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HMS Beagle The second voyage of HMS Beagle from 27 December 1831.

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Presentation on theme: "HMS Beagle The second voyage of HMS Beagle from 27 December 1831."— Presentation transcript:

1 HMS Beagle The second voyage of HMS Beagle from 27 December 1831 to 2 October 1836 was the second survey expedition of HMS Beagle Captain Robert FitzRoy accompanied by a student clergyman Charles Darwin Darwin made his name as a naturalist and became a renowned author with the publication of his journal which became known as The Voyage of the Beagle. The Beagle sailed across the Atlantic Ocean then carried out detailed hydrographic surveys around the coasts of the southern part of South America, returning via Tahiti and Australia having circumnavigated the Earth. While the expedition was originally planned to last two years, it lasted almost five. Born 12 Feb 1809 Medicine (Edinburgh University), Theology (Cambridge) 1859, publication of The Origin of Species

2 “The Beagle sailed round Chatham Island, and anchored in several bays. One night I slept on shore on a part of the island, where black truncated cones were extraordinarily numerous: from one small eminence I counted sixty of them, all surmounted by craters more or less perfect. The greater number consisted merely of a ring of red scoriae or slags, cemented together: and their height above the plain of lava was not more than from fifty to a hundred feet; none had been very lately active.” Download The Voyage of The Beagle from Project Gutenberg “The natural history of these islands is eminently curious, and well deserves attention. Most of the organic productions are aboriginal creations, found nowhere else; there is even a difference between the inhabitants of the different islands; yet all show a marked relationship with those of America, though separated from that continent by an open space of ocean, between 500 and 600 miles in width. The archipelago is a little world within itself, or rather a satellite attached to America, whence it has derived a few stray colonists, and has received the general character of its indigenous productions.” The Galapagos Account

3 “I have not as yet noticed by far the most remarkable feature in the natural history of this archipelago; it is, that the different islands to a considerable extent are inhabited by a different set of beings. My attention was first called to this fact by the Vice-Governor, Mr. Lawson, declaring that the tortoises differed from the different islands, and that he could with certainty tell from which island any one was brought.” Nesting Activity Darwin’s Checklist 1. Frogs – none! 2. Toads – none! 3. Lizards 4. Tortoises We will now turn to the order of reptiles, which gives the most striking character to the zoology of these islands. The species are not numerous, but the numbers of individuals of each species are extraordinarily great. Diet Adaptation

4 “When on board H.M.S. Beagle, as naturalist, I was much struck with certain facts in the distribution of the organic beings inhabiting South America, and in the geological relations of the present to the past inhabitants of that continent. These facts, as will be seen in the latter chapters of this volume, seemed to throw some light on the origin of species—that mystery of mysteries, as it has been called by one of our greatest philosophers. On my return home, it occurred to me, in 1837, that something might perhaps be made out on this question by patiently accumulating and reflecting on all sorts of facts which could possibly have any bearing on it. After five years' work I allowed myself to speculate on the subject, and drew up some short notes;” Introduction, “The Origin of The Species”


6 Natural Selection Predator-Prey Predator-Prey Survival of the Fittest Survival of the Fittest /wildlife/wolf,_gray.php Transmission of Traits Transmission of Traits

7 We behold the face of nature bright with gladness, we often see superabundance of food; we do not see or we forget that the birds which are idly singing round us mostly live on insects or seeds, and are thus constantly destroying life; or we forget how largely these songsters, or their eggs, or their nestlings, are destroyed by birds and beasts of prey; we do not always bear in mind, that, though food may be now superabundant, it is not so at all seasons of each recurring year.” Darwin, on discussing the struggle for existence in The Origin of Species

8 To keep our model simple, we will make some assumptions that would be unrealistic in most of these predator- prey situations. 1.the predator species is totally dependent on a single prey species as its only food supply, 2.the prey species has an unlimited food supply, and 3.there is no threat to the prey other than the specific predator. lions and gazelles birds and insects pandas and eucalyptus trees Venus fly traps and flies

9 Percentages of predators in the Fiume fish catch Vito Volterra ( ) was a famous Italian mathematician who retired from a distinguished career in pure mathematics in the early 1920s. His son-in-law, Humberto D'Ancona, was a biologist who studied the populations of various species of fish in the Adriatic Sea. In 1926 D'Ancona completed a statistical study of the numbers of each species sold on the fish markets of three ports: Fiume, Trieste, and Venice. The percentages of predator species (sharks, skates, rays, etc.) in the Fiume catch are shown in the above table. Alfred J. Lotka ( ) was an American mathematical biologist (and later actuary) who formulated many of the same models as Volterra, independently and at about the same time. His primary example of a predator- prey system comprised a plant population and an herbivorous animal dependent on that plant for food.

10 Prey Population = x(t) No predators: dx/dt = a x Predators exist: Predator Population = y(t) Encounters jointly proportional to xy : Thus  dx/dt = ax – bxy Let’s consider the predators y(t). No prey means: dy/dt =  cy But with food… dy/dt =  cy + pxy dx/dt = ax – bxy dy/dt =  cy + pxy

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