More on evolution

After i posted the questions about plant evolution, i got some answers in the form of lectures given by distinguished researchers. At the Natural History Museum, Dr. Ansell has done research into the chloroplast (the structure that makes plants green and is responsible for photosynthesis) genome. He says, roughly, that the genome is much more highly complex and variable than we previously thought, and that the variation within that DNA could be responsible for the extraordinary speciation we see in vascular plants.

Dr. Rieseberg, of Univ. of British Columbia, then gave an outstanding lecture which i attended, about the mechanisms of speciation in plants. He discussed the concept of a species, and systematically proved that its a good concept for plants (as has been debated and questioned by botanists since Darwin's time). He also talks about the spread of "advantageous mutations" and tested the inheritance of certain genetic traits in widespread plants. His conclusion is that a "species" is likely reinforced, or encouraged to remain separate from other similar plants, by the spread of advantageous mutations.

Which brings me to some speculative points:
Polunin says there are several "eras" or heydays of taxa: these are times when the organisms flourished, diversified, and occupied much of the planet. So the first heyday (in the early Paleozoic) was Fishes and Ferns. Then in the Mesozoic period was the rise of the Reptiles (including dinosaurs) and Gymnosperms. Now in the Cenozoic, we're in the age of Mammals (including us) and Angiosperms. My theory is that these explosions of proliferation and diversity among taxa have to do with the most available resources (water, heat, food), and with mutual benefits. So maybe its no accident that mammals and all animals depend on higher plants for their source of respiration: oxygen. And likewise, plants use what we breathe out - and maybe this lends weight to why we see a parallel rise of these groups now. So the recent rise of mammals and angiosperms could be (partly) about mutual benefit. This would favor the advantageous mutation theory too.

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