UNIT IV DIVERSITY OF LIVING THINGS Scientific Classification CLASSIFICATION • the grouping of organisms by similarities • Biological classifications are based on how organisms are related. Group A Group B Why Do We Classify Organisms? • Biologists group organisms to represent similarities and proposed relationships. • Classification systems change with expanding knowledge about new and well-known organisms. Classification • Binomial Nomenclature – Two part name (Genus, species) • Hierarchical Classification – Seven Taxonomic Catagroies • Systematics – Study of the evolution of biological diversity 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 phylogenetic relationships and show points at which various species have diverged from common ancestral forms. Animation - Phylogenetic Trees Taxonomic Diagrams Mammals Turtles Phylogenetic Tree Lizards and Snakes Crocodiles Birds Mammals Turtles Lizards and Snakes Crocodiles Cladogram Birds Tree of life Biology: Samples - HISTORY: • Aristotle- developed the 1st method of classification • He divided all living things into 2 major groups Aristotle’s Groups • 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 Bats, birds and flying insects were grouped together • Kingdom – largest group • Phylum (sing.) – Phyla (pl.)(Plants don’t have phyla, they have divisions.) • • • • • Class Order Family Genus Species Kingdom Phylum Class Order Family These two taxa make up the scientific name. Genus Species K__________ p__________ c_________ o___________ f________ g_________ s________. King Phillip came over for great soup. HISTORY: • Carolus Linnaeusdeveloped the modern system of classification • Father of Taxonomy Binomial Nomenclature • Carolus von Linnaeus • Two-word naming system – Genus • Noun, Capitalized, Underlined or Italicized – Species • Descriptive, Lower Case, Underlined or Italicized Binomial Nomenclature Binomial nomenclature is a standard way of identifying a species with a scientific twoword name. The first word is the genus name and the second the species name. 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: Homo sapiens Common Name: Albert Einstein Binomial Nomenclature Scientific Name: Rudbeckia hirta Common Name: Gloriosa daisy or Black-eyed Susan Binomial Nomenclature Scientific Name: Pinus virginianis Common Name: Virginia Pine Binomial Nomenclature Scientific Name: Harmonia axyridis Common Name: Asian Ladybug Binomial Nomenclature Scientific Name: Ophiophagus hannah Common Name: King Cobra MODERN CLASSIFICATION SYSTEM • Organisms are grouped together on the basis of: – Similarity in structure Panthera leo Felis rufus Felis domesticus Similarity in structure Canis lupus Similarity in structure Canis latrans Similarity in structure Canis domesticus Organisms are grouped together on the basis of: • 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. Organisms are grouped together on the basis of: • Similarity of embryonic development Evolution: Library: Common Past, Different Paths Organisms are grouped together on the basis of: • Similarity in evolutionary history – Phylogeny: the evolutionary history of a species based on comparing relationships between species using the fossil record Organisms are grouped together on the basis of: • Similarity in behavior Systematics: Evolutionary Classification of Organisms • Systematics is the study of the evolution of biological diversity, and combines data from the following areas. – – – – Fossil record Comparative homologies Cladistics Comparative sequencing of DNA/RNA among organisms – Molecular clocks • 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 • Classification is hierarchal – each successive level is smaller and more closely related than the one before it Species organisms that belong to the same species can mate AND produce FERTILE offspring. • Horses and donkeys can mate. – They produce a mule. • Mules are INFERTILE + = • Lions and tigers can mate. – They produce a liger. • Ligers are INFERTILE + = 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.