a characteristic is found in bacteria, fungi, pine trees, snakes & humans when did it most likely evolve? why?

Answer 1

The characteristic probably evolved very early if it is found in such a wide range of different life forms. One example of this is "Cytochrome C", a protein found in most living things. If the rate of mutation is considerd to be within a certain range of values, at least over very long periods of time, differences in Cytochrome C can be used as an indicator of how distantly related two different organisms are. Thus Cytochrome C from two different mammals, may differ by only one or two amino acids, while Cytochrome C from a human, and a bacterium, may have significant differences.

Answer 2

Most likely the characteristic evolved in bacteria, which are the most primitive forms of life on your list.

Why? The characteristic is shared by all of the forms of life on the list, the most likely explanation is that the characteristic evolved once, in the most primitive form of life. Otherwise the characteristic would have had to have evolved multiple times in multiple branches of the tree of life.

Answer 3

Negating convergent evolution in several species (the odds would be vanishingly small), it would be necessary that the characteristic developed first in the common ancestor.

This would have to be before animals, plants, fungi, and bacteria diverged. Due to the effect of the variable rates of evolution between the major kingdoms (animal, plant and fungi), it is still not determined the exact sequence of divergence of the kingdoms.

However, estimates of times of key events can still be formulated. All from evidence inferred from molecular sequence data, it appears that eukaryotes and bacteria shared their last common ancestor around 2 billion years ago.