The alternation of generations in gametophytes

Because they make just one type of spore and gametophyte, these non-vascular plants are called homosporic. This takes place because of reduction division or meiosis that takes place.

Gold is another—up to 0. In seed plants, the gametophyte is even more reduced at the minimum to only three cellsgaining all its nutrition from the sporophyte.

In still other flowers, individual sporophytes only give rise to a certain gender of flower.


Some flowers have both male and female gametophytes housed within. Both phases are diploid. When it reaches maturity, the gametophyte produces one or more gametangia singular: Note that the chromosome number here doubles from 'n' to '2n'.

In these species the strobilate branches appear first, and, after the spores are shed, the green vegetative shoots develop. Second, bryophytes do not have roots, but have rhizoids, which are relatively simple, sometimes multicellular filaments of thin-walled cells that extend from the photosynthetic tissue into the soil or other substrate.

Sexual reproduction results in gametes that combine two cells from different individuals. If the gametes are the same, it is called isogamy.

Alternation of Generations

There are tiny floating ferns used as "green fertilizer" in rice paddies because they partner with bacteria that pull nitrogen from the air and "fix" it in chemical compounds that other plants can use. They are the vascular plants those having xylem and phloem tissues that reproduce by releasing spores rather than seeds, and they include the highly diverse true ferns and other graceful, primarily forest-dwelling plants.

This alternation of generation refers to the alternation of two phases: A sporophyte of Dicksonia antarctica.

The Difference Between a Sporophyte and Gametophyte

There is a rich fossil record showing that pteridophytes have ancestors dating back nearly four hundred million years. The slender, herbaceous stems of Equisetum have hollow internodes. The order Hyeniales included shrublike plants with inconspicuous leaves arranged in rather indistinct whorls.

Sexual Reproduction The third characteristic of bryophytes is something that one could not guess by just looking at the conspicuous green tissue.

Gametophyte and Sporophyte

Its body comprises a long stalk topped by a capsule within which spore-producing cells undergo meiosis to form haploid spores. The same is true of the gametophyte. Horses foraging on stands of Equisetum have been known to die from severe intestinal inflammation.

Consider flowering plants for example. If both genders are housed on the same individual, the species is monoicous.


Further, the sporophyte or gametophyte may not be totally independent of the other generation. As plants colonized the land, they were initially isomorphic, or both the gametophytes and sporophytes looked and acted about the same. In the past, club moss spores provided the powder used to coat rubber gloves and prophylactics, and photographers used masses of these same spores as flash powder, since they could be easily and quickly ignited.

Alternation of Generations Illustration of diploid and haploid cells with common abbreviations Imagine if you looked exactly like your grandmother but nothing at all like your mother. Characteristics of Bryophytes There are several characteristic features of bryophytes.

Alternation of generations

First, the green tissue that makes up most of the plant body is not vascularized; it does not have xylem and phloem cells. This absence of specialized tissues for transporting water and dissolved food throughout the organism limits terrestrial forms to being very short.

Alternation of generations arose in green algae, and a green alga was the ancestor of land plants. Just goes to show how much you inherit from your family. BACK. The 'alternation of generations' in the life cycle is thus between a diploid (2n) generation of sporophytes and a haploid (n) generation of gametophytes.

Gametophyte of the fern Onoclea sensibilis (the flat thallus at the bottom of the picture) with a descendant sporophyte beginning to grow from it (the small frond at the top of the picture).

the land surface. There is a rich fossil record showing that pteridophytes have ancestors dating back nearly four hundred million years. Equisetopsida: Equisetopsida, (division Pteridophyta), class of primitive spore-bearing vascular plants. Most members of the group are extinct and known only from their fossilized remains.

The sole living genus, Equisetum, order Equisetales, is made up of 15 species of very ancient herbaceous plants, the.

The alternation of generations in gametophytes
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Alternation of Generations (Plant): Definition, Life Cycle | Biology Dictionary