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Q1 Who discovered cells, and how? Ans: Robert Hooke found cells in 1665 while analyzing a flimsy cut of stopper through a self-planned magnifying lens. He saw that the plug looked like the design of a honeycomb consisting of numerous little compartments. These little boxes are called cells.
Q2 Why is the cell called the structural and functional unit of life? Ans: A cell is able to freely do all fundamental exercises of life. Thus, they are called fundamental or useful units of life.
Chapter 5 The Fundamental Unit of Life
As the name of the chapter justify the cell is fundamental unit of life. As a house is made of thousand and million af brick similarly all organisms are made as these cell which perform all vital functions for our body. Together they form tissue then organ and organ system then a complete body cells have capability to divide and again form new cell to maintain continuity.
Download pdf of NCERT Solutions for Class Science Chapter 5 The Fundamental Unit of Life
Exercise 1
Exercise 2
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Q1 How do substances like CO2 and water move in and out of the cell? Discuss. Ans: CO2 moves by dispersion and H2O moves as a natural by-product through the cell layer.
Q2 Why is the plasma membrane called a selectively permeable membrane? Ans: It is called a specifically porous layer since it permits the section and exit of certain substances, not all.
Exercise 3
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Q1 Fill in the gaps in the following table illustrating differences between prokaryotic and eukaryotic cells. Prokaryotic Cell Eukaryotic Cell 1. Size : generally small (1-10 μm) 1 μm = 10-6 m 1. Size generally large (5-100 μm) 2. Nuclear region: ________________ and known as _________________ 2. Nuclear region: well defined andsurrounded by a nuclear membrane 3. Chromosome: single 3. More than one chromosome 4. Membrane-bound cell organelles absent 4. _______________________ _______________________ Ans: Prokaryotic Cell Eukaryotic Cell 1. Size : generally small (1-10 μm)
1 μm = 10-6 m1. Size generally large (5-100 μm) 2. Nuclear region is poorly defined due to absence of nuclear membrane and known as nucleoid. 2. Nuclear region: well defined and surrounded by a nuclear membrane 3. Chromosome: single 3. More than one chromosome 4. Membrane-bound cell organelles absent 4. Membrane-bound cell organelles present
Exercise 4
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Q1 Can you name the two organelles we have studied that contain their own genetic material? Ans: The two organelles which have their own genetic material are:
1. Mitochondria 2. PlastidsQ2 If the organisation of a cell is destroyed due to some physical or chemical influence, what will happen? Ans: The cell will not be able to revive and lysosomes will digest it.
Q3 Why are lysosomes known as suicide bags? Ans: At the point when the cell gets harmed, lysosomes may explode, and the compounds digest their own cell. In this manner lysosomes are known as suicide bags.
Q4 Where are proteins synthesised inside the cell? Ans: The proteins are integrated in the ribosomes that are otherwise called protein plants.
Exercise 5
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Q1 Make a comparison and write down ways in which plant cells are different from animal cells. Ans: Plant Cells
Animal Cells
1. Plant cells are generally bigger than animal cells.
1. Animal cells are relatively small.
2. Plant cells have cell walls.
2. Animal cells do not have cell walls.
3.Nucleus is not present in the centre of the cell.
3. Nucleus is there at the centre of the cell.
4.The size of the vacuole is large.
4. The size of the vacuole is small.
5. Chloroplast is present.
5. Chloroplast is absent.
Q2 How is a prokaryotic cell different from a eukaryotic cell? Ans: Prokaryotic cell is by and large more modest in size (1-10 pm), atomic region is ineffectively characterized, the cell organelles are not membrane bound and has a single chromosome.
Eukaryotic cells are for the most part bigger in size (5-100 pm), atomic locale is obvious with atomic membrane. Membrane bound cell organelles are available and have more than one chromosome.Q3 What would happen if the plasma membrane ruptures or breaks down? Ans: On the off chance that a plasma layer bursts or separates, atoms of certain substances will freely move in and out.
Q4 What would happen to the life of a cell if there was no Golgi apparatus? Ans: Golgi apparatus has the function of storage, alteration and packaging of the items in vesicles. On the off chance that there were no Golgi bodies, packaging and dispatching of materials synthesised by the cell will be stocked.
Q5 Which organelle is known as the powerhouse of the cell? Why? Ans: Mitochondria is known as the powerhouse of the cell because it releases the energy required for different activities of life.
Q6 Where do the lipids and proteins constituting the cell membrane get synthesised? Ans: Lipids and proteins are synthesised in ER [Endoplasmic Reticulum].
Q7 How does an Amoeba obtain its food? Ans: Amoeba have pseudopodia finger-like structure which can catch the food particles and take inside the amoeba and form a food vacuole and this food vacuole will break down into simple form which is digestible for amoeba.
Q8 What is osmosis? Ans: Osmosis is the cycle of development of water atoms from a region of higher water concentration through a semipermeable layer to a region of lower water concentration.
Q9 Carry out the following osmosis experiment: Take four peeled potato halves and scoos each one out to make potato cups. One of these potato cups should be made from a boiled potato. Put each potato cup in a trough containing water. Now, (a) Keep cup A empty (b) Put one teaspoon sugar in cup B (c) Put one teaspoon salt in cup C (d) Put one teaspoon sugar in the boiled potato cup D. Keep these for two hours. Then observe the four potato cups and answer the following: (i) Explain why water gathers in the hollowed portion of B and C. (ii) Why is potato A necessary for this experiment? (iii) Explain why water does not gather in the hollowed out portions of A and D. Ans:
(i) Water gathers in B and C in light of the fact that in both the circumstances there is contrast in the centralization of water in the box and water in some Potato. Therefore, osmosis happens as the potato cells go about as a semipermeable membrane.
(ii) Potato A is necessary for this experiment for comparison, it acts as a control.
(iii) Water doesn't gather in the emptied out parts of A and D. As some A doesn't have change in the concentration for water to stream. For osmosis to happen one of the concentrations ought to be higher than the other.
In cup D, the cells are dead and thus the semi-permeable membrane doesn't exist for the progression of water and no osmosis happens.
Popular Questions of Class 9 Science
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Abdul, while driving to school, computes the average speed for his trip to be 20 km h-1. On his return trip along the same route, there is less traffic and the average speed is 40 km h-1. What is the average speed for Abdul’s trip?
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An object of mass 40 kg is raised to a height of 5 m above the ground. What is its potential energy? If the object is allowed to fall, find its kinetic energy when it is half-way down.
- Q:-
Fig 8.11 shows the distance-time graph of three objects A,B and C. Study the graph and answer the following questions:
Fig. 8.11
(a) Which of the three is travelling the fastest?
(b) Are all three ever at the same point on the road?
(c) How far has C travelled when B passes A?
(d) How far has B travelled by the time it passes C? - Q:-
A driver of a car travelling at 52 km h-1 applies the brakes and accelerates uniformly in the opposite direction. The car stops in 5 s. Another driver going at 3 km h-1 in another car applies his brakes slowly and stops in 10 s. On the same graph paper, plot the speed versus time graphs for the two cars. Which of the two cars travelled farther after the brakes were applied?
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Soni says that the acceleration in an object could be zero even when several forces are acting on it. Do you agree with her? Why?
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Two objects, each of mass 1.5 kg, are moving in the same straight line but in opposite directions. The velocity of each object is 2.5 m s-1 before the collision during which they stick together. What will be the velocity of the combined object after collision?
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How do poriferan animals differ from coelenterate animals?
- Q:-
Two objects of masses 100 g and 200 g are moving along the same line and direction with velocities of 2 m s-1 and 1 m s-1, respectively. They collide and after the collision, the first object moves at a velocity of 1.67 m s-1. Determine the velocity of the second object.
- Q:-
What happens to the force between two objects, if
(i) the mass of one object is doubled?
(ii) the distance between the objects is doubled and tripled?
(iii) the masses of both objects are doubled? - Q:-
The speed-time graph for a car is shown is Fig. 8.12.
Fig. 8.12
(a) Find how far does the car travel in the first 4 seconds. Shade the area on the graph that represents the distance travelled by the car during the period.
(b) Which part of the graph represents uniform motion of the car?
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- NCERT Chapter