Constructing a Cladogram
Evidence of phylogeny (common ancestry) comes from comparing the traits that are shared among the
species being considered. Traits that are truly insightful must be identified or the cladogram won't "tell
the truth" about the ancestral phylogenetic relationships of the species being compared.
Select the traits by comparing the members of your "in-group" to determine what makes them more
like each other than those outside the group. To be insightful, a trait must be present in at least two of
the species being studied and must not occur in every member of the "in-group." Select an "out-group"
species that you believed split off long ago from a common ancestor of the "in-group." The out group
species does not share the traits you have identified in the in group. The traits become "doors" through
which only some of your species can pass.
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Examine the photo cards and consider what traits suggest relatedness
Choose 7 cards for your "ingroup" that you feel confident are distantly related
List your 7 animals on the worksheet as suggested below
List 7 insightful traits on the worksheet
Select an animal card for your "outgroup" as described above
Create a cladogram (tree) using at least 6 of the character states as shown below
Each character entered on your chart must be simplified to a YES / NO question
You cannot have variations (green head vs yellow head)
Instead, use GREEN HEAD – Absent or Present
Fur – Absent or Present
Some Possibly Informative Traits:
Body Plan / Structure:
Invertebrate - Soft Bodied – no bones
Backbone (internal skeleton - spine)
Reproduction / Development:
Mineralized Shell egg
Jelly covered eggs
Placental (live) birth
Locomotion:
No bony Limbs - (fish)
4 bony limbs (tetrapod)
Single Hooves (1toe) – horse, zebra
Split hooves (2 toes) – cow, deer
Split hooves (3 toes) pig
5 toes – dog, cat, primate
Opposable Thumb – (primates)
Upright bipedalism (primates)
Claws / nails
Body covering:
Epidermal scales (reptiles)
Feathers
Fur / hair
Diet: careful this can be trouble
Herbivore (plants only)
Carnivore (meat only)
Omnivore (plants and meat)
Behavior:
Tool use – careful with this
Spoken language (human)
Metabolism
Respiration / Gas Exchange:
Absorbs oxygen across skin
Water breathing with gills
Air breathing with lungs
Suction breather with trachea
Exothermic (fishes) – no body temp regulation
Ectothermic (reptiles) behavior body temp reg
Endothermic (mammals) body temp reg internal
Cardiovascular
Milk & protection (mammals)
Gathered food & protection (birds)
No care for babies
Two chambered heart (fish)
Three chambered heart (reptile & amphibian)
Four chambered heart (mammal & bird)
Care of offspring