Classification Chapter 17

History of Classification Early Systems of Classification Classification: grouping of objects or organisms based on a set of criteria o Biologists use a system of classification to organize information about the diversity of living things. o Aristotle and Linnaeus

Aristotle’s System o 394 – 322 BC o Developed 1 st widely accepted system of biological classification o Classified organisms as either animals or plants

Aristotle’s System o Animals were classified according to the presence or absence of “red blood.” o Animals were further grouped according to their habitats and morphology. o Plants were classified by average size and structure as trees, shrubs, or herbs.

Problems with Aristotle’s System o Based upon the idea that species are distinct and unchanging. Doesn’t account for evolution. o Many organisms didn’t fit into a category. o Example: Birds who don’t fly.

Linnaeus’ System o 1707 – 1778 o First formal system of taxonomy o Taxonomy: discipline of biology primarily concerned with identifying, naming, and classifying species based on natural relationships

Linnaeus’ System o Binomial Nomenclature: method of naming organisms that uses a TWO PART name for each species o Part One: Genus name o Part Two: Specific epithet (AKA specific name) NOTE: Latin is the basis for binomial nomenclature because it is an unchanging language.

Scientific Names vs. Common Names o Scientific names are used for species because: o Common names vary from person to person o Common names can be misleading o Example: Starfish are NOT fish. Horned owls do NOT have horns.

Scientific Name Rules o The first letter of the genus name always is capitalized, but the rest of the genus name and all letters of the specific epithet are lowercase. o If a scientific name is written in a printed book or magazine, it should be italicized. o When a scientific name is written by hand, both parts of the name should be underlined. o After the scientific name has been written completely, the genus name will be abbreviated to the first letter in later appearances (e.g., C. cardinalis).

Taxonomic Categories o The taxonomic categories used by scientists are part of a nested-hierarchal system. o Each category is contained within another, and they are arranged from broadest to most specific.

Species and Genus o Taxa: named group of organisms o A genus is a group of species that are closely related and share a common ancestor.

Genus Example Ursus americanus Ursus thibetanus Melursus ursinus

Family o A family is the next higher taxon, consisting of similar, related genera. o Example: Ursidae o Contains all bears ( Both Ursus and Melursus) o Contains NINE different species of bears

Higher Taxa o An order contains related families. o A class contains related orders. o A phylum or division contains related classes. o The taxon of related phyla or divisions is a kingdom. o The domain is the broadest of all the taxa and contains one or more kingdoms.

Classification Summary o Domain o Kingdom o Phylum o Class o Order o Family o Genus o Species

Domains and Kingdoms o The most widely used biological classification system has six kingdoms and three domains. o The three domains are Bacteria, Archaea, and Eukarya. o The six kingdoms are Bacteria, Archaea, Protists, Fungi, Plantae, and Animalia.

Domain Bacteria o Eubacteria are prokaryotes whose cell walls contain peptidoglycan. o Eubacteria are a diverse group that can survive in many different environments.

Domain Archaea o o Archaea are thought to be more ancient than bacteria and yet more closely related to our eukaryote ancestors. o o Archaea are diverse in shape and nutrition requirements. o o They are called extremophiles because they can live in extreme environments.

Domain Eukarya o o They are called extremophiles because they can live in extreme environments. o o Domain Eukarya contains Kingdom Protista, Kingdom Fungi, Kingdom Plantae, and Kingdom Animalia.

Kingdom Protista o Protists are eukaryotic organisms that can be unicellular, colonial, or multicellular. o Protists are classified into three different groups: plant- like, animal-like, and fungus-like.

Kingdom Fungi o A fungus is a unicellular or multicellular eukaryote that absorbs nutrients from organic materials in its environment o Members are heterotrophic, lack motility, and have cell walls.

Kingdom Plantae o o Members of Kingdom Plantae form the base of all terrestrial habitats. o o All plants are multicellular and have cell walls composed of cellulose. o o Most plants are autotrophs, but some are heterotrophic.

Kingdom Animalia o o All animals are heterotrophic, multicellular eukaryotes. o Animal organs often are organized into complex organ systems. o They live in the water, on land, and in the air.

Kingdom Summary