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LECTURE 4 CLASSIFYING THE DIVERSITY OF LIFE Classifying Living Organisms •Number of species known to science is approximately 1.8 million •To name organisms, biologists use a multilevel grouping of individuals: classification •Organisms were first classified more than 2,000 years ago by Aristotle –Living things were either plants or animals Carolus Linnaeus (1707-1778) The “father” of taxonomy •Binomial nomenclature •Hierarchical system of classification: large groups share general characteristics, and small groups share many characteristics kingdoms phyla classes orders families genera species Higher Categories •Taxonomists use a hierarchical system to classify organisms Classifying the Diversity Life Different approaches to classifying living organisms 1.10 Three Domain System Bacteria - prokaryotes Archaea - prokaryotes Eukarya - eukaryotes 2 Biological Classification: Domains and Kingdoms  Table 12.02 Bacteria and Archaea • form two of the three domains of the tree of life -are everywhere -found on every square centimeter of the earth’s surface, even inside deep sea vents, far underground, and in clouds -1 gram of soil has > 10,000 bacterial types; billions of cells - 500 species of prokaryotes live in your mouth -1013 cells in your body -1012 bacterial cells live on your skin -1014 bacterial and archaeal cells live in your stomach and intestine Prokaryotes - most abundant organisms on earth - play critical roles throughout the biosphere - decompose organic matter in sewage • cyanobacteria – • rhizobium – • bioremediation – • some bacteria are pathogenic 1.10 Prokaryotes can be extremists! Thermophiles: up to 300˚C Acidophiles : pH 1 - 2 Alkalophiles: pH 9 – 11 Halophiles: up to 30% salt Barophiles: high pressure Pyschrophiles: extreme cold The Diversity of Life - Animalia (a) Ant (Pseudomyrmex triplarinus) Potential source of arthritis treatment (b) Jellyfish (Aequorea victoria) Source of f luorescent protein, a useful labeling tool in microbiology (c) Horseshoe crab (Limulus polyphemus) Source of blood proteins used to test for pathogens in humans vertebrates only account for ~4% of animals invertebrates are far more numerous and diverse many invertebrates produce compounds found nowhere else in nature 3 The Diversity of Life - Plantae –Source of most naturally derived drugs –Aspirin –Digitalis –Morphine –Caffeine •Sources of pharmaceutical products: hundreds of compounds first found in plants  Table 12.06 The Diversity of Life - Fungi •hyphae of fungi can extend over a very large area Fungi produce a number of important drugs Antibiotics Cyclosporin Statins Diversity of Life - Protista –Protists are the simplest of the eukaryotes –oldest eukaryotic fossils are ~2
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