1. 1 Chapter 18: Classification

2. 2 18–1 Finding Order in Diversity  Life on Earth has been changing for more than 3.5 billion years  1.5 million species named  between 2 and 100 million additional species have yet to be discovered

3. 3 Why Classify?  organize living things into groups that have biological meaning  Taxonomy = discipline of classifying organisms and assigning each organism a universally accepted name

4. 4 Assigning Scientific Names  Common names are confusing and vary among languages or even regions –Ex: cougar, mountain lion, panther, puma –different species sometimes share a single common name  Ex: buzzard: hawk? Vulture?  Scientists have agreed to a single name for each species  Use Latin & Greek

5. 5 Binomial Nomenclature  Carolus Linnaeus, –a Swedish botanist, 1700s  binomial nomenclature = classification system in which each species is assigned a two-part scientific name –written in italics –first word is capitalized, the second word is lower case

6. 6 Scientific Names  grizzly bear is called Ursus arctos –Ursus — is the genus  Genus = group of closely related species –arctos – is the species  unique to each species within the genus  Often a Latinized description of some important trait of the organism or an indication of where the organism lives –Ursus maritimus, the polar bear  maritimus, referring to the sea

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8. 8 Linnaeus's System of Classification  Hierarchical - it consists of levels  includes seven levels –from smallest to largest—species, genus, family, order, class, phylum, and kingdom. –Each level is called a taxon or taxonomic category

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10. 10 Ursus arctos (Grizzly Bear)  Kingdom – Animalia  Phylum – Chordata  Class – Mammalia  Order – Carnivora  Family –Ursidae  Genus –Ursus  species - arctos

11. 11 Humans  Kingdom = Animalia  Phylum (Division for plants) = Chordata  Class = Mammalia  Order = Primates  Family = Hominidae  Genus = Homo  species = sapiens

12. 12  Taxonomic groups above the level of species are “invented” by researchers who decide how to distinguish between one genus, family, or phylum, and another.

13. 13  Phylogeny = the study of evolutionary relationships among organisms  Biologists now group organisms into categories that represent lines of evolutionary descent, or phylogeny, not just physical similarities.

14. 14  evolutionary classification = method of grouping organisms together according to their evolutionary history

15. 15  The higher the level of the taxon, the farther back in time is the common ancestor of all the organisms in the taxon.

16. 16  Cladogram = diagram that shows the evolutionary relationships among a group of organisms

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20. 20  The genes of many organisms show important similarities at the molecular level.  Similarities in DNA can be used to help determine classification and evolutionary relationships.  The more similar the DNA sequences of two species, the more recently they shared a common ancestor, and the more closely they are related in evolutionary terms.

21. 21 Dichotomous Key  A dichotomous key is a tool that allows the user to determine the identity of items in the natural world, such as trees, wildflowers, mammals, reptiles, rocks, and fish.  Keys consist of a series of choices that lead the user to the correct name of a given item.  "Dichotomous" means "divided into two parts". Therefore, dichotomous keys always give two choices in each step.

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23. 23 18–3 Kingdoms and Domains  There are now 6 Kingdoms – listed below.

24. 24  Domain = most inclusive taxonomic category; larger than a kingdom

25. 25 Eubacteria  Unicellular  Prokaryotic  Autotroph or heterotroph  Cell walls with peptidoglycan  Examples: E. coli, Streptococcus, Staph

26. 26 Archaebacteria  unicellular  prokaryotic  extreme environments –volcanic hot springs, brine pools, and black organic mud totally devoid of oxygen  Auto or heterotroph  cell walls lack peptidoglycan peptidoglycan

27. 27 Protista  eukaryotic  greatest variety  Most single-celled, some multi  photosynthetic or heterotrophic  Ex: kelp, amebas, slime mold, paramecium, euglena

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29. 29 Fungi  heterotrophs –feed on dead or decaying organic matter organic matter  Eukaryotic  Most multicellular, some uni  Cell walls of chitin  EX: mushroom, yeast

30. 30 Plantae  multicellular  photosynthetic autotrophs  Eukaryotic  Cells walls of cellulose

31. 31 Animalia  multicellular  heterotrophic  Eukaryotic  No cell walls