Alternation of Generations

∞ generated and posted on 2016.12.04 ∞

Possession by an organism of haploid multicellular bodies that beget diploid multicellular bodies, which in turn beget haploid multicellular bodies.

Alternation of generation is seen in certain algae as well as all sexually reproducing plants.

The process consists of a sequence that can be described, in plants, as consisting of spore (1n) → germinationmitosisgametophyte generation (1n) → mitosisgametes (1n) → fertilizationzygote (2n) → mitosissporophyte generation (2n) → meiosisspores (1n) where all structures and cell types are haploid (1n) except the zygote and the sporophyte generation which instead are diploid (2n).

Figure legend: Shown are the different generations of the plant life cycle along with the products of each generation. In particular, the spores are meiotically produced by the sporophyte generation while the gametes are mitotically produced by the gametophyte generation.

To reiterate, in alternation of generations the two generations that alternate are described as the gametophyte generation (which is haploid and which produces gametes mitotically) and the sporophyte generation (which is diploid and which produces the spores meiotically).

The following video shows the Life cycle of a moss; this is a professionally produced video :

The following video describes the life cycle of a moss:

The following video shows the life cycle of ferns and flowering plant life cycle:

The following vide presents the life cycle of a flowering plant; a nicely done video: