Reproduction in organism NCERT Question and Answer by mohanbio2013

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Reproduction in organism NCERT Question and Answer by mohanbio2013

  1. 1. Reproduction In Organism. Exercises • 1. Why is reproduction essential for organisms? • Reproduction is essential to the organisms for continuity of life on earth. • 2. Which is a better mode of reproduction: sexual or asexual? Why? • Sexual reproduction is better. • Because the progeny of sexual reproduction varies from parents. This helps to evolution.
  2. 2. • 3. Why is the offspring formed by asexual reproduction referred to as clone? • Because the offsprings formed by asexual reproduction are genetically identical to their parents. • 4. Offspring formed due to sexual reproduction have better chances of survival. Why? Is this statement always true? • In sexual reproduction, genetic variation occurs among the offsprings, which may adapt better with the environment. • Hence the statement is true for maxium.
  3. 3. • Q.5.How does the progeny formed from asexual reproduction differ from those formed by sexual reproduction? • Progeny from asexual reproduction have similar genetic make up and are exact copies of their parents, i.e., clone of the parent. • Variation is absent. • Progeny is less adaptable to changes in environment. • Progeny from sexual reproduction have different genetic make up and are dissimilar to the parent. • Variation occurs in progeny. • Progeny is more adaptable to changes in environment.
  4. 4. • Q.6. Distinguish between asexual and sexual reproduction. Why is vegetative reproduction also considered as a type of asexual reproduction? • Ans. Vegetative reproduction is considered as a type of asexual reproduction because: • single parental involves in reproduction. • There is no formation of gametes. • Vegetative progeny from are somatic cells.
  5. 5. • Q.7. What is vegetative propagation? Give two suitable examples. • Ans. In plants, the asexual reproduction which is capable of producing new offsprings is called vegetative propagation. • Examples: 1. Runner or stolon: in strawberry slender stem that grows horizontally to ground is called runner. Naturally it cut off and separated develops in to new individual. 2. Rhizome: In Ginger modified underground stem forms rhizome. If it separated into pieces, each piece give rise to a new plant. 3. Tuber: Potato tuber having buds when grown, develops into a new plant.
  6. 6. • Q.8. Define (i) Juvenile phase, (ii)Reproductive phase, • (iii) Senescent phase. • Ans. (i) The period of growth to attain maturity is called juvenile phase • (ii) Reproductive phase is the phase in the life cycle, where organisms possess all the capacity reproduce sexually. • (iii) The end of reproductive phase in which an organism slowly loses the rate of metabolism, reproductive potential and dies up.
  7. 7. • Q. 9. Higher organisms have resorted to sexual reproduction in spite of its complexity. Why? • Ans. Higher organisms have resorted to sexual reproduction to 1. To introduce variation to enable better adaptive capacity. 2. To restore vigour and vitality of the race. 3. To get proper parental care during.
  8. 8. • Q. 10. Explain why meiosis and gametogenesis are always interlinked? • Ans. Gametogenesis (formation of male and females gametes) is associated with reduction in chromosome number. • Thus gametogenesis is interlinked with meiosis because in meiosis, reduction of chromosome number from diploid set (2n) to haploid set (n) takes place.
  9. 9. • Q. 11. Identify each part in a flowering plant and write whether it is haploid(n) or diploid (2n). • (a) Ovary --------- Diploid • (b) Anther -------- Diploid • (c) Egg ------------- Haploid • (d) Pollen ---------- Haploid • (e) Male gamete --- Haploid • (f) Zygote. ----------- Diploid
  10. 10. • Q. 12. Define external fertilisation. Mention its disadvantages. • Ans. The fusion of gametes outside the body of an organism is called external fertilisation, e.g., in frog. • Disadvantages of external fertilisation: 1. It requires a media (water) for fusion of gametes. 2. Organism produces large number of gametes. 3. The predators destroys eggs and offsprings. 4. Less or no parental care is taken to young one. 5. The survivality rate of offspring to adult is less
  11. 11. Q.13. Differentiate between a zoospore and a zygote. • Zoospore: • (i) These are asexually produced unicellular, naked and motile spores having one or two flagella. • (ii) It may be haploid or diploid. • (iii) Zoospore takes part in dispersal. • Zygote: • (i) Zygote is diploid cell formed by fusion of male and female gametes. • (ii) It is always diploid. • (iii) Zygote do not have significant role in dispersal.
  12. 12. Q. 14. Differentiate between gametogenesis from embryogenesis. • Gametogenesis • (i) The formation of gametes from meiocytes (gamete mother cell). • (ii) This is a pre- fertilisation event. • (iii) The cell division during gametogenesis is meiotic. • (v) It produces haploid gamete. • Embryogenesis • (i) The formation of embryo from zygote cell. • (ii) This is a post- fertilisation event. • (iii) The cell division during embryogenesis is mitotic. • (v) It gives rise to diploid embryo.
  13. 13. • Q. 15. Describe the post-fertilisation changes in a flower. • After zygote formation, the sepals, petals and stamens of flower falls off. • In some plants like tomato, brinjal sepals persist with fruit. • The zygote develops into embryo. • The ovule develops into seed. • The ovary matures and develops into fruit (pericarp).
  14. 14. • Q. 16. What is a bisexual flower? • A flower which possess both the male and female reproductive structures, i.e., both stamen and carpel is called a bisexual flower. • Q. 17. Examine a few flowers of any cucurbit plant and try to identify the staminate and pistillate flowers. Do you know any other plant that bears unisexual flowers? • Ans. A staminate or male flower has only stamens and no carpel. A pistillate flower has only carpel and no stamens. • Plants that bear unisexual flowers are papaya and date palm.
  15. 15. • Q. 18. Why are offspring of oviparous animals at a greater risk as compared to offspring of viviparous animals? • Ans. In viviparous animals, the young one develops inside the body of the female organism. As a result of this, the young one gets better protection and nourishment for proper development. • In oviparous animals, they lay egg and the young one develops outside the body of the female. 1. The predators destroys eggs and offsprings. 2. Less or no parental care is taken to young one. 3. The survivality rate of offspring to adult is less

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