- A. Fill in the blanks.
- B. Match the following.
- C. Tick the correct option.
- D. Answer the following questions in brief.
- E. Answer the following questions.
DAV Class 8 Science Chapter 1 Question Answer
DAV Class 8 Science chapter 1 question answer The Cell – Its Structure and Functions is given below. Here DAV class 8 Science solutions is provided with great explanation. Here we will solve fill in the blanks, tick the correct option, true or false and long question.
A. Fill in the blanks.
1. All living organisms are made up of ___________.
2. The ___________ provides rigidity and protection to the plant cell.
3. All cellular activities are controlled by the ___________.
4. The ___________ is known as the powerhouse of the cell.
5. ___________ is a group of cells performing a specific function.
6. It was ___________ who observed cells for the first time.
Answer: (1) cells (2) cell wall (3) nucleus (4) mitochondria (5) tissue (6) Robert Hooke
B. Match the following.
Answer: (1) d, (2) e, (3) a, (4) b, (5) c
C. Tick the correct option.
1. The cell organelle, which acts as a storage bag for a cell, is known as the-
2. Hen’s egg is-
Answer: a single cell
3. The nucleus is separated from the cytoplasm by the-
Answer: nuclear membrane
4. Which of the following will not be found in an egg cell, human liver cell and an Amoeba?
Answer: cell wall
5. Which of the following represents the correct sequence?
Answer: cell → tissue → organ → organ system
6. Which, amongst the following pairs, can be found only in a plant cell but not in an animal cell?
Answer: cell wall and plastids
D. Answer the following questions in brief.
1. List the (main) factors that determine the shape of a cell.
Answer: The (main) factors that determine the shape of a cell are location and function.
2. Distinguish between unicellular and multicellular organisms. Give two examples of each.
Answer: Distinguish between unicellular and multicellular organisms are
Unicellular organisms are made up of a single cell. e.g., Euglena and Amoeba.
Multicellular organisms are made up of many cells. e.g., Humans and Birds.
3. Give reasons for the following:
(a) The cell is called the structural and functional unit of life.
Answer: All organisms are made up of cells. A cell is capable of independent existence. Due to this, cell is called the structural and functional unit of life.
(b) Plant cells are more rigid than the animal cells.
Answer: Cell wall is present in plant cell. Due to this, plant cells are more rigid than animal cells.
4. Which cell organelle is known as the ‘Powerhouse of the cell? Why is it so called?
Answer: Mitochondria is known as the Powerhouse of the cell.
Mitochondria are the site of cellular respiration. Energy is produced during this process. Due to this, mitochondria are called the Powerhouse of the cell.
5. Name the cell organelles responsible for imparting colour to the leaves and fruits of a plant.
Answer: Chloroplast is responsible for imparting colour to the leaves. Chromoplast is responsible for imparting colour to fruits.
6. What are cilia and flagella? Write one similarity and one dissimilarity between the two of them.
Answer: Cilia and flagella are extensions on the cell membrane, these help in locomotion and procurement of food in organisms like Amoeba and Paramoecium. Cilia are much smaller than flagella.
7. If onion peel cells and cheek cells are observed through a microscope, state the two major differences that the observer is likely to find.
Answer: the two major differences that the observer is likely to find are:
In Onion peel cells:
- Cells are arranged in rows.
- Cell wall is present.
In Cheek cells:
- Cells randomly arranged.
- Cell wall is absent.
8. Classify the following into cells, tissue and organ.
skin, fat cell, RBC, blood, ear, muscle
Answer: Cell: Fat cell and RBC.
Tissue: Blood and muscle.
Organ: Skin and ear.
E. Answer the following questions.
1. “All cells in an organism do not have the same shape.”
Justify the above statement by drawing at least three different cell types found in human beings.
Answer: three different cell types found in human beings are:
These figures clearly show that liver cell is irregular in shape, fat cell is spherical and muscle cell is spindle-shaped. This shows that all cells in an organism do not have the same shape.
2. Where, and how, are chromosomes formed? State their significance.
Answer: Chromosomes are formed in the nucleus during cell division. When the cell is ready to divide, the chromatin (in nucleus) condenses to form thicker, thread-like chromosomes. Chromosomes are responsible for inheritance of characters from one generation to the next generation.
3. With the help of well labelled diagrams, highlight three differences between a plant cell and an animal cell.
Answer: three differences between a plant cell and an animal cell are:
|Plant Cell||Animal cell|
|Cell wall is present||Cell wall is absent|
|Chloroplast is present||Chloroplast is absent|
|Vacuole a very large||Vacuoles are small|
4. Write the functions performed by the following cell organelles.
(a) Endoplasmic Reticulum- It is a network of membranes. It provides channels for transport of materials in a cell.
(b) Golgi Complex- They are sac-like structures stacked one above the other. They are involved in the processing and packaging of materials produced by the cell.
(c) Nucleus- a specialised structure in the cells, bound by the nuclear membrane; responsible for controlling all cellular activities.
(d) Chromoplasts- They are responsible for imparting colour (other than green) to the different parts of the plant.
(e) Vacuoles- It appears as an empty space in the cytoplasm. It is generally large in plant cells. It stores excess of water and waste products.
(f) Mitochondria- These are rod-shaped or spherical structures. They are responsible for cellular respiration and for generation of energy for different activities of life.
5. The cell membrane is a very important component of a cell. How is damage to the cell membrane likely to impact the functions of the cell?
Answer: When the cell membrane gets damaged, it exposes the cell’s contents to external environment. This results in stoppage of all functions of the cell, and eventually to cell death.
6. Define the term ‘cell’, for plants/animals. Name the different organelles that make a cell. Explain why none of these is called the structural and functional unit of life.
Answer: The cell is the basic structural, functional, and biological unit of all known organisms. A cell is the smallest unit of life, and therefore, cells are often described as the “building blocks of life”.
The different organelles that make a cell are nucleus, Golgi complex, mitochondria, chloroplast, endoplasmic reticulum, lysosome, vacuole and ribosome.
All these cell organelles work together to perform different functions of the cell. None of these is capable of independent existence. So, they are not called the structural and functional unit of life.
Following are the uses of Infrared radiations:
- They are used in photography at night.
- They are used in remote control of television.
- They are used as signals during war.
- The Infrared radiations are used for therapeutic purposes by doctors.
A beam of light travelling in a rectangular glass slab emerges into air. Draw a ray-diagram indicating the change in its path.
A ray of light travelling from the glass slabs and emerges into the air.
A ray of light travelling in glass emerges into air. State whether it will bend towards the normal or away from the normal.
The ray of light will bend away from the normal.
A ray of light travelling in air enters obliquely into water. Does the ray of light bend towards the normal or away from the normal ? Why ?