The position at which the pair of taxa (B) Crocodile and lizard could be reversed in the tree above without changing the meaning of the tree is the claws or nails node. Therefore , (B) Crocodile and lizard is correct .
A phylogenetic tree shows the evolutionary relationships between different groups of organisms. The branches of the tree represent different lineages, and the nodes represent common ancestors.
The position of a taxon on the tree indicates how closely related it is to other taxa.In the tree you have provided, the mouse and pigeon are both members of the class Aves, but they are in different subclasses:
Neornithes and Palaeognathae, respectively. The crocodile and lizard are both members of the class Reptilia, but they are in different subclasses: Diapsida and Anapsida, respectively.
If we reversed the positions of the mouse and pigeon, or the crocodile and lizard, it would not change the meaning of the tree, because they are both members of the same class.
However, if we reversed the positions of the crocodile and pigeon, it would change the meaning of the tree, because they are members of different classes.
Question
The position at which the following pairs of taxa could be reversed in the tree above without changing the meaning of the tree?
A) Mouse and pigeon
B) Crocodile and lizard
C) Crocodile and pigeon