tag:blogger.com,1999:blog-36693936735558911442024-03-08T00:22:37.535-08:00May I digress?lngndvshttp://www.blogger.com/profile/11895574214946388277noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-3669393673555891144.post-64005006938589745062008-04-11T23:06:00.000-07:002008-04-11T23:06:21.989-07:00As I see it: the idiot's guide to the history of animal classification<br /><p><strong>Chapter 1: Classification is a universal human attirbute. There seem to often be two categories.</strong></p><p><br />Traditional Micronesians seem to classify living things into two groups: Animals and Plants. But remember how german classifies the noun "maedchen" (maiden) as neutral, taking the neutral article "das"? Chuukese does something like that with counting classifiers. English uses counting classifiers trivially; but other languages incorporate explicit syntactic rules for applying them. In Chuukese, the classifier is obligatory (or WAS, because younger speakers don't learn their more sophisticated aspects). </p><p><br />The classifier for a long skinny item is "foch". Like a stick of gum, efoch gum = one stick on gum. ruefoch gum = two sticks of gum. </p><p><br />The classifier for an animal is "men". Emen pik = one pig; emen mwan = one man. Ruemen pik = two pigs, etc. But interestingly, for the octopus, ew kuus = one octopus, it is not given the classifier for animals! </p><p><br />And then, here's a stranger one still, I think: a saw or a knife IS given the classifier "men": Emen ngerenger = one saw.</p><p><br /><strong>Chapter 2: Early thinkers also posited two higher categories.</strong></p><p><br />More to come</p><p><br /></p>lngndvshttp://www.blogger.com/profile/11895574214946388277noreply@blogger.com0tag:blogger.com,1999:blog-3669393673555891144.post-39800297261322635412008-03-07T19:57:00.000-08:002008-03-07T20:52:38.211-08:00Monitoring / Red Flags / E. ColiBeginning from where? My Biology classes have been studying Mitosis. A bit out of sequence, but I stumbled upon several excellent Mitosis videos that clarified the air. Also included were two videos that cleared up confusion about Protein expression. With a self-congratulatory smile, I listened to students, again and again, saying "Now I get it." Just three hours collecting together Google Videos: time well worth wasting.<br /><br />Along the way, the second day, students were finishing their seatwork on the stages/snapshots of mitosis. I also showed 2 time lapse videos of bacterial fission. One of them concluded that in 48 hours of unbridled division at 20 minute intervals, the progeny of one <span style="font-style: italic;">E. coli</span> would have a mass 4 times that of the Earth.<br /><br />May I digress?<br /><br />What is <span style="font-style: italic;">E. coli</span>? <a href="http://en.wikipedia.org/wiki/Escherichia_coli"><span style="font-style: italic;">Escherichia coli</span></a> is a symbiont in the human gut:<br /><br /><blockquote><br /><p><i><b>Escherichia coli</b></i> (<a class="snap_shots" href="http://en.wikipedia.org/wiki/Help:Pronunciation" title="Help:Pronunciation">pronounced</a> <span title="Pronunciation in the International Phonetic Alphabet (IPA)" class="IPA">/ˌɛʃ<s>ɪ</s>ˈrɪkiə ˈkoʊlaɪ/</span>) (<i><b>E. coli</b></i>), is a <a href="http://en.wikipedia.org/wiki/Bacterium" class="mw-redirect snap_shots" title="Bacterium">bacterium</a> that is commonly found in the lower <a class="snap_shots" href="http://en.wikipedia.org/wiki/Gastrointestinal_tract" title="Gastrointestinal tract">intestine</a> of warm-blooded animals. Most <i>E. coli</i> <a class="snap_shots" href="http://en.wikipedia.org/wiki/Strain_%28biology%29" title="Strain (biology)">strains</a> are harmless, but some, such as <a class="snap_shots" href="http://en.wikipedia.org/wiki/Serovar" title="Serovar">serotype</a> <a class="snap_shots" href="http://en.wikipedia.org/wiki/Escherichia_coli_O157:H7" title="Escherichia coli O157:H7">O157:H7</a>, can cause serious <a class="snap_shots" href="http://en.wikipedia.org/wiki/Foodborne_illness" title="Foodborne illness">food poisoning</a> in humans, and are occasionally responsible for costly <a class="snap_shots" href="http://en.wikipedia.org/wiki/Product_recall" title="Product recall">product recalls</a>. The <a href="http://en.wiktionary.org/wiki/harmless" class="extiw" title="wikt:harmless">harmless</a> <a class="snap_shots" href="http://en.wikipedia.org/wiki/Strain_%28biology%29" title="Strain (biology)">strains</a> are part of the <a class="snap_shots" href="http://en.wikipedia.org/wiki/Human_flora" title="Human flora">normal flora</a> of the <a href="http://en.wikipedia.org/wiki/Gut" class="mw-redirect snap_shots" title="Gut">gut</a>, and can benefit their hosts by producing <a class="snap_shots" href="http://en.wikipedia.org/wiki/Vitamin_K" title="Vitamin K">vitamin K<sub>2</sub></a>,<span style="text-decoration: underline;"> </span> or by preventing the establishment of <a class="snap_shots" href="http://en.wikipedia.org/wiki/Pathogen" title="Pathogen">pathogenic</a> bacteria within the intestine.<sup id="_ref-Hudault_0" class="reference"><a class="snap_shots" href="http://en.wikipedia.org/wiki/Escherichia_coli#_note-Hudault" title=""></a></sup></p> <p><i>E. coli</i> are not always confined to the intestine, and their ability to survive for brief periods outside the body makes them an ideal <a class="snap_shots" href="http://en.wikipedia.org/wiki/Indicator_organism" title="Indicator organism">indicator organism</a> to test environmental samples for <a class="snap_shots" href="http://en.wikipedia.org/wiki/Feces" title="Feces">fecal contamination</a>.<sup id="_ref-Feng_2002_0" class="reference"><a class="snap_shots" href="http://en.wikipedia.org/wiki/Escherichia_coli#_note-Feng_2002" title=""></a></sup></p><br /><br /><script src="http://shots.snap.com//client/inject.js?site_name=0" type="text/javascript"></script><script src="http://shots.snap.com//client/inject.js?site_name=0" type="text/javascript"></script><script src="http://shots.snap.com//client/inject.js?site_name=0" type="text/javascript"></script></blockquote><br /><br /><br />The DEQ posts on line <a href="http://www.deq.gov.mp/section.aspx?secID=4">Beach Reports. </a>Red Flags refer to the beaches listed in these reports. Red Flags are also posted in the local newspapers. A separate web page explains the <a href="http://www.cnmicoralreef.net/wq/beachclose.htm">beach monitoring program</a>.lngndvshttp://www.blogger.com/profile/11895574214946388277noreply@blogger.com0tag:blogger.com,1999:blog-3669393673555891144.post-36166420927752226582008-02-25T03:36:00.000-08:002008-02-25T04:04:12.835-08:00Chicken to the Egg / Egg to the ChickenStarting from a basic coral reef life cycle, an odyssey.<br /><br />Why is it relevant to study coral life cycles on Saipan?<br /><br /><ol><li>Corals are cool</li><li>Corals live here: we would have no such island without corals</li><li>Coral development parallels development across the gamut of animals</li><li>We can allude to various points in the life cycle where corals are susceptible to human activities</li><ol><li>Fertilization (chicken first point of view), due to varoius causes<br /></li><li>Settlement</li><li>Adult life</li></ol><li>Leads to animal embryology</li><li>Specificity is a ubiquitous theme<br /></li><li><br /></li></ol>lngndvshttp://www.blogger.com/profile/11895574214946388277noreply@blogger.com0tag:blogger.com,1999:blog-3669393673555891144.post-8549625457359126432007-09-02T18:26:00.000-07:002007-09-02T20:57:29.742-07:00What is a Species?<span style="font-size:180%;">Starting from a <span style="font-weight: bold;">"Biological" definition of species</span></span>, one soon is convinced that the species idea in itself is flawed. Here I have collected some links and excerpts on this topic. Notes for a digression on species and speciation. These are frequent topics for classroom digressions.<br /><br />I found an article on line. For the criminally insane price of US$55.87 I could get a copy of this from the cartel at http://www.ingentaconnect.com/:<br /><blockquote><br /><strong></strong>Márquez L.M.; Van Oppen M.J.H.; Willis B.L.<a set="yes" linkindex="47" href="http://www.ingentaconnect.com/content/bsc/mecol/2002/00000011/00000008/art00009#aff_1"><sup>1</sup></a>; Reyes A.<a set="yes" linkindex="48" href="http://www.ingentaconnect.com/content/bsc/mecol/2002/00000011/00000008/art00009#aff_2"><sup>2</sup></a>; Miller D.J.<a set="yes" linkindex="49" href="http://www.ingentaconnect.com/content/bsc/mecol/2002/00000011/00000008/art00009#aff_2"><sup>2</sup></a>. 2002. <span style="font-size:130%;">The highly cross-fertile coral species, <i>Acropora hyacinthus</i> and <i>Acropora cytherea</i>, constitute statistically distinguishable lineages. </span><a set="yes" linkindex="50" href="http://www.ingentaconnect.com/content/bsc/mecol;jsessionid=3hj54gr3fi80.victoria" title="Molecular Ecology">Molecular Ecology</a>, Volume 11, Number 8, August 2002 , pp. 1339-1349(11). <br /></blockquote>Here are some other links:<br /><br /><ul><li><a href="http://striweb.si.edu/publications/PDFs/Knowlton_1997_SpUniBiod.pdf">http://striweb.si.edu/publications/PDFs/Knowlton_1997_SpUniBiod.pdf</a></li><li><a href="http://my.fit.edu/%7Ervw/Taxonomy/First%20taxa.htm">A presentation about Coral Taxonomy<br /></a></li><li><a href="http://www.elasmo-research.org/education/topics/ng_scientific_names.htm">A posting about species, focused on sharks.</a></li><li><a href="http://www.biolbull.org/cgi/reprint/196/1/80.pdf">Corals: Molecular Boundaries (open PDF)<br /></a></li></ul><br /><br />From Wikipedia article, Definitions of "Species"<br /><br /><h2><span class="mw-headline"></span></h2><blockquote><h2><span class="mw-headline">Definitions of species</span></h2> <p>The question of how best to define "species" is one that has occupied biologists for centuries, and the debate itself has become known as the <a set="yes" linkindex="126" href="http://en.wikipedia.org/wiki/Species_Problem" title="Species Problem">species problem</a>. One definition that is widely used is that a species is a group of actually or potentially interbreeding populations that are reproductively isolated from other such groups.</p> <p>The <a linkindex="127" href="http://en.wikipedia.org/wiki/Definition" title="Definition">definition</a> of a species given above is derived from the behavioral biologist Ernst Mayr, and is somewhat idealistic . Since it assumes <a linkindex="128" href="http://en.wikipedia.org/wiki/Sexual_reproduction" title="Sexual reproduction">sexual reproduction</a>, it leaves the term undefined for a large class of organisms that reproduce asexually. Biologists frequently do not know whether two morphologically similar groups of organisms are "potentially" capable of interbreeding. Further, there is considerable variation in the degree to which hybridization may succeed under natural and experimental conditions, or even in the degree to which some organisms use sexual reproduction between individuals to breed. Consequently, several lines of thought in the definition of <i>species</i> exist:</p> <dl><dt>Typological species </dt><dd>A group of organisms in which individuals are members of the species if they sufficiently conform to certain fixed properties. The clusters of variations or phenotypes within specimens (i.e. longer and shorter tails) would differentiate the species. This method was used as a "classical" method of determining species, such as with Linnaeus early in evolutionary theory. However, we now know that different phenotypes do not always constitute different species (e.g.: a 4-winged Drosophila born to a 2-winged mother is not a different species). Species named in this manner are called <i>morphospecies</i>.</dd></dl> <dl><dt>Morphological species </dt><dd>A population or group of populations that differs morphologically from other populations. For example, we can distinguish between a <a linkindex="129" href="http://en.wikipedia.org/wiki/Chicken" title="Chicken">chicken</a> and a <a linkindex="130" href="http://en.wikipedia.org/wiki/Duck" title="Duck">duck</a> because they have different shaped bills and the duck has webbed feet. Species have been defined in this way since well before the beginning of recorded history. This species concept is much criticised because more recent genetic data reveal that genetically distinct populations may look very similar and, contrarily, large morphological differences sometimes exist between very closely-related populations. Nonetheless, most species known have been described solely from <a linkindex="131" href="http://en.wikipedia.org/wiki/Morphology_%28biology%29" title="Morphology (biology)">morphology</a>.</dd></dl> <dl><dt>Biological / Isolation species </dt><dd>A set of actually or potentially interbreeding populations. This is generally a useful formulation for scientists working with living examples of the higher taxa like mammals, fish, and birds, but meaningless for <a linkindex="132" href="http://en.wikipedia.org/wiki/Organism" title="Organism">organisms</a> that do not reproduce sexually. It does not distinguish between the theoretical possibility of interbreeding and the actual likelihood of gene flow between populations and is thus impractical in instances of allopatric (geographically isolated) populations. The results of breeding experiments done in artificial conditions may or may not reflect what would happen if the same organisms encountered each other in the wild, making it difficult to gauge whether or not the results of such experiments are meaningful in reference to natural populations.</dd></dl> <dl><dt>Biological / reproductive species </dt><dd>Two organisms that are able to reproduce naturally to produce fertile offspring. Organisms that can reproduce to almost always make infertile hybrids, such as a <a set="yes" linkindex="133" href="http://en.wikipedia.org/wiki/Mule" title="Mule">mule</a> or <a linkindex="134" href="http://en.wikipedia.org/wiki/Hinny" title="Hinny">hinny</a>, are not considered to be the same species.</dd></dl> <dl><dt>Mate-recognition species </dt><dd>A group of organisms that are known to recognize one another as potential mates. Like the isolation species concept above, it applies only to organisms that reproduce sexually. Unlike the isolation species concept, it focuses specifically on pre-mating reproductive isolation.</dd></dl> <dl><dt>Phylogenetic (Cladistic)/ Evolutionary / Darwinian species<sup class="noprint Inline-Template"><span title="The material in the vicinity of this tag needs to be fact-checked with the cited source(s) since August 2007" style="white-space: nowrap;">[<i><a linkindex="135" href="http://en.wikipedia.org/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification needed</a></i>]</span></sup> </dt><dd>A group of organisms that shares an ancestor; a lineage that maintains its integrity with respect to other lineages through both time and space. At some point in the progress of such a group, members may diverge from one another: when such a divergence becomes sufficiently clear, the two populations are regarded as separate species. <a linkindex="136" href="http://en.wikipedia.org/wiki/Subspecies" title="Subspecies">Subspecies</a> as such are not recognized under this approach; either a population is a phylogenetic species or it is not taxonomically distinguishable.</dd></dl> <dl><dt>Ecological species</dt><dd>A set of organisms adapted to a particular set of resources, called a niche, in the environment. According to this concept, populations form the discrete phenetic clusters that we recognize as species because the ecological and evolutionary processes controlling how resources are divided up tend to produce those clusters</dd></dl> <dl><dt>Genetic species </dt><dd>based on similarity of DNA of individuals or populations. Techniques to compare similarity of DNA include <a linkindex="137" href="http://en.wikipedia.org/wiki/DNA-DNA_hybridization" title="DNA-DNA hybridization">DNA-DNA hybridization</a>, and <a linkindex="138" href="http://en.wikipedia.org/wiki/Genetic_fingerprinting" title="Genetic fingerprinting">genetic fingerprinting</a> (or <a linkindex="139" href="http://en.wikipedia.org/wiki/DNA_barcoding" title="DNA barcoding">DNA barcoding</a>).</dd></dl> <dl><dt>Phenetic species</dt><dd>based on <a linkindex="140" href="http://en.wikipedia.org/wiki/Phenotypes" title="Phenotypes">phenotypes</a></dd></dl> <dl><dt>Recognition species</dt><dd>based on behavioral interactions</dd></dl> <dl><dt>Microspecies </dt><dd>Species that reproduce without <a linkindex="141" href="http://en.wikipedia.org/wiki/Meiosis" title="Meiosis">meiosis</a> or fertilization so that each generation is genetically identical to the previous generation. See also <a linkindex="142" href="http://en.wikipedia.org/wiki/Apomixis" title="Apomixis">apomixis</a>.</dd></dl> <dl><dt>Cohesion species </dt><dd>Most inclusive population of individuals having the potential for phenotypic cohesion through intrinsic cohesion mechanisms. This is an expansion of the mate-recognition species concept to allow for post-mating isolation mechanisms; no matter whether populations can hybridize successfully, they are still distinct cohesion species if the amount of hybridization is insufficient to completely mix their respective <a linkindex="143" href="http://en.wikipedia.org/wiki/Gene_pool" title="Gene pool">gene pools</a>.</dd></dl> <dl><dt>Evolutionarily Significant Unit (ESU) </dt><dd>An <a set="yes" linkindex="144" href="http://en.wikipedia.org/wiki/Evolutionarily_significant_unit" title="Evolutionarily significant unit">evolutionarily significant unit</a> is a population of organisms that is considered distinct for purposes of conservation. Often referred to as a species or a <i>wildlife species</i>, an ESU also has several possible definitions, which coincide with definitions of species.</dd></dl> <p>In practice, these definitions often coincide, and the differences between them are more a matter of emphasis than of outright contradiction. Nevertheless, no species concept yet proposed is entirely objective, or can be applied in all cases without resorting to judgement. Given the complexity of life, some have argued that such an objective definition is in all likelihood impossible, and biologists should settle for the most practical definition. For most <a linkindex="145" href="http://en.wikipedia.org/wiki/Vertebrate" title="Vertebrate">vertebrates</a>, this is the biological species concept (BSC), and to a lesser extent (or for different purposes) the phylogenetic species concept (PSC). Many BSC <a linkindex="146" href="http://en.wikipedia.org/wiki/Subspecies" title="Subspecies">subspecies</a> are considered species under the PSC; the difference between the BSC and the PSC can be summed up insofar as that the BSC defines a species as a consequence of manifest evolutionary <i>history</i>, while the PSC defines a species as a consequence of manifest evolutionary <i>potential</i>. Thus, a PSC species is "made" as soon as an evolutionary lineage has started to separate, while a BSC species starts to exist only when the lineage separation is complete.</p></blockquote><p></p> <p><a name="Importance_in_biological_classification" id="Importance_in_biological_classification"></a></p> <h2><br /><span class="editsection"></span></h2>Another article from Wikipedia covers <a href="http://en.wikipedia.org/wiki/Species_problem">the species problem</a>. A historical review of the idea of the "species" is interesting. The idea of reproductive isolation is paramount.<br /><h2><span class="mw-headline"></span></h2><blockquote><h2><span class="mw-headline">Quotations on the species problem</span></h2> <p>"... I was much struck how entirely vague and arbitrary is the distinction between species and varieties" Darwin 1859 (p. 48)<sup id="_ref-darwin1859_1" class="reference"><a linkindex="133" href="http://en.wikipedia.org/wiki/Species_problem#_note-darwin1859" title="">[7]</a></sup></p> <p>"No term is more difficult to define than "species," and on no point are zoologists more divided than as to what should be understood by this word". Nicholson (1872) p. 20<sup id="_ref-nicholson1872_0" class="reference"><a linkindex="134" href="http://en.wikipedia.org/wiki/Species_problem#_note-nicholson1872" title="">[44]</a></sup></p> <p>"Of late, the futility of attempts to find a universally valid criterion for distinguishing species has come to be fairly generally, if reluctantly, recognized" Dobzhansky (1937) p.310 <sup id="_ref-dobzhansky1937_2" class="reference"><a linkindex="135" href="http://en.wikipedia.org/wiki/Species_problem#_note-dobzhansky1937" title="">[11]</a></sup></p> <p>"The concept of a species is a concession to our linguistic habits and neurological mechanisms" Haldane (1956) <sup id="_ref-haldane1956_1" class="reference"><a linkindex="136" href="http://en.wikipedia.org/wiki/Species_problem#_note-haldane1956" title="">[35]</a></sup></p> <p>"The species problem is the long-standing failure of biologists to agree on how we should identify species and how we should define the word 'species'." Hey (2001) <sup id="_ref-hey2001_1" class="reference"><a linkindex="137" href="http://en.wikipedia.org/wiki/Species_problem#_note-hey2001" title="">[39]</a></sup></p> <p>"First, the species problem is not primarily an empirical one, but it is rather fraught with philosophical questions that require-but cannot be settled by-empirical evidence." Pigliucci (2003) <sup id="_ref-pigliucci2003_1" class="reference"><a linkindex="138" href="http://en.wikipedia.org/wiki/Species_problem#_note-pigliucci2003" title="">[38]</a></sup></p></blockquote><p><sup id="_ref-pigliucci2003_1" class="reference"><a linkindex="138" href="http://en.wikipedia.org/wiki/Species_problem#_note-pigliucci2003" title=""></a></sup></p> <p><a name="See_also" id="See_also"></a></p> <h2><span class="editsection"><span style="font-size:130%;">Reproductive Isolation (Wikipedia):</span><br /></span> <span class="mw-headline"></span></h2><br /><h1 class="firstHeading">Reproductive isolation</h1> <h3 id="siteSub"></h3><h3 id="siteSub">Adapted from <a href="http://en.wikipedia.org">Wikipedia</a>, the free encyclopedia<br /></h3>(wikipedia also has an article on <a href="http://en.wikipedia.org/wiki/Speciation">Speciation</a>.<br /><br /><p>An important concept in evolutionary biology, <b>reproductive isolation</b> is a category of mechanisms that prevent two or more <a linkindex="3" href="http://en.wikipedia.org/wiki/Populations" title="Populations">populations</a> from exchanging genes. The separation of the <a linkindex="4" href="http://en.wikipedia.org/wiki/Gene_pool" title="Gene pool">gene pools</a> of populations, under some conditions, can lead to the genesis of distinct <a set="yes" linkindex="5" href="http://en.wikipedia.org/wiki/Species" title="Species">species</a>. Reproductive isolation can occur either by preventing <a linkindex="6" href="http://en.wikipedia.org/wiki/Fertilization" title="Fertilization">fertilization</a>, or by the creation of a degenerate or sterile <a linkindex="7" href="http://en.wikipedia.org/wiki/Hybrid" title="Hybrid">hybrid</a>, such as the case with the common <a linkindex="8" href="http://en.wikipedia.org/wiki/Mule" title="Mule">mule</a> and the <a linkindex="9" href="http://en.wikipedia.org/wiki/Hinny" title="Hinny">hinny</a>.</p> <div id="toctitle"><span class="toctoggle">Three sections:<br /></span></div> <ul><li class="toclevel-1"><a set="yes" linkindex="10" href="http://en.wikipedia.org/wiki/Reproductive_isolation#Fertilization_barriers_.28pre-zygotic.29"><span class="tocnumber">1</span> <span class="toctext">Fertilization barriers (pre-zygotic)</span></a></li></ul><p></p><blockquote><p>... Everything from a physical barrier (such as an ocean) formed between two populations, to ethological (behavioral) differences, to errors in cell division that cause incompatibility between populations.</p> <ol><li><a set="yes" linkindex="15" href="http://en.wikipedia.org/wiki/Speciation" title="Speciation">Speciation</a> by reproductive isolation is frequently seen in plants, with errors in division during <a linkindex="16" href="http://en.wikipedia.org/wiki/Mitosis" title="Mitosis">mitosis</a> doubling the number of <a set="yes" linkindex="17" href="http://en.wikipedia.org/wiki/Chromosome" title="Chromosome">chromosomes</a> and thereby preventing even pairing of chromosomes with normal <a set="yes" linkindex="18" href="http://en.wikipedia.org/wiki/Gamete" title="Gamete">gametes</a> during fertilization.<br /></li><li>For various species that <a set="yes" linkindex="19" href="http://en.wikipedia.org/wiki/Blossom" title="Blossom">bloom</a> seasonally, the time of gamete release can prevent hybridization, a temporal isolation.<br /></li><li>For animal species, mating might be stymied.<br /></li><ol><li>Incompatible <a linkindex="20" href="http://en.wikipedia.org/wiki/Genitalia" title="Genitalia">genitalia</a> forms a mechanical reproductive isolation,</li><li>members of opposite sexes often fail to recognize one another, due to some morphological difference used to identify a potential mate.</li></ol><li>The gametes of different species are frequently incompatible, and do not form a viable <a set="yes" linkindex="21" href="http://en.wikipedia.org/wiki/Zygote" title="Zygote">zygote</a>.<br /></li><ol><li>Sperm may not possess the proper enzymes for penetrating the coat of the <a linkindex="22" href="http://en.wikipedia.org/wiki/Ovum" title="Ovum">ovum</a>, or<br /></li><li>have the proper chemical markers to signal the egg cell to accept it.</li></ol></ol> </blockquote><p></p><br /><ul><li class="toclevel-1"><a set="yes" linkindex="11" href="http://en.wikipedia.org/wiki/Reproductive_isolation#Hybrid_barriers_.28post-zygotic.29"><span class="tocnumber">2</span> <span class="toctext">Hybrid barriers (post-zygotic)</span></a></li></ul><blockquote><ul><li>The first is gametic: the <a set="yes" linkindex="24" href="http://en.wikipedia.org/wiki/Gamete" title="Gamete">gametes</a> successfully combine, but then immediately die .<br /></li><li>The second is zygotic: the <a set="yes" linkindex="25" href="http://en.wikipedia.org/wiki/Zygote" title="Zygote">zygote</a> forms but quickly dies.<br /></li><li>The third is embryonic or larval: which is spontaneous abortion of the hybrid <a set="yes" linkindex="26" href="http://en.wikipedia.org/wiki/Fetus" title="Fetus">fetus</a>.<br /></li><li>The fourth is hybrid inviability: the offspring is born but is <a linkindex="27" href="http://en.wikipedia.org/wiki/Fitness_%28biology%29" title="Fitness (biology)">unfit</a>, quickly succumbs to environmental pressures, and dies.<br /></li><li>The fifth is hybrid sterility: the offspring can produce no offspring of its own, isolating its genes from both parental groups. Finally, hybrids that do produce offspring can, potentially, produce sterile progeny.</li></ul></blockquote><br /><ul><li class="toclevel-1"><a set="yes" linkindex="12" href="http://en.wikipedia.org/wiki/Reproductive_isolation#Interspersed_repeats"><span class="tocnumber">3</span> <span class="toctext">Interspersed repeats</span></a></li></ul><h1 class="abstract-heading"></h1> Genes move around on chromosomes, rendering the chromosomes incompatible.lngndvshttp://www.blogger.com/profile/11895574214946388277noreply@blogger.com0tag:blogger.com,1999:blog-3669393673555891144.post-61973944150746364082007-08-31T01:24:00.000-07:002007-08-31T06:27:26.151-07:00Digression 1: Vestigial structuresOne commonly cited evidence for evolution is <b><i>vestigial structures</i></b><i>. </i>Commonly cited vestigial structures are the pegs of snakes, remnants of ancestral legs; wings of flightless birds; and the human appendix.<br /><br />On Saipan was discovered in about 1995 a blind cave spider. Cave divers have come through Micronesia collecting cave fauna, including blind cave shrimps. We had been studying an evolution video---The Evidence for Evolution---and I needed to explain <b><i>vestigial structures</i></b>, one of the evidences for evolution.<br /><br />An article in <a href="http://en.wikipedia.org/">Wikipedia</a> about <b><a href="http://en.wikipedia.org/wiki/Vestigial_structure">vestigiality</a></b>.<br /><br />A burning question is how a vestigial structure loses its functional morphology. Blind cave-dwelling organisms, for example, have eyes, but they are mere suggestions of the functioning eyes of their close allies. How does that happen? What pressures result in this diminution of an organ?<br /><br />Darwin made some compelling arguments in <i>On the Origin of Species</i>, cited in the Wikipedia article noted above.<br /><br /><br /><br /><div align="center"><span style=";font-family:lucida grande;font-size:180%;" >Examples of vestigial structures. </span><br /><br /><div align="left">Here is a link to a <a href="http://www.livescience.com/animals/top10_vestigial_organs.html">Top Ten Useless Limbs and other vestigial organs</a>, including the nipples of the human male.<br /></div></div><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="http://www.biologycorner.com/resources/whale.gif"><img style="margin: 0pt 10px 10px 0pt; float: left; cursor: pointer;" src="http://www.biologycorner.com/resources/whale.gif" alt="" border="0" height="259" width="322" /></a><br /><br /><br />The leg bones of a whale.<br />(found at<br /><b><a href="http://school.discovery.com/quizzes6/muskopf/evolution1.html" target="_top">school.discovery.com/.../<wbr>muskopf/evolution1.html</a></b>)<br /><br /><br /><br /><br /><br /><br /><br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="http://www.geology.ohio-state.edu/%7Evonfrese/gs100/lect32/xfig32_05.jpg"><img style="margin: 0pt 0pt 10px 10px; float: right; cursor: pointer;" src="http://www.geology.ohio-state.edu/%7Evonfrese/gs100/lect32/xfig32_05.jpg" alt="" border="0" height="305" width="251" /></a><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br />Human Vestigial Structures --><br />(found at<br /><b><a href="http://www.geology.ohio-state.edu/%7Evonfrese/gs100/lect32/index.html" target="_top">www.geology.ohio-state.edu/.<wbr>../lect32/index.html</a></b>)<br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><br /><b><span style="font-size:130%;">A blind lobste<a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href="http://upload.wikimedia.org/wikipedia/en/thumb/9/99/Kiwahirsuta.jpg/250px-Kiwahirsuta.jpg"><img style="margin: 0pt 10px 10px 0pt; float: left; cursor: pointer; width: 200px;" src="http://upload.wikimedia.org/wikipedia/en/thumb/9/99/Kiwahirsuta.jpg/250px-Kiwahirsuta.jpg" alt="" border="0" /></a>r</span></b> was mentioned in the fascinating book <i>Within the Deep</i> found on Project Gutenberg: http://www.gutenberg.org/files/10617/10617-h/10617-h.htm. More recently is found a Wikipedia home page for <a href="http://en.wikipedia.org/wiki/Kiwa_hirsuta">a newly discovered deep sea hairy lobster, <i>Kiwa hirsuta</i></a>. The picture at left was found on that page.<br /><br />"The animal has strongly reduced eyes that lack <a href="http://en.wikipedia.org/wiki/Pigment" title="Pigment">pigment</a>, and is thought to be blind."<br /><br /><br /><b><span style="font-size:130%;">A vestigial gene</span></b>: (from http://www.bookrags.com/research/vestigial-structures-wap/)<br /><br /><p><span style="font-size:100%;">"Vestigial structures may also be molecular, as in the case of vestigial genes that exist in most species. For example, although humans cannot manufacture their own <a id="KonaLink1" target="_top" class="kLink" style="text-decoration: underline ! important; position: static;" href="http://www.bookrags.com/research/vestigial-structures-wap/#"><span style="color: rgb(103, 173, 6) ! important; font-weight: 400; position: static;font-family:Verdana,sans-serif;font-size:15;" ><span class="kLink" style="border-bottom: 1px solid rgb(103, 173, 6); color: rgb(103, 173, 6) ! important; font-weight: 400; position: static;font-family:Verdana,sans-serif;font-size:15;" >vitamin </span><span class="kLink" style="border-bottom: 1px solid rgb(103, 173, 6); color: rgb(103, 173, 6) ! important; font-weight: 400; position: static;font-family:Verdana,sans-serif;font-size:15;" >C</span></span></a>, most other mammals can because they possess a gene enabling them to produce an <a id="KonaLink2" target="_top" class="kLink" style="text-decoration: underline ! important; position: static;" href="http://www.bookrags.com/research/vestigial-structures-wap/#"><span style="color: rgb(103, 173, 6) ! important; font-weight: 400; position: static;font-family:Verdana,sans-serif;font-size:15;" ><span class="kLink" style="border-bottom: 1px solid rgb(103, 173, 6); color: rgb(103, 173, 6) ! important; font-weight: 400; position: static;font-family:Verdana,sans-serif;font-size:15;" >enzyme</span></span></a> (L-gulono-gamma-lactone oxidase) which in turn makes it possible for them to produce vitamin C. Humans possess a defective copy of this gene that does not produce the required enzyme (or any other product). This gene was presumably disabled by mutation at a time in primate evolution when its loss was not a significant disadvantage, and now remains as a vestigial genetic sequence."</span></p>lngndvshttp://www.blogger.com/profile/11895574214946388277noreply@blogger.com0