It was once assumed that all living things could be divided into two fundamental and exhaustive categories. Multicellular plants and animals, as well as many unicellular organisms, are eukaryotic—their large, complex cells have a well-formed nucleus and many organelles. On the other hand, the true bacteria are prokaryotic cell, which are simple and lack a nucleus. The distinction between eukaryotes and bacteria, initially defined in terms of subcellular structures visible with a microscope, was ultimately carried to the molecular level. Here prokaryotic and eukaryotic cells have many features in common. For instance, they translate genetic information into proteins according to the same type of genetic coding. But even where the molecular processes are the same, the details in the two forms are different and characteristic of the respective forms. For example, the amino acid sequences of various enzymes tend to be typically prokaryotic or eukaryotic. The differences between the groups and the similarities within each group made it seem certain to most biologists that the tree of life had only two stems. Moreover, arguments pointing out the extent of both structural and functional differences between eukaryotes and true bacteria convinced many biologists that the precursors of the eukaryotes must have diverged from the common ancestor before the bacteria arose. Although much of this picture has been sustained by more recent research, it seems fundamentally wrong in one respect. Among the bacteria, there are organisms that are significantly different both from the cells of eukaryotes and from the true bacteria, and it now appears that there are three stems in the tree of life. New techniques for determining the molecular sequence of the RNA of organisms have produced evolutionary information about the degree to which organisms are related, the time since they diverged from a common ancestor, and the reconstruction of ancestral versions of genes. These techniques have strongly suggested that although the true bacteria indeed form a large coherent group, certain other bacteria, the archaebacteria, which are also prokaryotes and which resemble true bacteria, represent a distinct evolutionary branch that far antedates the common ancestor of all true bacteria
To bring fresh water to the city, his hydraulic engineer, EugèneBelgrand, built a new aqueduct to bring clean water from the Vanne River in Champagne, and a new huge reservoir near the future ParcMontsouris. These two works increased the water supply of Paris from 87,000 to 400,000 cubic meters of water a day. He laid hundreds of kilometers of pipes to distribute the water throughout the city, and built a second network, using the less-clean water from the Ourq and the Seine, to wash the streets and water the new park and gardens.
The population of Paris had doubled since 1815, with no increase in its area. To accommodate the growing population and those who would be forced from the center by the new boulevards and squares Napoleon III planned to build, he issued a decree annexing eleven surrounding communes, and increasing the number of arrondissements from twelve to twenty, which enlarged the city to its modern boundaries. Beginning in 1854, in the centre of the city,
Haussmann’s workers tore down hundreds of old buildings and cut eighty kilometres of new avenues, connecting the central points of the city. Buildings along these avenues were required to be the same height and in a similar style, and to be faced with cream-coloured stone, creating the signature look of Paris boulevards.
Napoleon III also wanted to build new parks and gardens for the recreation and relaxation of the Parisians, particularly those in the new neighbourhoods of the expanding city, ]Napoleon Ill’s new parks were inspired by his memories of the parks in London, especially Hyde Park, where he had strolled and promenaded in a carriage while in exile; but he wanted to build on a much larger scale. Working with Haussmann and Jean-Charles Alphand, the engineer who headed the new Service of Promenades and Plantations, he laid out a plan for four major parks at the cardinal points of the compass around the city. Thousands of workers and gardeners began to dig lakes, build cascades, plant lawns, flowerbeds and trees, construct chalets and grottoes. Napoleon III created the Bois de Boulogne (1852-1858) to the west of Paris: the Bois de Vincennes (1860-1865) to the east; the Parc des Buttes-Chaumont (1865-1867) to the north, and ParcMontsouris (1865-1878) to the south