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BSC 2011- Week 1 Notes

by: Anton Nguyen

BSC 2011- Week 1 Notes BSC 2011

Anton Nguyen
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These notes are from Chapter 22
Bio II- Biological Diversity
Chantale Begin
Class Notes




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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


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