Unit 10: Speciation 10.4 Classification

Finding Order in Diversity Classification is the arrangement of organisms into orderly groups based on their similarities Classification is also known as taxonomy Taxonomists are scientists that identify and name organisms.

Benefits of Classifying Accurately and uniformly names organisms. Prevents misnomers such as starfish and jellyfish that aren’t really fish Uses the same language (Latin or some Greek) for all names

Aristotle’s system The Greek philosopher Aristotle grouped all the organisms he knew into two groups: plants and animals. He grouped organisms according to their physical structures and their habitat: land, sea, or air dwellers. As time passed, more organisms were discovered and some did not fit easily into Aristotle’s groups, but many centuries passed before Aristotle’s system was replaced.

Linnaeus’s System of Binomial Nomenclature 18th Century Taxonomist Classified organisms by their structure Developed the naming system still used today: binomial nomenclature Two word name (Genus and species) Latin or Greek Italicized in print Capitalize genus but not species Underline when writing

Binomial Nomenclature Which TWO are more closely related?

Classification Groups Taxon (taxa-plural) is a category into which related organisms are placed. There is a hierarchy of groups (taxa) from broadest to most specific Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Modern evolutionary Classification Because classifying organisms based on structure could be problematic, biologists now group organisms into categories that represent lines of evolutionary descent. We look for homologous structures, similar embryo development, and molecular similarities in DNA, RNA, or the amino acid sequence of proteins. Remember that the more two organisms share in common-the more closely related they are.

Crabs, Barnacles and Limpets Example Crabs, Barnacles and Limpets Until about 150 years ago, barnacles and limpets were grouped together because both had conical shells. However, we now group them because they share important evolutionary characteristics, such as: a segmented body and an exoskeleton that the organisms molts. Limpets do not share these characteristics.

Classification Using Cladograms A cladogram is a diagram that shows how organisms are related based on shared and derived characteristics. A derived characteristic is one that appears in recent parts of a lineage but not in its older members. Examples: feathers, hair, or scales. They show a probable evolution of organisms from ancestral groups.

Dinosaur Example Allosaurus Velociraptor Robin Archaeopteryx Sinornis Theropods Feathers with shaft, veins, and barbs Flight feathers; arms as long as legs 3-toed foot; wishbone Down feathers Light bones