Chapter 18 Classification

18.1 Find Order in Diversity dichotomous key- tool that allows the user to determine the identity of items in the natural world

2. Taxonomy - branch of biology that identifies, names, and classifies species based on their morphology and behavior

3. binomial nomenclature – naming system in which each species is assigned a two part scientific name p. (512)

4. Rules for binomial nomenclature: write both names and underline or if typing italicize. The first name will be capitalized. That is the genus name. The second name will be in all lower case letters. This is the species name.

5. species – group of similar organisms that can breed and produce fertile offspring 6. genus (genera: plural) – a group of closely related species p. (512) genus and species name for the polar bear Ursus maritimus

Canis lupus Anarrhichas lupus What do the following two organisms have in common? Can you identify an organism from just the species name?

7. systematics - study of the diversity of life and the evolutionary relationships between organisms p(512) 8. The goal of systematics is to organize living things into groups (called taxons) that have biological meaning.

9. taxon (plural: taxa)– group or level of organization into which organisms are classified p. (512)

10. Linnaeus – created a system of binomial nomenclature and developed a classification system that organized species into taxa that formed a hierarchy or set of ordered ranks.

11. Over time, Linnaeus’s original classification system expanded to include eight hierarchical taxa: species, genus, family, order, class, phylum, and kingdom, domain. 12. Family – in classification, group of similar genera that share many similarities p. (513) Polar bear- Family Ursidae

13. order- in classification, a group of closely related families p Polar bear order Carnivora 14. class – in classification, a group of closely related orders p. (514) Polar bear class Mammalia 15. phylum – in classification, a set of closely related classes p. (514) Polar bear phylum Chordata

16. kingdom – largest and most inclusive group in Linnaean classification p.(514) Polar bear kingdom - Animalia

17. Linnaeus grouped organisms strictly according to similarities and differences. 18. Scientists today try to assign species to a larger group in ways that reflect how closely members of those groups are related to each other.

A few more points … .. Assigning scientific names makes sure people are only using one name for a species to avoid confusion Useful classifications will group organisms so that the ones in the same group are more similar than organisms in another group Only taxa determined by animals is species.

There are problems with the Linnaeus system of taxonomy- Species change over time Some species have tremendous variation Doesn’t account for extinct species Doesn’t consider organisms that reproduce asexually Some different species can interbreed and produce fertile offspring.

18.2 Modern Evolutionary Classification 1.Phylogeny – the evolutionary history of a species (516) 2. The goal of evolutionary classification, is to group species into larger categories that reflect lines of evolutionary descent, rather than overall similarities and differences.

3. Classifying organisms according to these rules places them into groups called clades.

4.clade – evolutionary branch of a cladogram that includes a single ancestor and all its descendants p. (516)

5. Clades differ from Linnaean taxa because they are monophyletic.

6. monophyletic group – group that consists of a single ancestral species and all its descendants and excludes any organisms that are not descended from that common ancestor p. (516) 7. paraphylectic – group includes a common ancestor but excludes one or more groups of descendants.

8. cladogram – diagram representing patterns of shared characteristics among species p. (517)

9. A cladogram links groups of organisms by showing how evolutionary lines, or lineages, branched off from common ancestors.

10. A cladogram shows relative degrees of relatedness among lineages. 11. Lineages - descent from an ancestor; ancestry or pedigree.

12. Node – the point of splitting on a cladogram

13. derived character – trait that appears in recent parts of a lineage, but not in its older members(518)

Derived Characters Whether or not a character is derived depends on the level at which you’re grouping organisms. Four limbs, for example, is a derived character for the clade tetrapoda. Hair is a derived character for the clade Mammalia, but four limbs is not derived for mammals. If it were, only mammals would have four limbs!

Derived Characters Specialized shearing teeth is a derived character for the clade Carnivora—of which both the coyote and lion are members. Neither hair nor four limbs is a derived character for this clade. Retractable claws is a derived character for the clade Felidae (the cats). Notice that lions have this trait, but coyotes do not.

14. A wide range of organisms share a number of genes and show important homologies that can be used to determine evolutionary relationships.

15. The more derived genetic characters two species share, the more recently they shared a common ancestor and the more closely they are related in evolutionary terms.

16. The use of DNA characters in cladistics analysis has helped to make evolutionary trees more accurate.

Notes . . . . . The larger a taxon, the farther back in time all of its members shared a common ancestor .

When constructing a cladogram, think back to when an ancestral species split into two new ones. That event is the basis of each branch point or node

Naming is important in taxonomy but grouping organisms to reflect evolutionary relationships is also important.

18.3 Building the Tree of Life 1. The six-kingdom system of classification includes the kingdoms Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia.

2. domain – larger, more inclusive taxonomic category than a kingdom p

3. Bacteria – domain of unicellular prokaryotes that have cell walls containing peptidoglycan (carboyhydrate); corresponds to the kingdom eubacteria p. (525)

4. Archaea – domain consisting of unicellular prokaryotes that have cell walls that do not contain peptidoglycan; corresponds to the kingdom Archaebacteria p. (526)

Extremophiles are organisms that have been discovered on earth that survive in environments that were once thought not to be able to sustain life.

5. Eukarya – domain consisting of all organisms that have a nucleus; includes protists, plants, fungi, and animals(526)

a. Protists – most are unicellular, but some are multicellular; some are autotrophic while others are heterotrophic; some display characters that most closely resemble those of plants, fungi, or animals.

Protista is written with quotations because it is not a true clade. True clades are monophyletic. Protista are paraphyletic. (group includes a common ancestor but excludes one or more groups of descendants) No way to put all unicellular eukaryotes into a clade that contains a single common ancestor with all of its descendants and only those descendants.

b. Fungi – heterotrophs with cell walls containing chitin(carbohydrate); most feed on dead or decaying organic matter; secrete enzymes to break down food so that they may absorb nutrients. Mushrooms are multicellular; yeasts are unicellular

c. Plantae – autotrophs with cell walls containing cellulose (carbohydrate); nonmotile

d. Animalia – multicellular and heterotrophic; no cell walls; most are motile

6. The tree of life shows current hypotheses regarding evolutionary relationships among the taxa within the three domains of life.