BIO 203L- Lecture 2
BIO 203L- Lecture 2 BIOL 203L 005
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This 5 page Class Notes was uploaded by Karissa Sandoval on Tuesday January 26, 2016. The Class Notes belongs to BIOL 203L 005 at University of New Mexico taught by Dr. Kelly Miller and Dr. Scott Collins in Spring 2016. Since its upload, it has received 12 views. For similar materials see Ecology and Evolution Laboratory in Biology at University of New Mexico.
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Date Created: 01/26/16
BIO 203: Evolution Lecture 2 Natural Selection, Fitness and Adaptation Transmutation (aka Evolution) – “Immutability of species” was questioned before Darwin ‒ Transmutation • Can species become another species – Erasmus Darwin (Chuck’s grandpa) (1731-1802), English naturalist • Wrote possibilities of transmutation – Étienne Geoffroy Saint-Hillaire (1772-1844), French naturalist • The environment causes a change in form • Promoting idea that environment makes changes in forms – Robert Chambers (1802-1871), Scottish author • Vestiges of the Natural History of Creation • He promoted the same idea as Hillaire and life has created from a unity Lamarck – Jean-Baptiste Lamarck (1744-1829) • First comprehensive theory of transmutation • The environment causes change in organisms • Inheritance of acquired characteristics • Spontaneous generation of new species • Two forces leading to Great Chain of Being • Force driving to higher complexity (“upward movement”) • Force adapting organisms to the environment and making them different from each other (“lateral movement”) – Supposed that lineages did not branch nor become extinct – Developed a comprehensive theory of evolution – Environment put pressure on change – Spontaneous generation (simple life forms were generated for inanimate objects) got more complex – Ex: giraffe had a small neck and over time became longer in length because they needed to feed from tree branches that were higher up. Transmutation attacked! – Mutability of species was questioned intensely – Cuvier ‒ attacked Lamarck for the reasons being: • Parts of organisms are too closely correlated to change (you cant change individual parts) • No evidence of gradual change in fossil record (catastrophies instead) BIO 203: Evolution Lecture 2 • Ancient Egyptian drawings of animals and mummies of animals look the same as now – Idealists (Goethe, Hegel, Oken, Agassiz and, especially, Owen) – Progressive creation reflecting the ideas in the mind of the Creator • As creation occurred there was no change Darwin and Wallace – Charles Robert Darwin (1809-1882) and Alfred Russel Wallace (1823-1913) Darwin – 1809 – Darwin born – 1831-1836 – Beagle voyage, Darwin as “gentleman companion” to FitzRoy and this was his job for the time being, which he did the following: • Collected fossils • Collected animal specimens • Observed biological / geological features • Began to perceive adaptation and origin of species as closely related • Darwin took advantage of the opportunity of doing these tasks Darwin – 1838 – Darwin fully conceives his version of evolution by natural selection – 1844 – Darwin writes essay on natural selection and sends it to Lyell and Hutton, but does not publish it – 1859 – On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life Wallace – 1823 – Wallace born – 1848-1862 – Wallace explores S America, Australia and SE Asia – 1858 –Wallace sends paper on natural selection to Darwin for review – 1858 – Joint paper presented to Linnean Society meetings: On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection Darwin and Wallace Fundamental themes – Descent with modification (transmutation) – Promoted unity of life (diversification from a common ancestor = common origin of life) – Gradual change (gradualism) – Natural selection as mechanism for change History of life – Like a tree – multiple branches of a common trunk BIO 203: Evolution Lecture 2 – Twigs represent diversity of living things Darwin and credit – Why did Darwin get the credit? • On the Origin of Species • First comprehensive, consistent and unified theory of evolution • Extensive evidence and examples • Active proponents • Thomas Huxley (1825-1895), English biologist “Darwin’s Bulldog” • He forcefully enforced Darwin’s ideas through violence and that is why he was called “Bulldog” • Natural Selection Darwin attacked! – Transmutation not well accepted – Darwin’s mechanism (natural selection) not well accepted – Political implications – Richard Owen ("I used to be ashamed of hating him so much, but now I will carefully cherish my hatred & contempt to the last days of my life” ‒ Darwin in reference to Owen) – Darwin’s theory not well accepted until 1930s Natural selection – Ernst Mayr (1904-2005), German-American biologist – Natural selection sensu Darwin – 3 inferences and 5 observations • Observation #1 • In a species, population size would increase exponentially if all individuals born reproduced successfully • Observation #2 • Populations appear to be more-or-less stable over time (except for natural fluctuations due to seasons, etc.) • Malthusian Population Theory • Thomas Robert Malthus (1766-1834), English economist • Populations would grow but they don’t because there are limited resources • Observation #3 • Resources are limited so this is limitation to the population • Inference #1 • More individuals are produced than can be supported so as a result they die BIO 203: Evolution Lecture 2 • Leads to competition among individuals for existence • Some survive, others do not (“struggle for existence”) • Observation #4 • Members of a population vary in their characteristics • No two individuals are exactly alike (ex: eye color, hair color, gender, height) • Observation #5 • Much of the variation between individuals is heritable (genetic) • Inference #2 • Successful survival depends in part on heritable features • Individuals with heritable features that increase the probability of surviving and reproducing are likely to produce more offspring than other individuals • Inference #3 • Unequal ability of individuals to survive and reproduce will lead to a gradual change in the population, with favorable characteristics accumulating over generations Natural selection – Natural selection condensed • Heritable variation exists within populations of organisms (passed on) • Organisms produce more offspring than can survive (some die) • These offspring vary in their ability to survive and reproduce – Natural selection is a filter • Some things get through (survive) and some don’t (die) • The ones that get through are the more competitive ones Example – Antibiotic resistance • Antibiotics used to kill bacteria • Among huge populations of bacteria, some have heritable resistance to antibiotic • These will survive treatment to reproduce • New generation has larger proportion of resistant individuals • Eventually, with repeated treatments, all resulting bacteria may be resistant BIO 203: Evolution Lecture 2 • More resistant bacteria survive because they can survive still because in a sense they have become immune to the antibiotics Artificial selection – Humans have modified other species over many generations by selecting and breeding individuals that possess desired features Darwinian Fitness th – “Survival of the best fitted” – Herbert Spencer (in the 5 edition of The Origin) – Darwinian Fitness – Ability of an individual to produce offspring relative to other individuals in the population – Measurable quantity – Count offspring of one individual and compare with counts from other individuals – Usually applies to classes of individuals (such as “those homozygous for allele A for gene Z”) Adaptation – Adaptations – increase fitness of individuals within population – Adaptations are selected for in natural selection – Developed especially by Lamarck • Lamarck – giraffes stretching their necks in response to higher leaves resulted in giraffes having long necks passed on to next generation. • Darwin – more long-necked giraffes reproduce than short- necked giraffes and as such giraffes today have long necks. – The genetic basis for an adaptation is not induced by the environment, it exists within the population and is selected for by the environment. The existence of an adaptation is not a consequence of the environment, it existed as a variant and is subsequently selected. – Often in response to abiotic selection pressures – Can involve any type of feature • Anatomical • Behavioral • Physiological
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