18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationWarm-Up 3/24 What is a derived characteristic? What is a clade?

Circle a clade on the cladogram below.

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationChapter 18 – Classification 18.2 Modern Evolutionary 18.2 Modern Evolutionary ClassificationClassification

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationClassification is Based on Evolutionary Relationships (CLADISTICS) Phylogeny—the study of how living and extinct organisms are related to one another.

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationCladograms Cladogram - is an evolutionary tree made using cladistics (ancestral relationships) More closely related species share the most derived characteristics

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationDerived 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.

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationCladogram

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationClades 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 B is the ancestral species to… to…

I is the ancestral species I is the ancestral species to…to…

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationBuilding 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..

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationBuilding 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

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationBuilding Cladograms - 3 Represents the current understanding about evolutionary relationships among vertebrates. Question: Form one hypothesis about evolutionary relationships based off the cladogram below.

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationReading Cladograms This cladogram shows a simplified phylogeny of the cat family.

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationReading 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

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationReading 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

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationCladogram

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationCladogram 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!!

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationCladograms Facts Smaller clades are nested within the larger clades.

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationClades and Traditional Taxonomic Groups Today’s reptiles are all descended from a common ancestor.

Modern birds, however, are also descended from that ancestor.

18.2 – 18.2 – Modern Evolutionary ClassificationModern Evolutionary ClassificationGenes 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.