CLASSIFICATION Organizing Life’s Diversity
Classification • Classification – putting objects (or information) into groups based on their similarities. Grocery stores classify their products to make them easier for the customer to find.
Classification • Aristotle (384 -322 BCE) developed the first system of biological classification. – His system divided all living things into two groups: plants and animals. – Plants were subdivided by size: herbs, shrubs and trees. – Animals were subdivided by habitat and then by physical traits.
Classification • Problems with Aristotle’s classification system: – Animals were not grouped according to their evolutionary history. • Bats, birds and flying insects were all grouped together. – Aristotle had no knowledge of microbes or of the differences between plants and fungi. Grouping by habitat means that flying and flightless birds would be placed into different groups.
Linnaean System The major classification levels from largest group to smallest (Today, groups have been further divided. ) • • Kingdom Phylum Class Order Family Genus Species • • King Phillip Came Over For Great Soup This is a pneumonic device for remembering the correct sequence of large to small.
Taxonomy • Taxonomy is the branch of biology that groups and names organisms based on studies of their traits.
A Unique Name for Every Living Thing! • Binomial nomenclature: a two-word scientific naming system developed by Carolus Linneaus that provides a unique name for every living thing • Scientific name is always in italics (or, if handwritten, underlined), genus capitalized, species not capitalized. • Why is a unique name needed? • Clear communication • Why Latin? ! • Known by all scientists of that time period • Names give information about that organism • Dead language (meanings won’t change)
Examples of Linnaean Taxonomy Common Name: Siberian Tiger (Domain Eukarya) Kingdom Animalia Phylum Chordata Class Mammalia Order Carnivora Family Felidae Genus Panthera Species P. tigris Scientific name: Panthera tigris
Examples of Linnaean Taxonomy Common Name: Domestic Cat (Domain Eukarya) Kingdom Animalia Phylum Chordata Class Mammalia Order Carnivora Family Felidae Genus Felis Species F. catus Scientific name: Felis catus
Examples of Linnaean Taxonomy Common Name: Wildcat (Domain Eukarya) Kingdom Animalia Phylum Chordata Class Mammalia Order Carnivora Family Felidae Genus Felis Species F. sylvestris Scientific name: Felis sylvestris
Examples of Linnaean Taxonomy Common Name: Leopard (Domain Eukarya) Kingdom Animalia Phylum Chordata Class Mammalia Order Carnivora Family Felidae Genus Panthera Species P. pardus Scientific name: Panthera pardus
Examples of Linnaean Taxonomy Common Name: Gray Wolf (Domain Eukarya) Kingdom Animalia Phylum Chordata Class Mammalia Order Carnivora Family Canidae Genus Canis Species C. lupus Scientific name: Canis lupus
Examples of Linnaean Taxonomy Common Name: Human (Domain Eukarya) Kingdom Animalia Phylum Chordata Class Mammalia Order Primata Family Hominidae Genus Homo Species H. sapiens Scientific name: Homo sapiens
The Domain • Since Linnaeus’ time, biologists have discovered the need for more categories. • One major difference in today’s classification system is the addition of a category above (or more inclusive than) that of the kingdom – the domain. • The three domains are: Bacteria, Archaea, and Eukarya (or Eukaryota).
The Three Domains Domain Bacteria Kingdom Eubacteria • Unicellular prokaryotic organisms. • Cell walls contain peptidoglycan. • DNA is usually a single circular chromosome. • Found nearly everywhere. • Some need oxygen, others do not. Domain Archaea Kingdom Archaebacteria • Unicellular prokaryotic organisms. • Cell walls lack peptidoglycan. • Cell membranes have unusual lipids not seen in other groups. • DNA is usually a single circular chromosome. • Found in extreme environments like volcanic hot springs.
The Three Domains Domain Eukarya Includes the following Kingdoms: Ø Protista* Ø Fungi Ø Plantae Ø Animalia *Not really a single kingdom anymore, but no decision yet made on how many kingdoms will be created out of the old Kingdom Protista. All eukarya are eukaryotic. Some differences: Ø Plants and fungi both have cell walls, but fungi have cell walls that contain chitin, while plants have cell walls of cellulose. Ø Plants and some protists can photosynthesize their own food using chloroplasts. Ø Most protists are unicellular. Ø All animals can reproduce sexually and are motile at some life stage.
Using a Dichotomous Key: two-branching identification guide 1 A Plant. . . Go to 2 1 B Animal. . . Go to 7 2 A Waxy covering with many spines. . Cactus 2 B No waxy covering or spines. . . . Go to 3 1 A 2 A Cactus Be sure to show the steps you use!