Karnataka 2nd PUC Kannada Workbook Answers Pallava Chapter 2 Samanarthaka Galu

Karnataka 2nd PUC Chemistry Question Bank Chapter 16 Chemistry in Everyday Life

2nd PUC Chemistry Chemistry in Everyday Life NCERT Textbook Questions

Question 1.
Why do we need to classify drugs in different ways?
Answer:
The classification of drugs and the reason for classification are as follows:
1. On the basis of pharmacological effect: This classification provides doctor the whole range of drugs available for the treatment of a particular type of problem Hence, such a classification is very useful to doctors.

2. On the basis of drug action: This classification is based on the action of a drug on a particular biochemical process Thus, this classification is important.

3. On the basis of chemical structure: This classification provides the range of drugs sharing common structural features and often having similar pharmacological activity.

4. On the basis of molecular targets: This classification provides medicinal chemists the drugs having the same mechanism of action on targets Hence, is the most useful to medicinal chemists.

Question 2.
Explain the term, target molecules or drug targets as used in medicinal chemistry
Answer:
In medicinal chemistry, drug targets refer to the key molecules involve in certain metabolic pathways that result in specific diseases Carbohydrates, proteins, lipids, and nucleic acids are example of drug targets.

Drugs are chemical agents designed to inhibit these target molecules by binding with the active sites of the key molecules.

Question 3.
Name the macromolecules that are chosen as drug targets
Answer:
The macromolecules chosen as drug targets are carbohydrates, lipids, proteins and nucleic acids.

Question 4.
Why should not medicines be taken without consulting doctors?
Answer:
A medicine can bind to more than one receptor site, thus a medicine may be toxic for some receptor site Further, in most cases, medicines cause harmful effects when taken in higher dose than recommended As a result, medicines may be poisonours in such cases Hence, medicines should not be taken without consulting doctors.

Question 5.
Define the term chemotherapy
Answer:
The use of chemicals for therapeutic effect is called chemotherapy For example the use of chemicals in the diagnosis, prevention, and treatment of diseases.

Question 6.
Which forces are involved in holding the drugs to the active site of enzymes?
Answer:
Either of the following forces can be involved in holding drugs to the active sites of enzymes.

• Ionic bonding
• Hydrogen bonding
• Dipole-dipole interaction
• Van der Waals forces

Question 7.
While antacids and antiallergic drugs interfere with the function of histamines, why do these not interfere with the function of each other ?
Answer:
Specific drugs affect particular receptors Antacids and anti-allergic drugs work at different receptors This is the reason why antacids and anti-allergic drugs do not interfere with each others functions, but interfere with the functions of histamines.

Question 8.
Low level of noradrenaline is the cause of depression What type of drugs are needed to cure this problem? Name two drugs
Answer:
Anti-depressant drugs are needed to counteract the effect of depression These drugs inhibit enzymes catalysing the degradation of the neurotransmitters, nor adrenaline As a result, the important neurotransmitters is slowly metabolised and then it can activate its receptor for longer periods of time.
Two anti-depressant drugs are:

1. Iproniazid
2. Phenelzine

Question 9.
What is meant by the term ‘broad spectrum antibiotics? Explain
Answer:
Antibiotics that are effective against a wide range of gram-positive and gram-negative bacteria are known as broad spectrum antibiotics, chloramphenicol is a broad spectrum antibiotics.

It can be used for the treatment of typhoid, dysentery, acute fever, pneumonia, meningitis, and certain forms of urinary infections Two other broad spectrum antibiotics are vancomycin and ofloxacin Ampicillin and amoxycillin-synthetically modified from penicillin – are also broad spectrum antibiotics

Question 10.
How do antiseptics differ from disinfectants ? Give one example of each
Answer:
Antiseptics and disinfectants are effective against micro-organisms However antiseptics are applied to the living tissues such as wounds, cuts, ulcers, and diseased skin surfaces, while disinfectants are applied to inanimate objects such as floors, drainage system, instruments, etc Disinfectants are harmful to the living tissues.

Iodine is an example of a strong antiseptic Tincture of iodine (2-3 percent of solution of iodine in alcohol – water mixture) is applied to wounds 1 percent solution of phenol is used as a disinfectant.

Question 11.
Why are cimetidine and ranitidine better antacids than sodium hydrogen carbonate or magnesium or aluminium hydroxide ?
Answer:
Antacids such as sodium hydrogen carbonate, magnesium hydroxide, and aluminium hydroxide work by neutralising the excess hydrochloric acid present in the stomach However, the root cause for the release of excess acid remains untreated.

Cimetidine and ranitidine are better antacids as they control the root cause of acidity These drugs prevent the interaction of histamine with the receptors present in the stomach walls Consequently there is a decrease in the amount of acid release by the stomach This is why cimetidine and ranitidine are better antacids than sodium hydrogen carbonate, magnesium hydroxide, and aluminium hydroxide.

Question 12.
Name a substance which can be used as an antiseptic as well as disinfectant
Answer:
Phenol can be used as an antiseptic as well as a disinfectant 0.2 percent solution of phenol is used as an antiseptic, while 1 percent of its solution is used as a disinfectant.

Question 13.
What are the main constituents of dettol?
Answer:
The main constituents of dettol are chloroxylenol and α -terpineol

Question 14.
What is tincture of iodine? What is its use?
Answer:
Tincture of iodine is a 2-3 percent solution of iodine in alcohol-water mixture It is applied to wounds as an antiseptic.

Question 15.
What are food preservatives ?
Answer:
Food preservatives are chemicals that prevent food from spoilage due to microbial growth Table salt, sugar, vegetable oil, sodium benzoate (C₆H₃ COONa), and salts of propanoic acid are some examples of food preservatives.

Question 16.
Why is use of aspartame limited to cold foods and drinks?
Answer:
Aspartame becomes unstable at cooking temperature This is the reason why its use is limited to cold foods and drinks.

Question 17.
What are artificial sweetening agents ? Give two examples
Answer:
Artificial sweetening agents that sweeten food However, unlike natural sweeteners, they do not add calories to our body They do not harm the human body Some artificial sweeteners are aspartame, saccharin, sucralose, and alitame.

Question 18.
Name the sweetening agent used in the preparation of sweets for a diabetic patient
Answer:
Artificial sweetening agents such as saccharin, alitame, and aspartame can be used in preparing sweets for diabetic patients.

Question 19.
What problem arises in using alitame as artificial sweetener ?
Answer:
Alitame is a high potency sweetener It is difficult to control the sweetness of food while using alitame as an artificial sweetener.

Question 20.
How are synthetic detergents better than soaps?
Answer:
Soaps work in soft water, they are not effective in hard water In contrast synthetic detergents work both in soft water and hard water Therefore, synthetic detergents are better than soaps.

Question 21.
Explain the following terms with suitable examples
(i) cationic detergents
(ii) anionic detergents and
(iii) non-ionic detergents
Answer:
(i) Cationic detergents:
Cationic detergents are quarternary ammonium salts of acetates, chlorides, bromides This are called cationic detergents because the

Question 22.
What are biodegradable and non- biodegradable detergents ? Give one example of each
Explain the cleansing action of soaps
Answer:
Detergents that can be degraded by bacteria are called biodegradable detergents Such detergents have straight hydrocarbon chains For example: Sodium Lauryl sulphate.

Detergents that cannot be degraded have highly branched hydrocarbon chains For example: Sodium – 4- (1, 3, 5,7 – tetra methyl octyl) benzene sulphonate.

Soap molecules form micelles around an oil droplet (dirt) in such a way that the hydrophobic parts of the stearate ions attach themselves to the oil droplet and the hydrophilic parts project outside the oil droplet Due to the polar nature of the hydrophilic parts, the stearate ions (along with the dirt) are pulled into water, thereby removing the dirt from the cloth.

Question 23.
Why do soaps not work in hard water?
Answer:
Soaps are sodium or potassium salts of long-chain fatty acids Hard water contains calcium and magnesium ions When soaps are dissolved in hard water, these ions displace sodium or potassium from their salts and form insoluble calcium or magnesium salts of fatty acids The insoluble salts separate as scum.

this is the reason why soaps do not work in hard water.

Question 24.
Can you use soaps and synthetic detergents to check the hardness of water?
Answer:
Soaps get precipitated in hard water, but not in soft water Therefore, soaps can be used for checking the hardness of water However, synthetic detergents do not get precipitated either cationic part of these detergents contains a long hydrocarbon chain and a positive charge on the N atom
For example:

1. Anionic detergents: Anionic detergents are of two types
(a) Sodium alkyl sulphates: These detergents are sodium salts of long chain alcohols, they are prepared by first treating these alcohols with concentrated sulphuric acid and then with sodium hydroxide Examples of these detergents include sodium lauryl sulphate (C₁₁H₂₃CH₂OSO₃ Na⁺) and sodium stearyl sulphate (C₁₇H₃₅CH₂OSO₃ Na⁺)

(b) Sodium alkyl benzene sulphonates: These detergents are sodium salts of long chain alkyl benzene sulphonic acids They are prepared by Friedd-crafts alkylation of benzene with long chain alkyl halides or alkenes The obtained product is first treated with concentrated sulphuric acid and then with in sodium hydroxide Sodium 4 – (1 – dodecy) benzene sulphonate (SDS) is an example of anionic detergents.

2. Non-ionic detergents Molecules of these detergents do not contain any ions These detergents are esters of alcohols having high molecular mass They are obtained by reacting polyethylene glycol and stearic acid.

Question 25.
If water contains dissolved calcium hydrogen carbonate, out of soaps and synthetic detergents which one will you use for cleaning clothes?
Answer:
Synthetic detergents are preferred for cleaning clothes When soaps are dissolved in water containing calcium ions, these ions form insoluble salts that are of no further use, however when synthetic detergents are dissolved in water containing calcium ions, these ions from soluble salts that act as cleaning agents.

Question 26.
Label the hydrophilic and hydrophobic parts in the following compounds

Answer:

Question 27.
Sleeping pills are recommended by doctors to the patients suffering from sleeplessness but it is not advisable to make its dose without consultation with the doctor, Why?
Answer:
Most drugs when taken in doses higher than recommended may carry harmful effects and sometimes, may even lead to death Hence, a doctor should always be consulted before taking any medicine.

Question 28.
With reference to which classification has the statement, “ranitidine is an antacid” been given?
Answer:
The given statement refers to the classification of pharmacological effects of the drug This is because any drug that is used to counteract the effects of excess acid in the stomach is called an antacid.

Question 29.
Why do we require artificial sweetening agents
Answer:
A large number of people are suffering from diseases such as diabetes and obesity These people cannot take normal sugar ie sucrose as it is harmful for them Therefore artificial sweetening agents that do not add to the caloric intake of a person are required, Saccharin, aspartame, and ulitame are a few examples of artificial sweeteners.

Question 30.
Write the chemical equation for preparing sodium soap from glyceryl oleate and glyceryl palmitate Structural formulas of these compounds are given below
1. (C₁₅H₃₁COO)₃C₃H₅ – Glyceryl Palmitate
2. (C₁₇H₃₃COO)₃C₃H₅ – Glyceryl oleate
Answer:
1.

2.

Question 32.
Following type of non-ionic detergents are present in liquid detergents, emulsifying agents and wetting agents Label the hydrophilic and hydrophobic parts in the molecule Identify the functional group (s) present in the molecule
Answer:

Functional groups present in the molecule are:

• Ether, and
• primary alcoholic group.

 2nd PUC Chemistry Chemistry in Everyday Life Additional Questions

Question 1.
In order to wash clothes with water containing dissolved calcium hydrogen carbonate, which cleaning agent will you prefer and why: Soaps or synthetic detergents? Give one advantage of soaps – over synthetic detergents
Answer:
Water containing calcium hydrogen carbonate is hard water Detergents are preferred over soaps for cleaning clothes in hard water because calcium salts of detergents are soluble in water while calcium salts of soaps are insoluble As a result, lot of soap is wasted

Disadvantage of using detergents: Soaps are biodegradable while detergents having branched hydrocarbon chains are not biodegradable and hence cause water pollution in rivers and waterways.

Question 2.
Account for following
(i) Aspirin drug helps in prevention of heart attack
Answer:
Most of the heart attacks are due to blood clotting in the coronary arteries Aspirin helps to make the blood thinner and thus prevents the formation of blood clots in the coronary arteries thereby preventing heart attacks.

Question 3.
What are antihistamine? Give two examples
Answer:
Antihistamines are drugs which either reduce or inhabit the action of histamine in the body thereby preventing allergy Two important antihistamines are brompheniramine and terfenadine

Mode of action: Histamines interact with the binding sites of receptor in the body to produce allergy Antihistamines compete with histamines for these binding sites of receptor and thus do not allow histamine to produce allergy.

Question 4.
How does aspirin act as analgesic?
Answer:
Aspirin inhibits the synthesis of erostaglandis which stimulate inflammation of the tissue and cause pain.

Question 5.
What are barbiturates? To which class of drugs do they belong?
Answer:
55 derivatives of barbituric acid are called barbiturates They belong to class of tranquilizers.

Question 6.
What is salvarsan? To which class of drugs do they belong?
Answer:
Salvarsan is an antimicrobial agent It is used for the treatment of disease called syphillis

Question 7.
Give one example of artificial sweetner used by diabetic patients
Answer:
Saccharin (in form of sodium salt) is taken as artificial sweetner by diabetic patients.

Question 8.
Define a tranquilizer
Answer:
Tranquilizers are drugs which act on central nervous system to help in reducing anxiety.

Question 9.
What is the nature of an antacid?
Answer:
Substances which reduce the release of excess HCl by preventing the interaction of histamine with the receptors present in the stomach wall are called antacids Examples cimetidine and ranitidine.

Question 10.
Which alkaloid is used for
1. hypertension
2. malaria fever?
Answer:
1. Reserpine
2. Quinine

Karnataka 2nd PUC Physics Question Bank Chapter 1 Electric Charges and Fields

2nd PUC Physics Electric Charges and Fields NCERT Text Book Questions and Answers

Question 1.
What is the force between two small charged spheres having charges of
2× 10^-7 and 3 x 10^-7 C placed 30cm apart in air?
Answer:

Question 2.
The electrostatic force on a small sphere of charge 0.4 µ C due to another small sphere of charge – 0.8 µ C in air is 0.2 N.
(a) What is the distance between the two spheres ?
(b) What is the force on the second sphere due to the first?
Answer:

Question 3.
Check that the ratio ke²/Gm_e m_p is dimensionless. Look up a table of Physical constants and determine the value of this ratio. What does the ratio signify?
Answer:

This value represents the ratio of electrostatic force of gravitational force between an electron and a proton.

Question 4.
(a) Explain the meaning of the statement ‘electric charge of a body is quantised’,
(b) Why can one ignore quantisation of electric charges when dealing with macroscopic i.e large scale charges?
Answer:
(a) The magnitude of charge on a proton or an electron (e = 1.6 x 10¹⁹c) is called elementary charge. Since protons and electrons are only basic charged particles in a matter, the charge on an object must be integral multiple of ±e(1.6×10¹⁹c),
i.e. the charge possessed by an object cannot be a fraction of + e. Mathematically, the charge on any matter must be equal to q = ±ne, where n is an integer.

(b) In practice, the charge on any charged body is very large. On the other hand, the charge on an electron is very small. When electrons are added to a body (negatively charged body) or removed from a body (positively charged body), the change taking place in the total charge on the body is so small that the charge seems to be varying in a continuous manner. Therefore quantisation of electric charge can be ignored, when dealing with a large scale charged body.

Question 5.
When a glass rod is rubbed with a silk cloth, charges appear on both. A similar phenomenon is observed with many other pairs of bodies. Explain how this observation is consistent with the law of conservation of charge.
Answer:
Before rubbing, both the glass rod and the silk cloth are electrically neutral. In other words, the net charge on the glass rod and the silk cloth is zero. When the glass rod is rubbed with silk cloth, a few electrons from the glass rod get transferred to the silk cloth. As a result, the glass rod becomes positively charged and the silk cloth negatively charged. Since the magnitude of positive charge on the glass rod is the same as that of negative charge on the silk, the net charge on the system is zero. Thus the appearances of charge on the glass rod and the silk cloth is in accordance with the law of conservation of charges.

Question 6.
Four point charges q_A = 2 µC, q_B = -5 µC, q_c = 2 µC and q_D = -5 µC are located at the corners of a square ABCD of side 10cm. What is the force of a charge of 1 µC placed at the centre of the square?
Answer:
Consider the square ABCD of each side 10cm and centre O. The charge of 1 µC is placed at point O. The charge of 1 µC is placed at point O.

equal and opposite forces due to the charges q_A and q_c. Similarly, the charges of 1 µC experiences equal and opposite forces F_fi and F_d due to the charges q_B and q_D.

Hence, the net force on the charge of 1 p C due to the given arrangement of the charges is zero.

Question 7.
(a) An electrostatic field line is a continuous curve. That is a Held line cannot have sudden breaks. Why not?
(b) Explain why two field lines never cross each other at any point?
Answer:
(a) The tangent at a point on the electric line of force tells the direction of electric field changes from point to point. Therefore the line of force are, generally, curved lines. Further, they are continuous curves and cannot have sudden breaks. For if it is so, it will indicate the absence of electric field at the breakpoints

(b) The tangents at a point on the line of force gives the direction of electric field at that point. If two lines of forces intersect each other at a point, then electric field at that point will have two directions. As the same cannot be true, two lines of force will never intersect each other.

Question 8.
Two point charges q_A = 3 µC and q_B = -3 µC are located 20 cm apart in vacuum.
(a) What is the electric field at the midpoint O of the line AB joining the two charges?
(b) If a negative test charge of magnitude 1.5×10^-9C is placed at this point, what is the force experienced by the test charge?
Answer:


The force on the negative charge acts in a direction opposite to that of the electric field.

Question 9
A system has two charges q_A = 2.5× 10^-7C and q_B = -2.5 x 10^-7C located at points
A: (0, 0, -15cm), respectively. What are the total charge and electric dipole moment of the system?
Answer:
The charges q_A and q_B are located at the points A (0,0, – 15cm) and B (0, 0, +15cm). B The points A and B lie on z-axis as shown.
It follows that,
AB = OA + OB = 30ci = 0.3m

Question 10.
An electric dipole with dipole moment 4×10^-9cm is aligned at 30° with the direction of a uniform electric field of magnitude 5 × 10⁴ NC¹. Calculate the magnitude of the torque acting on the dipole.
Answer:

Question 11.
A polythene piece rubbed with wool is found to have a negative charge of 3x 10 ⁷C
(a) Estimate the number of electrons transferred (from which to which ?)
(b) Is there a transfer of mass from wool to polythene?
Answer:
(a) The total charge transferred,
q = -3 x 10^-7C
charge on an electron, e = -1.6x 10¹⁹C From quantization of charge, q = ne Therefore, number of electrons transferred,

(b) Since electrons are transferred from wool to polythene, there is transfer of mass also. This is because electrons are material particles and possess mass (m_e = 9.1 x 10^-31kg).

Question 12
(a) Two insulated charged copper spheres A and B have their centres separated by a distance of 50 cm. What is the mutual force of electrostatic repulsion if the charge on each is 6.5 x 10^-7C ? The radii of A and B are negligible compared to the distance of separation.

(b) What is the force of repulsion if each sphere is charged double the above amount and the distance between them is halved?
Answer:
(a) Charge on sphere A, q₁, = 6.5 x 10^-7c
charge on sphere B, q₂ = 6.5 x 10 ⁷c
Distance between the spheres A and B, r = 50 cm= 0.5m

Question 13
Suppose the spheres A and B in exercise 1.12 have identical sizes. A third sphere of the same size but uncharged is brought in contact with the first, then brought in contact with the second, and finally removed from both. What is the new force of repulsion between A and B?
Answer:
The charge on A and B, q₁ = q₂ = 6.5x 10⁷C.
The distance between the spheres r = 0.5m. Since the spheres are same size, they will possess equal charges on being brought in contact. When uncharged sphere c (q₃ = 0) is bought in contact with A, charge left on A.

Question 14.
Fig 1.33 shows tracks of three charged particles in a uniform electrostatic field. Give the signs of the three charges. Which particle has the highest charge to mass ratio?

Answer:
Charges (1) and (2) are negative as they were attracted by the positive plate and charge (3) is positive as it is deflected towards negative plate.
Thus charge (3) has highest charge to mass ratio (as it would be a positive figure)

Question 15.
Consider a uniform electric Held \(\vec { E } =3\times { 10 }^{ 3 }\hat { i } { N }/{ C }\)
(a) What is the flux of this field through a spheres A and B, charges inside the box. Therefore, if the net outward flux is zero, we cannot conclude that the charge inside the box is zero. One can only say that the net charge inside the box is zero.

(b) A point charge +10 p C is a distance 5cm directly above the centre of a square of side 10cm, as shown in fig. 1.34. What is the magnitude of the electric flux through the square of 10cm on a side whose plane is parallel to the yz plane?
(b) What is the flux through the same square if the normal to its plane makes a 60° angle with the x-axis ?
Answer:

Question 16.
What is the net flux of the uniform electric field of exercise 1.15 through a cube of side 20cm oriented so that its faces are parallel to the coordinate planes?
Answer:


In each plane, there is a set two faces of the cube. Through one face, electric flux enters and through the other face, an equal flux leaves. Therefore, net flux through the cube,

Question 17.
Carefid measurement of the electric field at the surface of a black box indicates that the net outward flux through the surface of the box is 8.0 ×10³Nm²/C.
(a) What is the net charge inside the box?
(b) If the net outward flux through the surface of the box were zero, could you conclude that there were no charges inside the box? Why or why not?
Answer:

(b) If the net outward flux through the surface of the box is zero, it cannot be concluded that there is no charge inside the box. There may be equal amount of positive and negative charges inside the box. Therefore, if the net outward flux is zero, we cannot conclude that the charge inside the box is zero. One can only say that the net charge inside the box is zero.

Question 18.
A point charge +10 µ C is a distance 5cm directly above the centre of a square of side 10cm, as shown in fig. 1.34. What is the magnitude of the electric flux through the square?

Answer:

consider that the charge q is at a distance of 5 cm from the square ABCD of each side 10cm as shown. The square ABCD can be considered as one of the six faces of a cube of each side 10cm. Then according to Gauss’ theorem, total electric flux through all the six faces of the cube,

Question 19.
A point charge of 2 p C is at the centre of a cubic Gaussian surface 9cm on edge. What is the net electric flux through the surface?
Answer:
Here, q = 2µC = 2 × 10^-6C
side of cube, a = 9cm = 0.09 m
According to Gauss’ law, the net electric flux through all the six faces of the cube,

Question 20.
A point charge causes an electric flux of  1 x 10³Nm²/C to pass through a spherical Gaussian surface of a 10cm radius centred on the charge.
(a) If the radius of the Gaussian surface were doubted, how much flux would pass through the surface?
(b) What is the value of the point charge?
Answer:
Here φ = -1 x 10³Nm²C^-1
radius of Gaussian surface, r = 10cm = 0. 1m.
(a) If the radius of the gaussian surface is doubled, the electric flux through the new surface will still remain the same i.e. -1 x 10³Nm²C^-1
This is because the same charge is enclosed by the gaussian surface in the two cases.

(b) Let q be the charge inside the surface:

Question 21.
A conducting sphere of radius 10cm has an unknown charge. If the electric field 20cm from the centre of the sphere is 1.5 x 10³N/C and the points radially inward, what is the net change on the sphere?
Answer:
Consider a sphere of radius
R = (=10cm = 0.1 m) and centre O.
Let the charge on the sphere be ‘q’. Further, let ‘P’ be a point at a distance r = 20cm from the centre of the sphere.

The electric field E( = 1.510³NC^-1) is directed radially inward as shown. So as to enclose the charged sphere, draw a sphere (gaussian surface) with the point O as centre and r as the radius. As the electric field is radial, it is normal to the gaussian surface everywhere. Therefore, electric flux through the gaussian surface,

Question 22.
A uniformly charged conducting sphere of 2.4 m diameter has a surface charged density of 80 µ c/m²
(a) Find the charge on the sphere.
(b) What is the total electric flux leaving the surface of the sphere?
Answer:

Question 23.
An infinite line charge produces a field of 9 x 10⁴N/C at a distance of 2cm. Calculate the linear charge density.
Answer:

Question 24.
Two large thin metal plates are parallel and close to each other. On their inner faces, the plates have surface charge densities of opposite signs and of magnitude 17x 10^-22C/m². What is \(\vec { E } \)  :
(a) In the outer region of the first plate
(b) In the outer region of the second plate, and
(c) Between the plates?
Answer:
Here, σ= 17 x 10^-22 Cm^-2
(a) To the left of plates.
The electric field at this region is zero

(b) To the right of the plates
The electric field in this region is zero.

(c) Between the two plates
The electric field at this region is given by

2nd PUC Physics Electric Charges and Fields Additional Exercises

Question 25.
An oil drop of 12 excess electrons is hold stationery under a constant electric field of 2.55 x 10⁴ NC^-1 in is 1.26 g em^-3. Estimate the radius of the drop, (g = 9.81 ms^-2; e = 1.60×10 ¹⁹c)
Answer:

Question 26.
Which among the curves shown in Fig 1.35 cannot possibly represent electrostatic field lines?

Answer:
(a) It is not. Because field lines are not normal to the surfaces of the conductors.
(b) It is not, because, field lines cannot start from negative charge.
(c) It is correct representation of electric field lines.
(d) It is not because, field lines cannot intersect each other.
(q) It is not, because field lines cannot form closed loops without having touching the source or any charge.

Question 27.
In a certain region of space, electric field is along the z-direction throughout. The magnitude of the electric field is, however, not constant but increases uniformly along the positive z-direction, at the rate of 10⁵Nc¹ per meter. What are the force and torque experienced by a system having a total dipole moment equal to 10^-7cm in the negative z-direction?
Answer:
Suppose that a dipole consisting of charges – q at A and +q at B is placed along z-axis, such that it has dipole moment along the negative z-direction. The dipole moment of the dipole along z axis, P_Z= -10^-7Cm

The negative sign has been taken for they reason that dipole moment is along the x negative z-axis.

The electric field is applied along the positive direction of z-axis, such that (along z-axis) In a non – uniform electric field, the force on dipole is given by,

The negative sign shows that force on the dipole is along negative z-axis.
Since the elctric dipole moment is along negative z-axis and the electric field is along positive z-axis, 0 = 180°.
Hence, torque on the dipole, τ = pE sin 180° = 0.

Question 28.
(a) A conductor A with a cavity as shown in Fig. 1.36 (a) is given a charge Q. Show that the entire charge must appear on the outer surface of the conductor.
Answer:

(b) Another conductor B with charge q is inserted into the cavity keeping B insulated from A. Show that the total charge on the outside surface of A is Q + q [Fig. 1.36(b)].
(c) A sensitive instrument is to be shielded from the strong electrostatic fields in its environment. Suggest a possible way.
Answer:

Consider the gaussian surface (dotted) so as to enclose the cavity by lying wholly inside the conductor A. Since the electric field inside a conductor is zero, the part of the conductor within the cavity does not contain any net charge. By extending the same argument, no charge can be present inside the gaussian surface, which lies just within the conductor. Hence the entire charge A must appear on the outer surface of the conductor A.

consider the gaussian surface (dotted), it encloses the cavity and the conductor B with ^ charge q inserted in the cavity.

As such, the electric flux will cross the gaussion surface and it would imply that the electric field exists inside the conductor A. But the electric field inside the conductor A must be zero. It will be true, only if the charge q on conductor B induces charge-q on the inner surface and +q on the outer surface of the

Conductor A. As there is already a charge +Q on the outer surface of the conductor A, the total charge on its outer surface becomes Q+q.

(c) The electric field inside a metallic conductor is zero. Therefore, instrument can be shielded from the strong electrostatic fields by enclosing n it with a hollow metallic structure.

Question 29.
A hollow charged conductor has a tiny hole cut into its surfaces. Show that the electric field in the hole is \(\left( { \sigma }/{ { 2\epsilon }_{ 0 } } \right) \hat { i } \), where q is the unit vector in the outward normal direction and a is the surface charge density near the hole.
Answer:
Let \(\vec { E } \)be the electric field in the hole due to rest of the charged conductor. In order to find \(\vec { E } \) consider that the hole in the conductor is plugged. Let \(\vec { E } \) be the electric field due to the charged conductor at a point’ outside it then,

After plugging the hole, the conductor becomes a closed one, the electric field inside it must be zero. It implies that inside the conductor, electric field due to the rest of the conductor must be equal and opposite to that due to the small portion of the conductor, that plugs the hole. However, outside the conductor, the two fields are in the same direction i.e. along the outward normal to the surface of the conductor. It therefore, follows that the electric field in the hole due to the rest of the conductor,

Question 30.
Obtain the formula for the electric field due to a long thin wire of uniform linear charge density X, without using Gauss’ law
Answer:
Consider a long thin wire of uniform linear charge density λ  Let us find electric field due to the wire at the point P at a normal distance. PN = r from the wire Let AB = dx be a small elementary portion of the wire at a distance x from point N.

Then charge on the elementary portion AB, dq= λ dn

Therefore, electric field due to the small portion AB at the point P,

The component dE sin θdue to the different small portions, such as AB, will cancel each other. Therefore, effective electric field due to the small portion AB,

Question 31.
It is now believed that protons and neutrons are themselves built out of more elementary of charge \(+\frac { 2e }{ 3 } \) and then’ down quarks’ denoted by ‘d’ of charge \(-\frac { e }{ 3 } \) together with electrons build up ordinary matter. Suggest a possible quark composition of a proton and neutron.
Answer:
The charge on up quark (u) = \(+\frac { 2e }{ 3 } \)
The charge on down quark = \(-\frac { e }{ 3 } \)
The charge on proton is +e and it is made of three quarks. Therefore the possible quark composition of a proton is ‘uud

On the other hand, neutron is a neutral particle but it is also made of three quarks. For this, the possible composition of the neutron is ‘udd’.

Question 32.
(a) Consider an arbitrary electrostatic field configuration. A small test charge is placed at a null point of the configuration. Show that the equilibrium of the test charge is necessarily unstable.

(b) Verify the result for the simple configuration of two charges of the same magnitude and sign placed a certain distance apart.
Ans:
(a) To prove the result, let us assume that the test charge placed at the null point is in stable equilibrium. If it is so, then on being displaced slightly away from the null point, the test charge should return to its position., It implies that if a closed surface is drawn around the test charge, there will be a net inward flux of the electric field through its surface. According to Gauss law, there cannot be any electric flux through its surface as it does not enclose any charge. Hence our assumption is wrong and the test

(b) For the configuration of the two charges of the same magnitude and sign, the null point is the mid point of the line joining the two charges. If the test charge is displaced slightly from the null point along the line, it will return back due to the restoring force that comes into the day. But if the charge is displaced slightly from the null – point along normal to the line it will not return. This is because the resultant force due to the configuration of two charges will take it away from the null point. For the test charge to be in stable equilibrium restoring force must come into play, when it is displaced in any direction. Hence the test charge cannot be in stable equilibrium.

Question 33.
A particle of mass m and change -q enters the region between the two plates initially moving along X-axis with speed \({ V }_{ \lambda }\). The length The length of plate is L and a uniform electric field £ is maintained between the plates. Show that the vertical deflection of the particle at the far edge of the plate is \(-\frac { qE{ L }^{ 2 } }{ 2m{ v }_{ \lambda }^{ 2 } } \)
Answer:
Let y be the vertical deflection of the charged particle since the particle is initially moving along x-axis, its initial speed along the vertical.
The electric field E is directed along vertical. Therefore, acceleration of the particle along the vertical, \({ U }_{ y }=0\)
The time for which the force due to the electric field acts on the particle,
\({ a }_{ y }=\frac { qE }{ m } \)

Question 34.
Suppose that the particle in exercise 1.33 is an electron projected with velocity V_x = 2x 10⁶ms¹. If E between the plates separated by 0.5 cm is 9.1 x 10²Nc^_1, where will the electron strike the upper plate? Given, e = 1.6 x 10¹⁹C; and M_e = 1 x 10³¹ kg.
Answer:
Suppose that the electron strikes the upper plate at a distance x from the end, where it enters the electric field. Therefore the expression for vertical deflection becomes

2nd PUC Physics Electric Charges and Fields Additional Entrance Examination Questions and Answers

Question 1.
A charge Q is placed at each of the opposite corners of a square. A charge q is placed at each
of the other two corners. If the net electrical force on the Q is zero, then ~ equals
(A) -1
(B) 1
(C) \(-2\sqrt { 2 } \)
(D) \({ -1 }/{ \sqrt { 2 } }\)
Answer:
(C) \(-2\sqrt { 2 } \)

Question 2.
Four charge equals to -Q are placed at the four corners of a square and a charge q is at its centre. If the system is in equilibrium, the value of q is

Answer:
(A)

Question 3.
If the amounts of electric flux entering and leaving an enclosed surface respectively are \({ \phi }_{ 1 }\) and <\({ \phi }_{ 1 }\) the electric charge inside the surface will be

Answer:
(A)

Question 4.
A charged particle q is placed at the centre O of the cube (ABCDEFGH) of length L. Another same charge q is placed at a distance L from 0. Then, the electric flux through ABCD is.

Answer:
(C)

Question 5.
A thin spherical shell of radius R has charge Q spread uniformly over its surface. Which of the following graphs most closely represents the electric field E (r) produced by the shell in the range o≤ r < ∞ where r is the distance from the centre of the shell ?


Answer:
(B)

Question 6.
Two-point charge +8q and -2q are located at x = 0 and x = L respectively. The location of a point on z-axis at which the net electric field due to these two point charges is zero is (CET 2009)
(A) 2L
(B) L/4
(C) 8L
(D) 4L
Answer:
(D) 4L

Question 7.
If a charge q is placed at the centre of the line joining two equal charges Q such that the system is in equilibrium then the value of q is (CET 2010)
(A) Q/2
(B) -Q/2
(C) Q/4
(D) -Q/4.
Answer:
(D) -Q/4.

Karnataka 2nd PUC Economics Question Bank Chapter 1 Introduction to Micro Economics

2nd PUC Economics Introduction to Micro Economics One Mark Questions and Answers

Question 1.
What do you mean by Economics?
Answer:
The term ‘Economics’ is derived from the Greek words ‘OIKOS” and “NOMOS which mean Household and management respectively. It studies the problem of choice at the individual social, national and international levels.

Question 2.
Define an economy.
Answer:
An economy is a mechanism through which the scarce resources are prioritized and organized for the production of goods and services. It also refers to a geographical-area where economic activities take place.

Question 3.
Why does an economic problem arise?
Answer:
An economic problem arises because of limited resources and unlimited wants and alternative uses of resources. While trying to allocate limited resources to satisfy unlimited wants, the problem of choice arises.

Question 4.
What is Planned economy?
Answer:
A Planned economy, also called as Socialistic economy is that economy where the economic activities are controlled by the central Government. Here, the Government takes decisions about the allocation of resources in accordance with objectives to attain economic and social welfare. Example, Russia, China, North Korea etc.

Question 5.
What is a Market economy?
Answer:
A Market economy also known as Capitalistic economy is that economy in which the economic decisions are undertaken on the basis of market mechanism by the private entrepreneurs It functions on demand and supply conditions. Example, USA.

Question 6.
What do you mean by mixed economy?
Answer:
A mixed economy is that economy in which we can see co-existence of both private and public sector enterprises. It is a combination of both Socialistic and Capitalistic features.

Question 7.
What is Positive economics?
Answer:
The Positive Economics is the study of ‘what was’ and ‘what is’ under the given set of circumstances. It deals with the scientific explanation of the working of the economy.

Question 8.
What is Normative Economics?
Answer:
The Normative Economics studies ‘what ought to be’. It explains about ‘what should be and should not be done’.

Question 9.
Define Micro Economics.
Answer:
Micro economics is the study of the economic actions of individuals and small groups of individuals. According to Boulding, “It is the study of particular firms, particular households, individual prices, wages, income, individual industries, particular commodities”.

Question 10.
Who first coined the terms ‘Micro’ and ‘Macro’ Economics?
Answer:
Prof.Ragner Frisch, the Nobel Prize winner in Economics (1920), coined the words Micro and Macro Economics for the first time.

Question 11.
Is the study of a sugar factory, a Micro-Economic study or a Macro-Economic study?
Answer:
The study of a Sugar factory is a Micro-Economic study.

Question 12.
What is Deductive Method of Economics?
Answer:
It is one of the methods of study of economics in which the conclusions are drawn from the general to the particular or from the universal to the individual.

2nd PUC Economics Introduction to Micro Economics Two Marks Questions and Answers

Question 1.
What is an economic problem and why does it arise?
Answer:
An economic problem is the problem of choice which arises because of limited resources and unlimited wants and the alternative uses of resources. The scarcity of resources is the main cause for this economic problem.

Question 2.
What are the basic functions of an economy?
Answer:
The basic functions of any economy are Production, Consumption, Distribution, Exchange, Economic planning and Social welfare.

Question 3.
Name the basic problems of an economy.
Answer:
The basic problems of an economy are What to produce, How to produce and for Whom to produce.

Question 4.
Name the types of economics.
Answer:
The types of economies are

1. Socialistic or Centrally planned Economy
2. Capitalistic or Market Economy and
3. Mixed Economy.

Question 5.
Give two examples of Centrally Planned economy.
Answer:
The Centrally planned or Socialistic economies are North Korea, Cuba, Russia, China and Vietnam.

Question 6.
Give two examples of a Capitalistic Economy.
Answer:
The examples for Capitalistic or Market Economy are USA, Japan, Australia, UK etc.

Question 7.
mention any two differences between Positive and Normative Economics.
Answer:

Question 8.
Write any four practical importances of Micro-Economics.
Answer:

1. It helps in allocation of resources.
2. Provides solution to the problem of choice.
3. Helps in formulating various.economic policies.
4. Explains determination of the price.
5. Helps to know the working of an economy.

Question 9:
Mention any two limitations of Micro Economics.
Answer:

1. It has unrealistic assumptions.
2. It is based on unrealistic analysis.
3. Narrow in scope.

Question 10:
What is Inductive Method of Economics?
Answer:
It is the process of reasoning from a part to the whole, from particular to general or from individual to the universal.

2nd PUC Economics Introduction to Micro Economics Five Marks Questions and Answers

Question 1.
What is a centrally planned economy? How does it solve basic problems?
Answer:
A centrally planned economy also called as socialistic economy is that economy where the economic activities are controlled by the central Government. Here, the Government takes decisions about the allocation of resources in accordance with objectives to attain economic . and social welfare. Example, Russia, China, North Korea etc.

Here, the basic economic problems are solved as follows:
The Government takes decisions about the allocation of resources in accordance with the predetermined goals and objectives to attain maximum social welfare. Government decides what to produce, how to produce and what prices are to be fixed.

• Regarding what to produce, the Government may produce those goods and services which are most useful for its society.
• Regarding how to produce, the most suitable technique in production is adopted whether labour intensive or capital intensive in accordance with the situation in the economy.
• Regarding for whom to produce, the goods and services are produced to help those people who are suffering from hunger or shortage though there is a loss.
• It gives importance to the quality of life rather than quantity of production.
• It focuses the resources on rapid economic development.

Question 2:
Write a short note on Market Economy.
Answer:
A Market Economy also known as Capitalistic Economy is that economy in which the economic decisions are undertaken on the basis of market mechanism by the private entrepreneurs. It functions on demand and supply conditions. In USA, Japan, Australia, UK and other countries we can see Market Economic systems.

In market economy, private individuals own the factors of production. Here, profit is the sole motive. There is least intervention by the Government.

Price mechanism plays a major role in market economy. It is a balancing wheel of the market mechanism. Prices coordinate decisions of the producers and consumers. The price is determined by demand and supply in the market. No individual organization or Government is responsible for the production and distribution or pricing of goods. All depend on market mechanism).

Regarding the basic problems of an economy, the problem of “What to produce”, is solved on the basis of demand and profit. The producers produce those products which bring more income.

The problem of “How the goods are to be produced”, is determined by the competition among different entrepreneurs. They select the least cost combination of technology so that they can get more returns with less cost.

In Market Economy, the/problem of “For whom to produce”, is decided on the basis of purchasing power of consumers. The producers produce commodities for the rich as they can afford to pay more but poorer sections of the society get neglected.

In Market Economy, profits and losses play a predominant role in growth and development of every producer.

Question 3.
Explain the nature of Mixed Economy. How does it differ from Market Economy?
Answer:
A Mixed Economy is that economy in which we can see co-existence of both private and public sector enterprises. It is the combination of Socialistic and Capitalistic features. The best example for this is India.

In a Mixed Economic system, the resources are owned by both the Government and Private individuals. Here, some areas of economic activities are totally governed by the Government and other sectors are open to the private sector also.

The Government involves in those activities which promote maximum social and economic welfare without any profit motive. The Private sector functions with the intention of maximizing profits. Here we find dual pricing system. For example, the supply of Rice through Government Fair Price shojis is low when compared to the private provision stores.

In this type of economy, the Government takes the responsibility to run certain essential sectors like Railways, Printing of currency notes, Atomic energy, public parks etc. Here, the basic problems are solved both by Public and Private Sectors.

Regarding what to produce,-consumers play a main role. But, the Government also interferes by imposing tax or giving subsidy. The problem of how to produce, the private sector will follow the least cost effective technology to maximize profit and public sector will select , the technology on the basis of composition of resources. The problem of for whom to produce depends on both the purchasing power of consumers and the Government policy towards weaker sections of society.

Question 4.
Is Economics Positive or Normative? Discuss.
Answer:
Positive Economics .

1. The positive economics is the study of ‘what was’ and ‘what is’ under the given set of circumstances. It is concerned with how the economy performs the basic functions of what to produce, how to produce and for whom to produce. It explains how the economy takes decisions about consumption, production and exchange of goods.

2. It deals with the scientific explanation of the working of the economy. It analyses every issue of economics from a positive perspective without passing any value judgments. It deals with the cause and effect relationship of economic variables.

Normative Economics:

1.The Normative economics studies ‘what ought to be’. It explains about ‘what should be and should not be done’. Here we try to understand that whether the mechanisms are desirable ornot. The normative economic statements are sometime called matters of op.nion or statements of value.

2. The advice given by various economists are mostly as per normative economics.
In India, Economic Advisers who are appointed by the Government are responsible for advising the Prime Minister as to which of the policies are good and beneficial to the country’s economy and which are bad and detrimental on the whole.

Economics is both Positive and Normative:

1. But, Economics is both a positive and normative science. The study of economics involves both scientific investigation and policy analysis. Economists first use science to explain the world and understand how the economy works, later policies are explored for the economic development.

Question 5.
What method would you prefer to formulate an economic theory?
Answer:
Economic theories are statements of economic tendencies of people. While developing economic theories, the Economists formulate assumptions. So, economic theory derives generalizations of economic facts through two methods: They are as follows:

Deductive Method: This method was developed by David Recardo, J.S.Mill, T.R.Malthus, Alfred Marshall and others. This method is also called as Analytical method.

under this method, the conclusions are drawn from the universal to the individual or from general to the particular. This method derives new conclusions from assumptions. It is also called as ‘Scientific Method’. It includes four stages viz.,

• Identification of the hypothesis to be tested.
• Generations of predictions from the hypothesis.
• Conducting experiments to check whether the predictions are correct.
• Confirming the hypothesis.

Inductive Method: This method was advocated by Frederic List, Rosher and Hilde Brand. Inductive method is a process of reasoning from particular to general or from individual to the universal. It functions in four stages viz.,

•  Selection of an economic problem and defining the same clearly.
• Collection of data using statistical techniques.
• Analysing the data.
• Observation and generalization to establish a general truth.

The inductive method is also called as historical method or concrete method and realistic method. In this method, we investigate particular facts or historical events and try to generalize the findings of the observation for the entire economic system.

It is concluded that both Deductive and inductive methods are e^ntial for the proper development of economic laws. According to Alfred Marshall, “Induction and deduction are both needed for scientific thought just as the right and left foot are both needed for walking”.

Question 6.
Explain the various limitations of Micro Economics.
Answer:
Micro Economics is the study of the economic actions of individuals and small groups of individuals. According to Boulding, “ It is the study of particular firms, particular households, individual prices, wages, income, individual industries, particular commodities”.
The major limitations of Micro Economics are as follows:

(a) Assumptions are unrealistic: The study of Micro-Economics assumes that ‘other tilings being constant’, which is not realistic. In fact, all factors are subject to change and not constant.

(b) Micro Economics is an unrealistic analysis: Micro-Economics uses static analysis. The conclusions drawn from Micro Economic analysis are not valid. For example, individual savings is good since it promotes individual economic prosperity. But if many people indulge in savings, it may lead to a fall in demand leading to less investment and causing unemployment.

(c) The assumption of full employment is incorrect: The microeconomics is based on the assumption of full employment i.e., all the resources are completely employed in production process, which is just imaginary and not correct.

(d) Laissez-faire policy (Minimum intervention of Government): The assumption of laissez faire policy is not practical in real world, where we see intervention of Government in economic activities.

(e) Ignores Macro economic analysis: The knowledge of an entire economy is very essential to the people as it includes all the economic elements. But the micro economics concentrates only on a small part of the whole economy.

(f) It is limited in scope: The scope of micro economics is limited and narrow. It does not include income theory, inflation, monetary policies etc. which are very important for economic analysis.

2nd PUC Economics Introduction to Micro Economics Ten Marks Questions and Answers

Question 1.
Discuss the basic problems of an economy.
Answer:
An economic system or economy is a mechanism where the scarce resources are channelized . on priority to produce goods and services. These goods and services produced by all the sectors of the economy determine the national income.

Generally, human wants are unlimited and resources to satisfy them are limited. If there was a perfect match between human wants and availability of resources there would have been no scarcity, no problem of choice and no economic problems at all. So, one has to select the most essential want to be satisfied with limited resources. In economics, this problem is called ’Problem of Choice’.

The problem of choice arising out of limited resources and unlimited wants is called economic problem. In every economy whether developed or underdeveloped, Capitalistic, Socialistic or Mixed economy, there will be three basic economic problems viz., What to produce, How to produce and For whom to produce. Let us discuss them in detail.

(a)What to Produce: Every country has to decide which goods are to be produced and in what quantities. Whether more guns should be produced or more foodgrains should be grown or whether more capital goods like machines, tools, etc., should be produced or more consumer goods (electrical goods, daily usable products etc.) will be produced. What goods to be produced and in what quantity depends on the economic system of.the country. In Socialistic economy, the Government decides and in Capitalistic economy market forces decide and in Mixed economy, both the Government and market forces provide solutions to this problem.

(b) How to Produce: There are various alternative techniques of producing a product. For example, cotton cloth can be produced with either handloom or power looms. Production of cloth with handloom requires more labour and production with power loom use of more machines and capital. It involves selection of technology to produce goods and services.

There are two types of techniques of production viz., (a) Labour intensive technology and (b) Capital intensive technology.
The society has to decide whether production be based on labour intensive or capital intensive techniques. Obviously, the choice of technology would depend on the availability of different factors of production (land, labour, capital) and their relative prices (rent, wages, interest).

(c) For whom to produce: Another important decision with economy has to take is for whom to produce. The economy cannot satisfy all wants of an the people. Therefore, it has to decide who should get how much of the total output of goods and services. The society has to decide about the shares of different groups of people- poor, middle class and the rich, in the national output.

Apart from above, an economy also faces other problems: they are as follows:

(a) The problem of economic efficiency: The efficient utilisation of existing resources of an economy has also become a major problem. The Optimum use of both natural and human resources is needed to prevent the wastage of these resources.

(b) The problem of full employment: Full employment means utilisation of resources to the fullest extent. Under utilisation of human resources leads to unemployment, disguised unemployment etc. If the natural resources are not used to the maximum, there is a wastage of potentiality of an economy.

(c) The problem of economic growth: Every nation wants to increase its Gross Domestic Product to achieve economic growth. This in turn improves the standard of living and reduces poverty and unemployment. Every economy has to increase its ability to produce more goods and services with the help of existing resources in order to achieve economic growth. But many developing countries are facing this problem of economic growth. So, the above are the basic problems of an economy common to all the economic systems of the world.

Question 2.
Explain the main types of Economic Systems.
Answer:
The main types of economic system are:

1. Socialistic/Centrally Planned Economy
2. Capitalistic/Market Economy and.
3. Mixed Economy.

1. Centrally Planned Economy or Socialistic Economy.
A planned economy also called as socialistic.economy is that economy where the economic activities are controlled by the central Government. Here, the Government takes decisions about the allocation of resources in accordance with objectives to attain economic and social welfare. Example, Russia, China,
North Korea etc. Here, the basic economic problems are solved as follows:

Government takes decisions about the allocation of resources in accordance with the predetermined goals and objectives to attain maximum social welfare. Government decides what to produce, how to produce and what prices are to be fixed.

• Regarding what to produce, the Government may produce those goods and services which are most useful for its society.
• Regarding how to produce, the most suitable technique in production is adopted whether labour intensive or capital intensive in accordance with the situation in the economy.
• Regarding for whom to produce, the goods and services are produced with the welfare of people who are suffering from hunger in mind even though there may be a loss.
• It gives importance to the quality of life rather than quantity of production.
• It focuses the resources on rapid economic development.

2. Market Economy:
A Market Economy also known as Capitalistic Economy is that economy in which the economic decisions are undertaken on the basis of market mechanism by the private entrepreneurs. It functions on demand and supply conditions. In USA, Japan, Australia, UK and other countries we can see Market Economic systems.

In Market Economy, private individuals own the factors of production. Here, the profit is the main goal of business. There is the least intervention of Government.

Price mechanism plays a major role in Market Economy. It is a balancing wheel of the market mechanism. Prices coordinate decisions of the producers and consumers. The price is determined by demand and supply in the market. No individual organization or Government is responsible for the production and distribution or pricing of goods. All depend on market mechanism.

Regarding basic problems of an economy, the problem of what to produce is solved on the basis of demand and profit. The producers produce those products which bring more income.

The problem of how the goods are to be produced is determined by the competition among different entrepreneurs. They select least cost effective combination of technologies so that they can get more returns for their investment.

In Market Economy, the problem of for whom to produce is decided on the basis of the purchasing power of the consumers. The producers produce commodities for the rich who can afford to pay more but poorer sections of the society are neglected.

In Market Economy, profits and losses play a predominant role in the growth and development of every producer.

3. Mixed Economy:
A mixed economy is that economy in which we can see co-existence of both private and public sector enterprises. It is the combination of Socialistic and Capitalistic features. The best example is India.

In a mixed economic system, the resources are owned by both the Government and Private individuals. Here, some areas of economic activities are totally governed by the Government and other sectors are open to the private sector.

The Government involves in those activities which promote maximum social and economic welfare without any profit motive. The Private sector functions with the intention of maximizing profits. Here we find dual pricing system. For example, the supply of rice through Government Fair Price shops is low when compared to the private provision stores.

In this type of economy, the Government takes the responsibility to run certain essential sectors like Railways, Printing of currency notes, Atomic energy, public parks etc. Here, the basic problems are solved both by Public and Private Sectors.

Regarding what to produce, consumers play the main role. But, the Government also interferes by imposing tax or giving subsidy. The problem of how to produce, the private sector will decide the best cost effective technology to maximize profits and public sector will select the technology on the basis of composition of resources. The problem of for whom to produce depends on both the purchasing’power of the consumers and the Government policy towards weaker sections of the society.

Question 3.
Explain the uses of Micro-Economics.
Answer:
Micro Economics is the study of the economic actions of individuals and small groups of . individuals. According to Boulding, “The study of particular firm, particular household, individual price, wage, income, individual industry, particular commodity, is Micro Economics.”

Micro Economics is an important method of economic analysis. It has both theoretical and practical importance.

(a) Helpful in the efficient employment of resources-allocation of resources: Micro Economics deals with the economizing of scarce resources with efficiency. The principal problem faced by modern Governments is the allocation of resources among competing wants. In this sense, Micro Economics is used by the Government in the efficient employment of resources and achieving economic growth With stability.

(b) Helps in understanding the working of the economy: Micro Economics is of utmost importance in understanding the working of a free economy. In such an economy, there is no agency to plan and coordinate the working of the economic system. The decisions like how to produce, what do produce etc., are taken by producers mid consumers without any outside influence.

(c) Provide tools for economic policies: Micro economics provides analytical tools for evaluating the economic policies of an Economy. Price mechanism or market mechanism is the tool which helps us in this respect. Micro Economics thus helps in formulating correct price policies.

(d) Useful in understanding the problems of Taxation: The study of micro economics helps in understanding some of the problems of taxation. It is used to explain the welfare implications of a tax. It studies the distribution of incidence of a commodity tax (excise duty/sales tax) between sellers and consumers.

(e) Helpful in International Trade: In the field of international trade, it is used to explain the gains from international trade, balance of payments and the determination of the foreign exchange rate.

(f) Helps us to know Market structure: The study of Micro Economics is useful in understanding the different market conditions like perfect competitive market, monopoly, duopoly, oligopoly etc.

(g) Construction and use of economic models: Micro Economics constructs and uses simple models for understanding the actual economic phenomena. It helps not only to describe the actual economic situation, but also suggests policies that would bring in the desired results;

(h) The basis of predictions: Micro Economic theory can be used as the basis for prediction. This does not mean that it will enable us to predict the future. It will enable the user to make conditional predictions.

(i) Solution to the problem of choice: The study of Micro Economics helps to find solution to the problem of choice by providing various guidelines for proper allocation of scarce
resources.

(j) Helps business executives: Micro Economics helps the business executives in the attainment of maximum productivity with existing resources. It is with its help that one is able to know the consumer demands and calculate the cost of production.

(k) Helps in formulation of economic planning: In order to solve the basic problems of an economy, conscious planning is required. The knowledge of micro economics helps the members of National Planning Commission to frame aims and objectives based on the availability of resources.

(l) Expands intellectual capacity of Human mind:- The study of economics helps individuals to develop their thinking and intelligence to take appropriate decisions in their daily life.

(m) To examine the conditions of economic welfare: Micro Economics can be used to examine the conditions of economic welfare. Welfare economics is related to maximization of social welfare. The study of Micro Economics may be the greatest help in raising the standard of living of the population.

(n) Helps different sections of the society: The knowledge of Micro Economics is very important to know the different sections of the society like poor, middle class, rich, male and female population, skilled and unskilled labourers etc. It helps us to understand the problems of these sections and to arrive at proper Solutions.
Thus, Micro Economics is considered as an efficient method of problem solving.

Karnataka 2nd PUC Biology Question Bank Chapter 13 Organisms and Populations

2nd PUC Biology Organisms and Populations NCERT Text Book Questions and Answers

Question 1.
How is diapause different from hibernation?
Answer:

Question 2.
If a marine fish is placed in a freshwater aquarium, will the fish be able to survive? Why or why not?
Answer:
It will not be able to survive for long because:-

• Water will enter the body by endosmosis
• As marine fishes drink lots of water, so excess water enters.
• It does not have salt absorbing mechanism as of freshwater fishes.

So, these fishes will die because of problem in osmolarity maintenance But due to hormonal mechanisms, migratory fishes are exceptions as they withstand the changes eg:- Hilsa, salmon

Question 3.
Define phenotypic adaptation. Give one example.
Answer:
Phenotypic adaptation:- It is non-genetic change in physical and physiological characteristics which develops in response to changes in environment and are useful to organisms in adjustment to prevailing Pvt. conditions.
eg:-

• Mountain sickness in normal people in high attitudes but tribes living in himalayas do not have mountain sickness
• Euphorbia hirta plant species.

Question 4.
Most living organisms cannot survive at temperature above 450C. How are some microbes able to live in habitats with temperatures exceeding 1000C?
Answer:
Temperature > 45°C causes precipitation of protoplasm and denaturation of enzymes. Therefore they die in most of organisms But some live in 1000°C (thermophiles) due to

• Branched-chain lipids that reduce fluidity of cell membranes.
• Inborn metabolism to produce heat-tolerant enzymes
• Reduced free water.

Question 5.
List the attributes that populations but not individuals possess.
Answer:

• Population density
• Birth rate
• Death rate
• Sex ratio
• Population growth
• Age distribution
• Population dispersal.

Question 6.
If a population growing exponentially double in size in 3 years, what is the intrinsic rate of increase (r) of the population?
Answer:

Question 7.
Name important defence mechanisms in plants against herbivory.
Answer:
Defence is of 2 types Morphological and chemical Defences.
Morphological defence –

• Thoms, spines, prickles, bristles
• Stinging hair, sticky hair, hairy coating
• Harbowing ants
• Resemblance to dreaded animals.

Chemical Defences

• Latex
• Alkaloids
• Tannins
• Silica
• Bitter taste, Offensive smell
• Irritating substance
• Poisonous cardiac glycosides.

Question 8.
An orchid plant is growing on the branch of mango tree. How do you describe this interaction between the orchid and the mango tree?
Answer:
Commensalism – orchid being space parasite benefitting from mango plant in obtaining space for residence but mango tree is not harmed.

Question 9.
What is the ecological principle behind the biological control method of managing with pest insects?
Answer:
The ecological principle behind control of pest insects is controlling growth of their population through natural enemies, predator, parasites.

Question 10.
Distinguish between the following:
(a) Hibernation and Aestivation
(b) Ectotherms and Endotherms
Answer:

(b)

Question 11.
Write a short note on
(a) Adaptations of desert plants and animals
Answer:
(a)
(1) Plants vegetation is sparse, grows during rains only. (Drought exoping)
(2) Annuals (Drought evaders)
(3) Succulents (Drought resisting) – stores water with mucilage and latex.
(4) Non succulent perennials (Drought enduring) – long roots and avoids transpiration by modification.
(5) Modifications

• leaves as spines and thorns
• Stems as water storage body with thick bark
• Long, deep roots with shoot system

Animals

• Lives in burrows
• Very little water requirement and can store water in modified body parts.
• Urine is concentrated and faeces is nearly solid with very little water and metabolic water is also used by them as source of water.
• Nasal counter- Current mechanism preventloss of water during breathing with small nostril size.
• Feeds on dry seeds and rehydrates and stores water when they reach a water body.
• Very small body surface are a so very less sweating so less water loss from body.

(b) Adaptations of plants to water scarcity
Answer:
same answer as above (drought/desert animals or plants).

(c) Behavioural adaptations in animals
Answer:
Snakes – in winter, the snakes will come out of their burrows and bask in the sun to warm their body for activity.

Desert lizards keep their body temperature fairly constant by their behaviour changes. When their body temperature drops below comfort zone, they would come out of burrow and bask in sun.

(d) Importance of light to plants
Answer:
In plants light influences photosynthesis growth and reproduction height influences flower induction, seed germination plant movement etc.

(e) Effect of temperature or water scarcity and the adaptations of animals.
Answer:
Animals living in arid areas are adapted to manage with scarcity of available water and reduce water loss to minimum.

Eg: Kangaroo rat feeds on dry seeds. Animals protect themselves from excessive cold by hibernation, thick for, constriction of peripheral blood vessel.

Question 12.
List the various abiotic environmental factors.
Answer:

• Atmospheric factors- Light, temperature, water, wind, humidity.
• Edaphic factors- Soil texture, soil water, soil air, soil pH soil micro organisms, minerals.
• Topographic factors – Slope, altitude, valley.

Question 13.
Give an example for:
(a) An endothermic animal
(b) An ectothermic animal
(c) An organism of benthic zone
Answer:
(a) An endothermic animal – Monkey (mammal)
(b) An endethsmml animal Frog (amphibian), snake (reptile)
(c) An organism of benthic zone – Angle Fish

Question 14.
Define population and community.
Answer:
Population Nearly/relatively permanent aggregation or grouping of interbreeding individuals of the same species present in a particular space or area at a given time who share the same gene pool.

Community (Biotic or Biological Community) Assemblage of different species present in the same area at the same time which show interactions and interdependence through trophic and spatial relationships.

Question 15.
Define the following terms and give one example for each:
(a) Commensalism
(b) Parasitism
(c) Camouflage
(d) Mutualism
(e) Interspecific competition
Answer:
(a) Commensalism:- Interaction where one species is benefitted and the other is neither benefitted nor harmed is called commensalism, eg: Clone Fish living in company of sea Anemones.

(b) Parasitism:- It is interspecific interaction in which small sized organism of one species obtains nourishment and spends a part or whole Of its life on or inside the body of large sized organism of other species, eg: Plasmodium in human, liver fluke in snail and fish.

(c) Camouflage:- Phenomenon of blending with surroundings with similar colour, marking, shape etc. to escape from predators and preys eg: Stick insect, leaf insect.

(d) Mutualism:- Interaction confers benefits on both the interacting species, eg: Lichen (fungus + Algae); Rhizobium and legumes.

(e) Interspecific competition :- struggle against, members of different species for obtaining some resource (food, water etc) eg: roots of plant species in same area of a forest
→ It is a potent force in organic evolution.

Question 16.
With the help of suitable diagram describe the logistic population growth curve.
Answer:

Logistic growth occurs because of natural selection. Here nature selects the filter (Survival of the fittest). Nature has resource to support maximum number of people (Carrying Capacity (K)) beyond which resources won’t support them due to their lock. This explain that log phase follows phase of acceleration. So we get sigmoid curve.

This growth is Verhulst-pearl Logistic Growth
\(D=\frac { dN }{ dt } =rN\left( \frac { K-N }{ K } \right) \)

N=Population density at time
K = Carrying capacity
r = Intrinsic rate of natural increase

Question 17.
Select the statement which explains best parasitism.
(a) One organism is benefited.
(b) Both the organisms are benefited.
(c) One organism is benefited, other is not affected.
(d) One organism is benefited, other is affected,
Answer:
(d) One organism is benefited, other is affected,

Question 18.
List any three important characteristics of a population and explain.
Answer:
Characteristics are: Population density, population growth, age distribution, birth rate, death rate, sex ratio etc.
(1) Population density:- Indicates size of population. It is number of individuals of a population found in a unit area or space at a given time. It is found out by total count
Random sampling.
\(D=\frac { N }{ S } \)

D – Population Density
N – total number of individuals of given area
S- unit of space or area

(2) Population growth:- It is increase in size of the population over a period of time.
N_t = N_o+ (natality +Immigration) – (Mortality +Emigration)
N_t= N_o +B + I-(D + E)
N_t = Population increase after time t;
N_o= Population at t = 0

(3) Age distribution :- Pre-reproductive, reproductive, post – reproductive.
it helps to provide information about the population – Expending, Declining or Stable population.

2nd PUC Biology Organisms and Populations Additional Questions and Answers

2nd PUC Biology Organisms and Populations One Mark Question

Question 1.
Define the term ecology.
Answer:
It is study of the relationships of living organisms with the biotic and abiotic components of the environment.

Question 2.
Name the factors essential for the formation ‘ of major biomes
Answer:

• The annual variation in the intensity and duration of temperature
• The annual variation in precipitation, account for the formation of major biomes.

Question 3.
Which one of the two stenothermals or eurythermals, shows wide range of distribution, on earth and why? (CBSE 2008)
Answer:
Eurythermals show a wide range of distribution as they can tolerate and thrive in a wide range of temperatures.

Question 4.
Between amphibians and birds, which will be stable to cope with global warming? (AI2008)
Answer:
Birds will be stable because they are eurythermals, which can tolerate wide range of temperatures.

Question 5.
Why many of the fresh water animals cannot live for long in sea water or vice versa. (Delhi 2008)
Answer:
This is because of the osmotic changes in the body.

Question 6.
Define homeostasis
Answer:
It is the self regulatory mechanism to maintain the internal environment constant despite changes in the external environment.

Question 7.
How do herbs and shrubs survive under the shadow of big canopied trees in the forest ? (AI 2008)
Answer:
They are adapted to photosynthesis optimally under very low light condition and hence survive under the shadow of big canopied trees.

Question 8.
Why is the polar region not a suitable habitat for tiny humming birds ? (AI 2008)
Answer:
The small birds have larger surface area to body volume ratio and tend to lose heat fast when it is cold outside; consequently they have to spend more energy to generate body heat.

Question 9.
Define the term migration
Answer:
Migration is the temporary, long-distance or short distance movements of animals from the stressful movement to a less stressful or comfortable environment and return to the original habitat when the stressful period is over.

Question 10.
Define the term hibernation.
Answer:
It is the process in which animals spend the winter in an inactive/dormant state,
eg: Frogs, polarbear.

Question 11.
When and why do some animals (frog, polarbear) go into hibernation (Delhi 2008)
Answer:
When the animals (like frog) are not able to migrate from unfavorable or stressful condition/habitat during very cold condition, they hibernate to avoid the stress by escaping in time.

Question 12.
Define the term aestivation?
Answer:
It is the process in which animals spend the dry, hot summer period in an inactive state,
eg: Snails.

Question 13.
When and why do some animals undergo into aestivation?
Answer:
When the snails are not able to migrate from stressful habitat in summers they undergo aestivation to avoid stress by escaping in time.

Question 14.
Define the term adaptation.
Answer:
The development of certain features in an organism in response to particular environment which may improve the chances of survivals are called adaptation.

Question 15.
What is Allen’s rule?
Answer:
Allen’s rule refers to the minimising of heat loss in animals by possessing shorter ears and limbs.

Question 16.
Why do people living in high altitude have a higher red blood cell count or total haemoglobin
Answer:
To compensate for the low atmospheric pressure and low oxygen content of air prevailing at high attitudes, people have higher, RBC count or total haemoglobin.

Question 17.
List any 2 physiological responses that help you to gradually get acclimatised to high attitudes when you go from the plains (Delhi 2008)
Answer:

• Increasing in breathing rate
• Decreasing in binding capacity of haemoglobin.
• Increase in RBC production.

Question 18.
Define Population density.
Answer:
The total number of individuals of a species present per unit area or volume at a given time.

Question 19.
Give an example where population estimation of an organism is done indirectly with out actually counting the organism. (AI2008)
Answer:

• The number of fish caught in a trap indicates the total population density in a lake
• The tiger census is based on the pug marks or faecal pellets.

Question 20.
When does a population growth curve become sigmoid?
Answer:
Sigmoid growth curve represents logistic growth where growth is slow initially and then becomes rapid the curve becomes steady due to resources become tending.

2nd PUC Biology Organisms and Populations Two Marks Questions

Question 1.
Why is thermoregulation more effectively achieved in larger animals than in smaller ones?
Answer:
Larger ones achieve thermoregulation more effectively than smaller ones because of less surface area/volume ratio in larger ones, hence lose body heat slowly.

Question 2.
Which one out of eurythermal or stenothermal species is likely to survive increased temperature?
Answer:
Eurythermal species as they can tolerate wide variations in environmental temperature; but stenothermal ones live with narrow range of temperature only.

Question 3.
Study 3 representative figure of age pyramids

(a). Mention names given to the 3 kinds of age profile (i), (ii), (iii).
Answer:
(i) Expanding population (Triangular)
(ii) Stable population (Bell shaped)
(iii) Declining population (Cube shaped)

(b). Which one of them is ideal for population and why?
Answer:
We take stable population pyramid as ideal because our aim is to stabilize the population.

(c). How do such age profile studies help policy makers get concerned about growing population?
Answer:
Age pyramid/profile can indicate

• Rate of growth of population
• Increase in elderly population and reproductive aged people.

These features help prepare for future planning on:

• Stress of family planning
• To help elderly and needful people to live comfortably.

Question 4.
(a) Write eg: for Verhulst Pearl logistic growth
Answer:
\(\frac { dN }{ dt } =rN\left( \frac { K-N }{ K } \right) \)
r=intrinsic rate of natural increase
N = Population density at time (t)
K = Carrying capacity.

(b) Draw graph for a population whose population density has reached the carrying capacity.
Answer:

(c) Why is logistic growth model considered more realistic one for most animal populations?
Answer:
Logistic growth model is considered realistic in animals because each area has a carrying capacity beyond which environmental resistance grows and restrict their growth. It decreases natality and increases mortality.

(d) Draw growth curve where resources are not limiting growth of population?
Answer:

Question 5.
In adjacent population growth curves

Answer:
Curve (a) – Non-limiting
curve (b) – Limiting and has reached carrying capacity.

(ii) In absence of predators which curve will be demonstrated?
Answer:
Curve (a) because of absence of controlling factor.

Question 6.
Mention any two significant roles predation plays in nature. (AI2008)
Answer:

• Predation is the natural way of energy transfer through trophic levels in a food chain.
• Predation keeps the prey population under control of ecosystem.
• Predation maintains spicies diversity.

Question 7.
List any two adaptive features evolved in parasites enabling them to live successfully on their hosts. (Delhi 2008)
Answer:
The adaptive features of parasites include

• Loss of unnecessary sense organs
• Presence of adhesive organs or suckers to cling on to the host.
• Loss of digestive system
• High reproductive capacity.

Question 8.
Name the four major biomes found in India.
Answer:

• Tropical rain forest
• Tropical deciduous forest
• Desert
• Seacoast

Question 9.
Write the influence of temperature in the life of organism.
Answer:

• The temperature affects the enzyme reaction in bur body.
• The thermal tolerance of organisms determines their geographical distribution.

Question 10.
Differentiate between Euryhaline and ‘ Stenohaline animals.
Answer:
Euryhaline animals Animals which can tolerate a wide range of salinity. Stenohaline animals Animals which can tolerate a narrow range of salinity.

Question 11.
What is the effect of light in the life of animals.
Answer:

• Intensity and duration of light influences the activities like foraging, migratory activities and reproduction.
• light influences the temperature and there by the metabolism of animals.

Question 12.
How do human being maintain constant body temperature?
Ans:

• In summer we sweat profusely; the evaporation of the sweat cools the body and brings the body temperature down.
• In winter, we shiver and that produces more ‘ heat, to raise the body temperature.

Question 13.
Mention 2 adaptations the mammals of colder region have, to minimize the loss of body heat.
Answer:

• Mammals of colder regions have shorter ears and limbs.
• Aquatic mammals of colder seas have thick layer of fat called blubber below the skin which acts as insulator reduces the loss of body heat.

Question 14.
Differentiate between Population size and Population Density.
Answer:

• Population size:- The number of individuals of a species, in a given area at a given time.
• Population density:- The number of individuals of a population per unit area at a given time.

Question 15.
Biomass is a more meaningful measure of population size. Explain.
Answer:

• If the population is huge, the total number is not as easily adaptable measure as counting takes a very long time or counting becomes practically impossible.
• For some ecological investigations, there is no need to know the absolute population size / density.

Question 16.
Define carrying capacity.
Answer:
Carrying capacity is the maximum number of individual of a population that can be sustained by a given habitat.

Question 17.
What is the role of predators in maintaining species diversity in an ecosystem?
Answer:
Predators help in maintaining species diversity in an ecosystem or community by reducing the intensity of competition among the competing prey species.

Question 18.
In what ways the prey species are adapted to escape from predators? Explain with example.
Answer:

• Some species of frogs and insects are cryptically coloured or camouflaged to avoid being detected easily by the predators.
• Some prey species are poisonous and are avoided by the predators.

Question 19.
(a) How is Cuscuta adapted to be a parasitic plant?
(b) Why do cattles avoid browsing on Calotropis plants? Explain. (CBSE foreign 2009)
Answer:
(a)

• Cuscuta has no chlorophyll and leaves.
• It develops haustoria to derive nutrition from the host it parasites.

(b) Calotropis plants possess a highly poisonous cardiac glycoside, which is fatal to animals.

Question 20.
Name two basic types of competition found amongst organisms. Which one of these is more intense and why?
Answer:
The two types of competitions are

• Interspecific competition and
• Intra specific competition

In this intra specific competition is more intense because it is an interaction among individuals of same species for similar requirements.

Question 21.
Explain interference competition with an example.
Answer:
In interference competition, even if the resource is abundant, the feeding efficiency of one species is reduced by the interfering and inhibitory presence of other species.
Eg: The Abingdon tortoise in Galapagos islands become extinct with in a decade due to the introduction of goat in that island.

Question 22.
Differentiate between commensalism and Amensatism.
Answer:

• Commensalism:- It is the interspecific interaction in which one species is benefited while the other is neither benefited nor affected.
• Amensatism:- It is an interspecific interaction in which one species is affected, while the other species is neither benefited or affected.

Question 23.
What is resource partitioning ? Give an example.
Answer:
It is the phenomenons in which two species competing for the same resource could avoid competition by choosing different patterns of foraging and different times of feeding. Eg:- Five closely related species of warblers living on the same tree have been shown to co exist and avoid competition by behavioural differences.

Question 24.
Give the interaction present in each.
(a) Cuckoo lays her eggs in the crow’s nest
(b) Orchid grows on a mango tree
(c) Cuscuta growing on a shoe flower plant
(d) Clown fish living among the tentacles of sea anemone
(e) Ticks live on the skin of dogs
(f) Mycorrhizae living on the roots of higher plants
(g) Sea anemone is often found in the shells of hermit crab (CBSE-Delhi 2008)
Answer:
(a) Brood parasitism
(b) Commensalism
(c) Commensalism
(d) Commensalism
(e) Parasitism
(f) Commensalism
(g) Commensalism.

Question 25.
Name and explain the interaction between fig trees and certain species of wasps.
Answer:
The interaction between fig trees and certain species of wasp is mutualism.

• The female wasp uses the ovary of flowers as a site of oviposition (egg laying) and the developing seeds as flood for the larvae.
• The flower is pollinated when the wasp is searching a place for oviposition.

Question 26.
What type of interaction is there between clown fish and sea anemone. Why?(AI 2008)
Answer:
The interaction between clown fish and sea anemone is commensalism. In this, one is benefitted and the other is neither benefitted nor harmed.
In this relation
(i) The sea anemone has stinging tentacles which keeps away the predators of clown fishes in this clown fish is getting benefit and the sea anemone is not getting any benefit or not harmed.

Question 27.
\(D=\frac { dN }{ dt } =rN\left( 1-\frac { N }{ K } \right) \)
(a) Which type of growth curve does it represents,
(b) What do the following notations represent
(i) \(\frac { dN }{ dt } \) (ii) r (iii) N (iv) K (CBSE 2005)
Answer:
(a) It represents logistic or Verhulst-Pearl logistic growth
(b) \(\frac { dN }{ dt } \) = rate of change in population size
r – intrinsic rate of natural increase
N – Number of ex histing individual
K – Carrying capacity.

Question 28.
Study the population growth curves shown in the diagam

(1) Identify curves ‘a’ and ‘b’
(2) Mentions the conditions responsible for the curves ‘a’ and ‘b’ respectively
(3) Give the equation for the curve ‘b'(CBSE 2006)
Answer:
(1) a – Exponential curve
b – logistic or sigmoid curve

(2)
a – Unlimited food and other resources
b – Limited food and other resources

(3)
\(\frac { dN }{ dt } =rN\left( \frac { K-N }{ K } \right) \)

Question 29.
Study the table given below in regard to population interactions and the questions given below.

[(+) plus – beneficial interaction; (-) minus – detrimental interaction; 0 (zero) – neutral interaction.
(a) Identify the interactions a to e
(b) Explain each one. (CBSE 2008 comptt)
Answer:
A – B
(a) Amensalism – Species A harmed species B unaffected
(b) Predation/parasitism – Species A benefited species B harmed
(c) Competition – Species A and B mutually inhibited
(d) Mutualism – Both A and B benefitted
(e) Commensalism – Species A is benefitted Species B is unaffected.

Question 30.
Is the statement in correctly matched ? If it is incorrect, rewrite the correct form Camoflague : An organism showing resemblance with external environment animals or plants for the purpose of protection
Answer:
Incorrect:- Camoflague is blending with the back ground or surroundings due to similar colours, shape or marketing so as to remain unnoticed by predators (for protection) and prey (advantage).

2nd PUC Biology Organisms and Populations Three Marks Questions

Question 1.
What are Conformers? Why they haven’t evolved mechanisms for temperature regulation or osmoregulation.
Answer:
Conformers are those organism, which change their body temperature, osmolarity etc. according to the external ‘environmental conditions.
(1) During the course of evolution, the costs and benefits of maintaining a constant internal environment are taken into consideration, when it is not advantageous, the organisms have not evolved mechanisms to maintain homeastasis.

(2) Heat loss or gain is a function of surface area and hence very small animals are not found in polar region i.e. they have become distributed according to the external conditions.

(3) Similarly aquatic animals, that are conformers can change the osmolarity of their body fluid according to the surroundings.

Question 2.
How do organisms manage with stressful conditions existing in their habitats for short duration ? Explain with an example.
Answer:
Under such conditions

• The organisms move away from the stressful habitat to hospital area and returned to that area when it becomes normal state. eg: Siberian birds migrates to Bharatpur sanctuary in Rajasthan.
• The organisms under go hiberation if they can’t migrate
  eg: Polarbear.
• In higher plants seeds and some other vegetative reproductive structure serve as means to tide over stress conditions.

Question 3.
Explain different types of interspecific interactions
Answer:
(1) Beneficial interaction:-

• The interspecific interaction which is beneficial to both the species is called mutualism.
• Beneficial to one, but neutral to other.
• Commensalism

(2) Detrimental interaction:-

• Competition is the type of interaction that is detrimental to both the species.
• Parasitism- Beneficial to one and detrimental to the other.
• Amensatism – Detrimental to one and neutral to the other.

(3) Neutral interaction:- Commensalism is a type in which interaction is detrimental one and beneficial to the other.

Question 4.
Differentiate between ectoparasite and endoparasite.
Answer:

Question 5.
What is brood parasitism? Give an example what adaptation has evolved in this phenomenon
Answer:
Brood parasitism is a phenomenon in which one species (parasite) lays eggs in the nest of other species (host) of bird and lets the host incubate them, eg: Cuckoo lays eggs in crow’s nest Cuckoo’s eggs shows resemblance with the eggs of crow in colour size etc which failed to identify by the crow with their eggs.

Question 6.
Name and explain the kind of interaction in the following
(1) Algae and fungi in lichens
(2) Head louse and humans
(3) Hermit crab and sea anemone.
Answer:
(1) Algae and fungi in lichens:-

• This is an example of mutualism in which both are benefited
• Fungi provide protection and helps in absorbing water and minerals where as the algae prepare food for the fungus.

(2) Head louse and human: This is an example of ectoparasitism the parasite gets shelter as well as food from human’s head.

(3) Hermit crab and sea anemone:- This is an example of commensalism in which sea anemone gets benefit for moving to places rich in nutrients while the hermit crab neither benefitted nor harmed.

Question 7.

The above graph shows the organisms response to abiotic environmental factors. Name the categories of animals. Which show the pattern a, b, and c respectively and define each of them.
Answer:
(a) Conformers:
These are organisms which cannot maintain a constant internal environment but change the body temperature and osmolarity of their body fluids according to the external conditions.

(b) Regulators:
These organisms which maintain a relatively constant environment called homeostasis.

(c) Partial regulators:
These are organisms which have evolved the capacity to regulate the internal environment of the body to a limited range of external factors beyond which they become conformers.

Question 8.
Explain the following
(i) Predators are conducts of energy transfer
(ii) Predators are prudent in nature
Answer:
(i)

• A predator in a food chain feeds on the prey and obtains energy
• When the predator becomes a prey to another animal in the food chain, it transfers the energy obtained from ‘its’ prey.

(ii) If a predator is too efficient and overexploits the prey, the prey population becomes extinct. As a result predator will also become extinct due to the lack of food and hence predator are said to be prudent in nature.

Question 9.
The Mediterranean orched Ophrys employs a method called sexual deceit to get the flowers pollinated. Explain the phenomenon.
Answer:
In the flower of Ophrys, one petal resembles the female of a bee species in size, colour markings etc.

• The male bee perceives it as a female and pseudo copulates with it.
• During the process the pollengrains from the anthers become dusted on the body of bees. When this bee is attracted to another flower of this orchid species, the process is repeated and the pollengrains falls on the stigma hence pollination is achieved.

Question 10.
Mention any 4 adaptations seen is Xerophytic plants to cope up with water scarcity.
Answer:

• Xerophytes (Desert plants) have thick cuticle on their leaf surface.
• Leaves are absent or reduced to spines to prevent transpiration.
• Presence of sunken stomata to reduce water loss.
• The photo synthetic function is taken up by green flattened stems.