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Chapter 14 – Classification 14:1 The Concept of Classification - the classification system provides order and logic The Need for Classifying Organisms - Taxa – biological categories - taxanomy – the science of classification - New organisms are continually being discovered. - Common names – not enough – can be confusing or sometimes too general - ex – worm – What is it? - ex – cougar, puma, panther, mountain lion – All are common names for the same organism - the need for scientific names became clear. - Scientific names are now in the Latin language Binomial Nomenclature - Aristole’s System – 2 groups: plants and animals - Plants – classified by structure and size: 1) herbs 2) shrubs 3) trees - Animals – classified by where they live: 1) air 2) land 3) sea - *each system should be based on one characteristic – some basis for all groupings - 18th century – Carolus Linnaeus – Came up with a classification system based only on structure - Linnaeus said each type of organism was a different species. - Different features – different species - *Linnaeus is also well know because he introduced a two-part system called binomial nomenclature for naming and classifying organisms. - Each organism is given a two word name - Binomial Nomenclature – - 1st word – a noun – genus to which the organism belongs ex – felis - 2nd word – an adjective – the specific name - together the genus and specific name tell the species name & scientific name of the organism. - *A single genus may contain many different species. - ex – Genus Felis - Felis sylvestris – wildcat Felis pardalis – ocelot Felis concolor – cougar Felis catus – house cat - Also for plants – ex – Quercus alba – white oak Quercus ruba – red oak The genus name can be abbreviated – ex – Q. ruba Determining Relationships - Theory of Evolution and theory of natural selection were both helpful to the science of taxonomy. - Classification is now based on ancestry of organisms. ex – cats – all same genus – have a common ancestor Classifying Based on Structure - Lines of evidence – 1) Fossil record 2) Homologous structure - Linnaeus used homologous structures to group organisms without really knowing it. - By doing this, he was grouping on the basis of evolutionary relationships - ex – Fossil record of horse – shows nearly the complete fossil record of the evolution of the horse - Sometimes the fossil record is incomplete and causes scientists to be mislead. Classifying Using Biochemistry & Development - Use of microscope and other tools – scientists had new information to use. - Comparative Embryology – shows that vertebrates are more closely related to Echinoderms (starfish) than other invertebrates – Looking only at adult forms this would not appear to be true. - Biochemistry – helped identify horseshoe crab closer to spiders than the crab Classifying on a Molecular Basis - Looking at organisms DNA or genes, or proteins. - *Organisms having many proteins or genes in common are closely related. - ex – guinea pigs – were classified with rodents (mice, rat, squirrels) but closer study of their proteins showed they were not closely related. Instead, they are now classified in a group of its own. - Using DNA studies, scientists have determined that chimpanzees and humans began to evolve from a common ancestor only 5 million years ago. - *Possible study of ancient DNA may tell scientists more about extinct animals. - ex – dinosaurs – may find DNA in dinosaur blood of a biting insect if the insect was trapped in specific conditions. Phylogeny – “evolutionary history” - ex – History of Giant Panda – Western Asia - 1869 - first classified with the bears – then with the raccoons - using DNA studies scientists learned that the giant panda is more closely related to the bears - A closer look at enzymes & proteins led to the same conclusion. Fig. 14-10 pg. 375 14:2 A System of Classification Taxa - categories in the biological classification system. - there are 7 different taxa (categories) 1) Kingdom – largest – broadest 2) Phylum 3) Class 4) Order 5) Family 6) Genus 7) Species – smallest – most specific – one type of organism. a subspecies – sometimes called breeds, varieties, or race Some Examples of Classification House Cat – Animal Kingdom – can’t make its own food Phylum Chordata – has a backbone – Subphylum – vertebrate Class Mammalia – has mammary glands, hair Order Carnivora – meat eating Family Felidae Genus Felis Species Felis catus Comparisons – pg. 377 Cat, Dog, Human, Grasshopper The Kingdom Problem - Most biologists use the 5 kingdom system - 1) Monerans 2) Protists 3) Fungi 4) Plants 5) Animals - Early classification systems – used only 2 kingdoms – 1) plants 2) animals - Microscopic organisms became a problem for biologists to classify – They didn’t fit well into either group – ex - Euglena - Euglena – mobile – like an animal autotrophic – like a plant - Can lose its chlorophyll and become heterotrophic - ex 2 – Fungi – can’t move – plant like heterotrophic – animal like - Sponges, Sea Anemones and Coral – All animals but they look more like plants. - The 5 kingdom classification system is not perfect. Biologists still have trouble with some organisms. - All monerans are prokaryotes. - One proposed new system involves 6 kingdoms. - The 6th kingdom includes ancient bacteria. - This book will use the 5 kingdom system.
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