CHAPTER 18 NOTES

Evolutionary Classification

Core Standard: Describe how biochemical, fossil, anatomical, developmental, and genetic findings are used to determine relationships among organisms and how those relationships are then used to produce modern classification systems.

 

Phylogeny: the evolutionary history of lineages.

 

The goal of evolutionary classification is to group species into larger categories that reflect line of evolutionary descent rather than overall similarities and differences.

 

Evolutionary classification (phylogenetic systematics) groups organisms into clades.

·     A clade is a group of species with a single common ancestor.

·     A clade includes all the descendants of the ancestor that are living or extinct.

·     A clade must be a monophyletic group (includes a single common ancestor and all of its descendants).

 

 

NOTE: Some of the taxa in the Linnaean classification system were paraphyletic meaning the group includes a common ancestor but excludes one or more groups of descendants.

 

Cladograms: links groups of organisms by showing evolutionary lines branched off from a common ancestor.

 

  

 

A.    Segmented Body       E. Jumping Legs

B.     Legs                           F. Wings

C.     6 legs                         G. Double wings

D.    Crushing mouthparts H. Curling antennae

Node: the last point at which the two new lineages shared a common ancestor.

 

Derived character: a trait that arose in the most recent common ancestor and was passed along to its descendants.

·     Smaller clades are nested within larger clades.

·     Whether or not a character is derived depends on the level of grouping.

 

Example: Hair is a derived character for the clade Mammalia but four limbs is NOT a derived character for the clade Mammalia. If it were then only mammals would have that trait.

 

·     Sometimes derived characters are lost by an organism but the ancestor had the derived character.

Example: Snakes are in the clade Reptilia which in the clade Tetrapoda. Snakes don’t have four limbs but their ancestors did.

·      DNA evidence is the most recent means of determining derived characters.

·     The more derived genetic characters, the more recent the common ancestor.

·     The more derived genetic characters, the more closely related two organisms are.

 

Different versions of the same cladogram:

         

 

 

3 domains and 6 kingdoms:

Domain

Bacteria

Archaea

Eukarya

Kingdom

Eubacteria

Archaebacteria

“Protista” not a true clade

Fungi

Plantae

Animalia

 

Cell Type

Prokaryote

Prokaryote

Eukaryote

 

Eukaryote

Eukaryote

Eukaryote

Cell Structures

Cell wall with peptidoglycan

Cell walls without peptidoglycan

Cell walls with cellulose in some

Cell walls of chitin

Cell wall of cellulose, chloroplasts

No cell walls or chloroplasts

Number of cells

Unicellular

Unicellular

Unicellular, some colonial

Most multicellular, a few unicellular

Multicellular

Multicellular

Mode of nutrition

Autotroph or heterotroph

Autotroph or heterotroph

Autotroph or heterotroph

Heterotroph

Autotroph

Heterotroph

Examples

Streptococcus, E. coli

Methogens, Sulfolobus

Amoeba, paramecium

Mushrooms, yeast

Mosses, fern, flowering plants

Sponges, worms, insect, fishes, mammals