1. Organizing Life’s Diversity Chapter 17

2. How Classification Began In order to better understand organisms scientists group them. Classification is the tool scientists use to group organisms Taxonomy is the branch of biology that groups and names organisms based on their characteristics. Taxonomists are scientists who study taxonomy.

3. Early Systems 1. Aristotle's System a. Only included plants and animals. b. Did not group organisms by evolutionary history. c. Many organisms did not fit. 2. Linnaeus’s System a. Based on physical and structural similarities. b. Still just plants and animals, but he further subdivided these groups. c. Some scientists proposed that structural similarities mirrored evolutionary relationships.

4. Today’s Classification System 3. Modern system a. Binomial nomenclature is a two name / word system that Linnaeus developed to identify species b. Written in Latin because this language does not change and is universal. c. The first word indicates the genus and the second the species (which is descriptive of the organism -sapiens means wise) i. Ex. Homo sapiens, H. sapiens, Homo sapiens, H. sapiens

5. How Living Organisms are Classified 1. Organisms are ranked from very broad taxa containing lots of species to very specific taxa.

6. Example: Humans Domain: Eukaryota Kingdom: Metazoa Phylum: Chordata Class: Mammalia Order: Primata Family: Hominidae Genus: Homo Species: sapiens

7. The Six Kingdoms

8. How many species are there in each kingdom? Archaebacteria = 500 Eubacteria = 10,000 Protista = 70,000 Fungi = 110,000 Plants = 510,000 Animals = 2,900,000

9. How Are Evolutionary Relationships Determined? 1. By looking at structural similarities 2. Observing breeding behavior 3. Geographic distribution 4. Comparing chromosome number and structures 5. Biochemical analysis of organisms (comparing DNA sequences).

10. Phylogenetic Classification: Models 1. Phylogeny is the evolutionary history of an organism (like your genealogy) and is depicted by a classification system 2. Cladistics is a system of classification based on phylogeny a. Scientists who use cladistics assume organisms diverge and evolve from a common ancestor b. Still retain some unique characteristics called derived traits. c. A cladogram uses the derived traits of a group in the form of a branching diagram

11. Cladogram

12. Other Phylogenetic Models 1. Fan shape a. May depict time organisms became extinct b. Or relative number of species in a group

13. Identifying Organisms 1. Use a manual or field guide 2. Ask a local expert 3. Use a Key – a set of descriptive steps that is subdivided into steps a. Ex. Dichotomous Key – two descriptions at each step. Just follow the steps until the key reveals the name of the organism.