CLASSIFICATION OF LIVING THINGS

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2 CLASSIFICATION OF LIVING THINGS 1. Taxonomy The branch of biology that deals with the classification of living organisms About 1.8 million species of plants and animals have been identified. Some scientists estimate that there may be as many as 5-50 million species! How do we keep track of them all? 2. History of Classification Aristotle was a Greek philosopher in the 4 th century B.C. who developed the first classification scheme. Classified organisms as either plants or animals using the environment they lived in as a basis for grouping. In the eighteenth century, a Swedish botanist, Carl von Linne improved the work of previous taxonomists and created a classification system based on structural similarities among organisms that separate them into categories. He developed scientific names for each organism in Latin & disposed of common names. He even Latinized his name to Carolus Linnaeus to sell his idea! Linnaeus used two words to name each organism, thus his naming system is known as binomial nomenclature. 3. Naming Organisms Linnaeus named each organism with a genus name followed by a species name. a) Genus Name - Is the first part of the name of an organism - Is always a noun - Always begins with a CAPITAL letter. b) Species Name - Is the second part of the name - Is always an adjective - Always begins with a small letter - **The genus and species name is always italicized or underlined Examples: Homo sapien = modern man; Canis familiaris = dog ** These can also be abbreviated (H. sapien, C. familiaris,)

3 4. Why Use Scientific Names? Because they are in Latin a) It is a dead language b) It is the universal language of scholars c) It has many descriptive words d) Words can be invented for newly discovered organisms e) Impossible to duplicate a name Relationships between organisms are obvious from their names. Examples: Canis familiaris = dog, Canis lupus = wolf Eliminates the use of common names which can be confusing and misleading. Examples: jackfish, jellyfish, silverfish, starfish (1 st is the only fish) cougar, mountain lion, panther (all the same animal) 5.The Linnaean System of Classification Organisms are classified based on structural similarities through 7 levels with Linnaeus binomial nomenclature forming the bottom 2 divisions. The 7 levels are: Kingdom, Phylum, Class, Order, Family, Genus, Species These levels begin with general characteristics and become more specific as we descend through the categories. (p. 488)

4 6. Modern Classification Taxonomists have expanded on Linnaeus classification system. Why? a) Linneaus system does not take into account convergent evolution b) As scientists discovered new organisms their ideas about what characteristics are important in classifying organisms changed. c) Technological advances have allowed scientists to compare organisms on the molecular level to determine similarities. (ie. DNA, amino acids) Based on molecular evidence organisms are now classified into 3 domains: Bacteria, Archaea, and Eukarya Within these domains are 6 kingdoms based on cell type, structure, and nutrition: Archaebacteria, Bacteria, Protista, Fungi, Plants, and Animals Prokaryote without a nucleus or other membrane-bound organelles Eukaryote contains membranebound nucleus and organelles

5 The 6 Kingdoms Number of Cells Energy Cell Type Examples Archaebacteria Unicellular some autotrophic, most chemotrophic prokaryote "extremophiles" Eubacteria Unicellular autotrophic and heterotrophic prokaryote bacteria, E. coli Protista most unicellular heterotrophic or autotrophic eukaryote ameba, paramecium, algae Fungae most multicellular Heterotrophic eukaryote mushrooms, yeast Plantae Multicellular Autotrophic eukaryote trees, grass Animalia Multicellular Heterotrophic eukaryote humans, insects, worms

6 7. Phylogeny The term phylogeny refers to the evolution or historical development of any species. This development can be represented through scientific diagrams called cladograms. Cladograms use derived characters to determine evolutionary relationships - the more closely related species are, the more derived characters they will share (p. 495) Cladograms should not be seen as evolutionary fact, but only as a possible path for speciation. Example: Cladogram for the Phylum Chordata The relationship between the six kingdoms is illustrated in a phylogenetic tree, a branching cladogram that shows relationships between species from an evolutionary perspective. The ancestor is in the tree trunk and organisms that have arisen from it are placed at the ends of tree branches. Branch lengths are proportional to the predicted evolutionary time between organisms. (p. 503)

7 Example: Phylogenetic Tree of Life

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10 CLASSIFICATION OF LIVING THINGS 1. Taxonomy The branch of biology that deals with the About species of plants and animals have been identified. Some scientists estimate that there may be as many as species! How do we keep track of them all? 2. History of Classification was a Greek philosopher in the 4 th century B.C. who developed the first classification scheme. Classified organisms as either or using the as a basis for grouping. In the eighteenth century, a Swedish botanist, improved the work of previous taxonomists and created a classification system based on similarities among organisms that separate them into categories. He developed for each organism in Latin and disposed of. He even Latinized his name to to sell his idea! Linnaeus used two words to name each organism, thus his naming system is known as. 3. Naming Organisms Linnaeus named each organism with a name followed by a name. a) Genus Name - Is the part of the name of an organism - Is always a - Always begins with a letter. b) Species Name - Is the part of the name - Is always an - Always begins with a letter **The genus and species name is always italicized or underlined Examples: ** These can also be abbreviated (H. sapien, C. familiaris, C. lupus) 4. Why Use Scientific Names? Because they are in Latin a) It is a language b) It is the language of scholars c) It has many

11 d) Words can be for newly discovered organisms e) to duplicate a name between organisms are obvious from their names. Examples: Eliminates the use of which can be confusing and misleading. Examples: 5. The Linnaean System of Classification Organisms are classified based on through 7 levels with Linnaeus binomial nomenclature forming the bottom 2 divisions. The 7 levels are: These levels begin with and become more as we descend through the categories. (p. 488) 6. Modern Classification Taxonomists have expanded on Linnaeus classification system. Why? a) Linneaus system does not take into account b) As scientists discovered new organisms their ideas about what characteristics are important in classifying organisms changed. c) Technological advances have allowed scientists to compare organisms on the to determine similarities. (ie. DNA, amino acids)

12 Based on organisms are now classified into 3 domains: Bacteria, Archaea, and Eukarya Within these domains are 6 kingdoms based on : Archaebacteria, Bacteria, Protista, Fungi, Plants, and Animals Prokaryote without a nucleus or other membrane-bound organelles Eukaryote contains membranebound nucleus and organelles

13 The Six Kingdoms Number of Cells Energy Cell Type Examples Archaebacteria unicellular some autotrophic, most chemotrophic prokaryote "extremophiles" Eubacteria unicellular autotrophic and heterotrophic prokaryote bacteria, E. coli Protista most unicellular heterotrophic or autotrophic eukaryote ameba, paramecium, algae Fungae most multicellular heterotrophic eukaryote mushrooms, yeast Plantae multicellular autotrophic eukaryote trees, grass Animalia multicellular heterotrophic eukaryote humans, insects, worms 7. Phylogeny The term phylogeny refers to the evolution or of any species. This development can be represented through scientific diagrams called. Cladograms use to determine evolutionary relationships - the more closely related species are, the more derived characters they will share (p. 495) Cladograms should not be seen as evolutionary fact, but only as a for speciation. Example: Cladogram for the Phylum Chordata

14 The relationship between the six kingdoms is illustrated in a, a branching cladogram that shows relationships between species from an perspective. The ancestor is in the tree trunk and organisms that have arisen from it are placed at the ends of tree branches. Branch lengths are proportional to the predicted evolutionary between organisms. Example: Phylogenetic Tree of Life