Classification

Taxonomy Science of grouping organisms according to their presumed natural relationships Artificial May change with new evidence

History of Classification

Aristotle Either plant or animal

Animals where they lived Land Dwellers Water Dwellers Air Dwellers

Plants based on stem differences Herbs Shrubs Trees

18 th Century New discovered organisms didn’t fit Used Latin Descriptions - Cumbersome

Common Names Everyday name given to organisms –D–Don’t describe accurately –S–Same name for two organisms –M–May have more than one common name

Carolus Linneaus Swedish Naturalist – Grouped organisms into a hierarchy Developed system called Binomial Nomenclature

Linneaus’ Hierarchy Kingdom Phylum Class Order Family Genus Species

Binomial Nomenclature Means “two names” Uses Genus and Species Also called Scientific Name

Rules for Scientific Names Describes organism, its range, or honors another scientist Name is always Latinized Genus – capitalized; Species – Lower Case Always italicized or underlined

Levels of Classification with Human Taxonomy Kingdom – Animalia Phylum – Chordata Class – Mammalia Order – Primates Family – Hominidae Genus – Homo “Man” Species – Sapiens “Wise One”

The Taxonomist’s Subgroups Subspecies – morphologically different; geographically separated Variety – morphologically different; not geographically separated Strain – biochemically dissimilar group in a species; microorganisms

Domains Bacteria – Kingdom Eubacteria Archea – Kingdom Archaebacteria Eukarya – Kingdoms Protista, Fungi, Plantae, and Animalia

Evidence used in Classification Comparative Morphology (Anatomy) Embryological Evidence Genetic Similarities Biochemical Comparisons Physiological Studies

Comparative Morphology Based on physical features Looks at structural similarities May or may not be completely accurate Identification often uses a Dichotomous Key – Set of written choices leading to organism’s name – Branches; selections become more specific

Embryological Evidence Usually used for upper categories – Phylum, Class, etc. Looks at origin of body organs Homologous Organs – common origin, similar function – bat’s wing, human’s arm Analogous Organs – Different origin, similar function – insect’s wing vs bird’s wing

Genetic Similarities Looks at DNA sequences – related species have more similarities Comparison of Karyotypes – picture of organism’s chromosomes Chromosome counts Chromosome shapes

Biochemical Comparisons Comparisons of amino acid sequences in common proteins in different species More similarities indicate closer relationship

Physiological Studies Useful in Bacterial Classification Looks at what chemical bacteria may use as food May look the same but have different physiologies

Phylogeny Evolutionary history of a species Uses evidence of probable evolutionary relationships Phylogenetic Tree (Cladogram) – model of inferred evolution

Phylogenetic Tree Species at branch ends – most recently evolved organisms Main Branches and Trunk – organisms which gave rise to more recent organisms Close branches imply close evolutionary history

Biosystematics Study of reproductive compatibility and gene flow Reproductive compatibility used to infer evolutionary relationship Studies speciation – evolution of one species into two new species

Kingdom Classifications Two Kingdoms Plants Animals Three Kingdoms Plants Animals Protists

Kingdom Classifications Four Kingdoms Plants Animals Protists Monera Five Kingdoms Plants Animals Protists Monera Fungi

Kingdom Classifications Six Kingdoms Plants Animals Protists Fungi Eubacteria Archaebacteria

Criteria for Defining Kingdoms Cell Structure – Prokaryote or Eukaryote Number of Cells – Unicellular or Multicellular Nutrition – Autotrophs or Heterotrophs Reproduction – Asexual or Sexual

Kingdom Characteristics Archaebacteria Prokaryotic Unicellular – Cell Walls without peptidoglycan Autotrophs and Heterotrophs Asexual/Sexual Live in extreme environments Eubacteria Prokaryotic Unicellular – Cell Walls with peptidoglycan Autotrophs and Heterotrophs Asexual/Sexual Typical Bacteria

Kingdom Characteristics Protista Eukaryotic Unicellular some Multicellular Autotrophs and Heterotrophs Asexual/Sexual Aquatic or Moist Habitats Fungi Eukaryotic Multicellular some Unicellular Heterotrophic by Absorption Sexual/Asexual Mostly terrestrial, some aquatic

Kingdom Characteristics Plantae Eukaryotic Multicellular Autotrophic Sexual/Asexual Aquatic and terrestrial Usually remain in one place Animalia Eukaryotic Multicellular Heterotrophic by ingestion Sexual/Asexual (lower species) Aquatic and terrestrial Most move about