BSC 2011- Week 1 Notes
BSC 2011- Week 1 Notes BSC 2011
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This 8 page Class Notes was uploaded by Anton Nguyen on Monday September 5, 2016. The Class Notes belongs to BSC 2011 at University of South Florida taught by Chantale Begin in Fall 2016. Since its upload, it has received 4 views. For similar materials see Bio II- Biological Diversity in Biology at University of South Florida.
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Date Created: 09/05/16
Chapter 22 Descent with Modification: A Darwinian View of Life 3 Key observations about life: o Striking ways in which organisms area suited for life in their environment* (* refers to other organisms as well as to physical aspects of surroundings) o The many shared characteristics (unity of life) o The rich diversity of life Charles Darwin was inspired to develop a scientific explanation for the three observations o He ushered in a scientific revolution of evolutionary biology when he published his hypothesis in his book The Origin of Species Evolution: Descent with modification o Phrase used by Darwin in proposing that many species are descendants of ancestral species that were rather different from presentday species o Evolution can also be defined more specifically as change in genetic composition of a population from generation to generation Which can be seen in 2 related, but different ways Process: Pattern: -Consists of mechanisms that -Revealed by data from produce an observed scientific fields (i.e. change chemistry, biology, etc.) -with said -This data is facts, mechanisms which are observations representing natural about the natural world causes of natural Various views on how life might’ve changed over time o Aristotle, a famous Greek philosopher who greatly influenced Western science Observed certain “affinities” among various organisms and viewed species as ficed He also concluded from these “affinities,” lifeforms can be arranged on a ladder or scale of increasing complexity, called scala naturae (scale of nature), with each form of life having a spot on the ladder o These ideas were consistent with the Old Testament story of creation, where God individually created various species and were therefore perfect o And many 1700s scientists remarked at how God made each species for a particular purpose Carolus Linneaus, a Swedish botanist and physician, wanted to classify life’s diversity “for the greater glory of God” He developed a binomial, or twopart, format for naming species, and also adopted the nested classification system. o S a i d system grouped similar species into increasingly general categories o However he couldn’t relate certain resemblances among species to evolution, but instead to the pattern of creation Even though Darwin would argue for classification based on evolution patterns Ideas about changes over time o Darwin drew information about evolution from scientists studying fossils, the remnants of organisms from the past With many fossils being found in various levels of strata (singular stratum), layers of compressed rock and dirt, formed at the bottom of seas, lakes, and swamps o Paleontology Study of fossils Developed by Georges Cuvier, a French scientist He noted that the older the strata was, the more different the fossils were from current lifeforms Inferred extinctions were common occurrences but staunchly opposed the idea of evolution He also speculated that each boundary between strata, represented a sudden catastrophe (like a flood) that destroyed many species in an area o And reasoned that the area was repopulated by different species o Others suggested profound change took place, but it was a slow and continuous process James Hutton, a Scottish geologist, proposed in 1795 that Earth’s geologic features could be explained by this process While Charles Lyell, the leading geologist of the time, incorporated Hutton’s ideas into his proposal which stated that the same geological processes operating today as in the past at the same rate These ideas had Darwin thinking Earth’s widely accepted age of a few thousand years o And from this, he reasoned that the slow and continuous processes could cause a large biological change Lamarck’s Hypothesis of Evolution o JeanBaptiste de Lamarck (17441829) French biologist Was the only person in the 18 Century to propose mechanism to how life changed over time And was remembered for his incorrectly proposed mechanism about evolution o Darwin rejected this idea but thought variation was introduced into the evolutionary process through inheritance of acquired traits And genetics can prove that Lamarck’s mechanisms of acquired traits aren’t passed on or inherited The only way organisms could have changes in their lifetimes is through gene expression, which can’t be passed on Charles Darwin (18091882) “Use and disuse” “Inheritance of acquired -The idea that parts of the characteristics” body that were used a lot were larger and stronger -Stated that organisms can pass modifications to their -While those not in use offspring deteriorated o Was sent to medical school but quit after finding it too horrifying Instead went to Cambridge in order to be a clergyman (as most scientists/scholars were) o While he was at Cambridge, he became the protégé of John Henslow, a botantist, who later referred him to an accomplished scientist, Captain Robert FitzRoy of the HMS Beagle a survey ship. o During the voyage, Darwin spent a lot of time onshore studying and observing thousands of plants and animals He described features of organisms that suited them to such diverse environments from humid Brazilian jungles to expansive grasslands of Argentina Experienced an earthquake along the Chilean coast and saw rocks along the coastline pushed higher into the air Inferred rocks containing fossils were pushed high into the Andes mountain range through similar earthquakes, after finding fossils high in the mountains This was also physical evidence that didn’t support that the Earth was only a few thousand years old o He also studied adaptations, inherited characteristics that better the chances of an organisms survival and reproduction in specific environments And that adaptations arose through natural selection, a process in which organisms with certain traits and characteristics survived and reproduced at higher rates because of those traits By the early 1840s, Darwin worked out the majority of his hypothesis but didn’t publish it until later after a man named Alfred Russel Wallace published a hypothesis almost like Darwin But Wallace gave Darwin the credit of the idea because of his work that was so extensive in developing natural selection o The Origin of Species Darwin published his hypothesis on natural selection in this book He never used the word evolution although instead he used descent with modification, which summarized his views on life While many organisms share characteristics, Darwin inferred unity and a common ancestor He also thought that descendants lived in various habitats, gradually acclimating to their environment with diverse adaptations Darwin viewed life as a tree with many branches going out from the trunk, showing the commonalities between various species With each fork being a common ancestor of the subsequent branches o Artificial selection, Natural selection, and Adaptations Darwin proposed natural selection to help explain the seen patterns of evolution First he talked about artificial breeding, with humans modifying other species over many generations, by selecting and breeding individuals that had desirable traits And then he reasoned that the similar process happened in nature, and based his argument on two observations: o 1) Members of a population vary in inherited traits o 2) All species can produce more offspring than their environment can survive and many offspring fail to survive and reproduce Also reasoned that an organism’s inherited traits influenced both its own performance o Such traits would be passed onto later generations and less favorable variations would slowly diminish Natural Selection: A Summary o Process in which individuals that have certain traits survive and reproduce at higher rate o Over time, it can increase the match between organisms and their environment o If the environment changes or individuals leave to a new region, and the traits possessed are adaptable to the new environment, this can lead to a new species o Individuals don’t evolve, populations do!! And over time, not an instantaneous process Evolution of Drug Resistant Bacteria o After the introduction of penicillin and other antibiotics in 1943, by 1945, a small but rapidly growing species of bacteria were already resistant to these powerful drugs due to having: Penicillinase, an enzyme that could destroy penicillin o Other strains were able to synthesize their cell walls with proteins that weren’t affected by penicillin And because they survived, they reproduced at a faster rate and exchanged genes with different species creating multidrug resistant strains o Drugs don’t create drug resistant pathogens, it selects resistant organisms already present in the population Homology o Definition of homology: similarities resulting from common ancestry o Homologous structures: Variations of underlying skeletal structures that were present in a common ancestor o Vestigial structures: Are remnants of features that were useful to an ancestor, but have no use nowadays for an organism descended from said ancestor o Similarities on the molecular level with all life having basically the same genetic code Homologies and “Tree Thinking” o All life shares the deepest level, the genetic code, and from there, smaller groups are formed adding their own homologies to the larger groups they are a part of o This nested pattern is an expected result of descent with modification o Biologist use an evolutionary tree to represent the patterns of descent from common ancestors With such evolutionary trees being hypotheses that summarize current beliefs and understandings of descent patterns Convergent evolution o Definition: independent evolution of similar features in different lineages Shows how distantly related specices can resemble one another in some way o Species that share features because of convergence are said to be analogous Such features share similar functions but not common ancestry While homologous features share a common ancestor, but not a similar function Fossil Record o More evidence on evolution comes from fossils Fossil records document evolution patterns, showing how past organisms differed from present day organisms They can show: Evolutionary changes in various groups of organisms Or reveal the origins of new groups of organisms How descent with modification produced enormous differences among related groups of organisms Biogeography o The scientific study of geographical distribution of species o Are influenced by many factors Such as continental drift, when all the continents were connected into one called Pangaea, but began to break apart roughly 200 million years ago This also leads to why many organisms are considered endemic, or found nowhere else in the world Which led to the rise of various species as they slowly adapted to their species