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Chapter 17

Chapter 17. Organizing Life’s Diversity. Section 17.1 Classification. FL Standard SC.912.L.15.4: Describe how and why organisms are hierarchically classified and based on evolutionary relationships. FL Standard SC.912.L.15.5: Explain the reasons for changes in how organisms are classified.

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Chapter 17

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  1. Chapter 17 Organizing Life’s Diversity

  2. Section 17.1 Classification • FL Standard SC.912.L.15.4: • Describe how and why organisms are hierarchically classified and based on evolutionary relationships. • FL Standard SC.912.L.15.5: • Explain the reasons for changes in how organisms are classified.

  3. Organization of Organisms • Why? • It helps scientists better understand organisms

  4. Organization of Organisms • How? • Classification • The grouping of objects or information based on similarities

  5. Taxonomy • The branch of biology that groups and names organisms based on studies of their different characteristics. • These scientists are called taxonomists.

  6. Aristotle • Grouped organisms into two groups: • Plants • Herbs • Shrubs • Trees • Animals • Grouped based on their habitat and physical differences

  7. Aristotle • The problem: • It didn’t group according to evolutionary history • There are other organisms that aren’t plants or animals

  8. Linnaeus • System of classification based on physical and structural similarities of organisms • Basis of modern classification system • Gave organisms scientific names using a two-word naming system —binomial nomenclature • First name—genus • Group of similar species • Second name—species identifier (a.k.a. specific epithet ) • Often describes a characteristic of the organism

  9. Scientific Names • How it’s done: • Written in Latin • Genus name is capitalized • Species identifier is lower case • Italicized when typing • Underlined when handwritten • Example: Homo sapiens • Homo means “man”, sapiens means “wise”

  10. Subspecies • Some organisms have subspecies, variations of a species that live in different geographic areas. • Capable of interbreeding • The subspecies’ name follows the species identifier

  11. Examples of Subspecies • Canis lupus familiaris(domestic dog) • Canis lupus lupus(wolf) • Canis lupus dingo (dingo)

  12. Modern Classification • Based on comparisons of external and internal structures, geographical distribution, genetic makeup • Helps establish evolutionary relationships between living and extinct species

  13. Example • Are dinosaurs more closely related to birds or reptiles? • Due to similarities in bone structures, taxonomists classify dinosaurs as more similar to birds than to reptiles.

  14. How can organisms be identified? • Scientists use a tool called a dichotomous key to identify organisms based on their external features

  15. The first step in the key will be organized the following way: 1. a. wings covered by an exoskeleton b. wings not covered by an exoskeleton Next, the statements need to lead the observer to the next step to narrow the identification further: 1. a. wings covered by an exoskeleton ………go to step 2 b. wings not covered by an exoskeleton ……….go to step 3 Step 2 needs to consist of a pair of statements that will allow for the identification of the ladybug and the grasshopper: 2. a. body has a round shape ……….ladybug b. body has an elongated shape ……….grasshopper Step 3 needs to consist of a pair of statements that will allow for the identification of the housefly and dragonfly: 3. a. wings point out from the side of the body ……….dragonfly b. wings point to the posterior of the body ……….housefly

  16. How Living Things are Classified • A group of organisms is a taxon. • Organisms are ranked in taxa from very broad characteristics to very specific ones • Smallest taxon is species—organisms that look alike and can successfully interbreed

  17. Taxa • Genus—A group of similar species that have similar features and are closely related • Family—Consists of a group of similar genera (pl. of genus) • Order—A taxon of similar families • Class—A taxon of similar orders • Phylum—A taxon of similar classes --Division is used in plants & bacteria only

  18. Taxa • Kingdom—A taxon of similar phyla or divisions • Domain—Contains one or more kingdoms

  19. Human Taxonomy • Domain: Eukarya • Kingdom: Animalia • Phylum: Chordata • Class: Mammalia • Order: Primates • Family: Hominidae* • Genus: Homo • Species: Homo sapiens *Classifications have changed.

  20. Cl

  21. Why do classifications change? • As more fossils and evolutionary relationships are discovered, changes to classifications are sometimes necessary.

  22. New Human Classification • Domain: Eukarya • Kingdom: Animalia • Phylum: Chordata • Class: Mammalia • Order: Primates • Suborder Hominoids – gibbons, orangutans, chimps, gorillas, humans, relatives • Family: Hominidae* (Hominids) – no gibbons • Subfamily Homininae – no orangutans • Tribe: Hominini (Hominins) – humans & extinct relatives • Genus: Homo • Species: Homo sapiens • Subspecies: Homo sapiens sapiens (to distinguish it from H. sapiens idaltu, discovered in 1997)

  23. A good way to remember • Can you come up with a mnemonic device to help you remember the order? • Domain-Kingdom-Phylum-Class-Order-Family-Genus-Species • Did King Phillip cut off four giant sunflowers?

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