Advanced BiologyChapter 23Systematics and Phylogenetic Revolution

SystematicsSystematics is the study of

evolutionary relationshipsPhylogeny is the study of

the patterns of relationships among species

Descent with Modification

Charles Darwin believed that all species had a common ancestor and that they changed over time like the branching on a tree

Cladistics

Method used to show derived characteristics in a phylogenetic pattern

Derived Characteristic - similarities inherited from recent common ancestor (hair in mammals)

Ancestoral Characteristic similarities that were inherited prior to recent common ancestor that other species do not share

Cladograms Cladograms is a diagram

to show a proposed evolutionary relationship between various species

Clade is a group of different species that share a derived characteristic

Separate using an outgrouping

Principle of Parsimony – simplest theory with fewest assumptions

Video on constructing a cladogramhttp://www.youtube.com/watch?v=46L_2RI1k3k

Terminology

Synapomorpy is a derived trait that is shared by two or more taxa within a clade and recent ancestor

Apomorphy is a derived trait that evolved within a tree

Pleisomorphy is another name for the ancestral characterstic (old trait)

Convergent Evolution aka Evolutionary Reversal

Photo taken by: Craig Pemberton http://www.flickr.com/photos/40154894@N06/3790813865

DNA

Instead of looking at characteristic traits, most scientist are now building phylogenetic trees based on the genetic code

Tree of Life

Classification

Classification is how species are placed into groups of hierarchy

Monophyletic group – includes recent common ancestor and all of its decendents

Paraphyletic group – includes the most recent common ancestor but NOT ALL DESCENDENTS

Polyphyletic group – unrelated organisms that does not include the most recent common ancestor of all groups

Monophyletic, polyphyletic and paraphyletic

Phylogenetic Species Concept

This is a concept that states that scientists should use evolution as the means of identifying a species instead of the biological species concept which states that a species is able to interbreed and produce viable offspring

Homologous structures come from the same body part such as legs of a horse and dolphins flipper

Homoplastic structures come from a different body part but are similar such as wings of birds and butterflies

Homologous Structures

Homplastic Structures

HIV (Human Immunodeficiency Virus)

HIV first detected in 1980s and currently infects more than 33 million people

Middle of the 80s discovered simian immunodeficiency virus (SIV). Found in laboratory monkeys

SIV showed similar characteristics as HIV but with slight differences.

It is now believed that HIV has been around for more than a million years and has been evolving

Use phylogenetic trees to trace HIV pathways