Exercise
Q1. Indicate whether the following statements are True (T) or False (F).
(a) Unicellular organisms have one-celled body. (T/F)
(b) Muscle cells are branched. (T/F)
(c) The basic living unit of an organism is an organ. (T/F)
(d) Amoeba has irregular shape. (T/F)
Answer : (a) (T), (b) (F), (c) (F), (d) (T).
Q2. Make a sketch of the human nerve cell. What function do nerve cells perform?.
Answer : The nerve cell receives and transfers messages, therby helping to control and coordinate the working of different parts of the body.
Q3. Write short notes on the following:
(a) Cytoplasm (b) Nucleus of a cell
Answer : (i) Cytoplasm : it is the jelly-like substance fou nd in between the nucleus and the cell membrane. It contains nucleus and many small structures called organelles. Cytoplasm, along with nucleoplasm, forms the living substance of the cell, called the protoplasm.
(ii) Nucleus : It is an important components of the living cell. It is generally spherical and located in the centre of the cell. It can be stained and seen easily with the help of a microscope. Nucleus is separted form the cytoplasm by a membrane called the nuclesr membrane. the liquid substance of the nucleus is termed as nucleoplasm.
Q4. Which part of the cell contains organelles?
Answer : Cytoplas m contains organelles of the cell.
Q5. Make sketches of animal and plant cells. State three differences between them.
Answer : Fig. 8.2. (a) Animal cell, (b) Plant cell.
Q6. State the difference between eukaryotes and prokaryotes.
Answer : Eukaryotes have well-organised nucleus with nuclear membrane while prokaryotes do not have this.
Q7. Where are chromosomes found in a cell? State their function.
Answer : Chromosomes are found in nucleus of the cell. They carry genes and help in inheritance i.e., transfer of characters from the parents to te offspring.
Q8. ‘Cells are the basic structural units of living organisms’. Explain.
Answer : Cells many Cells in the body acumulate to build tissue. Tissues form body organs and body organs form body system. All systems forms a body. As cells give shape to the body. This may be compared to bricks. Brickes are assembled to make a building. So, cell is called the basic structural unit of loiving organisms.
Q9. Explain why chloroplasts are found only in plant cells?
Answer : Chloroplast contain chlorophyll which synthesise food in plant by the process of photosynthesis. No photosynthesis occurs in animals. So, they do not contion chloroplasts.
Q10. Complete the crossword puzzle with the help of cules given below.
Across
1. This is necessary for photo - synthesis.
3. term for component presesnt in the cytoplasm.
6. The living substance in the cell.
8. Unit of inheritance present on the chromosomes.
Down
1. Green plastids.
2. Formed by collection of tissues.
4. It separates contents of the cell from the surrounding medium.
5. Empty structure in the cytoplasm.
7. A group of cells.
Answer:
