lec 1 Intro

lec 1 Intro - Welcome to BSCI 106 Please read the entire...

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Unformatted text preview: Welcome to BSCI 106 Please read the entire syllabus carefully "Nothing in Biology Makes Sense Except in the Light of Evolution" 1973 Theodosius Dobzhansky American Biology Teacher, 35:125-129. The evidence for biological evolution is so overwhelming, that it is recognized as the sole valid scientific explanation for the it diversification of life, and for how organisms achieve a high level of diversification complexity and adaptation. Because evolution is the mechanism driving organismal design one must understand evolution in order to t to effectively design study livig systems study Evolution is not anti-religious 1. Many religious denominations are OK with biological evolution: e.g. Roman Catholic, some Protestant, Jewish, and Islamic traditions 2. Biological scientists differ Pro - NIH Director Francis Collins , Anti Richard Dawkins Definitions/Key terms - 1 Evolution - genetic change in a population over time Phenotype - the “appearance” of a trait Genotype - the particular alleles present at a locus of interest in an individual Adaptations - complex traits with a clear functional design Key terms - 2 Natural selection - differential reproduction resulting from theeffect of the environment on phenotypic differences Heritability - the degree to which offspring resemble their parents relative to others in a population 3 Definitions of Evolution Genetic change in a population over time (microevolution) (microevolution) The process of making adaptations Diversification in living systems (macroevolution) The idea of evolution preceded Charles Darwin Jean Baptiste de Lamarck (1744 - 1829) -- evolution of acquired characters, spontaneous origin of simple organ isms, and a life characters, force driving increasing complexity . force Étienne Geoffroy Saint-Hilaire (1772-1844) –Adaptation to the environment (no clear mechanism), homology, unity of composition, environment no extinction Georges Cuvier (1769-) – Stratigraphy & fossil record, species Georges appeared then disappeared w/o change (evolution), extinction appeared Evolution by Natural Selection Darwin Wallace Evolution by Natural Selection the mechanism that explains adaptation and the species diversification. species Darwin made a five year trip around the world as a naturalist on the HMS Beagle that inspired his thinking on evolution. Evolution by Natural Selection Evolution by Natural Selection The Darwin-Wallace model Phenotypic variation Phenotypic Heritability of phenotype Heritability Differential reproduction of phenotypes Darwin’s additional assumptions Time – the earth is very old earth - allows time for evolutionary change and diversification Malthusian overproduction - more offspring are produced than can possibly survive- selection culls the all but the best Natural selection builds on past adaptation – earlier adaptations can become more complex and co-opted for new functions Malthusian overproduction Robert Thomas Malthus described the potential populations to expand beyond available resources He noted that most populations are controlled ny high death rates. A female cod fish produces 13,000,000 eggs in her lifetime but for a stable population only 2 need survive to reproduce - she but overproduces by 12,999,998 eggs! overproduces Malthusian overproduction Darwin saw the large proportion of individuals that failed to reproduce as creating an opportunity for natural selection to reproduce weed out those with poorer designs. weed . If the winners may have novel traits that help their reproduction, If then these traits could spread (evolve) quickly in the population. Natural selection builds on past adaptation – makes the production of new complex traits easier to evolve Critics of evolution argue that it’s improbable that natural Critics selection can produce complex adaptations. selection By building on structures already present complex traits are not By improbable improbable Natural selection builds on past adaptation – shown by homology Homology -- traits that have a common evolutionary origin Can often be traced in different forms across a lineage Organisms evolve from ancestors who have already complex Organisms traits that can be modified for new uses. traits Darwin -- gradual changes shown by sequence in different species suggests path to complex eyes Reason tells me, that if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist, each grade being useful to its possessor, as is certain the case; if further, the eye ever varies and the variations be inherited, as is likewise certainly the case; and if such useful variations should be useful to any animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be variations formed by natural selection, should not be considered as subversive of the theory. Some examples of natural selection 1. Darwin’s finches with large beaks reproduce more in poor years because they can eat a larger range of seed sizes. 2. Large male dung flies can better fight for and then reproduce with females. (sexual selection) 3. Male house Sparrows with intermediate characteristics survived freezing weather than males at the extremes. Conclusions about evolution by natural selection 1. The first workable evolution hypothesis. 1. 2. The only plausible hypothesis to explain adaptation and diversification. and 3. Next lecture: Evidence for evolution part 1 - age of the earth, fossils, homology. earth, ...
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This note was uploaded on 01/23/2012 for the course BIO 106 taught by Professor Jeffreyjensen during the Fall '10 term at NYU.

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