Division For Growth And Reproduction Class 9 Question 1.
The phase at which a cell prepares for division is called
Answer:
Interphase
9th Standard Biology Notes Kerala Syllabus Question 2.
………. takes place after karyokinesis
Answer:
Cytokinesis
Kerala Syllabus 9th Standard Biology Notes Question 3.
………… begins after interphase
Answer:
Cell division
9th Biology Kerala Syllabus Question 4.
What are changes that take place during interphase?
Answer:
a) Division of nucleus (Karyokinesis)
b) Division of Cytoplasm (Cytokinesis)
Biology Class 9 Kerala Syllabus Question 5.
State whether true or false
Cytokinesis takes place after karyokinesis
Answer:
True
Kerala Syllabus 9th Standard Biology Notes Pdf Question 6.
Main stages of cell division
Answer:
Interphase, Division of nucleus, Division of cytoplasm
Biology 9 Kerala Syllabus Question 7.
What are the important changes that take place during interphase?
Answer:
- Number of cell organelles increase
- Quantity of cytoplasm increases
- Cell size increases
- Genetic material duplicate
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 cell cycle.
9th Biology Notes Kerala Syllabus Question 8.
…………..is brought about by cell division and cell growth
Answer:
Growth of the body
Kerala Syllabus Biology 9th Standard Question 9.
What are the two types of cell division?
Answer:
Mitosis and meiosis.
Biology Class 9 Kerala Syllabus Question 10.
What do you mean by mitosis?
Answer:
A parent cell divides to form two daughter cells are called mitosis.
Karyokinesis
Question 11.
Point out the phases taken place in the changes in nucleus?
Answer:
Prophase, metaphase, anaphase and telophase
Question 12.
In which phase does the chromatin reticulum become chromosomes?
Answer:
Prophase
Question 13.
What changes occurs in telophase?
Answer:
In telophase chromosomes that moved to the poles become chromatin reticulum and daughter nuclei are formed.
Question 14.
State whether true or false in prophase chromosomes become chromatin reticulum.
Answer:
False
Question 15.
Complete the table of stages of nuclear division
Answer:
| Phases | Changes |
| Prophase | 1. Chromatin reticulum become chromosomes 2. Duplicated chromosomes. 3. Formation of spindle fibers 4. Nucleolus and nuclear membrane get disappeared |
| Metaphase | Chromosomes have moved to the middle of the cell and, chromosomes doubled. |
| Anaphase | 1. Chromatids are starting to separate from each other. 2. Formation of two sets of daughter chromosomes |
| Telophase | 1. Formation of daughter nuclei 2. Two daughter nuclei are formed. 3. There will be no change in chromosome number in each daughter nucleus |
Cytokinesis (Division Of Cytoplasm)
Question 16.
The division of the cytoplasm is taken place in plant is entirely different. Give reason?
Answer:
Because it is due to the presence of the cell wall in plant cell.
Question 17.
What is the significance of mitosis?
Answer:
The significance of mitosis is that there is no change in the number of chromosomes.
Question 18.
Mitosis helps ………… & ……….
Answer:
For the repair of tissues and growth.
Question 19.
Which condition leads to cancer?
Answer:
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.
Different Stages Of Growth
Question 20.
List out the different stages in the growth of human beings.
Answer:
- Zygote
- Infancy
- Old age
- Embryo
- Childhood
- Fetus
- Adolescence
- Youth
Question 21.
What are the physical peculiarities of old age?
Answer:
Rate of cell division decreases, Availability of oxygen to the cells decreases, Deterioration of cells increase Muscles shrink, Production of energy decrease
Question 22.
The elders should be cared. Do you agree with this statement? Why?
Answer:
Old age is inevitable in life. The aged who worked for the welfare of their family and society during their younger age deserve special consideration.
Question 23.
What are the differences between the growth in plants and animals? Draw a comparison and complete table
Answer:
| Animals | Plants |
| Animals grow only up to a certain stage Animals do not have localized centers of growth | Plants can grow throughout their lives Growth in plants is localized only at certain parts |
Question 24.
Plants grow due to the rapid division and differentiation of cells.
Answer:
Meristematic cells
Question 25.
What do you mean by meristematic cells?
Answer:
Meristematic cells are special types of cells that have the capacity for continuous division.
Question 26.
Plants can grow throughout their life due to the presence of
Answer:
Meristematic cells
Question 27.
……… helps to increase the length of root and stem.
Answer:
Apical meristem
Question 28.
……… helps to increase the girth of the stem.
Answer:
Lateral meristem
Question 29.
Name the meristematic cells which help to increase the length of the stem.
Answer:
Intercalary meristem
Question 30.
Where do you find intercalary meristem?
Answer:
It seen above the nodes of monocot plants.
Question 31.
The stem of monocots increases in length faster than dicots. Why?
Answer;
Because the intercalary meristem is visible only in the monocot plants.
Question 32.
Dicot plants: Lateral meristem
……………..: Intercalary meristem
Answer:
monocot plants
Question 33.
The stem of monocots does not increase its girth beyond an extent. Why?
Answer:
Because lateral meristem is absent in monocot plants.
Growth In Unicellular Organisms
Question 34.
Does cell division in unicellular organisms lead to growth or reproduction?
Answer:
Mitosis leads to reproduction in unicellular organisms.
Meiosis
Question 35.
What do you mean by meiosis? Explain.
Answer:
Meiosis is the mode of cell division in which gametes are formed. Meiosis occurs in the germinal cells of the reproductive organs. Human beings have 46 chromosomes. Germinal cells with 46 chromosomes divide continuously two times. These divisions in meiosis are known as meiosis I and meiosis II. Two daughter cells “with half the number of chromosomes (23 chromosomes) are formed in meiosis I. Each daughter cell again divides in meiosis II. There is no change in the chromosome number in this division. Hence meiosis II is similar to. mitosis. As a result of meiosis, four daughter cells, each with 23 chromosomes, are formed from a germinal cell.
Question 36.
What do you mean by polar body?
Answer:
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.
Question 37.
Complete the illustration
Answer:
a = 46
b = 23
c= 23
d = 23
e = 23
f = 23
g = 23
Question 38.
What is the number of chromosomes in germinal cells?
Answer:
46
Question 39.
What is the number of chromosomes in the daughter cells formed after meiosis I?
Answer:
23
Question 40.
What is the peculiarity of meiosis II?
Answer:
Each daughter cell again divides in meiosis II. There is no change in the chromosome number in this division. Hence meiosis II is similar to mitosis.
Question 41.
What are the kinds of cell division occur in sexually reproducing organisms?
Answer:
There are two kinds of cell division occur in sexually reproducing organisms that are mitosis and meiosis.
Question 42.
What are the different stages in the growth of human being?
Answer:
Infancy, childhood, adolescence, youth and old age.
Question 43.
Differentiate mitosis and Meiosis
Answer:
| Differences | Mitosis | Meiosis |
| Type of reproduction | Asexual | Sexual |
| Genetically Chromosome Number | Similar Remains same | Different Reduced by half |
| Takes place in | Somatic cells | Germ cells |
| Number of daughters | 2 diploid | 4 haploid |
| cells produced | cells | cells |
Let Us Assess
Question 1.
The stage of karyokinesis at which daughter nuclei are formed
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
Answer:
Telophase
Question 2.
List the meristems in various parts of the plant and list their functions
Answer:
| Meristem | Function |
| Apical meristem | Increase the length of root and stem |
| Lateral meristem | Helps to increases the girth of stem |
| Intercalary meristem | Helps to increase the length of the stem of monocot plants |
Question 3.
In females, only a single ovum is formed from a germinal cell, whereas in males, more than one sperm is formed. Give reason.
Answer:
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. So only a single ovum is formed from a germinal cell. But in males, after meiosis, four sperms having 23 chromosomes are formed form one germinal cell.
Question 4.
Observe the figures
a) Which stages of mitosis are indicated in the figures?
b) What are the changes that occur in the chromosomes during these stages?
Answer:
a) Metaphase
b) Chromosomes get aligned at the equator of the cell.
