Chapter 18: Classification

18-1: History of Taxonomy

Early Systems of Classification Taxonomy: branch of biology that names and groups organisms according to their characteristics and evolutionary history

Aristotle 2,000 years ago Plants: three categories based on their stems Animals: based on where they live Land Water Air

Problems Scientific exploration  discover MANY new species Common name did not describe actual animal Ex: Jellyfish: NOT a fish Common names varied by location

Linnaeus’ System Swedish naturalist, Carolus Linnaeus, (1707-78) Used organisms morphology to categorize it Form and structure

Levels of Classification Kingdom Phylum Class Order Family Genus Species Kings Play Chess On Funny Green Squares

Binomial Nomenclature Species name has two parts: Genus Species identifier: descriptive word Ex: Homo sapien Homo is the genus sapien means “wise”

Further Naming and Classifying Botanists (plants) further classify Varieties: subset of species Subspecies: zoologists refer to species that occur in different geographic locations Phylogeny: evolutionary history

18-2: Modern Phylogenetic Taxonomy Past: Morphology Preset: Chromosomal characteristics Nucleotide and amino acid sequences Embryonic development

Systematics Organizes tremendous diversity of living things in the context of evolution Phylogenetic tree: a family tree that shows the evolutionary relationships thought to exist among groups of organisms Represents a hypothesis Based on multiple lines of evidence Subject to change

The Fossil Record Often provides clues to evolutionary relationships HOWEVER: Some fossil records very complete (ocean-living invertebrates) others are missing large portions

Morphology Compare morphology of organism to morphology of other living things Homologous features show descent from common ancestors

Embryonic Patterns of Development Early on in development most living things look very similar As they develop it is easier to see how their morphology differs

Chromosomes and Macromolecules DNA, RNA, and proteins Number of amino acid differences is a clue to how long ago two species diverged from a shared ancestor Problem: ASSUMES all changes to sequence occur at random and NOT natural selection

Karyotype Some similar bands on chromosomes, more related two organisms are

Cladistics Uses shared derived characters of organisms to establish evolutionary relationships Derived characters: feature that apparently evolved only within the group under consideration Cladograms: ancestry diagrams made by means of cladistical analysis

18-3:Two Modern Systems of Classification

Six-Kingdom System Archaebacteria Eubacteria Protista Fungi Plantae Animalia

Kingdom Archaebacteria Unicellular prokaryotes Distinctive cell membrane Autotrophs: chemiosmosis (use elements/chemicals for energy)

Many live in very harsh environments Hot spring VERY salty water Anaerobic environments (No air) Archae- in Greek means “ancient” FIRST organisms on Earth Reproduce: Binary fission Nutrition: Autotrophs and heterotrophs

Kingdom Eubacteria Unicellular prokaryotes Eu- means “true” Most bacteria that affect your life Tooth decay Milk  yogurt Food poisoning Reproduce: Binary fission Nutrition: Autotrophs and heterotrophs

Kingdom Protista Eukaryotic and prokaryotic Difficult to describe All eukaryotes that are not fungi, plants, or animals Reproduction: sexual cycles unknown but they do exchange genetic info Nutrition: Autotrophs AND heterotrophs Euglena can photosynthesize Amoeba eats other organisms

Kingdom Fungi Unicellular and multicellular eukaryotes Reproduction: sexual cycles unknown but they do exchange genetic info Nutrition: Heterotrophs; Absorb nutrients Ex: puffballs, mushrooms, rusts, molds

Kingdom Plantae Multicellular plants Reproduction: most have sexual cycle based on meiosis Nutrition: All but a few are heterotrophic

Kingdom Animalia Multicellular Eukaryotic Reproduction: Sexual by means of meiosis forming gametes Nutrition: Heterotrophs Most have body symmetry and move about environment

Three-Domain System In 1977, molecular biologist, Carl Woese Classified by comparing ribosomal RNA Why? All organisms have ribosomes so we can look at every living thing’s rRNA and compare it with others Three main domains: Domain Archae Domain Bacteria Domain Eukarya

Domain Archae Same as the kingdom Archaebacteria (in six kingdom system)

Domain Bacteria Same as kingdom Eubacteria

Domain Eukarya Protists, fungi, plants, and animals Have nuclei with linear chromosomes and membrane bound organelles