exam 6 - EXAM 6 Darwin collected biological materials of...

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EXAM 6 Darwin collected biological materials of all kinds (including fossils) from many places Collected extensively in the Galapagos islans in the easter pacific The origin of species Darwin’s and wallace’s ideas The species inhabiting the earth have changed through time o By the mid 1850’s many people (including Darwin) had collected numerous fossils of species that appeared not to currently exist anywhere on earth, so a large and ever increasing body of evidence that the species inhabiting the earth had changed o The current estimate that 90% of all species have become extinct o Current species are descended from ancestoral species o Descent with modification (evolution) o The idea of evolution had been already been proposed earlier by others (Lamarck and darwin’s grandfather) The means (mechanism) by which decent with modification occurs is natural selection o This was a truly novel idea- and one that resulted in revolutionizing our understanding of biology o All species have the reproductive potential to increase exponentially in population, yet natural populations tend to remain stable in size o Environmental resources are limited o Production of more individuals than can be supported by th environment leads to a struggle for existence o Individuals in sexually reproducing species vary extensively in their characteristics- no two individuals are exactly alike(variation is heritable) Darwins inference The struggle to survive long enough to reproduce is not entirely random- those individuals whose genetic inheritance best fits them to their environment will be more likely to leave offspring Unequal abibity to reproduce will lead to gradual change in the species (or a population within a species) potentially producing new species Natural selection Sometimes referred to as survival of the fittest Natural selection is a process in which individuals that have certain heritable characteristics survive and reproduce at a higher rate than other individuals Important to remember that if the environment changes (which can happen quickly or gradually) different individuals will be more fit and more likely to reproduce Evidence The fossil record o Millions of fossils have been collected and analyzed o The pattern of appearance of certain types of fossils through time is consistent and predictable Anatomical homology o Similarity in structures resulting from common ancestry Molecular homology o Protein or DNA sequence similarities resulting from common ancestry Presence of vestigial organs in some species
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o Snakes retain vestigels of pelvis and leg bones Biogeographical patterns o The theory of evolution is the best (and only) scientific explanation that we have for the diversity of life on earth o The theory of evolution is fundamental concept in biology The theory of evolution is rather comlex to understand- partly because there are numerous
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exam 6 - EXAM 6 Darwin collected biological materials of...

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