Warm-Up 3/24 What is a derived characteristic? What is a clade? Circle a clade on the cladogram below.

Chapter 18 – Classification 18.2 Modern Evolutionary Classification

Classification is Based on Evolutionary Relationships (CLADISTICS) Phylogeny—the study of how living and extinct organisms are related to one another.

Cladograms Cladogram - is an evolutionary tree made using cladistics (ancestral relationships) More closely related species share the most derived characteristics

Derived Characteristics Diagram uses derived characters to organize & arrange species Derived Characteristic - a trait that arose in the most recent common ancestor of a particular lineage and was passed along to its descendants.

Cladogram

Clades Clade - a group of species that includes: A single common ancestor All descendants of that ancestor, both living and extinct. Cannot include any species that are not descended from that common ancestor. B is the ancestral species to… I is the ancestral species to…

Building Cladograms A speciation event = ancestral lineage branched into two new lineages – Branch point is called a node. The bottom of the tree represents the common ancestor shared by all organisms..

Building Cladograms -2 A cladogram’s branching patterns indicate degrees of relatedness among organisms. Which lineages are most closely related and why? 2&3 1&4 3&4 1&2

Building Cladograms - 3 Represents the current understanding about evolutionary relationships among vertebrates. Question: Form one hypothesis about evolutionary relationships based off the cladogram below.

Reading Cladograms This cladogram shows a simplified phylogeny of the cat family.

Reading Cladograms – Questions Which node represents the common ancestor of four- limbed animals in the cladogram? Branch point at Amphibians What does the order of the forks represent? Order in which various groups branched off over the course of evolution. All organisms on the cladogram share which derived characteristic? Four Limbs

Reading Cladograms – Questions Which derived character defines the clade Carnivora? Specialized shearing teeth Retractable claws is a derived character shared only by members of clade___________ . Felidae

Cladogram

Cladogram Facts Each derived character defines a clade. Derived characters that appear “lower” on the cladogram than the branch point for a clade are not derived for that particular clade. Is hair a derived character for the clade carnivora? No!! NO

Cladograms Facts Smaller clades are nested within the larger clades.

Clades and Traditional Taxonomic Groups Today’s reptiles are all descended from a common ancestor. Modern birds, however, are also descended from that ancestor.

Genes as Derived Characters All organisms carry genetic information in their DNA passed on from earlier generations. Wide ranges of organisms share a number of genes that can be used to determine evolutionary relationships.