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Correct Option (a) 2.68 x 10²² 

Explanation: 

As we know that at S.T.P. 22.4 litre of gas contains 6.023 x 10²³ molecules

1 litre of gas contain  6.023 x 10²³/22.4 = 2.68 x 10²² molecules.

(d) its temperature will increase

When tension is applied, the distance between the atoms of the wire increases, there by increasing the potential energy of the wire. When the tension is removed, the potential energy decreases. This energy is converted into heat energy. So the temperature of the wire increases.

Repeated bending of wire decreases elastic strength and therefore it can be broken easily.

Promises which form consideration or part of consideration for each other are called ‘reciprocal promise’.

Correct answer is (d) 0.7

Angle made by the resultant of normal reaction and limiting friction with the normal reaction is called angle of friction.

Poisson’s ratio is the ratio of lateral strain to the longitudinal strain. It has no units. 

It is the loss in strength of a material caused due to repeated alternating strains to which the material is subjected.

Angle of repose is defined as the angle that an inclined plane makes with the horizontal when a body placed on it just starts sliding.

The temporary loss of elastic properties because of the action of repeated alternating deforming force is called elastic fatigue. 

It is due to this reason : 

(i) Bridges are declared unsafe after a long time of their use. 

(ii) Spring balances show wrong readings after they have been used for a long time. 

(iii) We are able to break the wire by repeated bending.

The coefficient of static friction is defined as the ratio of limiting friction to the normal reaction between the surfaces.

Co-efficient of friction is a ratio, so it is unitless.

Spring force is the restoring force arising because of compression or extension of spring.

Spring force, F ∝ (-x)

F = −kx

Where x is the change in length

F = −kx

Where k is a constant called spring constant or force constant.

The negative sign indicates that the spring force is opposite to the direction of displacement of the spring from its normal position.

Friction is tangential to the wheel and in the direction opposite to motion.

The stone will move in the direction tangential from the point where it got cut.

The speed is uniform but direction is changing, so, there is a change in velocity (acceleration is non zero) Hence stone is under the influence of a net external force.

If a rod is fixed between two rigid supports, due to change in temperature its length will change and so it will exert a normal stress. This stress is called thermal stress. 

Thermal stress = Y α ∆θ. Force produced in the body = YA α∆θ.

Since it is moving with uniform speed, there no additional force (a = 0) So, apparent weight = m(g + 0) = (60 kg) × (10 ms^-2 ) = 600 N.

The coefficient of friction remain constant.

When the roads (dr tracks) are covered with snow then there is considerable reduction of frictional force between the tyres of the vehicle and the road (or between the track and the wheels of the train) which leads to the skidding of the vehicles. Thus, driving is not safe. When sand is thrown on the snow covered tracks or roads then the force of friction increases, so safe driving is possible.

If a tube of very narrow bore (called capillary) is dipped in a liquid, it is found that the liquid in the capillary either ascends or descends relative to the surrounding liquid. This phenomenon is called capillarity. 

The cause of capillarity is the difference in pressures on two sides curved surface of liquid.

Prop of magnetic field lines: 

(i) The magnetic field lines originate from the north pole of a magnet and end at its south pole. 

(ii) The strength of magnetic field is indicated by the degree of closeness of the field lines. Where the field lines are closest together, the magnetic field is the strongest there.

(i) The direction of magnetic field lines is from North to South outside the bar magnet and from South to North inside the magnet.

(ii) They never intersect each other.

Iron is the material used for making electromagnets because of its magnetic properties which makes it magnetize easily and makes it able to be magnetized for longer time.

An electromagnet is made by rounding a wire and make its shape as same as solenoid which acts as a bar magnet when electric current is passed through it. If we insert soft iron core in it, its magnetic field would increase.

There are 11 pairs of testes are present in Leech.

The dental formula of rabbit is 2033/1023

Leech respire through the skin.

The common name of Hirundinaria granulosa is Indian Cattle Leech.

1. False – Mammary gland in female is the most striking feature of mammals. 

2. True 

3. True 

4. False – Breathing movement in Rabbit are brought by Diaphragm

5. False – In rabbit pair of cowper’s gland and perineal gland are present both male and female

1. (c) Space in teeth line in mammals

2. (c) Diastema is present between incisors and premolars

3. (c) four

4. (a) 44 – 47

5. (d) Stopped

6. (b) dorsally incomplete

7. (c) pseudo coelom

8. (b) closed type

9. (b) Middle layer myocardium

10. (c) hirundinea

11. (c) Hirundinaria

12. (c) Hirudin

1. Annelida 

2. Oryctolagus cuniculus 

3. Metamerism 

4. Looping or crawling movement 

5. Proteolytic enzyme 

6. Epiglottis 

7. Diphyodont 

8. Caecum 

9. Fallopian tube 

10. Diaphragm

The digestion in leeches in very slow. So, the blood stored in the crop gives nourishment to the leech for several months. So there is not elaborate secretion of digestive juices and enzymes.

Leeches lead a parasitic mode of life, by sucking the blood of vertebrates. 

The adaptations are :

• Blood is sucked by the pharynx.
• Anterior and Posterior Suckers are provided, by which the animal attaches itself to the body of the host.
• The three Jaws, inside the mouth, causes a painless Y – shaped wound in the skin of the host,
• The salivary glands produce Hirudin, which does not allow the blood to coagulate. So, the continuous supply of blood is maintained
• Parapodia and Setae are absent.
• Blood is stored in the crop. It gives nourishment to the leech for several months. So there is no elaborate secretion of the digestive juices and enzymes.

The doctors would have replied that the leeches inject an anaesthetic substance, that prevents the host from feeling their bite.

1. last seven 

2. diphyodont 

3. anterior sucker 

4. sanguivorous 

5. Nephrons (kidney) 

6. 37 pair

The rabbit has three types of teeth – Incisors are front teeth used for cutting, premolar and molar are used for grinding. Canine is absent as rabbit are herbivores. The gap between the incisor and premolar is called diastema. It helps in mastication and chewing of food in herbivores animal.

The circulation in Leech is Haemocoelic system. There are no true blood vessels. The blood vessels are replaced by channels called Haemocoelic channels or canals, filled with blood like a fluid. The coelomic fluid contains Haemoglobin.

There are four longitudinal channels. One channel lies above (dorsal) to the Alimentary canal, one below (ventral) to the Alimentary canal. The other two channels lie on either (lateral) side of the Alimentary canal, which serves as a heart and have inner valves. All the four channels are connected together posteriorly in the 26th segment. Thus the circulatory system is designed in Leech to compensate the heart structure.

(d) All the above

1. Looping or Crawling movement : Looping movement is brought about by the contraction and relaxation of muscles. The two suckers serve for attachment during movement. The animal fixes its posterior sucker on the substratum.

2. Swimming movement : The animal swims in the water by undulating movements of the body.

(b) Warm blooded

2nd to 6th abdominal segment.

2 large ovaries are found lying laterally in the 2nd to 6th abdominal segment.

(a) Anterior sucker

Correct option is: (A) temperature difference.

(b) 33 segments

Two spermathecae are found in earthworm.

2 spermathecae are found in earthworm.

The glands which do not have ducts and pour their secretions directly into the blood are called endocrine glans. Their secretions are called hormones.

Heat can be transferred on account of difference in temperature of bodies by conduction and radiation