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Chapter 1

BIO305 CHAPTER 1 textbook notes

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T Conway

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CHAPTER 1 Lessons from the past -less was known and understood – as you go back further in time notice that the intellects of that era had to start their theories new as there was little knowledge known about a topic -must be aware that for every generation the range of theories that one could suggest is limited by what society and science views as acceptable or respectable -ex: debate of evolution -reactions to those scientists confronted with results or ideas that conflict with current dogma is either to reject them or view them as an exception Ecological vs historical biogeography and plants vs animals -most fundamental split in biogeography is between ecological and historical aspects -ecological biogeography – focus on short term periods of time, at a smaller scale, with local, within habitat or intracontinental questions and mainly with species or sub-species of living plants or animals -historical biogeography – focus on long term, evolutionary periods of time with larger often sometimes global areas and often with taxa above the level of the species and with taxa that may now be extinct -the form and growth of plants are more closely conditioned by environmental and ecological conditions due to the fact that they are static -easier to collect and preserve plants compared to animals however fossil plant remains are more rare and therefore difficult to interpret -more flowering plants than mammals -taxonomy of flowering plants based on characteristics of flower which are rarely preserved -biogeography of distant past largely the preserve of zoologists while plant scientists focused on ecological biogeography Biogeography and creation -biogeography began in mid 18 century when most people believed statements in the bible as the truth -earth created in a single series of events by God where everything He created was perfect and therefore nothing has evolved or changed since then or even gone extinct -gradually replaced by realization that everything is changing and driven by evolution and plate tectonics -Buffon’s Law – similar environments found in different regions of the world contained different groupings of organisms -Georges Buffon came up with many explanations -noticed many mammals of North America also found in Eurasia and pointed out that they could only have traveled between the two continents through Alaska when climates were much warmer -accepted that some animals had become extinct -noticed that even though the environments are similar, most mammals of South America are different from Africa -suggested all originally created in the Old World and that the two continents were at one point adjacent and therefore the animals chose whichever area they found most congenial – eventually the ocean separated the two continents -Buffon accepted that geography, climate, nature of the species was changeable and suggest that continents move laterally and seas encroach upon them -observations on mammals of 2 regions soon extended to land birds, reptiles, insects and plants The distribution of life today -Georg Forster found that Buffon’s Law also applied to plants and to any part of the world being separated from others by barriers of geography or climate -also realized there are gradients of diversity -more plant species closer to the equator and fewer as one heads towards the poles -Humboldt believed the world was divided into a number of natural regions where each has its own distinctive variety of animals and plants  originally used the term associate but is now commonly referred to as biomes Evolution – a flawed and dangerous idea! -Lamarck – different groups of organisms should be allocated to “lower” or “higher” places according to the level of “perfection” of their organization  humans would be at the top -suggested “lower” organisms would be found earlier in time and would have the potential to change into “higher” forms as a result of an inherent tendency of life to improve itself -therefore no organism had really gone extinct for it was possible that they had evolved into different and perhaps still-living descendants -Cuvier – used comparative anatomy to prove fossils of animals such as the mammoth were much different than those living today and therefore had gone extinct -believed these extinct creatures were very well adapted to their environment and there must have been a sudden catastrophic change in their environment to cause them to go extinct Enter Darwin – and Wallace -on Charles Darwin’s visit to the Galapagos Islands noticed different varieties of finches as well as tortoises between the different islands (ex: tortoise on well-watered islands who ate ground vegetation had rounded fronts to their shells…but the tortoises on the drier islands had notched fronts to their shells that allowed them to stretch their neck to reach higher leaves of bushes -Darwin found fossils in South America very similar yet larger than the living forms of the sloth, armadillo and guanaco -Alfred Russel Wallace was the first to notice and publish the fact that closely related species often were found close to another geographically with the clear implication that the two were linked by an evolutionary process -a pair of animals/plants produce more offspring than needed to simply replace them which results in competition for survival among the offspring -offspring vary slightly in their characteristics which some will be better suited to the mode of life than others -those with favourable characteristics will have a natural advantage in competing and will tend to survive -by surviving and eventual mating, natural selection will lead to the continuation of these favourable characteristics into the next generation -both Darwin and Wallace share credit for identifying natural selection but the majority of the credit goes to Darwin ad his book On the Origin of Species -now know that the appearance of mutations can quickly alter the nature of any species and it is only the constant action of natural selection in weeding out most of these that gives the species the appearance of unchanging stability World maps – the
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