Reproduction in Plants and Animals - Questions and Answers Part-2
1. What is the source of variation in population of organisms?
Answer: DNA replication is a source of variations in population of organisms.
2. Name a fruit in which the calyx is persistent.
Answer: A fruit in which the calyx is persistent is tomato.
3. Name the female floral organ.
Answer: Gynoecium or pistil.
4. What do you mean by self pollination?
Answer: The transfer of pollen grains from the anther of a flower to the stigma of the same flower or of another flower born on the same plant is called self pollination.
5. Name the parts of the flower shed during fruit formation.
Answer: The parts of the flower shed during fruit formation are - sepals, petals, stamens, style and stigma.
6. How many male gametes are produced by pollen grains on germination?
Answer: Two male gametes are produced by pollen grains on germination.
7. Which part of flower forms fruit after fertilisation?
Answer: The part of flower which forms fruit after fertilization is ovary.
8. Name the parts of flower which produce male and female gametes.
Answer: The parts of flower which produce male and female gametes are stamen and pistil.
9. Name the agencies through which cross pollination takes place.
Answer: The agencies through which cross pollination takes place are wind, water and animals.
Read more: Reproduction in Plants and Animals - Questions and Answers Class-X Part-3
10. Where is the zygote located in the flower after fertilisation?
Answer: After fertilization, zygote is located within the ovary of the flower.
11. How does the number of chromosomes in parents and offspring of a particular species remain constant?
Answer: The number of chromosomes in parents and offspring of a particular species remain constant through the process of meiosis, fertilization, and mitosis. Meiosis is the process by which a diploid cell (with two sets of chromosomes) divides into four haploid cells (with one set of chromosomes each). During fertilization, two haploid cells (one from each parent) combine to form a diploid zygote (with two sets of chromosomes). The zygote then undergoes mitosis to form the multicellular offspring. The number of chromosomes is constant because the diploid chromosome number is maintained through meiosis, and the fusion of gametes during fertilization restores the diploid chromosome number.
12. What do you mean by bisexual flower? Give any one example of it.
Answer: A bisexual flower is a flower that contains both male and female reproductive organs, such as stamens and pistils.
An example of a bisexual flower is the hibiscus flower.
13. What is the reason behind the fact that the offspring formed as a result of sexual reproduction exhibit more variations?
Answer: Sexual reproduction involves the fusion of gametes from two different parents, which results in offspring with a unique combination of genetic information. This increases the genetic variation in the population and enables adaptation to changing environments. In contrast, asexual reproduction involves the production of offspring that are genetically identical to the parent, which reduces the genetic diversity and limits adaptation.
14. Why can fertilisation not take place in flowers if pollination does not occur?
Answer: Fertilization is the fusion of male and female gametes to form a zygote, which develops into a new individual. Pollination is the transfer of pollen from the male reproductive organ to the female reproductive organ of a flower. If pollination does not occur, there will be no male gamete available to fuse with the female gamete, and fertilization cannot take place.
15. Give two reasons for the appearance of variations among the progeny formed by-sexual reproduction.
Answer: Two reasons for the appearance of variations among the progeny formed by sexual reproduction are:
- Independent assortment of chromosomes during meiosis: During meiosis, homologous chromosomes can align in different ways, resulting in a random distribution of maternal and paternal chromosomes in the gametes. This creates genetic diversity in the offspring.
- Crossing over during meiosis: Homologous chromosomes can exchange segments of DNA during meiosis, which results in new combinations of genetic information. This also creates genetic diversity in the offspring.
16. Mention the important post-fertilisation changes in the flower.
Answer: Some of the important post-fertilization changes in the flower are:
- The ovule develops into a seed, and the ovary develops into a fruit.
- The zygote divides and develops into an embryo.
- The endosperm, which is a nutritive tissue, is formed by the fusion of the two polar nuclei with a sperm cell.
- The ovule integuments harden and become the seed coat.
- The flower may wither and fall off, or it may remain attached to the fruit.
17. What is a seed? How does it help in reproduction in plants?
Answer: A seed is a mature ovule containing an embryo, stored food, and a protective seed coat.
It helps in reproduction in plants by providing a means of dispersing the offspring away from the parent plant and protecting the embryo and stored food until conditions are favorable for germination. When conditions are right, the seed germinates and grows into a new plant.
18.What is the role played by stamen and carpel in sexual reproduction?
Answer: The stamen and carpel are the male and female reproductive organs, respectively, in flowers. They play a crucial role in sexual reproduction by producing and protecting the gametes (sperm and egg cells) and facilitating their fusion to form a zygote. The stamen produces the pollen, which contains the male gametes, while the carpel contains the ovules, which contain the female gametes.
19. Explain double fertilisation in plants.
Answer: Double fertilization is a unique feature of angiosperms, in which two sperm cells fuse with two different cells in the female gametophyte. One sperm cell fuses with the egg cell to form a zygote, which develops into the embryo, while the other sperm cell fuses with the two polar nuclei to form the triploid endosperm, which provides nutrients to the developing embryo. This process ensures that the embryo is accompanied by a nutritive tissue, which is crucial for the development and survival of the seedling.
20. What do you know about the process of fertilisation?
Answer: Fertilisation is the process by which male and female gametes fused together to form a zygote, which develops into a new individual. In plants, fertilization occurs within the flower and involves the fusion of sperm nuclei and egg nuclei in the ovule. In animals, fertilization typically occurs in the female reproductive tract.
The process of fertilization in plants involves several steps:
Pollination: The transfer of pollen from the male reproductive organ (anther) to the female reproductive organ (stigma) of a flower. This can occur through wind, water, or animal vectors such as bees or butterflies.
Germination of pollen: The pollen grain germinates on the stigma, and a pollen tube grows through the style towards the ovary.
Double fertilization: Two sperm nuclei are released from the pollen tube into the ovule. One sperm nucleus fuses with the egg cell to form a zygote, which develops into an embryo. The other sperm nucleus fuses with two polar nuclei to form the endosperm, a nutrient-rich tissue that nourishes the developing embryo.
Seed development: The ovule develops into a seed, which contains the embryo, endosperm, and a protective seed coat. The ovary of the flower develops into a fruit, which helps to disperse the seed.
21. What is the function of anther? How does fusion of male and female gametes takes place in plants?
Answer: The anther is the male reproductive organ in a flower that produces and releases pollen grains. The function of the anther is to produce and store the male gametes (sperm cells) in the form of pollen grains, which are then transferred to the female reproductive organ of the same or another flower during pollination.
In plants, the fusion of male and female gametes occurs during double fertilization. After pollination, the pollen grain lands on the stigma and produces a pollen tube that grows through the style to the ovary, where the ovules are located. Inside the ovule, there are two female gametes: the egg cell and the two polar nuclei.
The pollen tube contains two sperm nuclei, which are released into the ovule. One sperm nucleus fuses with the egg cell, resulting in the formation of a zygote. This is the first fertilization event. The second sperm nucleus fuses with the two polar nuclei, resulting in the formation of the endosperm, which is a nutrient-rich tissue that nourishes the developing embryo.
Thus, in plants, the fusion of male and female gametes takes place within the ovule, which is located inside the ovary of the flower. This process is unique to angiosperms (flowering plants) and is known as double fertilization. The resulting zygote and endosperm develop into a seed, which is protected by the ovary and later dispersed by various means, such as wind or animals, to grow into a new plant.
22. How is zygote formed?
Answer: A zygote is formed through the process of fertilization, which occurs when the sperm cell from a male fuses with the egg cell from a female. This process typically occurs within the female reproductive system, usually in the fallopian tubes.
During fertilization, the sperm and the egg each contribute half of the genetic material that will make up the zygote. The sperm carries a single set of chromosomes containing DNA, while the egg also contains a single set of chromosomes. When the sperm penetrates the egg, their genetic material combines, creating a new cell with a full set of chromosomes.
The resulting cell, now called a zygote, begins to undergo rapid cell division, eventually forming an embryo that will develop into a fetus. The zygote contains all the genetic information necessary to create a new individual and serves as the starting point for the development of a new life.
23. Define double fertilization.
Answer: Double fertilization is the fusion of two male gametes brought by a pollen tube with two different structures of the same embryo sac, one forming embryo and the other forming endosperm.
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