18.1 Finding Order in Diversity

To study the diversity of life, biologists use a classification system to name organisms and group them in a logical manner. Taxonomy

Common names can be confusing and vary between regions. Scientists agreed to use Latin and Greek when assigning scientific names to organisms. This practice is still followed today as new organisms are discovered.

Two-word naming system used in differentiating a species Genus species A genus is a group of related species. Ursus arctos Ursus maritimus

Includes seven levels- from smallest to largest Species, Genus, Family, Order, Class, Phylum, Kingdom Each level is called a taxon.

Family Genera that share many characteristics Ursidae Ursidae Ursus arctos Ursidae Ursus maritimus Ursidae Ailuropoda melanoleuca

Order Broad taxanomic category composed of similar families Carnivora Examples: Canidae Felidae Ursidae

Class Composed of similar orders Mammalia Includes animals that are warm blooded, have body hair, and produce milk for their young.

Phylum Includes many different organisms that share important characteristics Chordata Mammalia Aves Reptilia Amphibia Several classes of fish

Kingdom Largest and most inclusive level Linnaeus started with only 2- Animals & Plants Now, we recognize 6! Plants, Animals, Protists, Fungi, Archaebacteria, Eubacteria.

18.2 Modern Evolutionary Classification

Organisms determine who belongs in their species by choosing whom they mate with! Scientists have “invented” larger taxa according to an organisms characteristics.

Strategy of grouping organisms together based on their evolutionary history Phylogeny- evolutionary relationships among organisms See Figure 18-7

Organisms that appear very similar may NOT, in fact, share a common ancestor. Because… natural selection operating on species in similar ecological environments has often caused convergent evolution.

Only identifies and considers characteristics of organisms that are evolutionary innovations New characteristics that arise as lineages evolve over time Derived Characters- appear in recent parts of a lineage but not in its older members. Can be used to construct a cladogram

Diagram that shows the evolutionary relationships among a group of organisms Useful for helping scientists understand how one lineage branched from another in the course of evolution Like a “Family Tree”

All organisms have DNA to pass on to future generations. The genes of many organisms show important similarities at the molecular level. Similarities in DNA can be used to help determine classification.

Comparison of DNA can be used to mark the passage the time that two species have been separated on the “family tree” The degree to which genes are dissimilar indicates how far in the past the two species shared a common ancestor.

18.3 Kingdoms & Domains

All science adapts to new discoveries. In the early days of classification Linnaeus proposed a 2-kingdom system. Today, because of new discoveries, we recognize a six- kingdom system of classification. Changing Number of Kingdoms Timeline Names of Kingdoms 1700sPlantaeAnimalia Late 1800sProtistaPlantaeAnimalia 1950sMoneraProtistaFungiPlantaeAnimalia 1990sEubacteriaArcheabacteriaProtistaFungiPlantaeAnimalia

Molecular clock model analysis has given rise to a new taxonomic category larger than the kingdoms. Domains Classification of Living Things DOMAIN BacteriaArchaeaEukarya KINGDOMEubacteriaArchaebacteriaProtistaFungiPlantaeAnimalia CELL TYPE Prokaryote Eukaryote CELL STRUCTURES Cell walls with peptidoglycan Cell walls without peptidoglycan Cell walls some with cellulose Cell walls of chitin Cell walls of cellulose; chloroplasts No cell walls or chloroplasts NUMBER OF CELLS Unicellular Most Unicellular Most Multicellular Multicellular MODE OF NUTRITION Autotroph or Heterotroph HeterotrophAutotrophHeterotroph

Unicellular Prokaryotic Thick, rigid cell walls Have peptidoglycan Corresponds with the kingdom Eubacteria Ecologically diverse Some need oxygen Some photosynthesize Some are free-living Some are parasites

Unicellular Prokaryotic Cell walls No peptidoglycan Unique lipids Extremophiles Hot springs Brine pools Anaerobic mud

Kingdom Protista Cannot be classified as animals, plants or fungi Most diverse kingdom Most unicellular Except multicellular algae Autotrophs or Heterotrophs Some share characteristics with plants, some with fungi and some with animals.

Kingdom Fungi Heterotrophs Feed on decaying organic matter Secrete a digestive enzyme and absorb their food Multicellular Mushrooms Unicellular Yeast

Kingdom Plantae Multicellular Photosynthetic autotrophs Nonmotile Cell walls with cellulose Includes mosses, ferns, cone-bearing and flowering plants

Kingdom Animalia Multicellular Heterotrophic No cell walls Very diverse group