Classification of Living Things Chapter 20

Taxonomy Identifying, naming and classifying organisms Latin base Aristotle first to classify, divided into 14 major Categories Subdivided them according to size John Ray All organisms should have a set name Divided them into groups based on how he thought they were related

Carolus Linnaeus 1707 - 1778 Binomial nomenclature – 2 part name Genus – contains many species Specific epithet (1 species) Usually descriptive, can have geographic descriptions When writing a scientific name Genus capitalized Species lower case Italics, underlined if handwritten Published Systema Naturae in 1735

species Interbreed and share the same gene pool Subspecies Variant types of organisms of a species that tend to interbreed where their populations overlap They could actually be different species hydridization

Classification categories Species Genus Family Order Class Phylum Kingdom Domain More than 30 categories: super, sub, infra Organisms put in categories based on characters, structural, chromosomal, or molecular features

Phylogenetic trees Systematics – study of the diversity of organisms at all levels of organization Taxonomy and classification Goal: determine phylogeny – evolutionary history Represented by Phylogenetic tree Shows divergence from a common ancestor Derived characters – individual characteristics

Tracing phylogeny Record data from: Fossil evidence Homology Molecular data Using this information you can determine common ancestors and classify organisms accordingly

Homology Includes comparative anatomy and embryological evidence Sometimes homology is challenging because of Convergent evolution – having the same or similar characters but distantly related due to adaptation to the environment Analogous structures – having same function but do not have common ancestor (wings of bat/insect) Parallel evolution – similarity in structure in related groups that cannot be traced to common ancestor

Molecular data Protein comparisons - limited RNA and DNA Comparisons DNA-DNA hybridization: compare single strands from different organisms and allowed to combine, if closely related, strands will stick together Nucleotide sequences Molecular clocks – nucleic acid changes used to indicate relatedness and evolutionary time

Cladistic Systematics Willi Hennig Uses shared derived characters to classify organisms and construct a cladogram Objective because it lists characters used to construct cladogram Figure 20.11, table 20.2

Phenetic systematics Species are classified by the number of their similarities Count the # of traits the two species share and estimate the degree of relatedness Figure 20.10

Traditional systematics Mainly use anatomical data to classify organisms Stress common ancestry and degree of structural difference among divergent groups Not as strict as cladists

Classification systems Began with 2 kingdoms: animal and plant 1880 Ernst Haeckel: Added kingdom Protista unicellular, microscopic 1969: RH Whittaker – expanded system to 5 kingdoms: monera, protista, fungi, plantae and animalia Based on type of cell, complexity, type of nutrition

3 Domain system Late 1970’s Carl Woese Used rRNA sequencing Proposed 2 groups of prokaryotes because they were so different Domains: Archea – prokaryotes that are not bacteria Bacteria – mostly prokaryotic bacteria Eukarya – contains Protista, Fungus, Plantae and Animalia