Finding Order in Diversity (Ch 18.1) Unit 5: Evolution

Assigning Scientific Names European scientists in the 18th century agreed to name organisms using Latin or Greek names to the species Scientific names used to be a description of characteristics of the organism The scientific names often lead to using dichotomous keys to identify the organisms Dichotomous Key: used to identify certain types of organisms based off of the visible characteristics of that organism

Dichotomous Key

Assigning Scientific Names Binomial Nomenclature Carl Linnaeus developed a system for naming organisms binomial nomenclature: each species is assigned a two-part scientific name Scientific names are in italics and the first word is capitalized and the second word is lowercased The first word is the genus and the second word is the species name Example: Ursus maritimus = Polar bear Genus: group of similar species (Ursus) It contains 5 other species of bears Species: a group of individuals capable of interbreeding and producing fertile offspring (maritimus) It contains only this species

Classifying Species into Larger Groups systematics: the science of naming and grouping organisms The goal of systematics is to organize living things into groups that have biological meaning Organisms in a particular group are more similar to one another than organisms of a different group (taxa) Example: teachers = general group Biology teachers = specific group

The Linnaean Classification System Linnaeus developed a system for classifying organisms into their taxa Linnaeus’s original classification system expanded to the seven hierarchical taxa: species, genus, family, order, class, phylum, kingdom Species: most specific name given to a specific organism Example: Camel with two bumps (bactrianus) Genus: groups of similar species that can breed and produce fertile offspring Example: Camel with two bumps (Camelus)

The Linnaean Classification System Family: Several genera that share many similarities Example: Camels and Llamas placed in the same family Camelidae Order: many closely related families Example: Camels, llamas, deer, and cattle are all placed in the family Artiodactyla Class: similar orders grouped together Example: Artiodactyla is placed in the class Mammalia which includes all animals that are warm blooded, have body hair, and produce milk for their young Phylum: classes that are grouped together because they share important characteristics Example: Mammalia, Aves, Reptilia, and Amphibia are in the phylum Chordata because they have a nerve chord along their backs Kingdom: the largest most inclusive group Example: All multicellular animals are placed in the kingdom Animalia

From Species to Kingdom Camelus bactrianus

Problems with Traditional Classification Linnaeus characterized species based on their visible similarities and differences – Which are more important or should be taken into account when classifying? This is difficult because sometimes organisms may appear to be similar and are not or may appear to be different and are not Many of Linnaeus’s classifications are valid today, but he worked on his concept before Darwin’s theory of descent with modification – how do we classify organisms based on their evolutionary relationships? Today, scientists assign species to groups to reflect how closely members of the group are related to one another (evolution)