To be useful for phylogenetic reconstruction, a taxonomic character must exhibit which of the following properties? select all that apply.
a. it must vary among the taxa being analyzed, but not within individual taxa.
b. it must be molecular (dna or protein).
c. it must be anatomical.
d. it must have a genetic basis.

The answers are A and B.

Explanation:

Phylogenetic is a field that looks for similar characteristics among one group of species in order to understand how the species are related to one another and understand some really important questions like the origin of some structures or genes. Therefore the species have to differ from one another but they MUST have a common ancestral characteristic (Synapomorphy) so that the researches are able to establish an initial relation that groups one taxon. Therefore, a character can have two or more status among the taxa, as answer A states but not within the same species. This is crucial because if one species present two statuses of one character that means that the character is not homologous among the taxa, and therefore could not be used for phylogenetic analysis. (For example if the ancestral character is β, then the group of species can have β or a derivative character called ω or π. But one species cannot have β and ω or π and ω, they can only express one.)

The answer B could not be mandatory, because molecular resources have starter being used recently, but it's necessary in some cases in order to solve some points where taxonomy cannot clarify the origin or nature of the character.

i think the miocene epoch spans the time from 23 million to 12 million years ago.

weathering is the answer.