It refers to protection of plants and animals, natural areas, important buildings from the damaging effects of human activity.

Instructions to be given by parents and teachers to the child are.
(i) Do not talk to any suspected person or strangers and to maintain a distance.
(ii) Not to be alone with any unknown person.
(iii) To be careful while traveling alone public or private transport.
(iv) Not to receive any money, toys, gifts or chocolates from person known or unknown to them without the knowledge of their parents,
(v) Not to allow any known or unknown person to touch them.

Methods of plant breeding to develop high yielding varieties are given below:
(i) Introduction of new varieties of plants.
(ii) Selection.
(iii) Polyploidy breeding.
(iv) Mutation breeding.
(v) Hybridization.

The device which helps in explaining the concepts easily through pictures is known as 'Visual Communication Device: For example photos, audio-visuals, drawings, animations all these can be created easily with the help of computer. Cinema is a good example for 'Visual Communication Device'.

Compound (A) with molecular formula C₂H₆O is ethanol C₂H₅OH.

A plant fossil is any preserved part of a plant that has died long back. Fossils may be a prehistoric impression that may be hundred to millions of years old. Majority of the plant fossils are disarticulated parts of plants, it is rare to find plants to be preserved as whole.

Myelin sheath of a neuron acts as insulator and ensures rapid transmission of nerve impulses.

(i) Temperature of the substance rises.
(ii) The substance may change its state from solid to liquid or liquid to gas.
(iii) The substance will expand when heated.

(i) Mie scattering takes place when the diameter of the scatterer is similar to or larger than the wavelength of the incident light. It is also an elastic scattering. The amount of scattering is independent of wave length.
(ii) Mie scattering is caused by pollen, dust, smoke, water droplets, and other particles in the lower portion of the atmosphere.

In SONAR, by measuring the change in the frequency between the sent signal and received signal, the speed of marine animals and submarines can be determined.

When iron is dipped in con. HNO₃ it becomes chemically passive or inert due to the formation of a layer of iron oxide (Fe₃O₄) on its surface.

(i) In the body cells of sexually reproducing organisms, the chromosomes generally occur in pairs. This condition is called diploid (2n).
(ii) The gametes produced by the organisms contain a single set of chromosomes. Hence, the gametes are said to be haploid (n).

The three cells in the micropylar end of a ovule in which middle one is the egg with two synergids on either side is called egg apparatus.

The door can be easily opened or closed if we apply the force at a point far away from the fixed edge.
(i) In this case, the effect of the force we apply is to rotate the door about the fixed edge.
(ii) This rotational effect of the applied force is more about the 'axis of rotation' when the distance between the fixed edge and the point of application of force is more.

(i) The female reproductive system of rabbit consists of a pair of ovaries which are small ovoid structures. They are located behind the kidneys in the abdominal cavity.
(ii) A pair of oviducts opens into the body cavity by a funnel shaped opening from each side of the ovary.
(iii) The anterior part of the oviduct is the fallopian tube. It leads into a wider tube called the uterus.
(iv) The uterus join together to form a median tube called vagina.
(v) The common tube is formed by the union of urinary bladder and the vagina and is called the urinogenital canal or vestibule. It runs backwards and opens to the exterior by a slit-like aperture called vulva.
(vi) A pair of Cowper's gland and perineal gland are the accessory glands present in the female reproductive system

(i) The dorsal and ventral surfaces of a dicot leaf can be clearly distinguished
(ii) The dorsal surface is darker is appearance and the ventral surface is lighter.
(iii) This is due to distribution of palisade parenchyma below the upper epidermis which as rich in chloroplasts.
(iv) Hence the dicot left is described as dorsiventral.

Yes. Sun is the ultimate source of energy. Directly or indirectly all forms of energy are got from solar energy examples are discussed below:
(i) Fossil fuels are formed due to the burial of plants and animals.
(ii) Renewable sources of energy are also got indirectly from the sun as follows.
(a) The water in lakes, rivers, evaporates due to solar energy and forms clouds. This brings rainfall.
(b) Wind energy is due to uneven heating of earth's surface by the sun rays.
(c) Solar energy is dependent on sunlight directly.

When smoke is inhaled the chemicals get absorbed by the tissues and cause the following harmful effects.
(i) Benzopyrene and polycyclic hydrocarbons present in tobacco smoke is carcinogenic causing lung cancer.
(ii) Causes inflammation of throat and bronchi leading to conditions like bronchitis and pulmonary tuberculosis.
(iii) Inflammation of lung alveoli decrease surface area for gas exchange and cause emphysema.
(iv) Carbon monoxide of tobacco smoke binds to hemoglobin of RBC and decreases its oxygen carrying capacity causing hypoxia in body tissues.
(v) Increased blood pressure caused by smoking leads to increased risk of heart disease.
(vi) Causes increased gastric secretion which leads to gastric and duodenal ulcers.
(vii) Tobacco chewing causes oral cancer (mouth cancer).

Selection is one of the oldest methods of plant breeding in which individual plants or groups of plants are sorted out from a mixed population based on the morphological characters.
Methods of selection:
There are three methods of selection. They are
a) Mass selection
b) Pure line selection
c) Clonal selection
a) Mass selection:
(i) Seeds of best plants showing desired characters are collected from a mixed population.
(ii) The collected seeds are allowed to raise the second generation. This process is carried out for seven or eight generations.
(iii) At the end, they will be multiplied and distributed to the farmers for cultivation. Eg: Groundnut varieties like TMV-2 and AK-10.
b) Pureline selection :
(i) Pureline is "the progeny of a single individual obtained by self breeding":
(ii) This is also called as individual plant selection. In pureline selection large numbers of plants are selected from a self pollinated crop and harvested individually.
(iii) Individual plant progenies from them are evaluated separately. The best one is released as a pureline variety.
(iv) Progeny is similar both genotypically and phenotypically.
c) Clonal selection:
(i) A group of plants produced from a single plant through vegetative or asexual reproduction are called clones.
(ii) All the plants of a clone are similar both in genotype and phenotype.
(iii) Selection of desirable clones from the mixed population of vegetatively propagated crop is called clonal selection.

(i) Pictures and Audio-Visuals give us more understanding than teaching and writing on black board. So, any visual representation of the concepts would help us to understand better and make teaching simple
(ii) Yes. Visual Communication helps us to easily conceptualize complicated theorems and concepts. When the teacher shows pictures / videos that represent the concept, we would easily relate to its application and firmly understand the concept without any mis-perception
(iii) Pictures, Audio-Visuals, animations provide additional information and helps us to easily correlate the concepts. We could easily remember the visuals than black board writing, and visualize it, so that we do not forget and we could easily recollect at the time of examination.

Organic compounds are classified into two types as follows:
(i) Acyclic or Open chain compounds:
These are the compounds in which the carbon atoms are linked in a linear pattern to form the chain. If all the carbon atoms in the chain are connected by single bonds, then the compound is called as saturated. If one or more double bonds or triple bonds exist between the carbon atoms, then the compound is said to unsaturated.

(ii) Cyclic Compounds:
Organic compounds in which the chain of carbon atoms is closed or cyclic are called Cyclic compounds. If the chain contains only carbon atoms, such compounds are called carbocyclic compounds. If the chain contains carbon and other atoms like oxygen, nitrogen, sulphur, etc., these compounds are called heterocyclic compounds. Carbocyclic compounds are further subdivided into alicyclic and aromatic compounds. In alicyclic compounds, the carbon cycle contains only single bonds whereas aromatic compounds contain one or more benzene rings (ring containing alternate double bonds between carbon atoms).
E.g:

When the thyroid gland fails to secrete the normal level of hormones, the condition is called thyroid dysfunction. It leads to the following conditions.
Hypothyroidism: It is caused due to the decreased secretion of the thyroid hormones. The abnormal conditions are simple goitre, cretinism and myxoedema.
Goitre:
(i) It is caused due to the inadequate supply of iodine in our diet.
(ii) This is commonly prevalent in Himalayan regions due to low level of iodine content in the soil.
(iii) It leads to the enlargement of thyroid gland which protrudes as a marked swelling in the neck and is called as goitre.
Cretinism:
(i) It is caused due to decreased secretion of the thyroid hormones in children.
(ii) The conditions are stunted growth, mental defect, lack of skeletal development and deformed bones. They are called as cretins
 Myxoedema:
(i) It is caused by deficiency of thyroid hormones in adults.
(ii) They are mentally sluggish, increase in body weight, puffiness of the face and hand, oedematous appearance.
Hyperthyroidism:
(i) It is caused due to the excess secretion of the thyroid hormones which leads to Grave's disease (Exopthalmic goitre).
(ii) The symptoms are protrusion of the eyeballs (Exopthalmia), increased metabolic rate, high body temperature, profuse sweating, loss of body weight and nervousness.

Use and disuse theory
(i) Lamarck's Use and Disuse theory states that if an organ is used constantly, the organ develops well and gets strengthened.
(ii) When an organ is not used for a long time, it gradually degenerates.
(iii) The ancestors of Giraffe were provided with short neck and short forelimbs.
(iv) Due to shortage of grass, they were forced to feed on leaves from trees. The continuous stretching of their neck and forelimbs resulted in the development of long neck and long forelimbs which is an example for constant use of an organ.
(v) The degenerated wing of Kiwi is an example for organ of disuse.

Reversible Reactions: A reversible reaction is a reaction that can be reversed, i.e., the products can be converted back to the reactants. A reversible reaction is represented by a double arrow with their heads in the direction opposite to each other. Thus, a reversible reaction can be kept

Explanation: The compound 'AB' undergoes decomposition to form the products 'A' and 'B'. It is the forward reaction. As soon as the products are formed, they combine together to form 'AB': It is the backward reaction
PCl₅(g) ⇌ PCl₃(g) + CI₂(g)
Irreversible Reactions: The reaction that cannot be reversed is called irreversible reaction. Consider the combustion of coal into carbon dioxide and water.
C_(s) + O_2(g) ⟶ CO_2(g)+ Heat
Coal oxygen Carbon dioxide
In this reaction, solid coal burns with oxygen and gets converted into carbon dioxide gas and water. As the product is a gas, as soon as it is formed it escapes out of the reaction container. It is hard to decompose a gas into a solid. Thus, the backward reaction is not possible in this case. So, it is an irreversible reaction

(i) Atom bomb is based on the principle of uncontrolled chain reaction.
(ii) In an uncontrolled chain reaction, the number of neutrons and the number of fission reactions multiply almost in a geometrical progression.
(iii) This releases a huge amount of energy in a very small time interval and leads to explosion.
Structure:
(i) An atom bomb consists of a piece of fissile material whose mass is sub critical.
(ii) This piece has a cylindrical void. It has a cylindrical fissile material which can fit into this void and its mass is also sub critical.
(iii) When the bomb has to be exploded, this cylinder is injected into the void using a conventional explosive.
(iv) Now, the two pieces of fissile material add up to form super critical mass which leads to an explosion.
(v) During this explosion tremendous amount of energy in the form of heat, light and radiation is released.
(vi) A very high temperature and pressure are experienced in fraction of second along with hazardous radiation like ૪ rays which adversely affect the living creatures.

Statement of Boyle's law:
When the temperature of a gas is kept constant, the volume of a fixed mass of gas is inversely proportional to its pressure.
∴ P α 1/V

In other words, for an invariable mass of a perfect gas, at constant temperature, the product of pressure and volume is a constant.
Pressure x Volume = constant
PV = constant

Yes. Hirudin is used as an anticoagulant in medical science.

Froth floatation:
(i) Principle: This process depends on the preferential wettability of the ore with oil (pine oil) and the gangue particles by water. Lighter ores, such as sulphide ores, are concentrated by this method. E.g. Zinc blende ZnS

(ii) Method: The crushed ore is taken in a large tank containing oil and water and agitated with a current of compressed air. The ore is wetted by the oil and gets separated from the gangue in the form of froth. Since the 4 ore is lighter, it comes on the surface with the froth and impurities are left behind

Based on the position of centromere, the chromosomes are classified as Telocentric, Acrocentric, Submetacentric andMetacentric.
(i) Telocentric - The centromere is found on the proximal end. They are rod shaped chromosomes.
(ii) Acrocentric - The centromere is found at the one end with a short arm and long arm. They are also rod - shaped chromosomes.
(iii) Submetacentric - The centromere is found near the centre of the chromosome. Thus forming two unequal arms. They are J

(iv) Metacentric - The centromere occurs in the centre of the chromosome and form two equal arms. They are V shaped chromosomes.

A small family is a happy family. If there are one or two children in a family, the parents can afford to give them good education, food, personal care and other facilities required for them to grow into healthy and happy individuals. Thus it is important for parents to plan a small family which will also build a healthy nation.

Applications of Avogadro's hypothesis
(i) It explains Gay-Lussac's law.
(ii) It helps in the determination of atomicity of gases.
(iii) Molecular formula of gases can be derived using Avogadro's law.
(iv) It determines the relation between molecular mass and vapour density.
(v) It helps to determine Gram molar volume of all gases (i.e. 22.4 lit at S.T.P)

Given
The energy released from one atom = 2.9 x 10^-8 J
For 350 atoms, E = 2.9 x 10^-8 x 350
To find: mass, m = ?
E = mc²,
\(m=\frac { E }{ { c }^{ 2 } } =\frac { 2.9\times { 10 }^{ 8 }350 }{ { ({ 3\times 10 }^{ 8 }) }^{ 2 } } \)
mass, m=1.13 x 10^-22kg

The coefficient of linear expansion,
α_L =24 K^-1
The coefficient of cubical expansion,
α_v =3α_L= 3 x 24
= 72 K^-1
The initial temperature, T₁ = 303 K
The initial volume, V₀ = 0.3 m³
The final volume, V₁ = 0.35 m³
Change in volume ΔV = 0.35 - 0.30
= 0.05 m³
To find: The final temperature T₂= ?
ΔV = α_v. V₀ (ΔT)
0.05 = 72 x 0.3 x (T₂ - 303)
0.05 = 21.6 (T₂ - 303)
= 21.6 T₂ - 6544.8
21.6 T₂ = 6544.8 - 0.05
T₂ =\(\frac { 6544.8 }{ 21.6 } \)
Final temperature, T₂ = 303K

Refractive index of diamond with respect to kerosene
=\(=\frac{\text { Refractive index of diamond }}{\text { Refractive index of kerosene }}\)
=\(\frac { 3.42 }{ 1.44 } \)=1.68

Given
Air temperature = 23°C
Velocity of sound in air, Vs = (331.4 + 0.61T) ms^-1
= 331.4 + 0.61 x 23
= 331.4 +13.8
V_s = 345.2 ms^-1

Mass of body 1, m₁ = 50 kg
Mass of body 2, m₂ = 10kg
Distance, R = 10m
Universal gravitation
constant, G = 6.67 x 10^-11 Nm² kg^-2
To find :Force of gravitation, F =\(\frac { G{ m }_{ 1 }{ m }_{ 2 } }{ { R }^{ 2 } } \)
F=\(\frac { 6.67\times 10^{ -11 }\times 50\times 10 }{ 10^{ 2 } } \)
Force, F = 33.35 x 10^-11 N

Given :
Potential V = 110 V
Current passing through bulb, I = 0.9 A
Time, t = 12h / day
For 30 days, time t = 12 x 30
= 360h
To find: Energy consumed, E = ?
Solution
E = VIt
= 0.9 x 110 x 12 x 30
= 35.64 kwh
Energy, E = 35.64 kwh

Atomic masses of C= 12, O= 16
Gram molecular mass of CO₂ = 1(C) + 2(O) = 1(12) + 2(16) = 12 + 32 = 44
Gram molecular mass of CO₂ = 44g.

An uncontrolled nuclear chain reaction can occur only when the uranium is greater than a certain minimum size. This is called critical size.

(a) The most reactive element is 'B' as it has displaced both 'A' and 'C' from their compounds
(b) The least reactive element is 'C' as it has been replaced by both 'A' and 'B'.

The colloidal solution is an example in which solid acts are the dispersion medium while liquid as the dispersed phase. It is also called gel. Reason for the choice. On pressing butter, liquid drops come out of it leaving behind a solid. This clearly shows the butter is a gel.

Heat produced per unit time = V^2/R
Now slope of V-I graph = R (resistance of wire).

Since slope of V-I graph for wire A is greater than the slope of V-I graph for wire B, therefore, resistance of wire A is greater than the resistance of wire B, Hence, more heat will be produced per unit time in wire B than in wire A.

Molecular (or Formula)
mass of pure NaCl = Atomic mass of Na + Atomic mass of CI
= 23 + 35.5 = 58.5 u
Percentage of chlorine in pure NaCl = \(\frac{35.5}{58.5}\) x 100 = 60.6
Now, if chlorine is 60.6 parts, NaCl = 100 parts
if chlorine is 45.5 parts, NaCl = \(\frac{45.5}{60.6}\) x 100 = 75
Thus, percentage of pure NaCl = 75%