Systematics

• Systematics - the field of study concerned with organizing biological diversity based upon phylogeny
• Taxonomy - the science of naming organized groups

How do we generate a phylogenetic tree?

• Study group - the species group under study
• Outgroup - species related to study group -
• used evaluate evolutionary novelties

What is unique to a study group can be regarded as an evolutionary novelty

• Example: "feathers" and "beak" are evolutionary novelties of the "bird group"
• Example: "amniotic egg" is an evolutionary novelty of the "human+bird group"

Using the above information, the following phylogenetic tree can be generated:

Groups with more shared characteristics are more closely related to each other than to groups donwtree

• Example: pigeons and parrots are more closely related to each other than to humans
• Example: humans are more closely related to parrots than they are to frogs

Monophyly - what groups are "real" groups

• A monophyletic group contains an ancestor and all of its descendants
• A paraphyletic group contains an ancestor and some, but not all of its descendants

• To be a taxonomically valid group, it must be a monophyletic group
• What are some well-known, yet not taxonomically valid groups?
• Reptiles
• Protists

All of the blue taxa are commonly called "reptiles," the red taxa are not

Linnaeus - the "father of taxonomy" Taxonomy - the science of naming organisms, based upon a systematic classification Binomial nomenclature - every species has two names genus + species: Homo sapiens System is hierarchical - smaller groups combine to form larger groups

Some examples of organisms classified under Linnaeus' system

So, in theory, a member of a given family should be more closely related to other members of the same family than it would be to any member of a different family.

Is this seen in reality? Let's take a look....

• Linnaeus proposed a two kingdom system
• Plants
• Animals
• This system has many faults - where do you put fungi, bacteria, amoebas?
• Whittaker proposed a five knigdom system
• Monera (bacteria)
• Protists
• Plants
• Animals
• Fungi
• Is this system any better? Look at the diagram below

• Notice how the lines for the Fungi, Plants, and Animals all come out of the Protistans
• Now, according to our systematic theories, shouldn't the Protistan ancestor to the plants be more closely related to the other Protistans than to the Plants (a member of another Kingdom)?
• This system is still used for simplicity, not for any real phylogenetic reasons.

A much better representation of the diversity of life is presented below: