Question

A cladogram is shown below. a) Why is the amoeba considered an outgroup in this cladogram?

b) What trait does a salmon have that an earthworm does not?







c) What does this cladogram tell you about the evolutionary relationship of the traits of jaws and limbs?






d) A squirrel glider is an organism with jaws, limbs, and hair. It does not use a placenta for reproduction. Where do you think this organism would belong in the cladogram?

Answer 1

a) The amoeba is an outgroup in this cladogram because it is unicellular, while all of the other organisms are multicellular.

b) The salmon has jaws, while the earthworm does not. The animal connected to the trait will have that trait, while the animal(s) to the left does not. The animal(s) to the right also do have that trait, unless it is contradictory (such as a multicellular organism being unable to be unicellular). Since the salmon is connected to the jaws trait, the animal to its left (earthworm) does not have jaws.

c) Not completely sure. Maybe limb traits developed after jaw traits? More animals have jaws than limbs?

d) Between the kangaroo and the cat. It does have hair, so it wouldn't fit to the kangaroo's left. But since the squirrel glider doesn't have a placenta, it could not be in the cat's spot or to the right of the cat. This means that it has to be between the kangaroo and the cat.