Read the article Dawkins (2004) The Salamander\'s Tail And come out with 4 Quest

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Read the article Dawkins (2004) The Salamander's Tail

And come out with 4 Questions to discuss in class?

I we Article 21 . If we must ceived r point hereas s proof The Salamander's Tale RICHARD DAWKINS Non-interbreeding is the recognised criterion for whether two secret that palaeontology is a controversial subject in populations deserve distinct species names. It therefore should which there are even some personal enmities. At least be straightforward to use the name Ensatina eschscholtzii for of Contention are in print. And if you the plain western species and Ensatina klauberi for the blotched ook at what two palacontologists are quarrelling about, as often eastern species-straightforward but for one remarkable circum ames are a menace in evolutionary history. It is no S, or stance, which is the nub of the tale. If you go up to the mountains that bound the north end of lis or a late Australopithecus? People evidently feel strongly he Central Valley, which up there is called the Sacramento Val about such questions they often turn out to be splitting hairs ley, you' find only one species of Ensatina. Its appearance Indeed, they resemble theological questions, which I suppose intermediate between the blotched and the plain species es a clue to why they arouse such passionate disagreements mostly brown, with rather indistinct blotches is not a hybrid The Obsession with discrete names is an example of what I call between the two: that is the wrong way to look at it. To discover the tyranny of the discontinuous mind. The Salamander's Tale the right way, make two expeditions south, sampling the sala- s it an archaic Homo sapiens? Is this one an early Homo habi strikes a blow against the discontinuous mind. mander populations as they fork to west and east on either sid The Central Valley runs much of the length of Califoria of Central Valley. On the east side, they become progressi bound the Coastal Range to the west and by the Sierra Nevada more pitched until they reach the extreme of klauberi in the far to the east. These long mountain ranges link up at the north south. On the west side, the salamanders become progressively and the south ends of the valley, which is therefore surrounded more like the plain escholtzii that we met in the zone of overlap at Camp Wolahi. by high ground. Throughout this high ground lives a genus of salamanders called Ensatina. The Central Valley itself, about This is why i is hard to treat Ensatina eschscholtzii and 40 miles wide, s not friendly to salamanders, and they are not Ensatina klauberi with confidence as separate species. They found there. They can move all round the valley but normally constitute a ring species'. You'l recognise them as separate not across it, in an elongated ring of more or less continuous species if you only sample in the south. Move north, however population. In practice any one salamander's short legs in its and they gradually turn into each other. Zoogists normally follow short lifetime don't carry it far from its birthplace. But genes Stebbins's lead and place them all in the same species, Ensatina persisting through a longer timescale are another matter. Indi- eschscholtzii, but give them a range of subspecies names. Start vidual salamanders can interbreed with neighbours whose par ing in the far south with Ensatina eschscholtzii eschscholtzi, ents may have interbred with neighbours further round the ring, the plain brown form, we move up the west side of the val and so on. There is therefore potentially gene flow all around the ley through Ensatina eschscholtzii xanthoptica and Ensatina ring. Potentially. What happens in practice has been elegantly esckschoirzii oregonensis which as its name suggests, is also worked out by the research of my old colleagues at the Univerfound further north in Oregon and Washington. At the north end of California at Berkeley, initiated by Robert Stebbins and of California's Central Valley is Ensatina eschscholtzii picta, continued by David Wake the semi-blotched form mentioned before. Moving on rou In a study area called Camp Wolahi, in the mountains tothe ring and down the east side of the valley, we pass through the south of the valley, there are two clearly distinct species of Ensatina eschscholtzii platensis which is a bit more blotched Ensatina which do not interbreed. One is conspicuously marked th picta, then Ensatina eschscholtzii croceater until we reach with yellow and black blotches. The other is a uniform light Ensatina eschsd klauberi (which is the very blotched one that brown with no blotches. Camp Wolahi is in a zone of overlap, we previously called Ensatina klauberi when we were consider ng it to be a separate species) but wider sampling shows that the blotched species is typical of tern side of the Central Valley which, here in Southern Stebbins believes that the ancestors of Ensatina arrived at the California, is known as the San Joaqin Valley. The light bwn north end of the Central Valley and evolved gradually down the species, on the contrary, is typically found on the western side two sides the valley, diverging as they went. An alternative pos- sibility is that started in the south as, say, Ensatina eschscholtzii of the San Joaquin.

Explanation / Answer

Why the two salamander species Ensatina Klauberi and Ensatina eschscholezii are considered as ring species? Are they two different species-Explain with reasons? When is a situation declared as an epidemic? Is it right to consider obesity as an epidemic disease? How the continuities of gene flow restricts the speciation process? How geographical barriers play a vital role here? How time barrier play role in human evolution?

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