Phylogeny & Classification

All of chapter 18. Yup, the whole thing in one class.

Linnaean Classification

This system was created long before scientists understood that organisms evolved. Because the Linnaean system is not based on evolution, most biologists are switching to a classification system that reflects the organisms' evolutionary history.

King Philip Came Over For Good Soup.

Binomial Nomenclature

Each species is assigned a two part scientific name.

Written in italics First word is capitalized Second word is lowercase

Binomial Nomenclature

Homo sapien

Oncorhynchus keta

human

chum salmon

Genus species

What is a Phylogeny?

The context of evolutionary biology is phylogeny

The connections between all groups of organisms as understood by ancestor/descendant relationships.

Different ways of drawing trees

When a lineage splits (speciation), it is represented as branching on

a phylogeny.

CladesA clade is a grouping that includes a common ancestor and all the descendents (living and extinct) of that ancestor. Using a phylogeny, it is easy to tell if a group of lineages forms a clade. Imagine clipping a single branch off the phylogeny—all of the organisms on that pruned branch make up a clade.                                                            

Identifying CladesAre reptiles a clade?

Sample Practice Question*

For the tree above, you would need to say: the frog and salamander are more closely related to each other than to the

lizard, snake, bird, and mouse the lizard and snake are more closely related to each other than to the bird,

mouse, frog, or salamander the bird is more closely related to the lizard and the snake than it is to the

mouse, frog, or slamander the mouse is more closely related to the lizard, snake, and bird than it is to the

frog or salamander

* Information for this practice question comes from: http://www.utm.edu/departments/cens/biology/rirwin/391/391Phylog.htm

Practice Question*

Note that the previous example gives four statements about the relationships: one for each ancestral species on the tree.  See if you can give the same kind of description of relationships for each of the phylogenies pictured above.

* Information for this practice question comes from: http://www.utm.edu/departments/cens/biology/rirwin/391/391Phylog.htm

Homologies help determine how species are related.

Homology vs. Analogy Homologies are similar

characteristics shared by two different organisms because they were inherited from a common ancestor.

Analogis are similar characteristics shared by two different organisms because of convergent evolution.

Molecular Biology is a powerful tool in classification DNA & RNA comparisons

A molecular clock can be calibrated in actual time. Possible to graph base substitutions against known evolutionary landmarks.

Molecular Clocks

Kingdoms & Domains Linnaeus’s two kingdoms, Animalia and Plantae don’t adequately

represent the full diversity of life. Instead, scientists made five kingdoms

Monera, Protista, Fungi, Plantae and Animalia

Then they split Monera into Eubacteria and Archaebacteria

Leading to the three kingdom system

Bacteria Archaea Eukarya

Eubacteria Archaebacteria Protista Fungi Plantae Animalia

Prokaryote Prokaryote Eukaryote

E.coli halophiles Amoeba Mushroom,yeast

Moss, ferns, flowering plants

Sponges, worms, insects, fishes, mammals