TAILIEUCHUNG - Linzey - Vertebrate Biology - Chapter 1
C H A P T E R 1 The Vertebrate Story: An Overview Life on Earth began some billion years ago when a series of reactions culminated in a molecule that could reproduce itself. Although life forms may exist elsewhere in our universe or even beyond, life as we know it occurs only on the planet Earth. | Linzey Vertebrate Biology 1. The Vertebrate Story An Text Overview The McGraw-Hill Companies 2003 CHAPTER 1 The Vertebrate Story An Overview INTRODUCTION Life on Earth began some billion years ago when a series of reactions culminated in a molecule that could reproduce itself. Although life forms may exist elsewhere in our universe or even beyond life as we know it occurs only on the planet Earth. From this beginning have arisen all of the vast variety of living organisms viruses bacteria fungi protozoans plants and multicellular animals that inhabit all parts of our planet. The diversity of life and the ability of life forms to adapt to seemingly harsh environments is astounding. Bacteria live in the hot thermal springs in Yellowstone National Park and in the deepest parts of the Pacific Ocean. Plants inhabit the oceans to the lower limit of light penetration and also cover land areas from the tropics to the icepacks in both the Northern and Southern Hemispheres. Unicellular and multicellular animals are found worldwide. Life on Earth is truly amazing Our knowledge of the processes that create and sustain life has grown over the years and continues to grow steadily as new discoveries are announced by scientists. But much remains to be discovered new species new drugs improved understanding of basic processes and much more. All forms oflife are classified into five major groups known as kingdoms. The generally recognized kingdoms are Mon-era bacteria Fungi fungi Protista single-celled organisms Plant plants and Animal multicellular animals . Within each kingdom each group of organisms with similar characteristics is classified into a category known as a phylum. Whereas many members of the Animal kingdom possess skeletal muscular digestive respiratory nervous and reproductive systems there is only one group of multicellular animals that possess the following combination of structures 1 a dorsal hollow nerve cord 2 a flexible supportive rod notochord running .
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