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Classification of Animals How many species? • • • described 8-10 million total estimate, some estimates as high as Standardized system : International Code of Zoological Nomenclature Disciplines of classification Taxonomy Systematics First taxonomist: Karl von Linne, aka 1778) (1707- Original Linnaean system Imperium ("Empire") - the phenomenal world Regnum ("Kingdom") - the three great divisions of nature at the time animal, vegetable, and mineral Classis ("Class") - subdivisions of the above, in the animal kingdom six were recognized (mammals, birds, amphibians, fish, insects, and worms) Ordo ("Order") - further subdivision of the above - the class Mammalia has eight Genus - further subdivisions of the order - in the mammalian order Primates there are four. e.g. Homo Species - subdivisions of genus, e.g. Homo sapiens. Varietas ("Variety") - species variant, e.g. Homo sapiens europaeus. Hierarchical classification Traditional mandatory taxa: Kingdom Phylum (phyla, pl) Class Order Family (-idae) Genus (genera, pl) 1 Species Current classification schemes taxonomy is a dynamic science 1st – 2-kingdom system – plants and animals (botany & zoology) 2nd – 3 kingdom – plants, animals & protists 3rd – Whittaker 5 kingdom system in 1970’s 4th – Woese-Fox 3 domain system Five kingdom system 1) 2) 3) 4) 5) Three domain system 1) 2) 3) Nomenclature system of naming objects Binomial system of nomenclature adopted for species for several reasons: 1) Common names - too many for some sp. 2) Some common names are used for diff. sp. 3) Scientific names - universal 4) two-part system indicates relationship with other similar organism Scientific name Genus name - first letter capitalized, either italicized or underlined Specific epithet - all lower case, underlined or italicized 2 – Common Tern named by Linnaeus – Least Tern scientific name revised since first description Systematics has to accomplish to two tasks: 1) 2) Attempt is made to classify organisms according to phylogenetic relationships Problems when classifying 1) convergent evolution – 2) traits used to determine phylogenies don’t always agree 3) different definitions of species Species definition Typological species – doesn’t address variations w/in species Biological species - Dobzhansky & Mayr – 1930s expanded in 1980s to include that species “occupies a specific niche in nature” not useful for fossils or asexual organisms Simpson 1940s “a single lineage of ancestor-descendant populations that maintains its identity from other such lineages and that has its own evolutionary tendencies and historical fate” uses mostly morphological features allows defining species in fossils & asexually reproducing species 3 Phylogenetic species concept Joel Cracraft 1989 “irreducible (basal) grouping of organisms diagnosably distinct from other such groupings and within which there is a parental pattern of ancestry and descent” tends to separate subspecies into species increases the number of species doesn’t involve evolutionary process Origin of taxa monophyletic paraphyletic – polyphyletic – Different evolutionary trees Evolutionary taxonomy version 1) life begins with: 2) from bacteria, evolved into nucleated organisms – 3) from protistans, multicellularity evolves into three major groups: Evolutionary tree according to cladistics cladistics – method of statistically looking at groups & classifying only by monophyletic groups the following tree used ribosomal RNA 1) 2) 3) Evolutionary trends in body plans symmetry - how parts of animal are arranged around a point, axis, or plane. 4 1) asymmetry 2) radial 3) bilateral – Cephalization formation of a head animals w/bilateral symmetry tend to always move in one direction (forward). accompanying bilateral symmetry was development of: Terms assoc. w/bilateral symmetry Planes: sagittal transverse frontal Orientation terms: anterior posterior dorsal ventral Layers of tissue in embryonic stages protoplasmic or unicellular - . cell specialization - multicellular w/no tissue differentiation diploblastic triploblastic 5 Body cavity in triploblastic animals acoelomate pseudocoelomate – Eucoelomate true coelom Deuterstomes vs. Protostomes Different developmental pathways Segmentation or metamerism repeating of similar body parts (segments) segments maybe very similar, e.g. annelids or start to specialize e.g., arthropods, & chordates 6