Angiosperm Life Cycle Overview

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Questions and Answers

What is the process of double fertilization in angiosperms?

Double fertilization is a process unique to angiosperms where two sperm nuclei, produced by the male gametophyte, are involved in fertilization. One sperm nucleus fertilizes the egg cell to form a diploid zygote, while the other sperm nucleus fuses with the two polar nuclei, which are located in the central cell of the female gametophyte, to form a triploid endosperm nucleus. This endosperm nucleus will eventually develop into endosperm tissue, which provides nourishment to the developing embryo.

What are the two main components of the male gametophyte, and what do they do in the process of fertilization?

The two main components of the male gametophyte are the generative cell and the tube cell. The tube cell forms the pollen tube, which grows towards the ovule and delivers the sperm nuclei from generative cell to the ovule. The generative cell divides mitotically to produce two sperm nuclei, which eventually fuse with the egg and central cell, leading to fertilization and development of the embryo and endosperm.

What is the function of the embryo sac in the angiosperm female gametophyte?

The embryo sac is a structure in the female gametophyte that, during fertilization, contains seven cells: one egg cell, two synergid cells, three antipodal cells, and the central cell that has two polar nuclei. When the pollen tube reaches the ovule, the sperm nuclei are delivered to the embryo sac, where fertilization occurs, leading to the development of the embryo and endosperm.

How does the endosperm develop in angiosperms?

The endosperm develops after double fertilization, when the second sperm nucleus from the male gametophyte fuses with the two polar nuclei in the central cell of the embryo sac. This results in a triploid endosperm nucleus, which eventually develops into a nutritive tissue that provides nourishment to the developing embryo. Signup and view all the answers

What is the significance of the process of pollination for angiosperms?

Pollination is the process by which pollen grains from an anther are transferred to the stigma of a flower. This enables fertilization and the formation of seed and fruit, effectively ensuring reproduction and continuation of the plant species. Signup and view all the answers

Describe the development of the female gametophyte within the angiosperm ovule, highlighting the key stages.

The female gametophyte, or embryo sac, develops from a single megaspore within the ovule. The megaspore undergoes meiosis, producing four haploid megaspores. Usually only one megaspore survives, the other three degenerate. The surviving megaspore undergoes three mitotic divisions without cytokinesis, resulting in one large cell with eight haploid nuclei. The multinucleate mass is then divided by membranes to form the embryo sac. Near the micropyle of the embryo sac, two synergid cells flank the egg and help attract and guide the pollen tube to the embryo sac. At the opposite end of the embryo sac are three antipodal cells of unknown function. The other two nuclei, called polar nuclei, are not partitioned into separate cells but share the cytoplasm of the large central cell of the embryo sac. The mature embryo sac thus consists of eight nuclei contained within seven cells. The ovule, which will become a seed if fertilized, now consists of the embryo sac, enclosed by the megasporangium (which eventually withers) and two surrounding integuments. Signup and view all the answers

Explain the role of the pollen tube in the fertilization process of angiosperms.

The pollen tube is a structure that develops from the tube cell of the male gametophyte following pollination. The pollen tube grows from the stigma towards the ovule, guided by chemical attractants, and eventually reaches the embryo sac. It delivers the two sperm nuclei from the generative cell to the embryo sac, where they participate in double fertilization, leading to the development of the embryo and endosperm. Signup and view all the answers

Explain how the development of the embryo sac differs from the development of the male gametophyte in angiosperms.

The development of the male gametophyte is relatively simple compared to the female gametophyte. The male gametophyte, or pollen grain, develops within the anther and is comprised of just two cells, the tube cell and the generative cell. In contrast, the female gametophyte, or embryo sac, develops within the ovule and undergoes a more complex series of developmental stages, including meiosis, mitosis, and cellular differentiation, resulting in a seven-celled structure with eight nuclei. Signup and view all the answers

The development of the angiosperm life cycle is a continuous process without any resting stages.

False (B) Signup and view all the answers

What are the four main stages of angiosperm development?

The four main stages of angiosperm development are: pollination, fertilization, seed development, and germination. Signup and view all the answers

Flashcards

Double Fertilization

The fusion of gametes in angiosperms, involving one sperm fertilizing the egg to form a zygote, and another sperm fusing with the polar nuclei to form a triploid nucleus.

Pollination

The process by which a pollen grain reaches the receptive stigma, potentially leading to fertilization.