Embryophyta ( higher plants ) ndash; is the transition from the haploid-diploid to diploid life cycle. Life cycle of higher plants is the alternation

Life cycle of Embryophyta [higher plants]

Embryophyta (higher plants) – is the transition from the haploid-diploid to diploid life cycle. Life cycle of higher plants is the alternation of two generations of organisms, multicellular haploid gametophyte and the diploid sporophyte. On gametophyte develops sexual organs — gametangia (from Greek “gamete” and” angeyon” — “jar”) in which gametes are produced by mitosis. Merging, they give rise to the generation of diploid organisms. At the stage of sporophyte by the meiosis form haploid spores (this type of meiosis is called sporic), of which gametophyte forms again. At the same time in the life cycle of the most simply organized living nowadays Embryophytes — mosses — clearly dominates the haploid stage and sporophyte that develops on the gametophyte, is short-lived. Quite naturally arises the question: is the sporophyte of mosses an independent organism? In moss, horsetails and ferns (diagram 98) prevails diploid sporophyte stage. In seed plants the gametophyte is reduced and is considered as part of the sporophyte, and therefore is not an independent organism. Thus, in gymnosperms and angiosperms life cycle passes without alternation of generations, and only on the diploid phase of development.

Diagram 98. The life cycle of a fern: 1 — sporangium; 2 — stage of four spores; 3 — young gametophyte; 4 — mature gametophyte; 5 — antheridium; 6 — archegonium; 7 — sperm; 8 — ovum; 9 — zygote; 10 — young sporophyte; 11 — mature sporophyte; 12 — sporangium
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