Class 9 Biology (English Medium) Chapter 07 Division for Growth and Reproduction - Questions and Answers
SCERT Solutions for Class 9 Biology Chapterwise
Biology Questions and Answers in English
Chapter 7: Division for Growth and Reproduction
1. Growth of the body is brought about by ………………………….
• cell division and cell growth.
2. What are the main stages of cell division?
• inter-phase and the division phase
3. What are the stages of the division phase?
• Division of nucleus (Karyokinesis)
• Division of cytoplasm (Cytokinesis)
4. Important changes that take place during interphase?
1. Number of cell organelles increases.
2. Quantity of cytoplasm increases.
3. Cell size increases.
4. Genetic material duplicates.
5. What is interphase?
• Interphase is the phase at which a cell prepares for division. (ie, Changes prior to cell division). During this phase, the number of cell organelles increases, the number of cytoplasm increases, size of cell increases and the genetic material duplicated.
6. What is the Cell Cycle?
• A cell attains its complete growth during interphase. The fully grown cell undergoes division and becomes daughter cells. As the interphase and the division phase get repeated in a cyclic manner, they together constitute the cell cycle
7. What are the two types of cell division?
• Mitosis:- (The division, seen in eukaryotes, in which two daughter cells form from a parent cell)
• Meiosis:- (The division, occurs in the germinal cells of the reproductive organs, to form gametes)
8. What is mitosis?
• Mitosis is the type of cell division that helps in the growth of the body. This is a process by which a mother cell divides into two daughter cells. It has two phases, karyokinesis and cytokinesis.
9. Which phase occurs first during mitosis?
• Karyokonesis
10. Division of nucleus is called…………………..
• Karyokonesis
11. Four phases in karyokinesis
12. Observe the figures.
• A.-metaphase B anaphase
13. Division of cytoplasm is known as ------------------
• Cytokinesis.
14. Cytokinesis in animal cell and plant cell
15. The main characteristics of mitosis?
• At each division, the cell divides after the duplication of genetic material. Hence, there will not be any change in the chromosome number even if the cell divides several times. Mitosis makes the repair of tissues and the growth of the body possible. These are the main characteristics of mitosis.
16. Which condition leads to cancer?
• Mitosis is a controlled process. A disruption in this controlled process leads to the excessive division of a cell and its proliferation. This condition leads to cancer.
17. List out the different stages in the growth of human beings
• Zygote
• Embryo
• Foetus
• Infancy
• Childhood
• Adolescence (10 -19 years)
• Youth
• Old age
18. The adolescent period is between………………….. of age.
• 10 to 19 years
19. What are the physical peculiarities of old age?
• rate of cell division decreases.
• availability of oxygen to cells decreases.
• deterioration of cells increases.
• muscles shrink.
• production of energy decreases.
• efficiency of sense organs decreases.
20. What are the differences between the growth in plants and animals?
Animals
• Animals grow only up to a certain stage
• Animals do not have localized centres of growth
Plants
• Plants can grow throughout their lives
• Growth in plants is localized only at certain parts
21. Plants grow due to the rapid division and differentiation of …………… cells
• meristematic cells
22. Plants can grow throughout their life due to the presence of……………….
• meristematic cells
23. What are meristems?
• Meristems are the growth occurring part of plants, where rapid dividing special young cells present.
24. List the meristems in various parts of the plant and list their functions
25. Why is it, that growth in plants is localised only at certain parts?
• In plants, the meristematic cells are located only at certain parts. so growth is localized in that parts
26. In some plants (dicotyledonous plants) the girth of stem and roots increases day by day, while in some other plants (monocotyledonous plants) only the height of stem increases. Why?
• In dicots like mango tree, jack tree or ficus, lateral meristem present which increases the girth of stem and roots. Monocots like coconut tree, areca nut plant or bamboo contain intercalary meristem, just above the nodes, helps to increase the length of the stem.
27. The stem of monocots increases in length faster than dicots. Why?
• In monocots, the intercalary meristem is seen which also increases the length of the stem along with apical meristem.
28. The stem of monocots does not increase its girth beyond an extent. Why?
• Because lateral meristem is absent in monocot plants.
29. ……………... leads to reproduction in unicellular organisms.
• Mitosis
30. Reproduction in Amoeba
31. There are……………………..chromosomes in a human cell.
• 46 chromosomes
32. Define chromosomes?
• Chromosomes are genetic material containing parts, seen in all cells. 46 chromosomes or chromatin reticulum are seen in each cell in a human being.
33. Zygote is formed by the fusion of …………………….
• male and female gametes
34. ……………... is the mode of cell division in which gametes are formed.
• Meiosis
35. Meiosis occurs in the ……………..of the reproductive organs.
• germinal cells
36. Analyse the illustration and answer the questions
i) Number of chromosomes in germinal cells.………….
• 46
ii) Difference of meiosis I from mitosis.
• In meiosis I, the chromosome number becomes half. But in mitosis no change in chromosome number
iii) Similarity between meiosis II and mitosis
• Meiosis II is similar to mitosis. In meiosis II the chromosome number does not change.
iv) Difference in the number of sperm and ovum formed from one germinal cell.
• In males, after meiosis, four sperms having 23 chromosomes are formed from a single germinal cell. But in females, only a single ovum is formed from one germinal cell.
37. Human chromosome number in the newly formed daughter cell will be the same as that of the dividing cell. Why?
• During mitosis duplication of genetic material (chromosomes) occur before the formation of daughter nuclei.
38.Human chromosome number in all generation is 46 or 2n. How does this remain constant?
• The chromosome number is reduced to half (n) in gametes due to meiosis of germinal cells.
39. What do you mean by the polar body?
• When meiosis occurs in the female germinal cell, a large ovum and three small cells are formed. The smaller cells are the polar bodies. These sterile cells get destroyed.
40. What is the significance of meiosis?
• In sexually reproducing organisms, it is through meiosis that the chromosome number is maintained constant even after generations.
41. Compare mitosis and meiosis and complete table
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