Bell Work List 2 sister groups in the phylogeny.

Intro to Biology – Lecture 60 Cladograms

Cladogram A diagram used to show relations among organisms.

What Does a Cladogram Look Like? Uses lines that branch off in different directions ending at groups of organisms. Many shapes but all have lines that branch off from other lines. The lines can be traced back to where they branch off.

Branching Off Points Branching off points represent a hypothetical ancestor which would have the combined traits of the lines above it. This hypothetical ancestor might then provide clues about what to look for in an actual evolutionary ancestor.

How are Cladograms Made Originally – made by observing morphological characteristics Today – made by sequencing DNA and RNA

Minor Differences Between Cladograms and Phylogeny The length of branches represents the time for a species to change. Relates organisms based on comparisons of the similarities/dissimilarities of their anatomies. Measures degrees of similarity. Concerned with who appears most similar to whom at one point in time. Branch length has no relevance to time. Attempts to trace evolutionary relationships directly by analyzing gene sequences. Traces the sharing of derived characters. Does not show how ancestors are related to descendants or how much they have changed

Cladogram vs Phylogeny

Cladogram and Phylogeny Often the two methods give the same tree, but sometimes they differ because of the minor differences in the way they are formed.

Cladogram and Phylogeny For the purpose of this class, we will assume that the two are the same.

The Same

More of the Same

Example Cladogram

Create a Cladogram Characteristic/Organism Cells Backbone Legs Hair Opposable Thumbs Slug Catfish Frog Tiger Human

Practice - Cladogram cells legs 6 legs wings Worm Spider Ant Fly

Cladogram Practice Characters Shark Bullfrog Kangaroo Human Vertebrae X Two pairs of limbs Mammary glands Placenta

Cladogram Practice TRAITS Kangaroo Monkey Bullfrog Human Snapping Turtle Tuna Dorsal Nerve Cord Notochord X Paired Appendages Vertebral column Paired legs Amnion (Amniotic sac) Mammary Glands Placenta Canine teeth short Foramen magnum fwd

Cladogram Practice Organism Vascular Tissue Flowers Seeds Mosses Pine Trees 1 Flowering Plants Ferns

DERIVED CHARACTERISTIC Cladogram Practice ORGANISM DERIVED CHARACTERISTIC BACKBONE LEGS HAIR EARTHWORM ABSENT TROUT PRESENT LIZARD HUMAN

Pop Quiz

Pop Quiz – Fill in the Chart and the Cladogram Correctly hair legs thumbs eyes Human Snake Monkey Mouse