Phylogeny & Classification Chapter 18

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. Kings Play Chess On Fridays Generally Speaking

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 human Genusspecies

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 All of these show the same relationships

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

Clades A 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 Clades

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:

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:

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

BacteriaArchaeaEukarya EubacteriaArchaebacteriaProtistaFungiPlantaeAnimalia Prokaryote Eukaryote E.colihalophilesAmoebaMushroom, yeast Moss, ferns, flowering plants Sponges, worms, insects, fishes, mammals