Alteration of gametophyte and sporophyte generations

All living species in their life cycle go through 2 phases or generations- the gametophytic and sporophytic-for cytogenetics we call it the N and 2N phases where N refers to the complement or set of chromosomes.

After browsing through one of my old books on botany I found graphs throughout this book showing alterations and dominance of these 2 cycles or phases. Basically there was a shift from dominance of the gametophytic or N generation found in the lower forms of life to the sporophytic or 2N degeneration in the higer forms of life like the gymnosperms and angiosperms. I cant imagine an animal kingdom sporophyte being a "parasite" first before shifting or evolving to the dominant phase in the higher forms of life but it would appear that this evolutionary shift also occurred in the animal kingdom.

Unfortunately, there is no way to include these cycles (diagrams) in a more descriptive blog because the book was published over a century ago. Still, this is a most fascinating piece of evolution and survival.

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