Origin of Life: early land life (Introduction)

by dhw, Monday, July 29, 2013, 15:09 (4136 days ago) @ Balance_Maintained

TONY: So we had a few billion years where plants could have exploded into infinite variety and complexity, with an atmosphere that was conducive to them, but they didn't.-DHW: Sorry, but how do you know the pre-Cambrian atmosphere was conducive to them? Was not being oxygen rich all that was needed to guarantee an explosion? Might it even be possible that the explosion in plant life actually resulted from the explosion in animal life, since the latter would have meant lots of new vegetarians on the prowl? Maybe plants found new ways of propagating, defending themselves, attracting pollinators. I wonder what your own explanation is.-TONY: We have a pretty strong estimate of what the early atmosphere was like. There is strong reason to suspect that the early atmosphere was laden with large levels of CO2, and limited oxygen. Plant respiration could use that and gradually bring the O2 levels up to the level where non-plant live could exist without dying. With the exception of extremophiles, the vast majority of animal life needs oxygen to survive. The logical conclusion is that the CO2 rich atmosphere was converted to the proper balance of O2 in the simplest manner, i.e. plants.-It's certainly a logical conclusion that plant life prepared the way for diversified animal life. That concept fits in nicely with evolution. We were asking, though, why there was no explosion in plant life until after the Cambrian, and so I thought you might have a teleological explanation, as opposed to my evolutionary ramblings.