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Evolution

2 3 Lifes Great famiLy the fog rises Amidst the foggy ideas of past centuries there arose occasional glimpses of a strange new notion that humanity, along with all other organisms, instead of being created outright, had instead arisen through a process of biological adaptationevolution. Publishing Systema Naturae in 1735, Carl Linnaeus 170778 replaced the classical categorization of animals by their mode of movement, with the system of kingdoms, phyla, classes, orders, families, genera and species still used today. It seemed evident that these families of animals and plants had evolved in some way from common ancestors, or from one another, and by the 1800s scientists were trying to work out exactly how. In 1809 JeanBaptiste Lamarck 1744 1829 proposed that species evolved via acquired characteristics, so that subtle and often useful changes made to their design during their own lifetimes e.g., a tennis players better developed arm muscles were passed on to their offspring. This theory, however, although popular, had serious flaws. It turned out that offspring often varied wildly from their parents, and, importantly, that characteristics acquired over a lifetime, such as injuries or larger muscles, could not be passed down the generations either. The theory was not working. Something was missing. Right Ernst Haeckels original tree of life, drawn in 1866, dividing living things into three basic groups, plants, animals and protists a diverse group of eukaryotes, or multicellular organisms, which do not fit into the other eukaryotic kingdoms. Haeckel coined the term protist for this diagram. Modern classifications vary from this diagram in certain important ways e.g. fungi are today considered a kingdom of their own. To see the modern versions of the tree of life, turn to the end pages of this book pages 5058. Left An early Linnaean tree of life, the kingdoms shown as a hierarchy with mammals at the top, and man at the summit. Although a breakthrough, these early versions were not so very far from the medieval Chain of Being, the hierachy of souls, with God at the top, then angels, humans, animals, vegetables and finally minerals, each kingdom having natural authority over and control of those beneath it.
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