1. Describe the structure of a flower.
Answer: A flower typically consists of four main parts: sepals (collectively called the calyx), petals (collectively called the corolla), stamens (the male reproductive organs), and carpels (the female reproductive organs). The stamen includes the anther and filament, while the carpel includes the stigma, style, and ovary.
2. Explain the development of male gametophytes in flowering plants.
Answer: Male gametophytes develop in the anthers. Microspores are produced by meiosis within pollen sacs. Each microspore undergoes mitosis to form a pollen grain, which contains the male gametophyte (generative cell and tube cell).
3. Explain the development of female gametophytes in flowering plants.
Answer: Female gametophytes develop in the ovules. A megaspore mother cell undergoes meiosis to produce four megaspores, three of which degenerate. The remaining megaspore undergoes mitotic divisions to form the embryo sac, containing the egg cell, two synergids, three antipodal cells, and a central cell with two polar nuclei.
4. What are the different types of pollination?
Answer: The different types of pollination include self-pollination (pollen transfer within the same flower or plant) and cross-pollination (pollen transfer between different plants). Cross-pollination can occur via various agencies such as wind (anemophily), water (hydrophily), insects (entomophily), birds (ornithophily), and bats (chiropterophily).
5. What are outbreeding devices in plants?
Answer: Outbreeding devices are mechanisms that promote cross-pollination and prevent self-pollination. Examples include self-incompatibility, dichogamy (staggered maturation of male and female organs), and herkogamy (physical separation of male and female organs).
6. Describe pollen-pistil interaction.
Answer: Pollen-pistil interaction involves recognition and acceptance or rejection of pollen by the pistil. This interaction ensures that only compatible pollen grains germinate on the stigma and grow a pollen tube through the style to reach the ovule for fertilization.
7. What is double fertilization in flowering plants?
Answer: Double fertilization is a unique process in flowering plants where one sperm cell fertilizes the egg cell to form a zygote, while the other sperm cell fuses with the two polar nuclei in the central cell to form the triploid endosperm.
8. Explain the post-fertilization development of endosperm and embryo.
Answer: After fertilization, the primary endosperm nucleus divides to form the endosperm, which provides nourishment to the developing embryo. The zygote undergoes mitotic divisions to form the embryo, which differentiates into the radicle, plumule, and cotyledons.
9. How do seeds develop and fruits form after fertilization?
Answer: After fertilization, the ovule develops into a seed, and the ovary wall becomes the fruit. The seed contains the embryo and stored food, while the fruit protects the seed and aids in its dispersal.
10. What are apomixis, parthenocarpy, and polyembryony?
Answer: Apomixis is a form of asexual reproduction that mimics sexual reproduction but does not involve fertilization. Parthenocarpy is the development of fruit without fertilization, resulting in seedless fruits. Polyembryony is the formation of multiple embryos from a single fertilized egg or ovule.
11. What is the significance of seed and fruit formation?
Answer: Seed and fruit formation are crucial for the reproduction and dispersal of flowering plants. Seeds contain the genetic material for the next generation and provide nourishment to the developing embryo. Fruits protect seeds and facilitate their dispersal by various agents such as animals, wind, and water.
12. Describe the male reproductive system in humans.
Answer: The male reproductive system includes the testes, which produce sperm and hormones; the epididymis, where sperm mature; the vas deferens, which transports sperm; the seminal vesicles, prostate gland, and bulbourethral glands, which produce seminal fluid; and the penis, which delivers sperm to the female reproductive system.
13. Describe the female reproductive system in humans.
Answer: The female reproductive system includes the ovaries, which produce eggs and hormones; the fallopian tubes, where fertilization occurs; the uterus, where the embryo implants and develops; the cervix, which connects the uterus to the vagina; and the vagina, which receives sperm and serves as the birth canal.
14. What is the microscopic anatomy of the testis and ovary?
Answer: The testis contains seminiferous tubules where spermatogenesis occurs, interstitial cells (Leydig cells) that produce testosterone, and Sertoli cells that support sperm development. The ovary contains follicles at various stages of development, each consisting of an oocyte surrounded by granulosa cells and theca cells, which produce estrogen and progesterone.
15. What are spermatogenesis and oogenesis?
Answer: Spermatogenesis is the process of sperm production in the testes, involving mitosis, meiosis, and spermiogenesis. Oogenesis is the process of egg production in the ovaries, involving the formation of primary oocytes during fetal development, which undergo meiosis to form a mature ovum during the menstrual cycle.
16. Describe the menstrual cycle.
Answer: The menstrual cycle is a 28-day cycle in women involving the preparation of the uterine lining for potential pregnancy. It consists of the menstrual phase (shedding of the uterine lining), the follicular phase (follicle development and estrogen production), ovulation (release of an egg), and the luteal phase (corpus luteum formation and progesterone production).
17. What is fertilization and embryo development up to blastocyst formation?
Answer: Fertilization is the fusion of a sperm and egg to form a zygote. The zygote undergoes cleavage divisions to form a morula and then a blastocyst, which consists of an inner cell mass (which becomes the embryo) and an outer trophoblast layer (which forms part of the placenta).
18. Explain pregnancy and placenta formation.
Answer: Pregnancy begins with the implantation of the blastocyst into the uterine lining. The placenta forms from the trophoblast and maternal tissues, providing nutrients, oxygen, and waste removal for the developing fetus, and producing hormones to maintain pregnancy.
19. Describe parturition and lactation.
Answer: Parturition is the process of childbirth, initiated by hormonal changes leading to uterine contractions and delivery of the baby. Lactation is the production and secretion of milk by the mammary glands, stimulated by prolactin and oxytocin hormones, to nourish the newborn.
20. What are the various methods of birth control and assisted reproductive technologies?
Answer: Birth control methods include barrier methods (condoms, diaphragms), hormonal methods (pills, patches), intrauterine devices (IUDs), and surgical methods (vasectomy, tubal ligation). Assisted reproductive technologies include In Vitro Fertilization (IVF), Zygote Intrafallopian Transfer (ZIFT), and Gamete Intrafallopian Transfer (GIFT), which help couples with infertility issues to conceive.
This set of questions and answers covers the key concepts related to reproduction in both plants and humans, as well as reproductive health.