Modern Evolutionary Classification Notes- Ch. 18.2

Evolutionary Classification Modern classification is based on evolutionary theory Phylogeny – study of how orgs are related to each other (their evo relationships) Evolutionary Classification – grouping organisms based on their evolutionary history Species within a genus are more closely related to each other than species in another genus because all members of a genus share a recent common ancestor All genera in a family share a common ancestor – further away in the past then the ancestor of any genus in the family Higher the level of the taxon, the farther back in time the common ancestor Similar appearance not necessarily sharing a recent common ancestor (barnacle/limpet example)

Homologous Structures One way to discover relationships is by comparing anatomical structures (body organs and parts). Parts that are alike in basic structure and origin in several organisms but are not used for the same reason are called homologous structures. Ex. All above have the same bones and number, used differently- evidence points to common ancestor.

Cladograms Certain features shared by different group of organisms are known as “derived characters.” Derived characters – characteristics that are in recent parts of lineage but not in older members Used to make cladograms (aka phylogenetic tree) The more derived characteristics two organisms share, the closer their evolutionary relationship Uses only characteristics that evolutionary innovations Evolutionary innovations – characteristics that arise as lineages evolve over time Cladograms show how one lineage branched from another in the course of evolution

Sample Evolutionary Tree Small difference Common Ancestor Largest difference Moderate difference Smallest difference Relative Time

TRADITIONAL CLASSIFICATION Traditional Classification Vs Cladogram Section 18-2 Appendages Conical Shells Crustaceans Gastropod Crab Barnacle Limpet Crab Barnacle Limpet Molted exoskeleton Segmentation Tiny free-swimming larva TRADITIONAL CLASSIFICATION CLADOGRAM Go to Section:

Traditional Classification Vs Cladogram TRADITIONAL CLASSIFICATION Section 18-2 Appendages Conical Shells Crustaceans Gastropod Crab Barnacle Limpet Crab Barnacle Limpet Molted exoskeleton Segmentation Tiny free-swimming larva TRADITIONAL CLASSIFICATION CLADOGRAM Go to Section:

DNA & RNA All living things have it Compare organisms by genes More similar = more recent common ancestor Genes of many organisms show important similarities at the molecular level. Similarities in DNA can be used to help determine classification and evolutionary relationships Human/yeast share common gene for myosin protein – found in muscles (humans) help internal movement (yeast) More two species have diverged from one another, or changed in comparison to one another during evolution

Molecular Clocks Estimates amount of time since species diverged Uses mutations as markers Compare similarities and differences in genes

Derived Characters in Organisms Quick Lab Derived Characters in Organisms Organism Derived Characters Backbone Legs Hair Earthworm Absent Trout Present Lizard Human Identify the organisms in the table that is the least closely related to the others. Construct a cladogram of these animals. Do NOT copy the table. Analysis questions on next slide.

3. Analysis Questions What trait separates the least closely related organism from the other animals? List the animals in your cladogram in order of distance from the least closely related organism. Explain if your cladogram indicates that lizards and humans share a more recent common ancestor than either does with an earthworm. Where would you insert a frog if you added it to the cladogram? Explain your answer. Direct students to start with org that lacks at least one characteristic that all others share (students should ID worm). Refer to Fig 18-7 to start cladogram Lack of backbone Trout, liz, human Yes, lizards and humans shared ancestor that had legs and a backbone and that evolved after the earthworm’s lineage branched off on another evolutionary pathway A frog would occuby a branch b/w liz andtrout because it has legs. Another characteristic, such as dry sky, would then have to be added to liz.

Derived Characters in Organisms Extra Practice Derived Characters in Organisms Organism Derived Characters Backbone Placenta Foramen Magnum Forward Tuna Present Absent Horse Human 1. Construct a cladogram for the info above. 2. Three previously unknown vertebrates have been discovered in a rainforest in South America. a. “rat-like creature” b. “iguana-like creature” c. “goldfish-like creature” Place these animals on your cladogram and justify your placement. (backbone) tuna (placenta) horse  (FM forward) human