B Evolution Classification Part 1

18.1 History of Taxonomy Taxonomy: the science of grouping organisms according to their presumed natural relationships  Aristotle • Classified organisms over 2000 years ago • Greek philosopher • Classified living things as either plants or animals o Animals: divided into land, water, and air dwellers o Plants: divided into three subcategories based on stem difference  New systems were developed in the 18th century  Common Name: an everyday name given to an organism (based on characteristics, habits, etc)  Latin is used to avoid confusion between common names Binomial Nomenclature  Based on the work of Carolus Linnaeus, a Swedish naturalist  Linnaeus developed a system of grouping organisms into hierarchical categories Taxons: Kingdom Phylum/Division (Subphylum) Class Order Family Genus Species (Subspecies)  Binomial Nomenclature: a system of naming organisms that uses the genus name plus a specific epithet (meaning: “two names”)  Scientific Name: the two-word (binomial) Latin name of a species, always italicicized Levels of Classification  Botanists use the term division in place of phylum when classifying plants  Species can be classified into: o Subspecies Are morphologically different and are often geographically separated ssp. Means “subspecies” ex. Canis lupis ssp. occidentalis

o Varieties Are morphologically different and often are not geographically separated var. means “variety” ex. Prunis persica var. nectarina

o Strains Biochemically dissimilar group within a species Usually used in reference to microorganisms

Often represented by letters or numbers ex. S. marcescens D1 and S. marcescens 993

18.2 Modern Taxonomy Phylogeny: classification based on evolutionary history; the analysis of evolutionary ancestry between different organisms Evidence Used in Classification Dichotomous Key: a written set of choices that leads to the name of an organism; a classification system used to differentiate specific traits of different organisms Physiology • study of the mechanical, physical, and biochemical functions of living organisms. Physiology has traditionally been divided between plant physiology and animal physiology but the principles of physiology are universal, no matter what particular organism is being studied. Morphology • The outward appearance of an organism (colour, shape, structure, pattern, …) • Usually used at the level of the larger classification categories Embryology • The study of the development of an embryo. Embryo: any organism in a stage before birth or hatching, or in plants, before germination occurs.

Analogous structures don’t provide any evidence of an evolutionary relationship between organisms. ex. the wings of a bird and the wings on an insect are analogous structures since they develop from different tissues in each embryo

Certain embryological evidence may indicate that seemingly dissimilar species may be related. ex. The bones of the forelimb in the lizard are embryologically similar to those in the cat.

Homologous structures (see above example) suggest that two organisms may share a similar phylogenetic origin Chromosomes • Number of chromosomes • Shape of chromosomes Biochemical • Comparing the proteins, amino acid sequences, DNA, and RNA in different organisms Inferring Phylogeny Infer: to derive by reasoning; conclude or judge from premises or evidence Taxonomists are able to infer the probable evolutionary relationships among species that have been classified on the basis of the kinds of evidence listed in the previous section.

Phylogenetic Tree: a visual model of the inferred evolutionary relationships among organisms Biosystematics • A form of taxonomy that examines reproductive compatibility and gene flow • Assesses the genetic variation in populations and among species • using this information allows inferences about the ancestral history of a species • Biosystematics o study speciation, the evolution of one species into two o collect data on variations in a population of organisms o then analyze the data to construct a model of the population’s genetics