Classification of Living Things

Classification Biology

Taxonomy Scientists classify organisms and assign each organism a universally accepted name

Why Should We Classify Organisms? To organize similar organisms So all scientists are discussing the same organisms (species) Species  population of organisms that share similar characteristics and can breed with one another and produce fertile offspring Identified 1.5 million species so far Estimate 2-100 million have yet to be discovered

What tools can we use to show similarities in organisms? Cladistic analysis  identifies and considers only those characteristics of organisms that are evolutionary innovations – new characteristics that arise as lineages evolve over time Cladogram – diagram that shows evolutionary relationships among a group of organisms

Modern Evolutionary Classification Darwin’s ideas about descent gave rise to the study of phylogeny – evolutionary relationships among organisms Evolutionary Classification – Grouping of organisms based on evolutionary history

Traditional Classification Versus Cladogram Appendages Conical Shells Crustaceans Gastropod Crab Barnacle Limpet Crab Barnacle Limpet Molted exoskeleton Segmentation Tiny free-swimming larva CLASSIFICATION BASED ON VISIBLE SIMILARITIES CLADOGRAM

Genes of many organisms show important similarities at a molecular level. Similarities in DNA can be used to help determine classification and evolutionary relationships

Carolus Linnaeus Swedish botanist that developed a two-word naming system called BINOMIAL NOMENCLATURE Gives the Genus and species name, written in italics or underlined Language is usually Latin Example: House cat – Felis domesticus Dog – Canis familaris Human – Homo sapien

Linnaeus’s System of Classification (8 Levels/ Taxa) Domain (most inclusive, less in common) Kingdom Phylum Class Order Family Genus Species (less inclusive, more in common) Each level is called a TAXON; taxa (plural)

Figure 18-5 Classification of Ursus arctos Giant panda Abert squirrel Coral snake Grizzly bear Black bear Red fox Sea star KINGDOM Animalia PHYLUM Chordata CLASS Mammalia ORDER Carnivora FAMILY Ursidae GENUS Ursus SPECIES Ursus arctos

Domains Currently, all organisms are grouped into 1 of 3 domains which reflect evolutionary relationships 1) Bacteria 2) Archaea 3) Eukarya EUKARYA ARCHAEA Kingdoms BACTERIA Eubacteria Archaebacteria Protista Plantae Fungi Animalia LUCA – last universal common ancestor