Question 1. Indicate whether the following statements are True or False.
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 irregular shape.
Solution :
a) True
b) False
c) False
d) True
Question 2. Make a sketch of the human nerve cell. What function do nerve cells perform?
Solution :
The main function of the nerve cell is to transmit messages to the brain from receptor organs and vice versa. It has a control over the working of different parts of the body.
Question 3. Write short notes on the following.
(a) Cytoplasm
(b)Nucleus of a cell
Solution :
(a) Cytoplasm: Cytoplasm is the jelly-like substance present between the cell membrane and the nucleus. Various other components or organelles like mitochondria, golgi bodies, ribosomes, etc. are present in the cytoplasm. Cytoplasm helps exchange and storage of substances among cell organelles. Most of the metabolic activities occur inside cytoplasm.(b) Nucleus of a cell:
Nucleus is an important component of the living cell. It is mostly spherical and located in the centre of the cell. It is separated from the cytoplasm by a membrane called the nuclear membrane. In addition, nucleus contains thread-like structures called chromosomes. These carry genes and help in inheritance or transfer of characters from the parents to the offspring. Nucleus, in addition to its role in inheritance, acts as control centre of the activities of the cell. The entire content of a living cell is known as protoplasm. It includes the cytoplasm and the nucleus.
(b)Nucleus of a cell: Nucleus is an important component of the living cell. It is mostly spherical and located in the centre of the cell. It is separated from the cytoplasm by a membrane called the nuclear membrane. In addition, nucleus contains thread-like structures called chromosomes. These carry genes and help in inheritance or transfer of characters from the parents to the offspring. Nucleus, in addition to its role in inheritance, acts as control centre of the activities of the cell. The entire content of a living cell is known as protoplasm. It includes the cytoplasm and the nucleus. Protoplasm is called the living substance of the cell.
Question 4. Which part of the cell contains organelles?
Solution : Cytoplasm is the part of cell which contains organelles such as mitochondria, ribosomes, golgi bodies, etc.
Question 5. Make sketches of animal and plant cells. State three differences between them.
Solution :
The differences between plant cell and animal cell are:
Question 6. State the difference between eukaryotes and prokaryotes.
Solution :
| Prokaryotes | Eukaryotes |
| Most of them are unicellular | Most of them are multicellular |
| There is no nuclear membrane. So, the nucleus is poorly defined. | There is a nuclear membrane. So, the nucleus is well defined. |
| Not all cell organelles are present | All the cell organelles are present. |
| Nucleolus is absent | Nucleolus is present |
| Eg: Blue green algae, Bacteria | Eg: Plant, Animal cells and Fungi. |
Question 7. Where are chromosomes found in a cell? State their function.
Solution : Chromosomes are found in the nucleus of the cell. They carry genes and help in inheritance of characters from the parents to the offspring.
Question 8. ‘Cells are the basic structural units of living organisms’. Explain.
Solution : All the living organisms are made of cells either unicellular or multicellular. The basic functions of life like respiration, assimilation and all major metabolic activities are carried inside the cell. So, cell is known as structural and functional units of living organism.
Question 9. Explain why chloroplasts are found only in plant cells?
Solution :
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.
Solution :
Across:
1.Chlorophyll
3.Organelle
6.Protoplasm
8.Genes
Down:
1.Chloroplasts
2.Organ
4.Membrane
5.Vacuole
7.Tissue