Consider the moon rocks that the crew of apollo 11 brought back from mare tranquillitatis. within the zircon crystals within these rocks, we find approximately 15 atoms of 207pb for every atom of 235u. how old is mare tranquillitatis?

How is it possible that phylogenies based on sequences from nuclear genomes and organellar genomes (i.e., chloroplasts and mitochondria) from the same group of species yield phylogenetic trees with different branching orders?   answer :   the genome of the endosymbiont is more closely related to members of the group in which it originally evolved, while the nuclear genome of the engulfing organism has its own evolutionary trajectory.