Taxonomic Classification Objectives Outline the binomial system of nomenclature. List seven levels in the hierarchy of taxonomy – kingdom, phylum, class, order, family, genus, and species – using an example from two different kingdoms for each level. Design and apply a key to distinguish a group of up to eight organisms. Naming things Taxonomy: the science of classifying living things (from Greek taxon meaning group (plural = taxa) Organisms are classified by similarity. Many attempts from Greek times. Ex: is something animal, mineral, or vegetable? The idea of a 2-word description for every living thing was developed around 1750 by Carrolus (Carl) Linnaeus of Sweden. The Linnaean system is called binomial nomenclature (twoname naming system); uses Latin. Naming things Binomial nomenclature Linnaeus preceded Darwin & didn’t know evolution, but classification by similarity supports this theory. Homologous structures: bird & bat wings - same bone structure so there was a common ancestor. But, must also consider analogous structures: Bats and butterflies both have wings, but are unrelated. DNA similarities support classifications. DNA mutates at a known rate; the more similar the sequences of DNA – the more closely related the creatures will be. Mutations pinpoint where creatures broke from some common ancestor. Naming things Why name organisms? Human need (for communication); beginning with the Book of Genesis 2:20. →→ So scientists can communicate without misunderstandings. For example, the words inu (Japanese), chien (French), perro (Spanish), and dog (English) all represent the same 4-legged barking animal. Adam naming the animals But Canis lupis familiaris (Latin) is recognized by any scientist anywhere. Naming things Why name organisms? The same word can be used differently even in English-speaking countries. Ex. American wheat is called “corn” in England. Even in America, things have different names among various regions or even age groups. Ex. Roly-poly, pillbug, or wood louse = Porcellio scaber Naming things Why choose Latin for naming things? Throughout the middle ages, Catholic monks kept Roman & Greek wisdom alive copying texts in monasteries. The Catholic church spoke & wrote in Latin. Scientists had religious educations. Binomial nomenclature The Linnean system has two main characteristics. 1) Each kind of organism has 2-part name, a binomial. 1st part, the genus; 2nd part, the species - in Latin. 1st letter of the genus is capitalized, & both names are italicized (or underlined) and latinized. Ex: Linnaeus assigned to humans the scientific name Homo sapiens, meaning “wise man”. Taxonomic hierarchies The Linnean system has two main characteristics. 2) Species are organized hierarchically into broader and broader groups of organisms. Closely-related species are grouped into the same genus. Ex: the leopard, belongs to a genus that includes the lion (P. leo) & the tiger (P. tigris). Hierarchy example #1, the panther Taxonomic hierarchies The Linnean system has two main characteristics. The genus is one part of a family – the cat family (Felidae), along with house cats, etc. Families combine to form an order – Carnivora, the meat eaters, including dogs. Orders form a class – Mammalia, whose creatures all have fur and produce milk. Classes form a phylum, in this case the Chordates, all having a spinal column. Hierarchy example #1, the panther Taxonomic hierarchies The Linnean system has two main characteristics. Several phyla – chordates, arthropods, different worms, sponges, etc. – form a kingdom, in this case Animalia, which are heterotrophic and whose cells lack a cell wall. The plant kingdom has cells that are autotrophic; the cell wall is of cellulose. The kingdoms of Animalia, Plantae, Fungi, etc. form a domain, in this case Eukarya – all the creatures whose cells contain a nucleus. Hierarchy example #1, the panther Taxonomic hierarchies The taxonomy of Mankind Domain= Eukarya Kingdom = Animalia Phylum = Chordata Class = Mammalia (up to this point we are united with felines) Order = Primates Family = Hominidae Genus = Homo Species = sapiens Hierarchy example #2, the human Taxonomic hierarchies Branches on the tree of life represent major changes in the way creatures develop as a result of evolution. Mutations happen, & the environment changes. Taxonomic hierarchies Mutations led to changes in the animal kingdom Dichotomous keys A dichotomous key is a method for identifying and classifying objects, where each feature selected to help identification requires a choice between two alternatives. A substitute teacher asks, “Which boy is James?” Proceed step-bystep to find him, always making one of two choices. 1, 2, 4, 8 Dichotomous = “two branches”. Go to #: Go to #: Dichotomous keys What should you ask here? Dichotomous keys What should you ask here? Taxonomic Classification (part 2) Taxonomic hierarchies Branches on the tree of life represent major changes in the way creatures develop as a result of evolution. Mutations happen, & the environment changes. Three Domains with Six Kingdoms of Life Note characteristics! Remember: viruses are not alive; they have no kingdom. Six Kingdoms of Life 2 kingdoms for prokaryotes (all unicellular with a cell wall) are distinguished by habitat. Archaebacteria (archae = ancient) Domain Archaea Live in extreme environments similar to early earth: hot springs, salty seas; oxygen is poisonous. Autotrophic (chemoautotrophic). Eubacteria Domain Bacteria Live all around us: on the floor, in our mouths, on our skin, etc. Auto- or heterotrophic. Six Kingdoms of Life Domain Eukarya: Cells with a nucleus; 4 kingdoms are distinguished by cellularity and nutrition. Plants are multicellular autotrophs (photosynthetic). Fungi are heterotrophic decomposers with extracellular digestion (most are multicellular; yeast are unicellular). Animals are multicellular heterotrophs; most digest their food within specialized cavities. No cell wall. Protists are either autotrophs (algae) or heterotrophs (like amoebas). All but seaweeds are unicellular. Dichotomous keys (Review) To set up a dichotomous key, choose questions that differentiate the subjects. Does it have: 1) a backbone? 2) a jaw? 3) legs? 4) an amniotic egg? 5) hair ? No. It’s a lancelet. Yes. Go to #2. No. It’s a lamprey. Yes. Go to #3. No. It’s a tuna. Yes. Go to #4. No. It’s a salamander. Yes. Go to #5. No. It’s a turtle. Yes. It’s a leopard. Cladograms A cladogram is a diagram that links groups of organisms by showing evolutionary linkages branched off from common ancestors. Can be based upon physical characteristics. Cladograms A clade is a group of species that includes a single common ancestor. Cladograms Cladograms can be formed using similarities in the genetic code – the DNA – which translates into proteins. This is evidence for evolution. Cladograms A key for several animal phyla. Based on: Presence of tissues Symmetry Body cavity Fetal development animal Changes in classification The classification system has changed over the years. Linnaeus only recognized two kingdoms: plants and animals. Today there are six kingdoms. Protista may be sub-divided one day into three or more new kingdoms.