Question 1.
Indicate whether the following statements are True (T) or False (F).
(a) Unicellular organisms have a one-celled body.
(b) Muscle cells are branched.
(c) The basic living unit of an organism is an organ.
(d) Amoeba has an irregular shape.
(a) True
(b) True
(c) False
(d) True
Question 2.
Make a sketch of the human nerve cell. What function do nerve cells perform?
Function of nerve cells: The function of the nerve cell is to receive and transfer messages, it helps to control and coordinate the working of different parts of the body.
Question 3.
Write short notes on the following.
(a) Cytoplasm
(b) Nucleus of a cell
(a) Cytoplasm: The jelly-like substance found between the nucleus and the cell membrane is called cytoplasm. It is made up of basic elements like C, H, O, N. Various other components or organelles, like mitochondria, Golgi bodies, ribosomes, etc., of cells are present in the cytoplasm.
(b) Nucleus of a cell: Nucleus of a cell is an important component of the living cell. It is located at the centre of the cell. It is separated from the cytoplasm by a membrane called nuclear membrane. It contains genetic material.
Question 4.
Which part of the cell contains organelles?
Cytoplasm
Question 5.
Make sketches of animal and plant cells. State three differences between them.
| Plant cells | Animal cells |
| (i) The outermost covering is a cell wall and it is made of cellulose. | (i) The outermost covering of animal cell is the plasma membrane. |
| (ii) Plastids are present in plant cells. | (ii) Plastids are absent in animal cells. |
| (iii) Large vacuoles are present in plant cells. | (iii) No or very small vacuoles are present in animal cells. |
| (iv) It lacks centrosomes and lysosomes. | (iv) They have centrosomes or lysosomes. |
Question 6.
State the difference between eukaryotes and prokaryotes.
| Eukaryotes | Prokaryotes |
| (i) Eukaryotes possess membrane-bound organelles. | (i) Prokaryotes lack membrane-bound organelles. |
| (ii) Nucleus of the cell has nuclear membrane. Example: higher plants and animals. | (ii) Nucleus is not bounded by membrane. Example: bacteria and blue-green algae. |
Question 7.
Where are chromosomes found in a cell? State their function.
Chromosomes are present in the nucleus. The functions of chromosomes is to carry genes on them and to transfer the character from parents to the next generation.
Question 8.
‘Cells are the basic structural units of living organisms.’ Explain.
Different cells combine to form tissues and tissues combine to form organs. Similarly, organs combine to form body. Thus they are termed as the basic structural unit of every living organism.
Question 9.
Explain why chloroplast are found only in plant cells?
Chloroplasts are plastids required for the food making process, called photosynthesis, and thus they are only present in plant cells.
Question 10.
Complete the crossword with the help of clues given below.
Across
1. This is necessary for photosynthesis.
3. Term for component present in the cytoplasm.
6. The living substance in the cell.
8. Units of inheritance present on the chromosomes.
Down
1. Green plastids.
2. Formed by collection of tissues.
4. It separates the contents of the cell from the surrounding medium.
5. Empty structure in the cytoplasm.
7. A group of cells.
Question 11.
………… is the outermost layer of an animal cell.
Plasma membrane/Cell membrane
Question 12.
What is the name given to the green plastids?
The green plastids are called chloroplasts.
Question 13.
Name two organelles present in the plant cell but not in the animal cell.
Cell walls and chloroplast are found in plant cells but not animal cells.
Question 14.
Which part of the cell contains organelles ?
Cell Cytoplasm contains the organelles.
Question 15.
Why cells could not be observed before 17th century ?
Cells could not be observed before 17th century because microscope was not available for viewing the cells.
Question 16.
Why Hooke had to take thin slices of cork ?
He made thin slices of cork because the cork was solid and its details could not be seen.
Question 17.
Where did Hooke demonstrate cork slice ?
Hooke demonstrated cork slice in Royal society of London.
Question 18.
Single celled organisms are also called unicellular organisms (True/False)
True.
Question 19.
Name the cells having branched structure.
Nerve cell.
Question 20.
Which cell is observable with unaided eye ?
Ostrich egg.
Question 21.
Name the outermost layer of animal cell.
Cell membrane or plasma membrane.
Question 22.
Mention the layer outside the plasma membrane of a plant cell.
Cell wall.
Question 23.
Which four basic elements constitute 90% of protoplasm ?
90% of protoplasm is made up of carbon, hydrogen, nitrogen and oxygen.
Question 24.
The term cell was coined by ………….
Robert Hooke.
Question 25.
Cell wall is present in …………. only.
Plant cell.
Question 26.
Which organism has smallest cell ?
Bacterium mycoplasmas has the smallest cell.
Question 27.
How do you differentiate protoplasm from cytoplasm ?
Cytoplasm is the jelly-like substance occupying most of the space inside the cell. Protoplasm includes the cell membrane, the cytoplasm and the nucleus.
Question 28.
Draw a typical cell. Label important organelles.
Question 29.
What name is given to living things having more than one cell ?
Multicellular organisms.
Question 30.
Can unicellular organisms be seen with the naked eye ?
Unicellular organisms can only be viewed with the help of a microscope.
Question 31.
Give two examples of unicellular animals.
Amoeba, paramoecium.
Question 32.
Name the parts of the cell.
The three parts of cell — The Cell membrane, Cytoplasm and Nucleus.
Question 33.
What is the jelly-like fluid inside the nucleus called ?
The jelly-like fluid inside the nucleus is called nucleoplasm.
Question 34.
What are chromosomes ?
Chromosomes are thread-like structures which play an important role in the inheritance of characters from one generation to another
Question 35.
What is the function of Golgi bodies ?
Golgi bodies collect and distribute the substances made in the cell.
Question 36.
Which part of the animal cell is concerned with cell division ?
Centrioles and centrosome.
Question 37.
Give other name for cell membrane.
Plasma membrane.
Question 38.
What are vacuoles ?
The clear spaces surrounded by a membrane present in the cytoplasm are called vacuoles.
Question 39.
What is meant by division of labour ?
In multicellular organisms, the cells are specialised to the perform certain functions. This is known as division of labour.
Question 40.
What is meant by cell division ?
New cells for growth and reproduction are formed by cell division.
Question 41.
Why are the nerve cells long and thread like ?
Nerve cells are long and thread-like projections, as they have to convey messages to different parts of the body.
Question 42.
Which cells in our body grow and divide all through the life ?
The cells of the skin grow and divide all through the life.
Question 43.
Name a unicellular organism which is about 10 cm in length.
An alga known as Acetabularia.
Question 44.
Human body has
- one million cells
- one billion cells
- one trillion cells
- more than a trillion cells
more than a trillion cells.
Question 45.
Name the basic structural and functional unit of life.
Cell.
Question 46.
What is a cell ? Name the longest cell in human body. Draw its diagram also.
All organisms are made of basic units known as Cell. Nerve Cell is the longest cell in hyman body.
Question 47.
Why are mitochondria known as the “power house of the cell” ?
Mitochondria is known as the power house of the cell because they perform the function of respiration and provide the cell with energy.
Question 48.
Are the cells of an elephant larger than cells of a rat ?
No, the size of the cell has no relation with the size of the body of the animal or plant.
Question 49.
What are the “building blocks of life” ? Why are they so called ?
Cells are building blocks of life because all living things are made up of one or more cells.
Question 50.
What is the difference between tissue and organ ?
Group of cells of the same type make up the different tissues of the organisms, e.g., muscle tissue.
Several different types of tissues together form an organ, e.g., a stomach.