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Kerala State Syllabus 9th Standard Biology Solutions Chapter 8 Division for Growth and Reproduction

Division for Growth and Reproduction Textual Questions and Answers

Question 1.
The phase at which a cell prepares for division is called
Answer:
Interphase

Question 2.
………. takes place after karyokinesis
Answer:
Cytokinesis

Question 3.
………… begins after interphase
Answer:
Cell division

Question 4.
What are changes that take place during interphase?
Answer:
a) Division of nucleus (Karyokinesis)
b) Division of Cytoplasm (Cytokinesis)

Question 5.
State whether true or false
Cytokinesis takes place after karyokinesis
Answer:
True

Question 6.
Main stages of cell division
Answer:
Interphase, Division of nucleus, Division of cytoplasm

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.

Question 8.
…………..is brought about by cell division and cell growth
Answer:
Growth of the body

Question 9.
What are the two types of cell division?
Answer:
Mitosis and meiosis.

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?
Kerala Syllabus 9th Standard Biology Solutions Chapter 7 Division for Growth and Reproduction 1
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
Kerala Syllabus 9th Standard Biology Solutions Chapter 7 Division for Growth and Reproduction 2
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
Kerala Syllabus 9th Standard Biology Solutions Chapter 7 Division for Growth and Reproduction 3
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
Kerala Syllabus 9th Standard Biology Solutions Chapter 7 Division for Growth and Reproduction 4
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.