Scientific Classification CLASSIFICATION Defn. The grouping of organisms by similarities TAXONOMY: the branch of biology concerned with the grouping and naming of organisms; the study of classification Taxonomy Organisms are classified into a hierarchy of groups and subgroups based on similarities that reflect their relationships over a period of time. Cladogram or Phylogenic Tree A branching, treelike diagram in which the endpoints of the branches represent specific species of organisms. It is used to illustrate relationships and show points at which various species have diverged from common ancestral forms. What is wrong with this picture? Think-Pair-Share: Why was Aristotle’s system flawed? Why does it not “work”? HISTORY: Aristotle- developed the 1st method of classification He divided all living things into 2 major groups 1. Plants classified by size and structure 2. Animals classified by habitat (where they lived) HISTORY: Aristotle Problems with his system: Frogs live in both water and on land HISTORY: Aristotle Problems with his system: Bats, birds and flying insects were grouped together HISTORY: Carolus Linnaeusdeveloped the modern system of classification Father of Taxonomy MODERN CLASSIFICATION SYSTEM Organisms are grouped together on the basis of: 1. Similarity in structure Panthera leo Felis rufus Felis domesticus 2. Similarity in genetic makeup (biochemistry) Similarities among organisms on the structural and metabolic levels are reflected in the large degree of similarity in proteins and nucleic acids of different organisms. Diversity is the product of variations in these molecules. 3. Similarity of embryonic development 4. Similarity in evolutionary history Phylogeny: the evolutionary history of a species based on comparing relationships between species using the fossil record 5. Similarity in behavior Check for Understanding: With your partner, develop 2 possible explanations as to why the modern system of classification is “better” and easier to use than the original system of classification. TIME: 2 minutes Classification is based on close evolutionary relationships of organisms. Organisms classified in the same taxa (pl.) (taxon, sing.) share a common ancestry. They have evolved from the same common ancestral organism. Evolutionary Relationships Levels of Classification Domain- highest level; bacteria, archaea & Eukarya Kingdom – 6 Kingdoms Phylum (sing.) Phyla (pl.)(Plants don’t have phyla, they have divisions.) Class Order Family Genus These two taxa make up the Species scientific name. Binomial Nomenclature This system was developed by Linnaeus Binomial nomenclature is a standard way of identifying a species with a scientific two-word name. The first word is the genus name and the second the species name. Binomial Nomenclature Scientific name - 2 Latin names Genus and species Capitalize the first letter of the genus Do NOT capitalize the species ALWAYS underline or use italics Ex. Homo sapiens Binomial Nomenclature Scientific Name: Pinus virginianis Common Name: Virginia Pine What defines a “Species”? organisms that belong to the same species can mate AND produce FERTILE offspring. Why use scientific names? Common names do not indicate how organisms are related or classified. Common names can be misleading. (e.g., seahorse, weeping willow) Organisms with more than one common name leads to mass confusion. Why Latin? Latin is no longer spoken, and therefore, does not change as spoken languages do. So, scientific names remain the same forever.