The comprehensive approach in SCERT Class 8 Basic Science Textbook Solutions Chapter 9 Cells and Cell Clusters Important Questions ensure conceptual clarity.
Cells and Cell Clusters Extra Questions and Answers Class 8 Basic Science Chapter 9 Kerala Syllabus
Cells and Cell Clusters Class 8 Important Questions
Question 1.
Choose the correct answer.
Statement 1: Theodor Schwann discovered that all plants are made of cells.
Statement 2: Matthias Jakob Schleiden discovered that all animals are made of cells.
(A) Statement 1 and 2 are correct
(B) Statement 1 and 2 are incorrect
(C) Statement 1 is correct Statement 2 is incorrect
(D) Statement 1 is incorrect Statement 2 is correct
Answer:
(B) Statement 1 and 2 are incorrect
Question 2.
Which statement is not true regarding the cell theory?
(A) Only animals are made of cells
(B) All living things are made of one or more cells.
(C) The cell is the basic unit of life.
(D) New cells are formed from pre-existing cells.
Answer:
(A) Only animals are made of cells
Question 3.
Complete the statement.
In sufficient light, the human eye can distinguish between two points 0.2 millimetres apart. This distance is known as the eye’s ………………………..
Answer:
Resolution
Question 4.
Which of the following statements is correct regarding electron microscopes?
(A) It helps in seeing up to a thousand times larger.
(B) It helps in detailed observation of living cells, viruses and molecular structures.
(C) It uses electron beam.
(D) It uses light.
Answer:
(B) and (C).
Question 5.
Choose the correct answer and write it down.
Which cannot be observed under a normal microscope.
(a) Mitochondria
(b) Virus
(c) Bacterium
(d) Paramecium
Answer:
(b) Virus
Question 6.
Identify and fill in the word pairs. Also, write the relationship between the word pairs.
The energy production centre of the cell: Mitochondria
Protein production centre: ………………..
Answer:
Ribosome, cell organelles and their functions.
Question 7.
Which one is isolated? Write the common characteristic of the others.
Mitochondria, lysosomes, ribosomes, and Golgi apparatus
Answer:
Lysosome, other organelles found in both plant and animal cells
Question 8.
What is the function of the plant tissue shown in the picture?
Answer:
Providing strength and support to plant parts (Sclerenchyma)
Question 9.
Who invented the electron microscope?
Answer:
German scientists Ernest Raska and Max Knoll invented the electron microscope
Question 10.
Choose and write the correct pairs.
(A) Matthias Jacob Schleiden discovered that all plants are made of cells
(B) Theodor Schwann – introduced the idea that new cells arise from existing cells
(C) Rudolf Virchow discovered that all animals are made of cells
(D) Ernst Ruska and Max Knoll invented the electron microscope.
Answer:
(A) Matthias Jacob Schleiden discovered that all plants are made of cells and (D) Ernst Ruska and Max Knoll invented the electron microscope.
Question 11.
Complete the illustration.
Answer:
(a) All organisms are made up of one or more cells.
(b) New cells originate from pre-existing cells.
Question 12.
List the statements given below.
(A) Multiple lenses are used.
(B) Objects can be seen up to ten times larger.
(C) Only one lens is used.
(D) Objects can be seen up to a thousand times larger.
| Simple microscope | Compound microscope |
Answer:
Simple microscope: (B) and (C).
Compound microscope: (A) and (D)
Question 13.
Completed the table.
| Feature | Compound microscope | Electron microscope |
| The need for light | ……(a)…… | An electron beam is used instead of light. |
| Magnification Power | Up to 1000 times. | ……(b)…… |
| Lens | ……(c)…… | ……(d)…… |
Answer:
(a) Light is needed,
(b) Magnifies objects more than a million times,
(c) Using multiple lenses,
(d) Electromagnets are used.
Question 14.
What is the role of the following in preparing the object of observation?
(a) Stain
(b) Glycerin
Answer:
(a) Stain – to give colour to the object of observation
(b) Glycerin – to prevent the object of observation from drying out
Question 15.
If there is a mistake in the statements given below, correct the mistake by changing only the underlined word.
a) The cell wall is the hard outer layer of the cell membrane.
b) The cell membrane provides protection and shape to the cell.
c) The cell wall in plants is mainly made of cellulose.
d) Substances enter and leave the cell through the Golgi apparatus.
Answer:
b) The cell wall provides protection and shape to the cell.
d) Substances enter and leave the cell through the cell membrane.
Question 16.
Write the differences between cytoplasm and protoplasm.
Answer:
Cytoplasm is a jelly-like fluid that fills the cell. It maintains all the organelles in their place and serves as the medium for chemical reactions.
Protoplasm consists of all the components inside the cell membrane, including the nucleus and cytoplasm.
Question 17.
Observe the picture and answer the questions below.
(a) Which organelle is represented by the picture?
(b) What is the function of this organelle?
Answer:
(a) Endoplasmic reticulum
(b) These organelles appear as a network of tubules within the cell, serve as pathways for conducting materials. It helps in the synthesis and removal of materials required by the cell.
Question 18.
Observe the picture and answer the questions below.
(a) Which is the complex tissue represented by the picture?
(b) What is the function of this complex tissue?
Answer:
(a) Xylem
(b) The conduction of water and salt to the leaves takes place through the xylem.
Question 19.
Choose the answer to the statements given below from the box and write it down.
| Muscle tissue, Connective tissue, Epithelial tissue, Neural tissue |
a) Connects different parts of the body.
b) Controls and coordinates bodily functions.
Answer:
a) Connective tissue
b) Neural tissue
Question 20.
Observe the picture and answer the questions below.
(a) Which are the organelles indicated by A and B in the picture?
(b) What is the function of these organelles?
Answer:
(a) A – Mitochondria, B – Centriole
(b) A – Mitochondria – Energy production centre of the cell. It stores the energy obtained from the oxidation of glucose and distributes it as needed.
B – Centriole – Helps in cell division
Question 21.
Copy the picture and identify and mark the parts according to the statements given below.
(a) The control center of the cell.
(b) The energy production center of the cell.
Answer:
Question 22.
Arrange the items in the box in order of their size.
| Red blood cell, protein, animal cell, mitochondria, paramecium, virus |
Answer:
Protein, virus, Mitochondria, red blood cell, animal cell, paramecium.
Question 23.
Choose the answer to the statements given below from the box and write it down.
| Theodor Schawnn, Ernst Ruska, Anton van Leeuwenhoek, Max Knoll, Robert Hooke, Rudolf Virchow, Matthias Jakob Schleiden |
(a) Invented the electron microscope.
(b) Small parts like boxes that are stacked are called ‘cells’, meaning chambers.
(c) Found that all plants are made of cells.
(d) Introduced the idea that new cells arise from existing cells.
(e) Observed water taken from a pond with the help of a better microscope and discovered microorganisms in it.
(f) Found that all animals are made of cells
Answer:
(a) Ernst Ruska, Max Knoll
(b) Robert Hooke
(c) Matthias Jakob Schleiden
(d) Rudolf Virchow
(e) Anton van Leeuwenhoek
(f) Theodor Schwann.
Question 24.
From the statements given below, select and write the one related to the compound microscope.
(a) Requires light.
(b) Magnifies objects more than a million times.
(c) Uses electron beams
(d) Magnifies up to a thousand times.
(e) Uses multiple lenses
(f) Uses electromagnets.
Answer:
(a) Requires light, (d) Magnifies up to a thousand times,(e) Uses multiple lenses
Question 25.
Observe the picture and answer the questions below.
(a) What does the picture indicate?
(b) What are the parts indicated by A and B?
(c) What are the characteristics of the part indicated by A?
Answer:
(a) Nucleus
(b) A – Chromatin reticulum B – Nucleolus
(c) Characteristics of chromatin reticulum: Chromatin network is the structure that appears like a network of threads within the nucleoplasm. During cell division, these chromatin networks condense into chromosomes.
Question 26.
Complete the illustration.
Answer:
(a) Chloroplast,
(b) They contain pigments that impart red, orange and yellow colours. They attract the animals for pollination and seed dispersal,
(c) Leucoplasts.
Question 27.
List the statements given below.
(a) Thin cell wall. Intercellular spaces are present.
(b) Cell wall made of substances like cellulose and pectin.
(c) Helps maintain the shape of plant parts.
(d) Cells in some parts have the ability to divide.
(e) Performs functions like photosynthesis and food storage.
(f) The cell wall is thicker only in some parts.
| Collenchyma | Parenchyma |
Answer:
| Collenchyma | Parenchyma |
| (b), (c), (f), | (a), (d), (e). |
Question 28.
What are the different types of meristematic tissues?
Answer:
Meristems are actively dividing cells that are of three major types: apical meristem, lateral meristem and intercalary meristem. The apical meristem is seen at the tip of the root and stem. Those seen at the lateral sides are called the lateral meristem. In monocot plants, the meristem seen between two nodes is called the intercalary meristem.
Question 29.
Observe the picture and answer the questions below.
(a) Which animal tissue is represented in the picture?
(b) What are the functions of this animal tissue?
Answer:
(a) Neural tissue
(b) Makes impulse transmission possible. It controls and coordinates bodily activities.
Question 30.
Stem cells have special importance in modern medicine.
(a) What are stem cells?
(b) What are the characteristics of stem cells?
Answer:
(a) Stem cells are specialised cells that can develop into various types of cells such as muscle cells, nerve cells, blood cells, etc.
(b) Stem cells have the ability to create new types of cells. Hence, they are referred to as the body’s master cells. Stem cells help to eliminate damaged cells, promote the growth of new cells and maintain healthy tissues. In modem medicine, stem cells hold significant importance.
Question 31.
What was the contribution of Robert Hooke and Anton van Leeuwenhoek to cell biology?
Answer:
Robert Hooke, a scientist, was observing a thin piece of cork through his microscope. He observed small parts like boxes stacked together. He called them ‘cells’, meaning chambers. Anton van Leeuwenhoek observed water taken from a pond with the help of a much better microscope and discovered microorganisms in it.
Question 32.
What is cell biology?
Answer:
Cell biology is the study of cells.
Question 33.
Write down the scientists who made important discoveries in the field of cell biology and their discoveries.
Answer:
HISTORY OF CELL BIOLOGY
- Cell biology is the study of cells.
- Matthias Jakob Schleiden discovered that all plants are composed of cells.
- Theodor Schwann discovered that all animals are composed of cells.
- Rudolf Virchow introduced the concept that new cells are formed from pre-existing cells.
Cell Theory
-
- All organisms are made up of one or more cells.
- The cell is the basic unit of life.
- New cells originate from pre-existing cells.
- Different types of microscopes are used to observe very small or tiny cells. In simple microscopes, lenses are used to magnify objects.
- The human eye can distinguish two spots having a distance of 0.2 mm in adequate light. This distance is called the resolution of the eye.
- A lens is required to distinguish spots having a distance of less than 0.2 mm.
- A simple microscope in which a single lens is used can magnify an object upto 10 times than its original size.
- A compound microscope, in which more than one lens is used, can magnify an object up to 1000 times.
- The magnification power of a lens is its ability to magnify objects. If eye piece lens magnifies the object to 10 x (10 times) and objective lens magnifies it into 40 x (40 times), the magnification power of the lens is 400 x.
Electron microscope
- An instrument that magnifies objects more than a million times.
- It helps to observe cells, viruses and molecular structure in detail.
- In an electron microscope electron beam is used instead of light.
- In 1934, German scientists Ernest Raska and Max Knoll invented the electron microscope.
- In an electron microscope, electromagnetic lenses are used to focus a beam of electrons onto the specimen, allowing for much higher resolution imaging compared to light microscopes.
Question 34.
What is cell theory?
Answer:
In the 19th century, the cell theory was formed by synthesizing all the observations by various scientists. It is the basic theory of cell biology.
Question 35.
What are the ideas in cell theory?
Answer:
Cell Theory
-
- All organisms are made up of one or more cells.
- The cell is the basic unit of life.
- New cells originate from pre-existing cells.
- Different types of microscopes are used to observe very small or tiny cells. In simple microscopes, lenses are used to magnify objects.
- The human eye can distinguish two spots having a distance of 0.2 mm in adequate light. This distance is called the resolution of the eye.
- A lens is required to distinguish spots having a distance of less than 0.2 mm.
- A simple microscope in which a single lens is used can magnify an object upto 10 times than its original size.
- A compound microscope, in which more than one lens is used, can magnify an object up to 1000 times.
- The magnification power of a lens is its ability to magnify objects. If eye piece lens magnifies the object to 10 x (10 times) and objective lens magnifies it into 40 x (40 times), the magnification power of the lens is 400 x.
Question 36.
What are the uses of lenses in microscopes?
Answer:
Various types of microscopes are used to observe microscopic cells. In ordinary microscopes, lenses help to magnify objects.
Question 37.
What is resolution?
Answer:
In sufficient light, the human eye can distinguish between two points 0.2 millimetres apart. This distance is the resolution of the eye. A lens is required to distinguish points less than 0.2 millimetres apart.
Question 38.
How is a simple microscope different from a compound microscope?
Answer:
A simple microscope, which uses only a single lens, can magnify objects up to ten times. However, a compound microscope, which uses multiple lenses, can magnify objects up to a thousand times.
Question 39.
What is the magnification power?
Answer:
The Magnification power of a lens is its ability to magnify objects. If eye piece lens magnifies the object to 10 x (10 times) and objective lens magnifies it into 40 x (40 times), the magnification power of the lens is 400 x.
Question 40.
What are the features of an electron microscope?
Answer:
An electron microscope is an instrument that magnifies objects more than a million times. It helps to observe cells, viruses and molecular structure in detail. In an electron microscope electron beam is used instead of light. In 1934, German scientists Ernest Raska and Max Knoll invented the electron microscope. In an electron-microscope, electromagnetic lenses are used to focus a beam of electrons onto the specimen, allowing for much higher resolution imaging compared to light microscopes.
Question 41.
What are the different types of electron microscopes in use today?
Answer:
a) Transmission electron microscope (TEM): Sends electrons through a very thin sample. Provides 2D images.
b) Scanning electron microscope (SEM): Sends electrons across the surface of an object. Provides 3D images.
c) Scanning Transmission Electron Microscope (STEM): Combines TEM and SEM techniques. Provides high-quality images.
Question 42.
What is a cell wall? Write its characteristics.
Answer:
The cell wall is the tough outer layer of the cell membrane. It provides protection and shape to the cell. The cell wall in plants is made primarily of a substance called cellulose.
Question 43.
Which is known as the cell membrane or plasma membrane?
Answer:
The cell membrane is a thin, flexible layer that surrounds the cell.
Question 44.
What is the function of the cell membrane?
Answer:
Substances enter and exit the cell through the cell membrane.
Question 45.
Why plasma membrane is known as a semi-permeable membrane?
Answer:
The plasma membrane does not allow all substances to pass through. Therefore, the plasma membrane is known as the semi-permeable membrane.
Question 46.
What are cell organelles?
Answer:
Organelles are the parts found in the cytoplasm that perform functions necessary for the survival of the cell. The main organelles are the cytoplasm, Golgi apparatus, endoplasmic reticulum, and mitochondria.
Question 47.
Prepare a note about the nucleus of a cell.
Answer:
The Nucleus is the centre that controls the cell. Chromatin network is the structure that appears like a network of threads within the nucleoplasm. During cell division, these chromatin networks condense into chromosomes. There is also a part called nucleolus within the nucleus.
Question 48.
What are the characteristics and functions of parenchyma?
Answer:
They contain living cells, a thin cell wall, and intercellular spaces are present. Perform functions such as photosynthesis and food storage. Cells in some parts have the ability to divide.
Question 49.
List the characteristics and functions of collenchyma.
Answer:
Collenchyma tissues are made up of living cells. The cell wall is made of substances such as cellulose and pectin. The cell wall is thicker only in some parts. Its function is to help maintain the shape of plant parts.
Question 50.
Describe the characteristic features and functions of sclerenchyma tissues.
Answer:
Sclerenchyma is a tissue composed of dead cells, characterised by a thick cell wall. The cell wall is of uniform thickness throughout, providing strength and support to plant parts.
Question 51.
Make a note of the differences between simple tissues and complex tissues.
Answer:
Tissues that are composed of similar types of cells are known as simple tissues. Parenchyma, collenchyma, and sclerenchyma are examples of simple tissues.
Xylem and phloem are made up of cells of different shapes and sizes. Therefore, they are called complex tissues. The transport of water and salts to the leaves takes place through the xylem. The phloem tissues transport the food produced by the leaves to various parts.
Question 52.
What are permanent tissues? Give some examples.
Answer:
Cells that have lost the ability to divide are called permanent tissues. Parenchyma, sclerenchyma, collenchyma, xylem, and phloem are examples of permanent tissues.
Question 53.
Plants like bamboo do not gain weight. Why?
Answer:
Lateral meristem helps in gaining weight. Lateral meristem is not found in plants like bamboo. Therefore, plants like bamboo do not gain weight.
Question 54.
What are the different types of animal tissues?
Answer:
Epithelial tissue, connective tissue, muscle tissue, and neural tissue.
Question 55.
What are stem cells? What is their speciality?
Answer:
Stem cells are specialized cells in the body that can develop into different types of cells, such as muscle cells, nerve cells, and blood cells. They are called the master cells of the body because they can create new types of cells. Stem cells help new cells to grow by replacing worn-out cells and heal wounds.
Question 56.
Write the characteristic features of different types of animal tissues.
Answer:
| Animal tissues | Characteristic features |
| Epithelial tissue | • Covers and protects the surfaces of the body and internal organs. • Helps in the absorption of various substances. • It produces secretions like mucus. |
| Connective tissue | • Provides support to various parts of the body. • Connects various parts together. • Bone, blood, fibrous tissue, etc. are connective tissues. |
| Muscle tissue | • Helps in body movement and locomotion. • Composed of cells capable of contraction and relaxation. |
| Neural tissue | • Makes impulse transmission possible. • Controls and coordinates bodily activities. |