Understanding Taxonomy: The Science of Classifying Organisms in the Tree of Life

1. Classification Chapter 18

2. Finding Order in Diversity • Why Classify? • Scientists classify organisms into groups in a logical manner to make it easier to study the diversity of life. • Taxonomy: The discipline of classifying organisms and assigning each a universally accepted name. • Assigning Scientific Names • Each species has been assigned a name for classification purposes. • Binomial Nomenclature: The two part scientific naming system used in classification. • The fist name is always capitalized and represents the Genus of the animal. • Genus: A group of closely related animals, for example; bears • The second name is specific to that type of animal.

3. Linnaeus’s System of Classification • Carolus Linnaeus: Developed binomial nomenclature. • Linnaeus’s hierarchical system of classification includes seven levels. • The seven layers from smallest to larges are as follows. • Taxon: A group or level of organization into which organisms are classified. • Species  Genus Family  Order  Class Phylum  Kingdom. • Linnaeus grouped organisms based on physical similarities and he only had two kingdoms; Animalia & Plantae.

4. Linnaeus System Cont… • Species: A group of similar organisms that can breed and produce fertile offspring. • Genus: A group of closely related species. • Family: A group of genera that share many characteristics. • Order: A group of similar families. • Class: A group of similar orders. • Phylum: A group of closely related classes. • Kingdom: Large taxonomic group, consisting of closely related phyla.

5. Linnaeus’s Hierarchical System

6. Classifying Organisms • Dichotomous Key:A key used to identify a plant or animal in which each stage presents descriptions of two distinguishing characters, with a direction to another stage in the key, until the species is identified.

7. Modern Evolutionary Classification • Phylogeny: The study of evolutionary relationships among animals. • Evolutionary Classification: The strategy of grouping organisms together based on their evolutionary history. • Biologist group organisms based on evolutionary descent or phylogeny, not just physical characteristics. • Derived characters: Characteristics that show up in recent organism lineage but not in older organisms. • Cladogram: A diagram that shows evolutionary relationships.

8. Kingdoms and Domains • There are six (6) kingdoms in modern classification; Eubacteria, Archaebacteria, Protista, Fungi, Plantae, and Animalia. • The Three-Domain System: • Modern Biologist have created a new taxonomic category called domain. • Domain: is a more inclusive category and is larger than a kingdom. • There are three domains: Eukarya, Bacteria, and Archaea.

9. Three Domains • Eukarya: Eukaryotic, complex, maybe multi-cellular. • Kingdoms: Protista, Fungi, Plantae, Animalia • Bacteria: Unicellular, prokaryotic • Kingdom: Eubacteria • Archaea: Unicellular, prokaryotic, live in extreme environments. • Kingdom: Archaebacteria

11. Tree of Life