Final Review: Angiosperm Life Cycle and Other

micro: three cells

mega: sevencells

Differs from gymnosperms because the microgametophyte has three to four cells and the megagametophyte develops  completely differently. It doesn’t have much other than the archegonia, which angiosperms do not have, the stored food, which develop differently (from the female gametophye in gymnosperms and from the fusion of the sperm with polar nuclei in angiosperms), chambers, micropyle (which they both have).

megasporogenesis

megagametogenesis

involves meiosis and results in the formation of megaspores within the ovule in the nucellus

developemtn of megaspore into embryo sac, which is the megagametophyte (ovule)

- Within the anthers, microsporocytes develop meiosis microspores each microspore divides once to form a tube cell and generative cell, which is the IMMATURE MICROGAMETOPHYE (pollen grain) germination generative cell divides, forming two sperm conveyed to egg as a mature male gametophyte

- Within the ovule, a single megasporocyte develops meiosisfour megaspores, three of which disintegrate fourth develops into megagametophyte

• - Pollen grain germinates on the stigma, producing a pollen tube, which grows down the style into the ovary, entering the ovary through the micropyle- One sperm fuses with egg zygote
• - Another sperm fuses with two polar nuclei (2n) of the embryo sac, producing a triploid endosperm nucleus
• - The embryo develops within the embryo sac, and the integuments become the seed coat
• - Eventually, the seed is shed from the fruit

Diploid megasporocyte meiosis four haploid megaspores three disintegrate and one (farthest from the micropyle survives) enlarges with expansion of the nucellus nucleus of the megaspore divides by mitosis four nuclei mitoses (three of them)  eight nuclei arranged in two groups of four at opposite ends of the megagameophyte one from each ends migrates to the center to become the polar nuclei cell awll formation around the other six cells to become the egg cell, synergids, and antipodals 8-nucleate, seven celled structure called the megagametophyte (embryo sac)

Sporogenous cells of the anther become microsporocytes meiosis haploid microspores (pollen grains) during meiosis, each division is followed by cell wall formation to form the major features of the pollen grains microspores divide mitotically, forming the tube cell and generative cell, which moves to the interior of the pollen grain (2-cell structure is the immature microgametophyte) generative cell divides mitotically to produce the sperm 3-celled mature microgametophyte

when the sperm develop

- Because the seeds aresitting on the cone scale without any protective covering

o FALSE: In the cycads, there are two. In the conifers, there are about eight to ten.

o There is a part that becomes a shoot. There is a root hypocotyls axis. Hard to tell when the hypocotyls and root starts. The hypocotyls is the region between the cotyledon and where the root starts. Hypocotyl literally means underneath the cotyledon

General Sherman tree

- False: The plant is toxic. The female plant hasseeds and leaves that can kill kids due to alkaloids. But, the outer fleshy red covering is not. Plant male plants only so the attraction is not there. This plant is toxic.

- They have xylem vessels. No other gymnosperms but these havethem.

- Gnetum and Welwitschia do not have archegonia. Ephedra has two or three.

- Double fertilization occurs in Gnetum and Ephedra. However, the second fertilized egg simply aborts. It does not become the food like in angiosperms.

- Their strobili resemble inflorescent flowers

- It does not usually happen until the ovules have been shed from the parent tree.

angiosperms: insects

gymnosperms: usually wind