Question

give the schematic representation of a life cycle of angiosperms​

Answer 1

Answer:

your answer is this

Explanation:

Microspores develop into pollen grains, which are the male gametophytes, while megaspores form an ovule that contains the female gametophytes.

In the ovule, the megasporocyte undergoes meiosis, generating four megaspores; three small and one large; only the large megaspore survives and produces the female gametophyte (embryo sac).

When the pollen grain reaches the stigma, it extends its pollen tube to enter the ovule and deposits two sperm cells in the embryo sac.

The two available sperm cells allow for double fertilization to occur, which results in a diploid zygote (the future embryo) and a triploid cell (the future endosperm), which acts as a food store.

1. Some species are hermaphroditic (stamens and pistils are contained on a single flower), some species are monoecious (stamens and pistils occur on separate flowers, but the same plant), and some are dioecious (staminate and pistillate flowers occur on separate plants).

Key Terms

cotyledon: the leaf of the embryo of a seed-bearing plant; after germination it becomes the first leaves of the seedling

heterosporous: producing both male and female gametophytes

synergid: either of two nucleated cells at the top of the embryo sac that aid in the production of the embryo; helper cells

The Life Cycle of an Angiosperm

The adult, or sporophyte, phase is the main phase of an angiosperm’s life cycle. As with gymnosperms, angiosperms are heterosporous. Therefore, they generate microspores, which will produce pollen grains as the male gametophytes, and megaspores, which will form an ovule that contains female gametophytes. Inside the anthers’ microsporangia, male gametophytes divide by meiosis to generate haploid microspores, which, in turn, undergo mitosis and give rise to pollen grains. Each pollen grain contains two cells: one generative cell that will divide into two sperm and a second cell that will become the pollen tube cell.

Life cycle of angiosperms: The life cycle of an angiosperm is shown. Anthers and carpels are structures that shelter the actual gametophytes: the pollen grain and embryo sac. Double fertilization is a process unique to angiosperms.

The ovule, sheltered within the ovary of the carpel, contains the megasporangium protected by two layers of integuments and the ovary wall. Within each megasporangium, a megasporocyte undergoes meiosis, generating four megaspores: three small and one large. Only the large megaspore survives; it produces the female gametophyte referred to as the embryo sac. The megaspore divides three times to form an eight-cell stage. Four of these cells migrate to each pole of the embryo sac; two come to the equator and will eventually fuse to form a 2n polar nucleus. The three cells away from the egg form antipodals while the two cells closest to the egg become the synergids.

The mature embryo sac contains one egg cell, two synergids (“helper” cells), three antipodal cells, and two polar nuclei in a central cell. When a pollen grain reaches the stigma, a pollen tube extends from the grain, grows down the style, and enters through the micropyle, an opening in the integuments of the ovule. The two sperm cells are deposited in the embryo sac.

A double fertilization event then occurs. One sperm and the egg combine, forming a diploid zygote, the future embryo. The other sperm fuses with the 2n polar nuclei, forming a triploid cell that will develop into the endosperm, which is tissue that serves as a food reserve. The zygote develops into an embryo with a radicle, or small root, and one ( monocot ) or two (dicot) leaf-like organs called cotyledons.