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Chapter 17 Organizing Life’s Diversity. Section 1: The History of Classification. Section 2: Modern Classification. Section 3: Domains and Kingdoms. Organizing Life’s Diversity. Chapter 17. 17.2 Modern Classification. Characters. - PowerPoint PPT Presentation
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Chapter 17 Organizing Life’s Diversity
Section 1: The History of Classification
Section 2: Modern Classification
Section 3: Domains and Kingdoms
Characters To classify a species, scientists construct patterns of descent by using characters.
Characters can be morphological or biochemical.
Organizing Life’s Diversity
17.2 Modern ClassificationChapter 17
Morphological Characters Shared morphological characters suggest that species are related closely and evolved from a recent common ancestor.
Organizing Life’s Diversity
17.2 Modern ClassificationChapter 17
Morphological Characters Analogous characters
are those that have the same function but different underlying construction
Organizing Life’s Diversity
17.2 Modern ClassificationChapter 17
Morphological Characters Homologous characters might perform different functions, but show an anatomical similarity inherited from a common ancestor.
Organizing Life’s Diversity
17.2 Modern ClassificationChapter 17
Birds and Dinosaurs
Organizing Life’s Diversity
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
17.2 Modern ClassificationChapter 17
Biochemical Characters
Organizing Life’s Diversity
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.
17.2 Modern ClassificationChapter 17
Organizing Life’s Diversity
The similar appearance of chromosomes amongchimpanzees, gorillas, and orangutans suggests a shared ancestry.
17.2 Modern ClassificationChapter 17
Phylogenetic Reconstruction
Organizing Life’s Diversity
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.
17.2 Modern Classification
Chapter 17
Cladograms
Organizing Life’s Diversity
The greater the number of derived characters shared by groups, the more recently the groups share a common ancestor.
17.2 Modern ClassificationChapter 17
Cladograms
Dichotomous Keys• 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.
