Alternation of Generations Life Cycle

It comprises two different generations, namely:

1. Sporophyte generation 
2. Gametophyte generation

Sporophyte generation

It is an asexual phase in which a diploid (having two sets of chromosomes) plant develops and eventually produces spores. By mitosis, this sporophyte creates haploid (having a single set of chromosomes) spores germinating and developing into gametophytes for the next generation. A diploid zygote is formed when two gametes combine during fertilization. This zygote then divides through mitosis to create a new sporophyte. As soon as spores are produced, they can only influence the next phase of alternation if they are released, carried away by air and water, and land in an environment that supports germination and gametophyte growth.

Gametophyte generation

It is a sexual phase in which a haploid male and female organs (gametangia) develop and produce eggs and sperm (gametes) through simple mitosis for sexual reproduction. A zygote formed from two gametes, either from the same organism or from different members of the same species, develops into the diploid (having two sets of chromosomes) sporophyte phase, which by meiotic division produces produce unicellular spores. This cycle continues to occur.

While the sporophyte generation predominates in angiosperms and gymnosperms, the gametophyte generation is the primary life phase in bryophytes like mosses and liverworts. In fungi, the haploid phase predominates as well. Many species of algae also alternate between the sexual and asexual phases.