Matric Notes Biology Class 10th Ch 14 Reproduction Long Questions
Q1: Describe the alternation of generation in a flowering plant.
Ans: Generation in a flowering plant:- In the life cycle of flowering plant two generation comes one after the other which is called alternation of generation.
These generation are
2. Gametophyte generation.
1. Sporophyte generation: The whole plant body including roots leaves stems and flowers make sporophyte generation is diploid (2n).
2. Gametophyte generation: Gametophyte generation of the plant is produced inside the flower gametophyte generation male and female gametes are produced. That’s why they are called gametophyte generation.
Flower has male and female parts which produce micro gametophyte and mega gametophyte.
i. Micro gametophyte:- The germinated pollen grain having pollen tube and two sperms is known as micro gametophyte. Stamen is the male part of the flower. Pollen grains are produced in the anther of the stamen.
ii. Mega gametophyte: Eight nucleated embryo sac of the mature ovule is called mega gametophyte. Carpel is the female part of the flower. Ovules are produced in the ovary of the carpel.
Double fertilization: The fusion of one sperm of pollen grain with the egg cell of ovule to produce a diploid (2n) zygote is known as fertilization but when the other sperm fuses with the endospermic nucleus (2n) is known as double fertilization is triploid (3n) endosperm. Double fertilization is unique characteristic of flowering.
Development of seed and fruit: The mature ovule after fertilization develops into seed. The mature ovary after fertilization is known as fruit.The seed when germinate in the favorable conditions again, a saprophyte plants as produced. In this way the life cycle of flowering plants completed.
Q2: Explain the different plant structures modified for vegetative propagation.
Ans: Vegetative propagation in plants:- Vegetative propagation is type of asexual reproduction in which new cells are produced from the vegetative parts of the parents plant such as from stem, leaves and roots. Vegetative propagation occurs naturally without human involvement but it can be performed artificially. Various methods of vegetative propagation are given.
1. Vegetative propagation through leaves:-
ii. These buds form roots at their base.
iii. When these shoots break off from the original leaf on the ground and survive as independent plant.
2. Vegetative propagation through stem:-
b. These plants spread by having arching shoots which touch the soil.
c. The rubbing of the stem on the soil and the horizontal position of the stem along the soil surface cause plant hormone auxin to build up there.
d. The developing roots produce a plant hormone called cytokinin.
e. Theses hormone induce more shoot formation.
3. Vegetative propagation through root:-
b. These plants produce root sprouts.
c. The roots of these plants produce a hormone called cytokinins.
d. These hormones accumulate in the roots and induce shoot formation.
e. Near the base of the plant, a new shoot arises.
f. If these root sprouts detached from the original plant, then they can survive independently.
Q3: Explain gametogenesis.
Ans: Sexual reproduction in animals:- Sexual reproduction is the method of producing new generation in most animals. The male and female animals make gametes in their gonads. This process is called gametogenesis. The male gametes join with the female gamete to form zygote, which develops into a new individual.
Formation of gametes- gametogenesis:- In animals, sex cells or gametes are produced in special organ called gonads (testes in males and ovaries in females). The formation of gametes involves meiosis. Meiosis results in a reduction of the number of the chromosomes gametes in haploid (n) as compared to the diploid (2n) number in other body cells. The formation of male gametes or sperms is called spermatogenesis while the formation of female gamete or ovum is called oogenesis.
Spermatogenesis:- In the testes, there are many diploid gametes mother cells called primary spermatocytes. Each primary spermatocytes divides by meiosis and makes four haploid (n) cells called spermatids. Each spermatid develops into a motile sperm.
Oogenesis:- In the follicle of the ovary, there are diploid gametes mother cells called primary oocytes. These divide by meiosis. As a result of the first meiotic division, two haploid cells are produced. The larger cells is called the secondary oocytes while the smaller cell is called the first polar body. In meiosis II, the secondary oocytes produces two haploid cells I-e a second polar body and an egg.
Q4: How are seeds produced? What is the structure of a seed?
Ans: Seed: The unit of reproduction of a flowering plant, capable of developing into another such plant.
Production of seed:
Seed and fruit formation:- After fertilization, the zygote develops into an embryo and the triploid nucleus develops into endosperm tissue. After these developments, the ovule is said to be matured and now called the seed.
Development of sporophytes: When seeds mature, they are dispersed. If seeds get suitable conditions, their embryos develop into new plants (the saprophytes of the next generation).
Structure of a seed: A seed (mature ovule) is a miniature plant with a protective cover. Typically a seed consists of the following structures.
Seed coat: The outer covering of a seed is called the seed coat or testa. It is black or brown in colour and protects the embryo.
Hilum: On one end of the seed coat, is a small scar or hilum. It indicates the place of attachment of the seed in the fruit.
Micropyle: It is a minute pore near the helium. The seed absorb, water through the micropyle at the time generation.
Embryo: It is present beneath the seed coat. The embryo consists of the following parts.
Cotyledons: In a monocot seed there is one leaf- cotyledon. In a dicot seed, there are two large, fleshly, cotyledons.
Plumule and radicle: There is a minute bud (plumule) at the upper end of the hypocotyle. It gives rise to the future root. The portion between the plumule and the cotyledons is called the epicotyl. The portion between the cotyledons and the radicle is called the hypocotyl.
Endosperm: This tissue is formed from endosperm nucleus. It stores nutrients. Dicots seed have endosperm while monocot seeds have endosperm. In these seeds, the cotyledon absorbs nutrients from the endosperm and transfer them to the embryo.
Q5: Write a comprehensive note on a seed germination and its types.
Ans: Seed germination:- The development of the embryo of the seed, into a seedling is called seed germination. The dry seed of the embryo is alive but inactive. When it is placed in the soil under suitable conditions, the embryo becomes active and grows into a seedling. Germination of the seed starts with the absorption of water through the micropyle. This is followed by the emergence of the radicle, which forms the first root. After the radicle breaks the seed coat, the plumule begins to grow to form a shoot.
Types of germination:- On the basis of growth of the plumule there are two types of germinations.
Epigeal and hypogeol germinations:
2. During hypogeal germination, the epicotyle elongates and the cotyledons remain below the surface of the ground. e.g. Maize grain, pea etc.
Conditions necessary for germination of seeds:-
Viable or living seeds should have sufficient food for germination. Moreover, the following environmental conditions should also be in place which are necessary for the germinations of seeds.
1. Water:- Seed absorb water through the micropyle. Water softens the seed coat and makes it burst. Water also helps to activate enzyme that digest the food of seeds, and make it available make it available to the growing embryo.
2. Oxygen: Oxygen is also necessary for seed germination. The cells of the seed embryo use oxygen for cellular respiration so that they can get energy from stored food.
3. Suitable temperature: Germinations of seeds occurs over a wide range of temperature between 5◦C to 30◦C. A suitable temperature is necessary for the enzymes of function properly.
Q6: Write the mode of reproduction of an onion, corn, ginger and potato.
Ans: Mode of reproduction of onion: Onions reproduce either with seeds or by bulbils (little bulbs) that form from lateral buds. After the first growing season, mature bulbs can be left in the ground or dug up and replanted. Either way the plant will undergo a period of dormancy, then grow during the next growing season.
Mode of reproduction of corn: Pollination occurs when pollen falls on the exposed silks. Following pollination, a male sex cell grows down each silk to a single egg and fertilization (the union of the male and female sex cells) occurs. The fertilized egg develops into a kernel and inside each kernel is a single embryo (a new plant).
Mode of reproduction of ginger: Ginger has low genetic diversity because it reproduces asexually by vegetative propagation. Zingiber officinale primarily produces from spreading the rhizome. The stem generated from the plants' rhizome forms a bud that becomes a complete plant, a clone of the original plant.
Mode of reproduction of potato: Potato growers plant small potatoes ("seed potatoes") in fields then let them sprout roots and shoots from which potato plants grow above the soil.
Q7: Make a list of ripened seeds and fruits that are eaten in our society.
Ans: Ripened seeds:
2. Beans
3. Peanuts
4. Rice
5. Cereals
Ripened fruits:
2. Mango
3. Apple
4. Strawberries
5. Figs
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