differential survival or reproduction of individuals causes some genetic types to replace others Convergent Evolution The independent origin of similar traits in separate lineages Homology Characteristics are similar in two or more species because they inherited them from a common ancestor. Synapomorphies A derived form of a trait that is shared by a group of related species. 1.2 Viruses: The Deadly Escape Artists Mutations Any change to the genomic sequence of an organism - Some mutations affect the ability of organisms to replicate. For viruses a mutation may leave a virus unable to invade a host cell. However, other viruses can enable the virus to replicate faster. - These viruses allow their descendents to dominate the virus population. Flu viruses are evolving extraordinarily fast. - Scientists ran an experiment in which the vaccinated mice against flu and them exposed them to the virus. These mice were then exposed to other mice allowing them to infect other mice. The vaccinated mice’s hemagglutinin proteins were altered at the tip, which allowed the virus to be unrecognized by the immune system. While the hemagglutinin in non-vaccinated mice didn’t change. - All human flu’s descend from strains that infected other animals. - The number of different mutations in two lineages provides clue to how long ago these viruses diverged from a common ancestor. Reassortment When genetic material from different strains gets mixed into new combinations within a single individual. Triple Reassortment When the genes of three viral strains exchange genes (H1N1 involves strains from swine, birds and human. Chapter 2: 2.1 Nature before Darwin: - Carl Linnaeus (father of modern taxonomy) organized all living things at the time into a single hierarchy of groups (taxa). He could assign every species to a particular genus, family, or order according the traits it shared with other species. He believed that the overall patterns of life’s diversity had not changed since the biblical creation of the world. - Nicolaus Steno studied a shark’s teeth and it occurred that they looked like triangular rocks which were known as tongue stones. He proposed that tongue stones had started out as teeth in living sharks. After sharks died their teeth turned to stone. However, how could animals that lived in the ocean end up so far away on mountains? He argued that originally a sea must have covered the mountains. Shelled animals then died and were covered over in sediment and turned to rock. He was known as the father of geology and stratigraphy since he studied the layering in rock. Taxon A group of organisms that a taxonomist judges to be a taxonomic unit, such as a species or order. Taxonomy The science of describing, naming, and classifying species of living or fossil organisms. 2.2 Evolution before Darwin: - Georges-Louis Buffon proposed that new varieties of a species could arise in response to new habitats. However, he did not believe that species could arise this way. A comet struck the sun, he argued, breaking off debris that formed a planet. Earth cooled and hardened and oceans formed this process he said took 70,000 years. He argued that each species had a supply of organic particles that somehow transferred an egg or seed into its adult form. These animals first came to exist in hot ocean of early earth then migrated to warm tropics, overall argued that life had changed over time. - Georges Cuvier compared elephant fossils to skeletons of living elephants and documented that these species had become extinct. - James Hutton realized rocks formed through slow changes, such as rain, molten etc. Eroded sediments form and erode away again like a cycle. The world has deep history shaped by gradual transformations of landscapes. - William Smith noticed that the same kinds of fossils tended to appear in older rocks, but different ones appeared in younger rocks. He could find the same set of fossils in rocks separated by hundreds of miles. Created first geological map . - Jean-Baptiste de Lamarck proposed that life was driven inexorably from simplicity to complexity and that human and other large species descended from microbes. He argued that primitive life was being spontaneously generated all the time. He believed that organisms could adapt to their environment and did not accept extinction. For example if a giraffe stretched its neck for leaves a nervous fluid would flow to its neck and make it longer. Paleontology The study of prehistoric life Extinction The permanent loss of a population or species, arising with failure or death to breed last individual 2.3 The Unofficial Naturalist: - Darwin was sent to school in Edinburgh to become a Doctor when he realized he would much rather be studying nature. In 1831, Darwin went on a voyage on the HMS beagle from England to South America. He recognized layers of rocks that had gradually formed and experienced an earthquake in Chile observing the shoreline being lifted. - Darwin read Charles Lyell’s book, “ The Principles of Geology”, which made the argument that the Earth’s landscapes had been created not by gigantic catastrophes but by a series of many small changes (uniformitarianism). Viewing the earthquake it made him a passionate “Lyellian”. - Darwin observed the dramatically different beak sizes of finches in Galapagos and concluded that they adapted to their environment. In 858 Darwin received a letter from Alfred Russell Wallace presenting his own ideas this made Darwin publish his work before Wallace had a chance. - Thomas
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