RBSE Class 9 Science Chapter 6 Structure of Living Organism Solutions help students to get a proper grasp of all the concepts of the chapter thoroughly, thus gaining high scores in the exams. The solutions are also the most significant resource used to revise the chapter properly. Practising these solutions help the students to master the subject thoroughly. Also, solving these questions taken from the RBSE Class 9 Solutions for Chapter 6 Science cover all the key topics taken from the chapter. These chapterwise important topics and questions from the RBSE Class 9 Science will help the students to prepare most competently for the Class 9 exams. Meanwhile, in order to improve their performance and for the students to master the concepts taught in class, the students are encouraged to implement a strategic learning process.
In this article, we have mentioned a list of important questions from Chapter 6 of RBSE Class 9 Science Textbook. Doing these questions will provide enough practice for the students to score high marks. Students who have mastered the subject will be able to learn the basics of the subject, before moving to higher classes and it will also help them to score high marks.
Rajasthan Board Class 9 Science Chapter 6- BYJU’S Important Questions & Answers
RBSE Class 9 Science Chapter 6 Objective Questions-Important Questions and Solutions
1. Which cell organelle is known as the suicide bag ?
Answer: (b) Lysosomes
2. The nucleus was discovered by :
(a) Robert Brown
(b) Robert Hooke
Answer: (a) Robert Brown
3. DNA is synthesized during which stage of cell cycle ?
(a) G-1 phase
(b) S phase
(c) M phase
(d) G-2 phase
Answer: (b) Synthetic Phase or S Phase
4. The tissue responsible for imparting flexible strength to plants is :
(d) None of the above
Answer: (b) Collenchyma
5. Write the name of the scientist who observed a living cell for the first time.
Answer: In 1674, itt was Van Leeuwenhock who improved the microscope and observed living cells.
6. Write the names of any two unicellular organisms.
Answer: Amoeba and Paramecium are two unicellular organisms.
7. Name the longest cell of the human body.
Answer: The longest cell of the human body is a neuron.
8. What is the function of a cell wall in a plant cell?
Answer: A cell wall provides a definite shape and extra protection for the plant cell.
9. Name the plastids present in the plant cell.
Answer: The plastids present in the plant cell are Chloroplast, Chromoplast and leucoplast.
10. What is the function of ribosomes in a cell?
Answer: Ribosomes synthesise proteins
11. Which type of cell division takes place in somatic cells?
Answer: Mitosis is the cell division that takes place in all the somatic cells.
12. Why is the meiotic division also known as the reductive division?
Answer: In the first stage of meiosis, the parent cell is divided to form two cells in which the number of chromosomes is reduced to half of that present in the parent cell. Hence, this stage of meiosis is also known as the reductive division.
13. Cytokinesis takes place in plant cells by which method?
Answer: Cytokinesis takes place in plant cells by the formation of cell plates.
14. Which substance is deposited on the cell wall of the collenchymatous tissue?
Answer: Cellulose and pectin are deposited on the cell wall of the collenchymatous tissue.
RBSE Class 9 Science Chapter 6 Short Answer Type Questions-Important Questions and Solutions
1. What are unicellular and multicellular organisms? Give examples.
Answer: An organism whose body is made up of one cell is called a unicellular organism. Examples include Amoeba, Chlamydomonas and so on. Meanwhile, multicellular organisms are organisms whose body is made up of more than one cell. Examples for multicellular organisms are human beings, animals, birds, insects and more.
2. Explain the cell theory.
Answer: Cell theory was propounded in the year 1838 to 39 by Zoologist Theodor Schwann and Botanist Mathias Schleiden. According to the theory, the body of every living organism is made up of one or more cells. The cell is considered as the basic unit of life and all the life processes of a living being takes place inside the cell. At the same time, the cell is the unit of heredity because hereditary material is present in the nucleus. New cells are also developed from the pre-existing cells. However, on the basis of modern discoveries the cell theory does not appear to be logical at many points. Here is an example of the virus. It does not have a cellular structure; all the organisms are not made up of cells and a prominent nucleus is not present in all the cells.
3. Explain the structure and function of mitochondria.
Answer: Mitochondria also known as the ‘powerhouse’ of the cell because it produces the energy required by the cell, can be found only in the eukaryotic cells and are absent in the prokaryotic cells. Even in different cells of the same organisms, they are present in different numbers. There are more mitochondria in the cells that require more energy. Mitochondria has a double membrane. Outer membrane is smooth and flat, while the inner membrane is projected in the cavity in the form of a cristae. There are numerous stalked particles known as Oxysomes on the surface of the cristae. The region inner to the cristae is known as the matrix consisting of 65% to 70% protein, 25% phospholipid and 0.5% RNA. Mitochondria also contains DNA and ribosomes in it. The enzymes present in the mitochondria are responsible for the oxidation of nutrient substances during respiration.
4. Write four differences between animal cell and plant cell.
Answer: Basic structure of an animal cell and plant cell are the same. However, there are some differences, which are listed in the table below:
In plant cells, a non-living cell wall made up of cellulose is present around the cell membrane.
Animal cell lacks cell wall
In plant cells, the photosynthesizing
Organelle, chloroplast is present.
In animal cells, chloroplast is not present
In plant cells, two or more vacuoles are present
In animal cells, vacuoles are very small or absent
Centrosomes are absent in the plant cells
Centrosomes are present in the animal cells
5. Why lysosomes are known as the suicide bags.
Answer: Lysosome is a single membrane bound, sac like organelle discovered by de Duve responsible for the breakdown of dead cell-organelles and cells. The enzymes present in it digests the entire cell once it’s membrane ruptures, therefore earning the name of suicidal bags. Lysosomes are filled with granular fluid containing many hydrolytic enzymes, which break
down sugar, fat, protein, nucleic acid and so on into simple molecules.
6. Describe the structure and function of the nucleus.
Answer: Discovered in 1831 by Robert Brown, the nucleus is the most important organelle of the cell. The animal cell nucleus is spherical and is present in the center of the cell. However, a plant cell nucleus is present near the periphery because of the presence of a large vacuole in the center. Nucleus is a double membrane bound organelle. Its membrane is known as the nuclear membrane with minute pores in it, through which there is exchange of substances between the cytoplasm and the nucleoplasm. A fluid nucleoplasm is present in the nucleus consisting of proteins, nucleic acid and other carbonic compounds. One or more small spherical structures present in the nucleus, are known as the nucleolus. A network of thin thread-like structures present in the nucleoplasm is known as the chromatin network. At the time of cell division the threads of the chromatin network known as chromosomes coils and appear thickened. Nucleus is the main controlling organelle of the cell.
7. Explain the cell cycle.
Answer: In the process of cell division, the daughter cell is produced by the division of the parent cell and the daughter cell further re-divides to produce new cells. The various stages, from the formation of new cells to its division, are together known as the cell cycle. The main phases of the cell division includes the Interphase, during which the substances essential for cell division are synthesized. Interphase includes three stages such as G-I phase, Synthetic period or S-phase and Second growth period or G-II Phase. The G-I phase takes place for nearly 30%-40% of the time of the entire cell cycle. During this period the cell grows and the proteins and RNAs required for DNA synthesis are formed. It is the Gap-I (G-I) period. Next, the Synthetic period or S-phase consumes a total of 20% to 30% of the total cell cycle span, during which period the DNA is synthesized. Then the Second growth period or G-II Phase takes up 10% to 20% time of the cell cycle. This is the Gap-2 or G-2 period in which the proteins required for the cell are synthesized. Then, finally, there is Division Phase (M-Phase) allotted for the rest 5% to 10% of the cell cycle duration. During this step the nucleus of the cell divides to form two daughter nuclei and later on the cytoplasm also divides resulting in the formation of two
8. Explain the methods of cytokinesis in plant and animal cells.
Answer: The process of dividing the cytoplasm in eukaryotic cells to produce two distinct daughter cells that are identical to each other is called Cytokinesis.Cytokinesis in plant cell takes place by the formation of cell plate while in animal cell it is by means of cleavage method. Cytokinesis normally occurs at the end of mitosis, after telophase-I. In animals, it might also start sometimes at the end of anaphase or beginning of telophase, just to make sure that the chromosomes have been segregated completely.
9. Explain the metaphase of mitotic division with the help of a suitable diagram.
Answer: Mitosis takes place in all the somatic cells i.e. in all the cells except the reproductive cells. The stages occurring during mitosis can be divided into following:
(a) Interphase : This is the period in between two successive divisions when the cell prepares itself for division.
(b) Karyokinesis : During this phase, the nucleus divides into two daughter nuclei. To simplify its study, this stage has been divided into four phases- Prophase, Metaphase, Anaphase and Telophase. Metaphase : (i) Major events of the phase is the formation of Spindle fibres and
arrangement of chromosomes in the middle region of the spindle. Astral rays radiate out from each centriole, which together form the spindle fibres that connect the centromere with the poles.
(ii) Chromosomes move towards the equatorial region and arrange themselves in such a manner that their centromeres lie at the metaphase plate with the arms of chromatids, extending outward, towards poles.
10. Explain the anaphase movement in relation to the cell division.
Answer: During the anaphase stage of mitosis, the centromere divides, resulting in the separation of two chromatids from each other. These two chromatids are now known as Daughter Chromatids. The daughter chromatids separate from each other and move towards the opposite poles.
11. Write the significance of meiosis.
Answer: Meiosis happens in the diploid reproductive cells at the time of reproduction resulting in the formation of haploid gametes. In this type of division, the number of chromosomes in the daughter cells formed, is half of that present in the parent cell. Meiosis is completed in two stages. In this division, the cell divides twice and results in the formation of four haploid cells from a single diploid cell. The two stages are- Meiosis I and Meiosis II. The number
of chromosomes in the vegetative cells of the organisms, reproducing sexually, remains the same from generation to generation. New combinations of hereditary characters are formed by the crossing over that take place during prophase I of Meiosis. It produces hereditary variations in the organism, forming the basis of organic evolution.
12. Explain the structure and function of xylem.
Answer: Xylem is a complex tissue of vascular plants involved in transporting water and mineral salts from the root to the leaves, upward. Students can check structure and function of xylem, for more details. .
13. Draw a well labelled diagram of a neuron.
14. Describe the various types of muscles present in animals.
Answer: Click the link and learn more about the types of muscles that are present in animals.
15. Explain the structure of a virus and draw a well labelled diagram of a bacteriophage.
Answer: Viruses are so small, 30 nm to 300 nm in size and are observed only with the help of electron microscopes. Each particle of the virus is known as the virion, consisting of a protein coat, known as capsid that encloses the nucleic acid: DNA or RNA. Based on their source of nourishment, viruses are of three types- animal virus, plant virus and bacteriophage.
1. Draw a well labelled diagram of a plant cell and describe the structure and function of the following organelles :
(b) Endoplasmic reticulum
(a) Chloroplast is the organelle of the cell in which carbohydrates are synthesised by the process of photosynthesis. Chloroplast is a double membrane bound organelle, which is known as the outer membrane and the inner membrane.
(b) The network of microtubules present between the nucleus and the cell membrane is known as the endoplasmic reticulum. This also is a single membrane- bound structure.
(c) Mitochondria are present only in the eukaryotic cells and are absent in the prokaryotic cells.
Mitochondria is also known as the ‘powerhouse’ of the cell because it produces the energy required by the cell. Mitochondria has a double-membrane.
(d) Nucleus is the most important organelle of the cell. Normally only one nucleus is
present in each cell. In some cells more than one nuclei may be present.
For further information check out the structure and functions of the plant-cell.
2. What is mitosis? Describe the various phases of mitosis with the help of suitable diagrams.
Answer: “Mitosis is that step in the cell cycle where the newly formed DNA is separated and two new cells are formed with the same number and kind of chromosomes as the parent nucleus.” For various phases of mitosis and to find the suitable diagrams, check out Mitosis-Equational Division.
3. What is a tissue? Describe the types of simple tissue with the help of suitable diagrams.
Answer: “A group of cells having similar origin, development and functions, is known as a tissue.” Made of only one type of cells, simple tissues are similar in structure and function. Simple tissues are of three types namely parenchyma, collenchyma and sclerenchyma.
Find the complete answer in three simple plant tissues.
4. Describe the various types of tissues present in the animals.
Answer: The four major types of tissues found in animals are
- 1. Epithelial Tissue
- 2. Connective Tissue
- 3. Muscle Tissue
- 4. Nervous Tissue
For a detailed answer, students can check out Animal and Plant Tissues web page.
5. Give account of the following :
(a) Vascular bundle
Answer: (a) Xylem and phloem, present in the vascular tissue system together form the vascular bundles that perform the function of transportation of different substances, like water, minerals, food etc. in the plant body.
(b) “Neurons are the fundamental unit of the nervous system specialized to transmit information to different parts of the body.” A neuron varies in shape and size depending upon their function and location. All neurons have three different parts – dendrites, cell body and axon.
Functions of the different parts of the neuron are mentioned below:
- Dendrites- Branch-like structures that receive messages from other neurons and enable the transmission of messages to the cell body.
- Cell Body– Every neuron has a cell body with a nucleus, golgi body, endoplasmic reticulum, mitochondria and other components.
- Axon-a tube-like structure that carries electrical impulse from the cell body to the axon terminals that passes the impulse to another neuron
(c) The virus which is parasitic on bacteria is known as the bacteriophage. The hereditary material in bacteriophage is DNA. The bacteriophage is parasitic on Escherichia coli bacteria and has a hexagonal head, a small neck, a collar and a long cylindrical tail. There is a double stranded circular DNA in the head region.
(d) The cells of this tissue are generally elongated, narrow with tapering ends. The cell wall is uniformly thickened because of the lignin deposition. Their lumen is destroyed i.e. is not present and the mature cells lack cytoplasm. They are dead cells and are present in hard parts of the plant. It provides mechanical strength to the plant.
1.Who observed the dead cells in 1665?
(a) Robert Brown
(d) Robert Hooke
Answer: (d) Robert Hooke
2. What are living organisms made up of?
Answer: Living organisms are made up of cells.
3. What is cytology?
Answer: The branch of science concerned with the structure and function of cells is known as Cytology.
4. Zoologist Theodor Schwann and Botanist Mathias Schleiden propounded the ____theory in the year 1838-39.
Answer: (a) Cell
5. The space surrounded by inner membrane of a cytoplasm is known as ____
Answer: (a) Stroma
6. What are the components of a typical eukaryotic cell?
Answer: The main components of a typical eukaryotic cell are Cell membrane, Cytoplasm and Nucleus.
7. What is a matrix of the organelles Mitochondria?
Answer: Mitochondria has a double-membrane, where the outer membrane is smooth and flat
and the inner membrane is projected in the cavity in the form of cristae. The region inner to the cristae is known as the matrix. Matrix is made up of 65-70% protein, 25% phospholipid and 0.5% RNA.
8. What are plastids?
Answer: Plastids are present in the plant cells. Plastids appear to be of different colour because of the presence of various pigments in it. Plastids are of different types on the basis of the different pigments present in them. For example : Chloroplast, Chromoplast and leucoplast.
9. Ribosome was discovered by ___________
(a) de Duve
(d) Camillo Golgi
Answer: (b) Claude
10. What are vacuole? Explain.
Answer: Vacuoles are the small or big, bubble-like structures present in the cytoplasm of the cell. They are enclosed by a membrane termed as the tonoplast and the fluid present in the vacuole is known as the cell sap. Water, along with excretory substances and other waste products are present in the cell sap. Vacuoles keep the cells turgid and collect water and other waste substances. In plant cells,vacuole is present in large numbers.
11. What is centrosome?
Answer: Mainly present in the animal cell near the nucleus in the form of a star shaped structure, the centrosome is made up of two centrioles that are perpendicular to each other.
Centrosome was discovered by Van Beneden and is responsible for the formation of spindle fibers in animal cells at the time of cell division. It forms the tail (flagellum) of the sperm. It
forms the basal bodies of the locomotory organs of the microorganisms i.e. the flagella and cilia.
12. What is a chromatin network?
Answer: A network of thin thread -like structures present in the nucleoplasm is known as chromatin network. At the time of cell division the threads of the chromatin network coils
13. What is a mother cell or parental cell?
Answer: New cells are always formed from the pre-existing cells. This pre-existing cell is called the mother cell or parental cell.
14. Define a virus.
Answer: Considered as an incomplete cell, Virus has only one characteristic feature out of the four of a typical cell. It has the capability of reproduction, heredity and mutation, since it is hereditary material DNA or RNA. Viruses can reproduce only in a living system. They can synthesise proteins and nucleic acids, upon entering in a living cell, using its bio-synthetic
Machinery, thus increasing in their number. They are parasites and are found in the
cells of animals, plants and bacteria. The virus remains inactive outside the nutritive cell and can be stored in bottles like the crystalline particles of chemical compounds.
15. Draw the diagram of a Epithelial Tissue and label the following:
(b) Sieve plate
16. What is Adipose tissue?
Answer: Adipose tissue is a loose connective tissue which is present beneath the skin. Fat is stored in the cells of this tissue.
Meanwhile, mastering the textbooks and revising the entire concepts help students to score well in the subject. They can also depend on these RBSE Class 9 Science Solutions to self-analyse their performance. Additionally, other resources that the students can find to prepare most competently for the exams are the RBSE textbooks and sample papers.
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