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Chapter 4

Chapter 4 the geography of life.doc
Chapter 4 the geography of life.doc

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University of Toronto St. George
June Larkin

Chapter 4 the geography of life:lec 2 The main lesson from this chapter is that only evolution can explain the diversity and distribution of life on continents and islands. Topics included in the chapter include convergent evolution, dispersal to islands and how it favours some groups and not others, human origins in Africa, and differences in the biotas of continental vs. oceanic islands - Some of the loneliest places on earth are the isolated volcanic islands of the southern oceans - Alexander selcraig sailing on ship demanded to be put on shore hoping for rescue of the Clinique ports to take him on from the mas a tierra island - Mas a tierra was unhabited and the only mammals were goats, rats, and cats - After a while Selkirk adapted to the ways of life by hunting goats - He was rescued by 1709 spending 4 and a half years there by a English ship and headed t England - When there he made a journals of his adventures called The Englishman but he could not adapt to ashore so he returned to sea and died in 1720 from fever - Selkirik was a story of contingencies and time - Selrick did not know that mas a tierra now called alejandro Selkirk was inhabited by earlier decendedents of castaways –plants, birds, insects who found their way thousands of years before silkirk - He was living in a lab of evolutionary change - The island juan Fernandez has rare and exotic plants and animals that are endemic- found nowhere else in the world - These include species such as 5inch rust brown humming bird 126 plants , fur seal, and handful of insects - The island however is missing many things such as: amphibian, reptile, or mammal –groups common on continents around the world - This endemic, and absent groups are repeated over and over on oceanic islands giving evidence for evolution - It was Darwin who took a look at these patterns and realized that evolution was necessary not just to explain the origins and forms but of plants and animls but also their distribution around the globe - Darwin answered questions as to why this is the way it is in origins by the field of biogeography- study of distribution of species on earth and evolutionary explanation of geo of life - Roots of biogeorgraphy lie deep in religion because natural theologian tried to show distribution of organisms can be reconciled with noahs ark in the bible – all animals were descendents of the paris noah tool aboard but explanation had problems – how did kangaroos and earth wroms come from ocean to Australia?? - So another theory came: multiple creations distributed across earth – Louis who said that their distributions were static and distributions were the sight of their creation but Charles lelly proved his theory wrong saying that he found evidence that earth is not old - Beagle voyage Darwin discovered fossils like seashells high in andes proving what is now mountain was once underwater - In conclusion land could rise and sink and that continents we see today may have been smaller or larger in the past - Why was flora in south Africa similar to souther south America?? Because all continents were connected by land bridges - Darwin proposed: this distribution of species were not by creation but by evolution - If plants and animlas could disperse over large distances and evolve into new species after dispersing with shifts of the earth could explain biogeography - Darwin turned out to be right- not completelyt though , yes it is true many facts in biogeography made sense if you thought of dispersal, evolution and changing of the earth bu what about ostriches? Who can’t fly are in afric, south America and australlia and if they all had a common ancestor how could they be dispersed? Or why does china vs east north amercia share plants? - We now have answers that Darwin could not figure out which is continental drift and molecular taxonomy - DNA 40 years ago also heloed us too by explaining not only evolutionary relationships but their times of diverging from common ancestors - Evolutionary theory- species diverge from common ancesto
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