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.
Ans
1. Cells
2. Cell Wall
3. Nucleus
4. Mitochondria
5. Tissue
6. Robert Hooke
B. Match the Following
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-
Answer: Vacuole
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: Cells → 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.
The shape of the cell depends upon its location in the organism and the functions that have to be performed by the cell.
2. Distinguish between unicellular and multicellular organisms. Give two examples of each.
Unicellular Organism: Organisms made of single cell are known as unicellular organisms. Ex. Amoeba
Multicellular organism: Organisms that are made up of more than one cell are known as multicellular organisms.
3. Give reasons for the following:
(a) The cell is called the structural and functional unit of life.
Cells are responsible for the structure and existence of the organism. All the functions of an organism are performed by a group of cells. This is the reason, the cells are called the structural and functional unit of life for an organism.
(b) Plant cells are more rigid than the animal cells.
Answer: Plant comprises of a cell wall. The cell wall provide rigidity to the plant cells.
4. Which cell organelle is known as the ‘Powerhouse of the cell? Why is it so called?
Mitochondria is known as the powerhouse of the cell. The energy of the cell is stored inside the mitochondria of the cell. It is also the site for cellular respiration.
5. Name the cell organelles responsible for imparting colour to the leaves and fruits of a plant.
Chloroplast is responsible for imparting the colour to the leaves and fruits of the plants. The green colour is because of the presence of chlorophyll. Likewise the colour of the fruits is because of different chloroplasts.
6. What are cilia and flagella? Write one similarity and one dissimilarity between the two of them.
Cilia and Flagella are present in different organisms like Amoeba, Paramecium etc. They help in the movement of the organism and other locomotor functions. They both help in locomotion in unicellular organisms.
Cilia is present in organisms such as paramecium, flagella can be found in bacteria and sperm cells.
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.
Onion peel Cells
- Cells are arranged in rows.
- Cell wall is present.
Cheek cells
- Cells are randomly arranged in case of cheek cells.
- Cell wall is not present in the cheek cells.
8. Classify the following into cells, tissue, and organs.
Skin, fat cell, RBC, blood, ear, muscle
Answer: We have categorized all of them:-
Cell: Fat cells and RBC (Red blood cells)
Organ: Skin and ear.
Tissue: Blood and muscle.
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.
Ans. Please refer to your textbook for the diagrams.
2. Where, and how, are chromosomes formed? State their significance.
Chromosomes are found in the nucleus. They are formed during the process of cell division, thick thread-like structures are formed during the cell division. They are known as Chromosomes. Their main significance is that they are responsible for the inheritance of characteristics from parents to offspring.
3. With the help of well labelled diagrams, highlight three differences between a plant cell and an animal cell.
Plant Cells
Cell Wall is present
Vacuoles are quite large.
Chloroplast is present in the plant cell.
Animal Cell
Cell Wall is absent
Vacuoles are small in size.
Chloroplast is absent in the animal cells.
4. Write the functions performed by the following cell organelles.
Endoplasmic Reticulum: It is basically a network of membranes. Different materials are transferred within the cell with the help of ER.
Golgi Complex: These are structures like a sac packed over one another. They help in the packaging of materials produced by the cell.
Nucleus: It is present in the center of the cell. It helps in cell division, contain chromosomes responsible for transfer of characteristics from parents to their children.
Chromoplast: They are present for imparting colour to different part of the plant like leaves and the fruits. The colours of the fruits is because of presence of chromoplast.
Mitochondria It helps in cellular respiration and the energy of the cell is stored in the mitochondria which is why they are also known as the powerhouse of the cell.
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: Cell membrane is responsible for the entry and exit of substances from the cell. If the cell membrane is damaged it becomes easier for foreign substances to enter the cell. It can cause damage to the complete cell.
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 life, be it for plants or animals. Animals are also made up of cells. The different organelles that make a cell are Golgi complex, mitochondria, chloroplast, endoplasmic reticulum, lysosome, vacuole, and ribosome. These cell organelles can not exist independently, they function in synchronization with each other.
That is why none of them is called as the structural and functional unit of life.
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