Evolutionary Histories A Phylogeny the evolutionary history of

Evolutionary Histories A. Phylogeny – the evolutionary history of an organism p Phylogenies can be shown as branching tree diagrams called phylogentic trees. B. Cladistics is a classification system based on common ancestry; it reconstructs phylogenies by inferring relationships based on shared characters q Cladistics can be shown using a branching diagram called a cladogram.

p A cladogram is a branching, treelike diagram in which the endpoints of the branches represent specific species of organisms.

A node is the intersection of two branches. p A node represents the most recent common ancestor. p

p A clade is a group of organisms that share certain traits derived from a common ancestor. A group that has none of the characters is known as an out-group.

ancestral characters – are characters that evolved in a common ancestor of both groups p derived characters – a character that evolved in one group but not in the other. . . a new trait p

Derived Characters Ancestral Characters

FYI: The organism that has ALL the characters will be at the top of the cladogram and the organism with the least characters will be at the bottom of the cladogram. Remember, the most distantly related organism is called an out-group.

Cladogram: 1. What organism is most closely related to Crocodile the bird? 2. What organisms have the derived character of hair? Primates, rodents, rabbits 3. What ancestral character is common to ALL the organisms? vertebrae 4. Circle the node that represents a common ancestor of the primates, rodents & rabbits, crocodiles, birds?

Phylogenetic Tree A node is the intersection of two branches. A node represents the most recent common ancestor.

Phylogenetic Tree: 1. Which organisms are most closely related? a. cow and camel 4 b. camel and goat 5 c. minke whale and cow 3 2. Which organisms are least closely related? a. cow and sheep 2 b. sheep and minke whale 4 c. camel and sheep 5

Two different ways of representing the same pattern of evolutionary histories: Cladogram Phylogenetic Tree