1. Structural similarities Reveal relationships Presence of many shared physical structures implies that species are closely related or may have a common ancestor Ex. Lynx and Bobcat 2. Breeding Behavior provides important clues to relationships Ex. Frogs Hyla versicolor and Hyla chrysoscelis Live in same area and look similar but have different breeding behaviors making them 2 separate species. 3. Geographical distribution location of species on Earth helps biologists determine their relationships with other species. 4. Chromosome comparisons number and structure of chromosomes provide evidence for relationships. Ex. Similar appearance of chromosomes in chimps, humans, and gorillas 5. Biochemistry Closely related species have similar DNA sequences, therefore they have similar proteins. Ex. Red panda vs. giant panda More closely related to raccoons More closely related to bears Phylogeny = evolutionary history of a species Cladistics: Biological classification system based on phylogeny. Assumes that groups of organisms diverge and evolve from a common ancestor and retain unique inherited characteristics called derived traits. Cladogram used to identify a groups derived traits. Similar to pedigrees and is a model of phylogeny of a species. There are currently 6 kingdoms all organisms can be placed into one of those 6. Classification into a kingdom is based on certain criteria o Number of cells o How it obtains energy o Type of cell Number of cells: unicellular = 1 multicellular = many Energy: make own food = autotrophic get food elsewhere = heterotrophic Cell Type: (all have DNA) no nucleus = prokaryotic nucleus = eukaryotic 1.Archaebacteria (few species) Oldest organisms Found in extreme environments Ex. Hydrothermal vents, swamps, salt rich environments. 2. Eubacteria (10,000 species) live in moist habitats some cause disease while others are harmless = common bacteria (E. coli, Salmonella) 3. Protista Protist = eukaryote that lacks complex organ systems and lives in moist environments. Some are autotrophic and others are heterotrophic. ParameciumEuglena 4. Fungi (100,000 plus species) Fungus = unicellular or multicellular organism that absorbs nutrients from organic material. (decomposers) Morel Amanita Chicken Mushroom 5. Plantae (500,000 plus species) multicellular, photosynthetic autotrophs Oak Tree Ferns 6. Animalia multicellular heterotrophs complex organ systems most abundant kingdom Carl Woese and George Fox determined that all living organisms belong to one of three domains (placed higher than kingdoms) based on nucleotide sequences of rRNAs. 1.Archaea 2.Bacteria 3.Eucarya - Universal Phylogenetic Tree - Evolutionary relationships based on rRNA comparisons Three Domain System Three Domain System Domain Eukarya - includes organisms composed of eukaryotic cells (plants, animals, fungi, protists) Domain Bacteria - includes all prokaryotic cells, Kingdom Eubacteria Domain Archaea - includes only "ancient" bacteria, Archaebacteria Chapter 18 Test Targets Use taxonomy and classification terms Correctly write & identify scientific names Read & answer questions about a cladogram Use a dichotomous key and construct your own dichotomous keys