Life cycle of moss Essay

Submitted By Ranga1012
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Life cycle of moss

Haploid: each cell has only one single set of chromosomes
Gametophyte: produces an abundance of leafy plants which may be erect, simple or sparsely forked, and growing in tufts and producing archegonia at the stem tips or, alternatively, plants may be prostrate, freely branched, growing in intertangled mats, and producing archegonia laterally. (haploid)
Define the different generations
Sporophyte: (diploid)
One generation is often very small, even microscopic.

There are two parts or generations of the life cycle of a moss, the haploid and the diploid. This is called the alternation of generations

Life cycle of a moss
The life cycle of bryophytes consists of an alternation of two stages, or generations, called the sporophyte and the gametophyte. Each generation has a different physical form. When a spore germinates, it usually produces the protonema, which precedes the appearance of the more elaborately organized gametophytic plant, the gametophyte, which produces the sex organs. The female sex organ is a flask-shaped structure called the archegonium. The archegonium contains a single egg in a swollen lower portion that is more than one cell thick. The neck of the archegonium is a single cell layer thick and sheathes a single thread of cells that forms the neck canal. When mature and completely moist, the neck canal cells of the archegonium disintegrate, releasing a column of fluid to the neck canal and the surrounding water. The egg remains in the base of the archegonium, ready for fertilization. The male sex organ, the antheridium, is a saclike structure made up of a jacket of sterile cells one cell thick; it encloses many cells, each of which, when mature, produces one sperm. When wet, the jacket of the mature antheridium ruptures to release the sperm into the water. When a sperm enters the field of the fluid diffused from the neck canal, it swims toward the site of greatest concentration of this fluid, therefore down the neck canal to the egg. Upon reaching the egg, the sperm burrows into its wall, and the egg nucleus unites with the sperm nucleus to produce the diploid zygote. The zygote remains in the archegonium and undergoes many mitotic cell divisions to produce an embryonic sporophyte. Mature bryophytes have a single sporangium (spore-producing structure) on each sporophyte. The sporangium generally terminates an elongate stalk, or seta, when the sporangium is ready to shed its spores and is capped by a lid, or operculum. The sporangium rupture usually involves specialized structures that enhance expulsion of the spores away from the parent gametophyte.

Life Cycle of a Moss

The life cycle of moss consists of the alternation of two stages or generations, the sporophyte and gametophyte. Alternation of generations is a life cycle that includes both haploid and diploid multicellular stages. A diploid cell will have two complete sets of chromosomes where a haploid cell has only a single set of unpaired chromosomes.

The gametophyte generation begins as a spore produced by meiosis. These germinating spores develop into the protonemata stage which forms a mat of green filaments. The leafy green gametophyte is at the haploid stage of the life cycle and therefore it has one chromosome per cell.

The gametophyte uses the photosynthesis process to create a source of energy to be used in the production of the sexual reproductive structures. The gametangia structures become either male (antheridia) or female (archegonia) organs for the reproduction of spores.

Hundreds of sperm are produced within the antheridia while the female organ, archegonia contains only one egg. The sperm and egg cells, known as gametes have not changed their number of chromosomes through this cell division process. When the conditions are right and there is enough water for the sperm to make their way to the egg down the canal of the archegonia the egg becomes fertilized and has now