Chapter 17 Organizing Life’s Diversity

2. Chapter 17 Organizing Life’s Diversity Section 1: The History of Classification Section2: Modern Classification Section 3: Domains and Kingdoms

3. Organizing Life’s Diversity Chapter 17 17.2 Modern Classification Characters • To classify a species, scientists construct patterns of descent by using characters. • Characters can be morphological or biochemical.

4. Organizing Life’s Diversity Chapter 17 17.2 Modern Classification • Shared morphological characters suggest that species are related closely and evolved from a recent common ancestor. Morphological Characters

5. Organizing Life’s Diversity Chapter 17 17.2 Modern Classification Morphological Characters • Analogous characters are those that have the same function but different underlying construction

6. Organizing Life’s Diversity Chapter 17 17.2 Modern Classification Morphological Characters • Homologous characters might perform different functions, but show an anatomical similarity inherited from a common ancestor.

7. Organizing Life’s Diversity Chapter 17 17.2 Modern Classification Birds and Dinosaurs • Compare birds and dinosaurs: • Hollow bones • Theropods have leg, wrist, hip, and shoulder structures similar to birds. • Some theropods may have had feathers. Haliaeetus leucocephalus Oviraptor philoceratops

8. Organizing Life’s Diversity Chapter 17 17.2 Modern Classification • Scientists use biochemical characters, such as amino acids and nucleotides, to help them determine evolutionary relationships among species. • DNA and RNA analyses are powerful tools for reconstructing phylogenies. Biochemical Characters

9. The similar appearance of chromosomes among chimpanzees, gorillas, and orangutans suggests a shared ancestry. Organizing Life’s Diversity Chapter 17 17.2 Modern Classification

10. Organizing Life’s Diversity Chapter 17 17.2 Modern Classification Phylogenetic Reconstruction • Cladistics reconstructs phylogenies based on shared characters. • Scientists consider two main types of characters when doing cladistic analysis. • An ancestral character is found within the entire line of descent of a group of organisms. • Derived characters are present members of one group of the line but not in the common ancestor.

11. Organizing Life’s Diversity Chapter 17 17.2 Modern Classification Cladograms • The greater the number of derived characters shared by groups, the more recently the groups share a common ancestor.

12. Cladograms

13. Taxonomists have developed special guides known as dichotomous keys to aid in identifying unknown organisms. A dichotomous key consists of several pairs of descriptive statements that have only two responses. Dichotomous Keys