BESC 201 1st Edition Lecture 7 Outline of Last Lecture I Evolution Outline of Current Lecture II Biodiversity Current Lecture Evolution generates biological diversity Biodiversity the variety of life across all levels of biological organization including diversity of species their genes their populations and their communities Speciation produces new types of organism Speciation the process by which new species are generated Allopatric speciation species formation due to the physical separation of populations over some geographic distance considered main mode of speciation Distance means mutations in one population will not spread to the other and the 2 will evolve independently and get to the point where they cannot mate with each other We can learn the history of life s diversification Phylogenetic trees treelike diagrams with branches that represent life s history show relationships between species or populations Fossils also hold clues of life s history Average time a species spends on Earth is 1 10 million years The number of species in existence at any one time number added through speciation number removed by extinction These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Some species are more vulnerable to extinction than others Small populations and species narrowly specialized on some particular resource or way of life are more vulnerable to extinction from environmental change Endemic phenomenon that occurs nowhere else on Earth Earth has seen several episodes of mass extinction Background extinction rate rate at which one species at a time becomes extinct the way extinction normally works Mass extinction events massive extinction proportions occurring at widely spaced intervals killing 50 95 species at a time The sixth mass extinction is upon us Changes to natural systems population growth development and resource depletion is causing next one Species extinction is the biggest environmental problem because it can t be reversed
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