Here's an additional "spoke" to stick in the biblical "wheel" or just for thinking out loud:
If the original created paradisaic environment containing plant, animal, ocean and human life was perfect, then explain the logic behind the limitation in their lifespans (other than mankind's pending reward with the tree of life prospect).
If sin had not existed, would Adam have fed the animals and sea creatures from the tree of life so they could enjoy eternity too? If not, for what purpose would their deaths serve other than fertilizer? Obviously, they were not needed for sacrificing since sin had not occurred, thus precluding any arrangement for atonement.
How would the Creator help Adam cope with the eventual deaths of animals he may have befriended and raised as companions? What explanation would be given him, or does human perfection entail an absence of emotions other than joy? Interesting, huh? Why would the omniscient Creator develop life forms with term limitations in so many millions of species? If eternal life is the grand reward awaiting humans someday, will it include a full-range sampling of all species (plant, insect, mammal, reptile, amphibian, cellular, fish, even dinosaur) of life as we know it today?
Did the introduction of sin (disobedience?) and punishment cause enough imperfection to mutate the once perfect genes in all the main varieties and species of creatures to spring forth and evolve into the many unpleasant types we are not usually fond of today?