The Classification of Organisms

Transcription

1 Biology Chapter 8 The Classification of Organisms 8A - The Necessity of Classifying People group things together for convenience. (spices, pans, tools, instruments in orchestra) Taxonomy (or systematics) from Greek taxis arrangement, order definition- arranging organisms into groups based on similarities (the science of classifying organisms into groups.) Why do we need a biological classification system? 1)It is necessary for accurate communication among scientists. -Quite often a common name applies to several different organisms. -"gophers" salamander, turtle, frog, snake, large rodent (50 types) 2)It allows information about organisms to be studied and used in an organized way. -Taxonomist has over 1 million different kinds of organisms to group -approximately 5,200 species are being discovered and added to the classification system each year The Classification Hierarchy first recorded classification of organisms was attempted by Aristotle: Greek scientist and philosopher He classified living organisms into 1 of 3 plant or 3 animal groups: PLANTS 1)Herbs- if they lacked woody parts 2)Shrubs- if they had several short woody stems 3)Trees- 1 large, woody stem ANIMALS 1)Fish- lived in water 2)Birds- if the could fly 3)Land animals- those that lived on land Artificial classification system- based on appearance Aristotle's system was used for approximately 2,000 years. Mid 1700's Carolus Linnaeus, a Swedish naturalist, set forth a new classification system also based on appearance.

2 10 th BiologyChapter 8 / The Classification of Organisms 2 Linnaeus developed his classification system using some ideas of John Ray an English clergyman who devoted much of his time to natural studies and became very well known for his work with plants. It was John Ray who clarified the concept of species. In 1691, toward the end of his career, John Ray published a book called The Wisdom of God Manifested in the Creation. In this book, which became very popular and was translated into several languages, Ray illustrated the wisdom of God by describing the design in nature. This work by John Ray became a foundation for Linnaeus's study. Linnaeus published his findings in 2 books: Species Plantarum- dealing with plants (1753) Systema Naturae- dealing with animals (1758) -Linnaeus' system is still used today. -It's flexible and it has had some changes. - International scientific committees meet every few years to decide questions of taxonomy and recommend changes in the classification system. Today's System of Classification 7 basic levels in the modern classification hierarchy: Kingdom, phylum, class, order, family, genus, species -The outline moves from general to specific. -The kingdoms are general groups that include many animals or plants. -The species are specific groups that usually include only 1 or a very few organisms. General rules for using the biological classification hierarchy: 1) Each group on one level of the hierarchy may be divided into several groups on the next lower level. 2) Each group in the hierarchy has various characteristics that all of the levels under the group possess. 3) Each level of the hierarchy can be divided into various smaller units before reaching the next lower level. see p. 222 [Example: subphyla sub(below) infra(below) supra(above) ] The There is a disagreement among taxonomists as to the number of kingdoms that exist. Aristotle- 2 main divisions: plants and animals Linnaeus- 2 groups: Kingdom Plantae and Kingdom Animalia Linnaeus did not include people in his classification scheme because he recognized their special creation in the image of God. These men had no knowledge of microscopic organisms.

3 10 th BiologyChapter 8 / The Classification of Organisms 3 Two Linnaeus 1750's (Traditiona l) 1.PLANTAE Vascular plants Bryopgytes True fungi Slime molds Algae Prochlorophytes 2 Blue-green algae Bacteria 2.ANIMALIA Multicellular animals Protozoa Sponges Three kingdoms Hogg and Haeckel 1860's Four Copeland 1930's Five Whittaker 1960's Two Superkingdoms, Four Parker, Corliss, and Bock 1980's 1.PLANTAE 1.PLANTAE 1.PLANTAE Superkingdom Eukaryotae 3 See p Know the material on the chart on p A-5 Scientific Names Binomial Nomenclature: a system of naming an organism with two names. binomial-"two names" nomenclature-"naming" Carolus Linnaus proposed and consistently used this system. Linnaus used Latin and Latinized Greek-the scientific languages of this day Why did Linnaus use Latin? 1) unchanging (since it was no longer in use it would not change) 2) descriptive (many Latin words were very well suited for describing the traits of organism) 3) a root of many modern languages (Latin was under by the scientist of all countries)

4 10 th BiologyChapter 8 / The Classification of Organisms 4 see p Know the material in the chart p a-5 Scientific Names: binomial "2-name" nomenclature "naming" def.- a system of naming organisms in which each organism is given a genus species name. Carolus Linnaius proposed and consistently used this system. Linnaius used Latin and Latinized Greek ( the scientific language of his day) Why did Linnaius choose Latin? (1)unchanging (since it was no longer in use it would not change) (2)descriptive (many Latin words were very well suited for describing the traits) (3)a root of many modern languages ( Latin was understood by the scientist of all countries) genus- species names The scientific name of an organism's is actually the name of the genus to which it belongs and the species which it is in. Because it's a foreign term it is printed in italics; if written or typed the name is underlined. Only the genus name is usually a noun and the species name an adjective. Linnaius used the genus and species name in much the same way that your own family and given names are used (1)To tell what family you are a member (2)TO distinguish you from all the other members of your family varieties- different forms or types of organisms within a species. Read pp B - The Species and the Kind Species def. - a group of similar organisms Two commonly accepted parts of the def. of a species: 1. Members of a species are structurally similar but do have a degree of variation. 2. Members of a species can interbreed and produce fertile offspring under natural conditions. Problems with the species concept: Artificial characteristics Why is there a problem with grouping members of a species by physical characteristics? Environment can greatly affect physical appearance (example: p. 228 tiger salamander and axolotls - lacked iodine) Problems with species concept: Interbreeding Why is there a problem with grouping members of a species on the basis of interbreeding? 1. Many organisms reproduce by means other than sexual reproduction. (example: bacteria and some protozoans don't reproduce sexually)

5 10 th BiologyChapter 8 / The Classification of Organisms 5 2. After many generations of breeding, the offspring of one ecotype may be able to interbreed with another ecotype that it normally would not have been able to breed with. (example: chihuahua and St. Bernard, see p. 229; also Rana pipiens - green, spotted grass frog) Ecotype - organisms that appear the same but are suited for one environment rather than another and often cannot interbred. The Key to keep in mind "the classification of organisms was done by man for convenience" The Biblical "Kind" Gen. 1:9-25 tells us that the organisms God created were designed to reproduce "after its kind." Kind - Hebrew: min means group of organisms that can interbreed freely in nature What is the primary characteristic which would place an organism into a biblical kind? The ability to reproduce Read pp and Natural system of classification - based on genetic similarities Evolutionists emphasize migration, adaptation, and selection since they are crucial parts of their theory. (They do happen but evolutionists twist them around to fit their need.) Migration - the moving of organisms from one area to another Adaptation - according to evolutionists, the change of an organism that enables it to survive in a new environment. (Resembles Lamarck's theories of need, use and disuse, and inheritance of acquired characteristics.) Selection - nonrandom mating Evolutionists state that migration and selection bring about a new species. They combine this with adaptation to claim the development of a new species. migration, selection, & adaptation: do not produce or develop new genes or new species. They only account for rearrangement and selection of already existing ones. (The 8 people on the ark are the ancestors of all people alive today.)