Answer:
C. The plant exists as a diploid organism, a and at other times as haploid.
Step-by-step explanation:
Plant generations alternate. They go back and forth between sporophyte and gametophyte.
A gametophyte is a generation. Haploid gametophytes exist. They therefore possess a single pair of chromosomes. Spora are the source of gametophytes. Gametophytes develop into large, tall organisms before producing gametes. Thus, the name. A plant embryo is created when these gametes—which are the sperm and eggs of a plant—combine. This embryo occasionally has a covering of seed surrounding it for protection. In certain cases, the seed is even surrounded by fruit.
the sporophyte develops from the embryo. Sporophytes, like you and I, are diploid. They therefore have two sets of chromosomes that are identical ("di"=2). Sporophytes develop into large, tall organisms before producing spores. Thus, the name. Since meiosis is how these spores are produced, they only contain one set of chromosomes. The spores disperse into the environment and develop into gametophytes.
So, to summarize, gametophyte > gametes > embryo > sporophyte > sporophyte > sopre > gametophyte > gametes > and so on. Until a chance genetic mutation results in a significant alteration.
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A generation that alternates between haploid and diploid (or tetraploid/diploid, hexaploidy/triploid, etc.) is said to be alternating.
On the surface, this alternating of generations between most land plants resembles animal gametes, but in plants, the cells formed during meiosis are not the gametes themselves; instead, the gametes are later created by those cells during mitosis. Consequently, in place of:
2n -> Meiosis -> n (gamete) -> fusion -> 2n
we have
2n -> meiosis -> n (gametophyte e.g. pollen) -> mitosis -> n (gamete e.g. sperm) -> fusion -> 2n
The haploid generation is morphologically identical to the diploid generation in many lower plants. The dominant theory holds that plants' capacity to go through mitosis after meiosis but before fusion spontaneously developed. The less popular theory contends that plants have alternated generations throughout time and that as land plants got more specialized over time, natural selection drove the gametophyte to drastically decrease over time. These are referred to as the homologous and antithetic hypotheses, respectively.
The primary evolutionary benefit of diploid organisms is their ability to conceal harmful genes using two gene copies. The high level of specialization offered for each generation, one for growth and one for reproduction, is another benefit.