SB3C. Examine the evolutionary basis of modern classification systems. Evolutionary Classification (17.2) State Standard SB3C. Examine the evolutionary basis of modern classification systems.

Phylogenetic Species Concept Chapter 17 Organizing Life’s Diversity 17.2 Modern Classification Phylogenetic Species Concept Phylogeny is the evolutionary history of a species. The phylogenetic species concept defines a species as a cluster of organisms that is distinct from other clusters and shows evidence of a pattern of ancestry and descent. It also takes into account DNA similarities.

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

Morphological Characters Chapter 17 Organizing Life’s Diversity 17.2 Modern Classification Morphological Characters Shared morphological characters suggest that species are related closely and evolved from a recent common ancestor. Ex. Hawks & Eagles Analogous characters are those that have the same function but different underlying construction. No indication of common ancestry Homologous characters might perform different functions, but show an anatomical similarity inherited from a common ancestor.

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

Biochemical Characters Chapter 17 Organizing Life’s Diversity 17.2 Modern Classification Biochemical Characters Scientists use biochemical characters, such as amino acids and nucleotides, to help them determine evolutionary relationships among species. Chromosome structure & number is a powerful clue for determining species similarities. DNA and RNA analyses are powerful tools for reconstructing phylogenies.

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

Chapter 17 Organizing Life’s Diversity 17.2 Modern Classification Molecular Clocks Scientists use molecular clocks to compare the DNA sequences or amino acid sequences of genes that are shared by different species.

The differences between the genes indicate the presence of mutations. Chapter 17 Organizing Life’s Diversity 17.2 Modern Classification The differences between the genes indicate the presence of mutations. The more mutations that have accumulated, the more time that has passed since divergence of the species from the common ancestor.

What does this image represent? Chapter 17 Organizing Life’s Diversity Chapter Assessment Questions What does this image represent? phylogeny of species molecular clock cladogram tree of life A B C D CAQ 1

What do the colored bands in the figure represent? Chapter 17 Organizing Life’s Diversity Chapter Assessment Questions What do the colored bands in the figure represent? mutations molecular clock time gene A B C D CAQ 2

Which pair of organisms is more closely related? Chapter 17 Organizing Life’s Diversity Standardized Test Practice Which pair of organisms is more closely related? Quercus alba Cornus alba Quercus rubra A B C 1 and 2 2 and 3 1 and 3 STP 2

Standardized Test Practice Chapter 17 Organizing Life’s Diversity Standardized Test Practice How do systematists use this model to determine the degree of relationship among species? It shows the chromosomal structure of different species. It shows the genetic makeup of a common ancestor. It shows the rate of mutation for different species. It shows the relative time of divergence of a species. A B C D STP 3

Section 2 Vocabulary phylogeny character molecular clock cladistics Chapter 17 Organizing Life’s Diversity Vocabulary Section 2 phylogeny character molecular clock cladistics cladogram