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CLASS X MATHES CH. 5 QUADRATIC EQUATIONS
STUDY MATERIALS.

Quadratic Equation: An equation of the form
ax2 + bx +c = 0, where a, b and c ∈ R and a ≠ 0 is called a quadratic equation with real co-efficients in the variable x.
Roots of a quadratic equation: A real number α is called a root of the quadratic equation ax2 + bx +c = 0, a ≠ 0 if aα2 + bα +c = 0.
Algebraic method of solving a quadratic equation:
(i). Method of factorization &
(ii) Method of Completing Perfect Square.
Solve ax2 + bx +c = 0, by method of completing perfect square.
We have, ax2 + bx +c = 0, ax2 + bx +c = 0
4a2x2 + 4abx + 4ac = 0 (Multiply both sides by 4a)
(2ax)2 + 2.2ax.b + b2 – b2 + 4ac = 0
(2ax + b)2 = b2 – 4ac
2ax + b = ± √b2 – 4ac (squaring both sides)
x =
Thus, the roots of the equation ax2 + bx +c = 0, a ≠ 0
are x = and x =
Quadratic formula: Roots of a quadratic equation ax2 + bx +c = 0, a ≠ 0 can be found directly by using the formula x = . This formula is known as quadratic formula.
Discriminant: The quantity of b2 – 4ac is called the discriminant of the quadratic equation ax2+bx+c = 0.
Nature of the roots:
(i). If the discriminant is equal to zero, (b2 – 4ac = 0) the roots are real and equal.
(ii). If the discriminant is greater than zero,
(b2 – 4ac > 0) and
(a). are perfect squares, the roots are rational and unequal.
(b). are not perfect squares, the roots are
irrational and unequal.
(iii). If the discriminant is equal less than zero,
(b2 – 4ac < 0) the roots are not real and unequal.
(No roots).
Relations between roots and co-efficients:
The roots of the equation ax2 + bx +c = 0, a ≠ 0
are α = and β =
(i). α + β = Sum of the roots
= + β =
=
= =
=
(ii). α. β = Product of the roots
x =
=
= = =
=
Formation of Quadratic Equation when the roots are given:
Let ax2 + bx +c = 0 be the required equation whose roots are α and β
Now, ax2 + bx +c = 0
x2 – ( )x + = 0
x2 – (α +β)x + α. β =

Electricity Class X CH 8.
Why is electricity considered as the most convenient form of energy? 1m HSLC ’18.
Ans:- Because it can be manipulated to our requirements much better than any other source of energy.
What is electric charge? What is its SI units? 2m
Ans:- The electric charge is a fundamental physical quantity of matter due to which electric phenomena are produced in the matter.
The SI unit of electric charge is coulomb (C ).
What is meant by electric current? What is its SI units? 2m
Ans:- The continuous flow of electric charges through a conductor constitutes an electric current. Or, The rate of flow of electric charges through a cross section of a conductor per unit time.
The SI unit of electric current is ampere (A ).
What is meant by electric circuit?
Ans:- A closed path of a continuous flow of electric current is called an electric circuit.
What is the conventional direction of electric current?
Ans:- The conventional direction of electric current is from positive terminal of a cell or a battery to the negative terminal through the outer circuit.
However, the actual direction of electron flows is from negative terminal to the positive terminal which is opposite to the direction of conventional current.

Expression of electric current: If a net ‘Q’ flows across any cross section of a conductor, perpendicular to the direction of current ‘I’ flow in time ‘t’ then the current through the cross section is I = Q/t
Define one ampere of current.
Ans:- One ampere of electric current is constituted by the flow of one coulomb of charge per second, that is given by 1A = 1C/1s
NB: 1 electron = 1.6 × 10-19 C, 1C = 6 × 1018 electrons.
Define one coulomb of electric charge.
Ans:- 1C of electric charge is the amount of charge conveyed by 1 Ampere in 1 Second. Q = It or 1C = 1A × 1s.
Name a device/instrument that is used to measure electric current in a circuit. How is it connected in an electrical circuit?
Ans:- Ammeter.
NB: Smaller quantities of current are expressed in milliampere, microampere or in nanoampere.
1 milliampere (1mA)= 10-3 A
1 microampere (1μA) = 10-6 A
1 nanoampere (1nA) = 10-9 A
Ammeter is always connected in series in an electrical circuit.
A current of 0.4 A is made to pass through an electric circuit for 15 minutes. Find the amount of electric charge that flows through the circuit.
Ans:- Given, I = 0.4 A; t = 15min = 15 × 60 sec
We have, Q = It
= 0.4 A × (15 × 60)sec = 4 × 15 × 6 As = 360C.
Calculate the number of electrons in 4.8 C of electric charge.
Ans:- Total Charge (Q) = No. of electrons × Charge of an electron
Therefore No. of electrons = (Total charge (Q))/(Charge of an electron)
1 electron = 1.6 × 10-19 C
Therefore, No. of electron = (4.8)/(1.6×10¯19)
= 3 × 1019 electrons
Electric potential and potential Difference
What is meant by electric potential?
Ans:- The electric potential is a physical quantity which determines the flow of electric charges from one point to another irrespective of the path followed.
What is meant by electric potential difference? What is its SI unit? HSLC ’11.
Ans:- The potential difference between the two points in an electric circuit carrying current is the amount of work done to move a unit charge from one point to the other.
Thus, potential difference, V between two points = (work done(W))/(Charge (Q) )
The SI unit of potential difference is Volt (V)
Define 1 Volt. 1m HSLC 2017
Ans:- 1 Volt is the electric potential difference between the two points in a current carrying conductor when 1 joule of work is to be done to move one coulomb of charge from one point to another.
Potential difference, V = (work done(W))/(Charge (Q) )
i. e 1 Volt = (1 joule)/1coulomb
i. e 1V = 1J/1C = 1JC—1
What is a voltmeter? How is it connected in electrical circuit?
Ans:- The voltmeter is an instrument used for measuring electrical potential difference.
The voltmeter is always connected in parallel across the points whose potential difference is to be measured.
Try to answer : Book Page 148.
What is the device that can maintain a potential difference across a conductor?
Ans:- A battery connected across two points of a conductor can maintain a potential difference between the two points.
What is meant by saying that the potential difference between the two points is 1 Volt?
Ans:- The meaning is that when 1 joule of electrical work is done by the flow of 1 coulomb of electric charge from one point to the other, the potential difference that exists between the two points is 1 Volt.
How much energy is given to 2 coulomb of charge passing through a cell of 1.5V?
What constitutes electric current in a conductor?
Ans:- The motion of electrons through a conductor constitute electric current in the conductor.
State Ohm’s Law. (Current – voltage relationship)
Ans:- Ohm’s Law states that at a constant temperature, the current flowing through a conductor is directly proportional to the potential difference across its ends.
EXPRESSION OF OHM’S LAW:
If ‘I’ is the current flowing through a conductor and ‘V’ is the potential difference (or voltage) across its ends.
Then, V ∝ I
Or V/I = a constant (R)
Or V = IR
Define 1 Ohm ( Ω ).
Ans:- 1 Ohm ( Ω ) is the electrical resistance of a conductor which allows a current of 1 ampere to flow through the conductor when there is a potential difference of 1 Volt across the ends of the conductor.
Thus, 1 Ω = 1V/1A
What is a rheostat?
Ans:- A component or a device generally used to regulate the quantity of current in the circuit without changing the voltage of the source is called a rheostat.
Thus, it is used to change the resistance in the circuit.

RESISTANCE OF CONDUCTORS:
What is meant by electrical resistance of a conductor? What is its SI unit?
Ans:- The inherent property of a conductor to resist the flow of charges through it is called resistance.
The SI Unit of resistance is Ohm ( Ω ).
On what factors does resistance depend.
Or, What are the factors on which the resistance of a metallic character depends? - 3m (2m HSLC 2013)
Ans:- The factors on which the resistance of a metallic character depends on are-
Length of the conductor i.e R ∝ l
Cross section area i.e R ∝ 1/A
Nature of the material
Temperature of the conductor.
Obtain the relation of electrical resistivity of a conductor. 3m (HSLC 2015)
Ans:- We have, R ∝ l and R ∝ 1/A
Combining these two factors we get,
R ∝ l/A

R = ρ l/A
Thus, ρ = RA/l , Where ρ = Resistivity of the conductor.
A 1.0m long wire has 1mm diameter and resistance of 7Ω. Calculate the resistivity of the material. - 2m (HSLC 2017)
Ans:- Here, l = 1.0m, d = 1mm = 1 × 10-3 m, R = 7 Ω
Thus, ρ = RA/l
ρ = (Rπd^2)/4l
ρ = (7× 22 (1 × 10¯^3 )^2)/(4×7 ×1)
ρ = 11/2 × 10-6
ρ = 5.5 × 10-6 Ωm
The resistance of a wire is 50Ω at 20°C. If the length and diameter of the wire are 1m and 5 × 10-4 m respectively, calculate the resistivity of the material of the wire. (Example 8.6)
Ans:-

COMBINATION OF RESISTANCES (OR RESISTORS)
There are two methods of joining two or more resistors. (i) Series Combination and (ii) Parallel Combination.
Derive an expression for the resultant resistance of a number of resistance connected in series.
Ans:- Let the resistances R1, R2 and R3 be connected end-to-end in series.
The same current (I) flows through all resistors.
The potential difference V1, V2and V3 across the resistances R1, R2 and R3 are given by V1 = IR1, V2 = IR2 and V3 = IR3
The potential difference (V) across the series combination is equal to the sum of the potential difference across the individual resistances.
V = V1 + V2 + V3.
The resistances connected in series may be replaced by a single resistance (Rs), having a potential difference V across its ends, while a current I flows through it, so that V = IRs
Hence, V = V1 + V2 + V3.
IRs = IR1 + IR2 + IR3
IRs = I(R1 + R2 + R3)
Rs = R1 + R2 + R3, which is the required expression.
Thus, the resultant resistance is equal to the sum of the individual resistances and is greater than the greatest of the individuals.

Derive an expression for the resultant resistance of a number of resistance connected in parallel.
Ans:- Let the resistances R1, R2 and R3 be connected in parallel with one each of their terminals joined together at a point and the other terminals joined together at another point.
The potential difference (V) across all the resistances is the same, while the current are different.
Thus the currents I1, I2, and I3 across the resistance R1, R2 and R3 are respectively given by
I1 = V/R1, I2 = V/R2 and I3 = V/R3
The total current in the circuit is equal to the sum of the individual currents.
I = I1+ I2 + I3
The resistances connected in parallel may be replaced by a single resistance (Rp), having a potential difference V across its ends, while a current I flows through it, so that
I = V/RP
I = I1+ I2 + I3
V/RP = V/R1 + V/R2 + V/R3
V/RP = V(1/R1 + 1/R2 + 1/R3)
1/RP = 1/R1 + 1/R2 + 1/R3, which is the required expression.
Thus, the reciprocal of the resultant resistance is equal to the sum of the reciprocals of the individual resistances. The result is lesser than the least of the individuals.

LAWS OF COMBINATION OF RESISTANCES
Series combination:
The combined resistance of any number of resistors connected in series is equal to the sum of the individual resistances. i. e Rs = R1 + R2 + R3
The same current flows through all resistors irrespective of the value of resistance.
The potential difference across each individual resistor is directly proportional to the resistance.
Parallel Combination:
The reciprocal of the combined resistance of any number of resistors connected in parallel is equal to the sum of the reciprocal of all the resistances.
The potential difference across each individual resistor remains same, irrespective of the values of the resistance.
The current flowing through each of the resistors is inversely proportional to the value of resistance.

HOW ARE THE HOUSEHOLD ELECTRIC APPLIANCES/COMPONENTS CONNECTED TO THE MAIN SUPPLY:

What are the disadvantages of series connection of Household Electric Appliances with the main supply?
Ans:- The disadvantages of series connection of Household Electric Appliances with the main supply are as follows:-
(i) In series connection, the same current flows through all appliances. But, the appliances may need currents of widely different values for operation. Hence operation of all appliances may not be practicable.

(ii) The resultant resistance increases in series connection with the increasing number of appliances. Hence, the current may be much reduced insufficient for operation of same or all of the appliances.

(iii) When one of the components gets fused, the circuit is broken and none of the components will work further.
(iv) It is troublesome to check the wrong thing wherever it is there in the connecting system. Hence series arrangement of electrical components is not used for domestic circuit.

What are the advantages of parallel connection of Household Electrical Appliances with the Mains supply?
[Or, Why is Household electrical wiring done in parallel circuits.]
Ans: (i) In parallel connection, the current from the Mains supply is divided in accordance with the current carrying capacity of the individual components. Hence operation of all appliances is practicable.
The resultant resistance decreases in parallel connection with the increasing number of appliances. Hence the current may be increased and divided among the components for operation.
When one of the components gets fused or fails, the other components are not affected.
All the appliances operate with the same voltage. Hence interchange of the appliances with need in position is practicable.

Why parallel connection is preferred in household circuits? - 2m (HSLC 2011)
Ans:- # It can minimize the equivalent resistance
# All the appliances get the same voltage.
# When are appliances gets fused or fails the other appliances will continue to work.

HEATING EFFECT OF ELECTRIC CURRENT

How is heating effect of electric current produced ?
Ans: When an electric appliance is fitted with a power source, some of the electrical energy of the source is expended in doing useful work of the appliance. The remaining part of the electrical energy, by the law of transformation of energy is transformed into the heat energy. As a result, the appliance gets heated up. Thus, heating effect of electric current is produced.

State Joule's law of heating effect of electric current.
Ans: The heat (H) produced in a resistor is directly proportional to
(i) the square of the current (I²) passing through the resistor, when the resistance (R) of the resistor is constant i.e. H ∝ I², when R is constant
(ii) the resistance (R), when the current (I) is constant i.e. H ∝ R, when I is constant
(iii) the time (t) for which the current flows through the resistors, when both R and I are constant i. e H ∝ t, when both R and I are constant.
Thus, we have, H = I²Rt, which is known as Joule’s law of heating effect of electric current.

Prove Joules Law of Heating effect mathematically.
Or, Show that the amount of heat energy produced on an electrical conductor is directly proportional to the resistance and to the square of the current flowing through it. (3m 2001)
Ans:- When the current (I) flows through a resistor of resistance R for time t in potential difference V expending charge Q then,
Amount of work done(W) in the form of Heat energy (H) = VQ
H = IRIt [since v = IR and Q = It]
H = I²Rt.

APPLICATION OF HEATING EFFECT OF ELECTRIC CURRENT
How is heating effect of electric current utilised in household electrical appliances? Give some examples.
Ans: When an electrical appliance having a high resistance is in an electrical circuit, much heat is evolved in the heating element of the appliance. The connecting wires are of very low resistance. Hence negligible heat is produced in the connecting wires. As a result, the heating element of the appliance glows while the connecting wires do not glow.

Example :
Electric Bulb: The filament of an electric bulb is made of a material of high resistance such as tungsten. At the same time, the filament is of very small cross-section (fine) and appreciable length. Thus, when an electric current flows through the filament, much heat is evolved. A large part of the power consumed by the filament appears as heat while a smaller part of it is in the form of light radiation.

Other appliances: The heating effect of electric current (Joule heating effect) is also utilised in many useful household electrical appliances such as electric iron, electric cooker, electric kettle, electric heater, etc.
What is electric safety fuse ? Describe its construction and principle of action.
Ans: The electric safety fuse is a device to produce a cut in the electric circuit when there is overloading in the circuit so as to save things from electric damage.
Construction : The fuse wire is made of a metal or alloy of low melting and of high electrical resistivity. It is generally made of an alloy of tin and copper. The thickness and length of the fuse wire depend upon the maximum current permissible for the circuit. It is normally encased in a cartridge of porcelain with metal ends. There is a marking of rated maximum current to be put in use.
Principle of action : The fuse wire is connected in series with the live-line of the electric mains. When there is overloading in the electric circuit, the fuse wire gets heated up to such an extent that it melts and breaks the circuit. Thus, consuming stations are saved from electric damage.

ELECTRICAL POWER, WORK AND ENERGY :
Define Electric Power.
Ans: The rate of dissipation or consumption of electrical energy is called electric power.

Electric Power (P) = (Electric energy )/time
P = (V× Q)/t
P = (V× I× t)/t
P = V × I
P = IR × I
P = I²R
P = (V/R)² × R
P = V²/R
What is the SI unit of electric Power ? Define it.
Ans: The SI unit of electric power is watt (W).
1 watt is the rate of dissipation or consumption of 1 joule of electric energy. 1W = 1J/S, Or, 1J = 1W x 1S.
[1 watt may also be defined as the power consumed by a device when operated with a current of 1 ampere under a potential difference of 1 volt.
1W = 1 V × 1A
Define watt hour.
Ans: The electric energy consumed when 1watt of power is used for 1 hour, is called watt hour (Wh).
It is the unit of electrical energy.
What is the commercial unit of electrical energy? Define it.
[Or, Define one unit of electrical energy]
Ans: The commercial unit of electrical energy is called kilowatt hour (KWh).
The electric energy consumed when 1 kilowatt of power is used for 1 hour, is called kilowatt hour (KWh).
The KWh = 1000 watt x 1 hour
= 1000 watt x (60 x 60) second
= 3.6 x 10^6 watt-second
= 3.6 x 10^6 joule (J).

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CLASS X BIOLOGY CHAPTER 13 - LIFE PROCESSES SOLUTIONS
TEXTUAL QUESTIONS & ANSWERS

Let us answer (Page no. 255)
Q.1. How can we know that something is alive?
Ans: We can know that something is alive on the basis of the unique features such as growth, respiration, reproduction and presence of organized structures such as cells, tissues and organs etc. which are absent in non-living things.
Q.2. In which form the living organisms get energy from outside the body?
Ans: The living organisms get energy in the form of food from outside the body.
Q.3. What are life processes?
Ans: The processes necessary for the maintenance of the functions of the body such as nutrition, respiration, transportation and excretion are called life processes.
Q.4. No specific organ for gaseous exchange is needed in a unicellular organism. Why is it so?
Ans: In a unicellular organism the entire body surface is in contact with the environment, hence there is no specific organ or organ system for taking in food, exchange of gases or removal of wastes.
Let us answer (page no. 260)
Q.1. What are the differences between autotrophic and heterotrophic nutrition?
Ans:
DIFFERENCE
Autotrophic Nutrition Heterotrophic Nutrition
Autotrophs can manufacture their own food. Heterotrophs cannot manufacture their own food.
Chlorophyll and light are necessary. Chlorophyll and light are not necessary.
They use simple inorganic raw materials like CO2 and H2O and occur in green plants and some bacteria. They use readymade organic and inorganic compound and occurs in animals, fungi and some protists.


Q.2. From where plants get raw materials required for photosynthesis?
Ans: Plants obtain raw materials such as carbon dioxide (CO2) from atmosphere through stomata and water (H2O) from soil by roots system. Moreover, chlorophyll present in the green leaves absorb light energy.
Q.3. What are the different types of heterotrophic nutrition?
Ans: The different types of heterotrophic nutrition are:
i) Holozoic Nutrition: Mode of nutrition in which organisms ingest complex food material and break down inside the body . e.g. Amoeba, Man, etc.
ii) Saprozoic Nutrition: Mode of nutrition in which organisms feed on soluble organic matter in solution. e.g. Roundworms, Flatworms etc.
iii) Saprophytic Nutrition: Mode of nutrition in which organism breaks down food materials from decaying organic matter and then absorbs it . e.g. Some bacteria , fungi iv) Parasitic Nutrition: Mode of nutrition in which organisms derive food from another living organism called host. e.g. Cuscuta (Plant), Ticks, Leeches, etc.

Q.4. Write the role of HCl in our stomach.
Ans: The role of HCl in our stomach:
 It creates an acidic medium which is necessary for activation of the enzyme pepsin.
 Also kills harmful bacteria entering the stomach along with the food.

Let us answer (page no. 264)
Q.1. What advantage does a terrestrial animal get with regard to obtain oxygen during respiration over an aquatic animal?
Ans: Terrestrial animal can get more amount of oxygen without any effort at a time than aquatic animals because the amount of oxygen dissolved in water is less than the amount of oxygen present in atmosphere. Therefore, aquatic animals have higher rate of breathing than terrestrial one in obtaining the same amount of oxygen from environment.
Q.2. How is oxygen and carbon dioxide transported in human beings?
Ans: Oxygen is transported from lungs to different parts of the body combined with haemoglobin inside RBC while carbon dioxide is transported in dissolved form in the plasma.
Q.3. “The human lungs are designed to have maximum surface area for exchange of gases”. Explain.
Ans: Inside the lungs the bronchi divide repeatedly into smaller branches called bronchioles which end in tiny alveolar sac having several folds of surface, where the exchange of gases takes place between blood and alveoli. Hence, lungs provide a vast surface area for exchange of gases and the estimated total surface area of alveoli of human lungs is about 80 m2.
Let us answer (page no. 269)
Q1. Name the components of the transport system in human being. Write the functions of the components.
Ans: The components of transport system in human being are : heart, blood and blood vessels (arteries and veins).
i) Heart : supply of oxygenated blood to different parts of the body and removal of waste by maintaining a continuous flow of blood.
ii) Blood : transport digested food materials, CO2, waste, hormones etc. in the body moreover fight infections and also help in clotting of blood. iii) Arteries : carry blood from the heart to different parts of body.
iv) Veins : collect blood from different parts of body and bring back to the heart while capillaries help in exchange of material between blood and surrounding cells.
Q.2. What are the advantages of separation of oxygenated and deoxygenated blood in birds and mammals ?
Ans: Birds and mammals constantly use energy to maintain their body temperature where the separation of oxygenated and deoxygenated blood gives efficient supply of oxygen to the cells to generate larger amount of energy to meet their cellular demand.
Q.3. What are the components of the transport system in highly organized plants?
Ans: Transport system of highly organized plants consists of Xylem and Phloem :
 Xylem is used in the transport of water and minerals from soil to the aerial parts of the plant body.
 Phloem is used in translocation of food from the leaves to different parts of the plant body or vice-versa .


Q.4. How are water and minerals transported in plants?
Ans: Water and minerals are transported from soil to the leaves through xylem. The water conducting components of xylem like tracheids and vessels of the roots, stems and leaves are interconnected to form a continuous system reaching all parts of plants ; water from soil enter the cells of root and from where to the xylem of roots then stem and leaves.
So, there is a steady movement of water into xylem generating root pressure. During day time, the continuous loss of water in the form of vapour from leaves through transpiration create a suction which pull water to the aerial parts while minerals are also transported along with in dissolved form.
Q.5. How is food transported in plants?
Ans: Phloem transports food materials from the leaves to different parts of the plant by utilizing energy from ATP through sieve tubes with the help of companion cells of phloem. The soluble products of photosynthesis like sucrose get transferred into the phloem tissue and increases osmotic pressure causing water to move into it. Thus food is transported from the region of higher pressure to the region of lower pressure along a pressure gradient.
Let us answer (page no. 271)
Q.1. What are the methods used by plants to get rid of excretory products?
Ans. The various methods used by plants to get rid of excretory products are :
i) Plants give out O2 from photosynthesis and CO2 from respiration while excess water are released as vapour in day time and as liquid in night. ii) Excess minerals get stored in the leaves that fall off. iii) Wastes like resins, tannins, gums are stored in old xylem. iv) Roots also exude waste materials in the soil.
Q.2. Which organs are responsible for excretion in Platyhelminthes and insects?
Ans: Flame cells in Platyhelminthes and Malpighian tubules for Insects respectively.

TEXTUAL EXERCISES
Q.1. What is the function of xylem?
Ans: The upward movement of water and dissolved minerals from roots to aerials parts against the gravitational force occurs through xylem besides providing mechanical support.
Q.2. Which part of the alimentary canal absorbs the digested food?
Ans: The villi of small intestine absorbs the digested food.
Q.3. In which part of the cell, the 3-carbon compound pyruvate is broken down to give CO2, H2O and energy?
Ans: Inside the mitochondria of the cell.
Q.4. What is the function of kidney?
Ans: The function of kidney is urine formation and removal of metabolic waste.
Q.5. Describe the structure and function of nephrons.
Ans: Nephrons are the structural and functional units of kidneys (consisting of two parts : malpighian body and renal tubule).
Structure of Nephron:
Nephrons are the functional units of kidney, each nephron is a highly coiled, closely packed tubule closed at one side and at the other end it has a cup-shaped structure called
Bowman’s capsule associated with clusters of capillaries called glomerulus. Bowman’s capsule leads to tubular part of nephron that finally join collecting duct.
Function of Nephron:
The function of nephron is filtration of blood and elimination of waste from the body. The glomerular pressure causes filtration of blood into its lumen while some useful substances like glucose, amino acids, salts and large amount of water are selectively reabsorbed into the blood as the filtrate passes all along the renal tubule. Finally, the urine produced in each kidney enters urinary bladder by ureter and are released outside through the urethra.

Q.6. Describe double circulation in human being ?
Ans : The flow of deoxygenated blood from right ventricle to the lungs and return of oxygenated blood into the left atrium is called pulmonary circulation. Similarly, oxygenated blood from left ventricle passes through the system and deoxygenated blood return into the right atrium. In this way, blood goes through the heart twice during one the one cycle of flow round the body. This is known as double circulation.

Q.7. How are the alveoli designed to maximize the exchange of gases?
Ans: Human lungs have a highly branched network of tubes in which trachea divides into two bronchi that enter the lungs and further divide repeatedly into smaller branches called bronchioles. The bronchioles end in tiny sacs called alveoli with several folds of membrane where exchange of gases takes place between blood and alveoli. The walls of alveoli possess a network of capillaries, providing a larger surface area which is estimated about 80 m2.

Q.8. What is the role of saliva in the digestion of food?
Ans: Saliva breaks down starch (carbohydrates) into sugars with the help of salivary amylase. It also softens the food for easy swallowing
Q.9. How does the small intestine designed to absorb digested food?
Ans: The small intestine has millions of tiny finger-like projections called villi. These villi increase the surface area for more efficient food absorption. The villi are richly supplied with blood vessels that absorb the digested food and carry it to the blood stream.

Q.10. What are the differences between the transport of materials in xylem and phloem?
Ans: The differences between the transport of materials in xylem and phloem are listed below:
DIFFERENCE
Transport of material in xylem Transport of material in phloem
Xylem is responsible for transport of water and dissolved minerals. Phloem is responsible for translocation of soluble products of photosynthesis.
It is always from roots to the aerials parts of the plants i.e. unidirectional. It occurs in upward and downward direction i.e. bidirectional.
ATP is not utilized, driving force is transpiration pull. ATP is utilized, driving force is pressure gradient.

Q.11. What are the differences between aerobic and anaerobic respiration ? Name some organisms that use the anaerobic mode of respiration.
Ans: The differences between aerobic and anaerobic respiration are given in the table below :
DIFFERENCE
Aerobic Respiration Anaerobic Respiration
It takes place in the presence of oxygen. It takes place in the absence of oxygen.
Complete breakdown of food into carbon dioxide and water. Incomplete breakdown of food into ethanol or lactic acid and carbon dioxide.
It occurs inside the cytoplasm and mitochondria. It occurs inside the cytoplasm.
Larger amount of energy is liberated. Smaller amount of energy is liberated.
Examples – Many Plants and Animals (eukaryotes) Examples – Yeast and some Bacteria
(prokaryotes), in human muscle cells
(eukaryotes)


Q.12. What are the necessary conditions for autotrophic nutrition?
Ans: The necessary conditions are:
i) Presence of sunlight as a source of energy and chlorophyll to trap the light energy.
iii) Carbon dioxide and water as the raw material for the process.

Q.13. What would be the consequences of a deficiency of haemoglobin in our bodies ?
Ans: The consequences will be reduced amount of oxygen reaching different cells of our body leading to anaemia associated with breathlessness, tiredness or weakness (which are common symptoms of anaemia).
Q.14. Compare the alveoli in the lungs and nephrons in the kidneys with respect to their structure and function.
Ans: Comparison between alveoli and nephrons are given in the tables below:
Alveoli Nephrons
Structure :
 Structural and functional unit of lungs.
 Tiny Sac like structure present in lungs. Structure :
 Structural and functional unit of Kidneys.
 Tubular and highly coiled structures.
Function :
 Alveoli are the site of exchange of gases.
 Facilitates supply of O2 and removes CO2 from the blood . Function :
 Filtration of blood to form urine.

 Facilitates removal nitrogenous waste from the blood.

Q.15. Draw and label the sectional view of the human heart.

Fig: A Sectional View of Human Heart


QUESTIONS & ANSWERS
Q.1. Give two significances of transpiration.
Ans. It provides cooling effects to the leaves.
It creates transpiration pull for upward transport of water in plants.
Q. 2. What is excretion? Why is excretion considered as an essential process of life?
Ans: The process of elimination of metabolic waste is called excretion.
It is an essential life process because accumulation of metabolic waste beyond a limit is harmful to the organism and need to be removed.
Q. 3. Describe the process of opening and closing of stomata.
Ans: The opening and closing of stomata is brought about by the changes in the shape of the guard cells ; the stomata remain open when the guard cell swell due to the absorption of water and closed when the guard cell shrink.
Q.4. Why do the arteries have thicker walls than the veins?
Ans: Arteries have thicker walls than the veins in order to carry blood emerging under high pressure from the heart to various organs. While veins collect the blood from different organs and bring it back to the heart which is not under pressure.
Q.5. What is photolysis of water?
Ans. Photolysis is the process of splitting of water molecule into hydrogen and oxygen under the influence of sunlight.
Q.6. Write the three main events occurred during photosynthesis.
Ans. The three events are :
 Chlorophyll of the plant traps the light energy.
 Conversion of light energy into chemical energy and splitting of water molecules into hydrogen and evolution of oxygen.
 Reduction of carbon-dioxide to carbohydrates.
Q.7. How are fats digested in our bodies? Where does this process take place in?
Ans. Bile breakdown larger fat globules into smaller globules and this is known as emulsification. The pancreatic enzyme lipase can only digest emulsified fats into fatty acids and glycerol which are subsequently absorbed .The process occur in intestine.
Q.8. Illustrate the function of capillaries.
Ans. Capillaries are one-celled thickness and arranged in such a way that each and every cell is in contact with blood so that exchange of materials between the blood and surrounding cells takes place across them efficiently.
Q.9. Illustrate the major differences between arteries and veins by giving three points.
Ans.
DIFFERENCE
Arteries Veins
Carry blood from heart to different parts of the body. Carry blood from different parts of the body towards the heart.
Arteries are thick walled. Veins are thin walled.
They lack valves. They possess valves.

Q.10. Give any two point of difference between Trypsin and Pepsin.
Ans. The two point of differences are given below :
Trypsin Pepsin
Trypsin is a protein digesting enzyme present in pancreatic juice. Pepsin is a protein digesting enzyme present in gastric juice.
It is secreted by pancreas and acts in alkaline medium. It is secreted by gastric glands and acts in acidic medium.

Q.11. Discuss in brief the functioning of human heart.
Ans. Human heart is a muscular pumping organ as big as our fist. It has complete four separate chambers, two thin-walled atria and two thick-walled ventricles. There is filling of oxygenated blood from lungs into left atrium and deoxygenated blood from different parts of the body into right atrium. Both the atria contract and blood enter their corresponding ventricles ; Left ventricles pump blood to various organs while right ventricles pump blood to lungs for oxygenation. Thus blood passes through the heart twice during each cycle and this is known as double circulation.