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• Such traits are not inherited by their progeny it is because these are the changes which does not have any effect on DNA of the germ cells. 
• As the traits acquired during life time of an individual does not interfere with the genetic makeup of the DNA of the germ cells, they are not inherited.

• This is because sodium and magnesium are more reactive than carbon. 
• This means that carbon cannot reduce the oxides of these metals. 
• The two metals are above carbon in the reactivity series and thus have a high affinity to oxygen than carbon does and thus cannot be reduced by it.
• These metals are less reactive than the neighbouring alkali metal. 
• Magnesium is less active than sodium; calcium is less active than potassium; and so on. 
• These metals become more active as we go down the column.
• Magnesium is more active than beryllium; calcium is more active than magnesium; and so on.
• Metals of high reactivity; such as sodium, calcium, magnesium, aluminium, etc. are extracted from their ores by electrolytic reduction.
• These metals cannot be reduced using carbon because carbon is less reactive than them.

• Each kidney consists of millions of functional units called nephrons. 
• Urine is formed in the kidneys through a filtration of blood. 
• The urine is then passed through the ureters to the bladder, where it is stored. 
• During urination, the urine is passed from the bladder through the urethra to the outside of the body.

(i) Element (E) Si only form covalent compounds.

(ii) Oxygen with a valency 2. 

(iii) Beryllium is a metal with valency 2. 

(iv) Argon (F) has largest size. 

(v) Helium, Neon, Argon (H, C, F) belongs to inert gas group.

• Aquatic animals take in the oxygen dissolved in water. The amount of dissolved oxygen in water is fairly low compared to the amount of oxygen in the air.
• Therefore, rate of breathing in aquatic organisms is much faster than in terrestrial organisms. 
• The breathing rate of aquatic animals is faster than that of terrestrial animals because the amount of dissolved oxygen in the water in much less than the amount on land, 
• So they have to breathe more in order to get more oxygen.

• The excretory system is the system of an organism's body that performs the function of excretion, the bodily process of discharging wastes.
• The Excretory system is responsible for the elimination of wastes produced by homeostasis.
• There are several parts of the body that are involved in this process, such as sweat glands, the liver, the lungs and the kidney system.
• Every human has two kidneys.
• Each kidney is made up of three sections: the renal cortex, the renal medulla and the renal pelvis.
• The blood arrives at the kidney via the renal artery, which splits into many afferent arterioles.
• These arterioles go to the Bowman's Capsules of nephrons, where the wastes are taken out of the blood by pressure filtration. 
• Peritubular capillaries also surround the nephron so substances can be taken in and out of the blood.
• The renal cortex is the outer layer of the kidney and the medulla is the inner layer of the kidney.
• The renal pelvis takes urine away from the kidney via the ureter.
• Both of the ureters lead the urine into the body's only urinary bladder, which expands and sends nerve impulses when full.
• From there, urine is expelled through the urethra and out of the body.

Correct pH for water will be 7, because it is neutral in nature.

Differences between Acquired Trait and Inherited Trait :

Aluminium sulphate is colourless and it does not undergo any change as iron does not react with it. Copper sulphate solution is blue which changes into green due to the formation of FeSO₄ which is green in colour

A repeater which is a combination of a transmitter, on amplifier and a receiver which picks up signal from the transmitter, amplifies and retransmits it to the receiver.

Large amount of fossil fuels are burnt everyday in power stations to heat up water to produce steam which further runs the turbine to generate electricity. Many thermal power plants are set up near coal or oil field. In these plants, fuel is burnt to produce heat energy which is converted into electrical energy.

(i) Two reasons for the conservation of the environment are : 

(a) To save air, water and soil from pollution. 

(b) To maintain ecological balance in nature. 

(ii) Green dustbins (for biodegradable waste), and blue dustbins (for non-biodegradable waste) are meant for proper disposal of waste without wasting time and energy in segregating the biodegradable and non-biodegradable wastes.

The lining of alimentary canal has muscles that contract rhythmically in order to push the food forward. These are peristaltic movements.

Large number of spores are produced in each sporangium which can easily help the Rhizopus to spread.

Since ventricles have to pump blood into various organs, they have thicker muscular walls than atria do.

Three techniques that have been developed to prevent pregnancy are : 

(i) Barrier method : Physical methods such as condom, diaphragm and cervical caps are used to prevent entry of sperms in females. 

(ii) Chemical methods : Drugs such as oral pills and vaginal pills are used by females. 

(iii) Surgical methods : Vasectomy in males and tubectomy in females. 

Chemical techniques are not meant for males. 

The use of these techniques helps in controlling population explosion thus providing better living conditions. 

It helps in keeping proper gap between siblings thus gives better health to mother as well as children.

Three techniques that have been developed to prevent pregnancy are :
(i) Barrier method : Physical methods such as condom, diaphragm and cervical caps are used to prevent entry of sperms in females.
(ii) Chemical methods : Drugs such as oral pills and vaginal pills are used by females.
(iii) Surgical methods such as vasectomy in males and tubectomy in females. Chemical techniques are not meant for males. The use of these techniques helps in controlling population explosion thus providing better living conditions.
It helps in keeping proper gap between siblings thus gives better health to mother as well as children. 

(a) Taking smack is considered as abuse because it is highly addictive drug. It is a depressant and slows down body functions. It can cause psychologicai and physical dependence. It causes constipation, nausea,/vomiting, lightheadedness, histamine launch, itching, xerostomia, excessive sweating, somnolence (sleepy or perhaps tired sensation), hypotension (reduced blood pressure), inspiration (sense of intensive satisfaction, pleasure, excitement along with joy), inflammation of the liver organ. 

(b) Chemical name of smack is diacetylmorphine. Its source plants is Papaver somniferum (poppy). 

(c) Syringe and needles are used to inject drugs usually intravenously so that the abusers can have the effects of drug very quickly and have a stronger effect. This mode of drug administration ensures availability of drug in higher amounts in the body which has increased chances of overdose which has proven fatal in most of the cases. Chances of addiction are higher in these cases. Infected syringes also predispose the user to catch diseases like AIDS. 

The difference in temperature of water at the surface of ocean and at deeper levels (at depths up to 2 km) should be 20°C or more.

Mercury is a metal which is liquid at room temperature. Iodine is a non-metal which is lustrous.

Pollen grain –

(i) It is produced by anthers
(ii) It Contains male germ cells.
Ovule – 

(i) It is produced by ovary
(ii) It contains female germ cells.

The receptors in our body collect information about changes in the environment around us in the form of stimuli, e.g., photoreceptors, gustatoreceptors, olfactory receptors. These receptors then passes the information in the form of nerve impulses to central nervous system (spinal cord and/or brain) where message is interpreted and appropriate instructions are sent to effectors (glands or muscles) which reveal responses. When receptors do not function normally, the environmental stimuli are not able to create nerve impulses and body does not respond. For example, if our gustatory receptors located in the tongue do not work properly we will not perceive the taste of food such as sour, sweet, salty or bitter.

(i) The glass slab should be perfectly rectangular with all its faces smooth.
(ii) While fixing the pins P₁ and P₂ or the pins P₃ and P₄, care should be taken to maintain a distance of about 5 cm between the two pins. This would help in tracing the direction of incident ray and that of emergent ray with greater accuracy.

The development which can be maintained for a longtime without undue damage to the environment.
Two objectives :
(i) To provide the economic well being to the present and future generation.
(ii) To maintain a healthy environment and life support system.

This is because of scattering of light. Light from the Sun near the horizon passes through larger distance in the earth’s atmosphere before reaching our eyes. So, most of the blue light and shorter wavelengths are scattered away by the particles. Therefore, the light that reaches our eyes is of longer wavelengths. This gives rise to the reddish appearance. But during the day shorter wavelengths are scattered more by molecules of air and the scattered blue light enters our eyes.

The development which can be maintained for a longtime without undue damage to the environment is known as sustainable developments. 

Two objectives : 

(i) To provide the economic well being to the present and future generation. 

(ii) To maintain a healthy environment and life support system.

(i) Metals lie on the left-hand side of the Periodic table whereas non-metals are found on the right-hand side. The element A is in group 17. Group 17 is on the right side of the Periodic table. Thus, element A is a nonmetal
(called halogen).
(ii) The chemical reactivity of non-metals decreases on going down in a group. In group 17, the chemical reactivity decreases on going down in a group. So, element C is less reactive than A.
(iii) The atomic size decreases in moving from left to right along a period. So, atom C will be smaller in size than B.
(iv) The element A of group 17 has 7 valence electrons. So, it will gain one electron to form a negatively charged ion (A–). The negatively charged ion is called an anion. So, element A will form an anion.

(i) Calcium Phosphate Ca₃(PO₄)₂
(ii) Bacteria present in the mouth produce acids by degradation of sugar and food particles left after eating chocolate and sweets. This causes damage to the teeth. Cleaning the mouth using a toothpaste, which is basic in nature, can prevent tooth decay.

(i) Elements of the same group have similar properties because of the equal number of valence shell electrons.
(ii) Atomic size decreases in a period with increase in atomic number. This is due to increase in nuclear charge or increase in force of attraction between nucleus and electrons.
(iii) Mg: 2,8,2 (KLM Shell). It belongs to 3rd period. Ca: 2,8,8,2 (KLMN Shell). It belongs to 4th period.

Feedback mechanism of hormones is the mechanism that controls the flow of hormones

(i) Inverted image 

(ii) Magnified 

(iii) Concave mirror 

(iv) Real image

Three differences between metals and non-metals on the basis of chemical properties : 

Feedback mechanism of hormones is the mechanism that controls the flow of hormones.

The feedback mechanism of hormones is the mechanism through which the balance of hormone in the blood/body is maintained. The increase or decrease in the concentration of that hormone can either stimulate the secretion of that particular hormone or inhibit the hormone secretion. This is called feedback.

For Example, When we eat carbohydrate rich food, the glucose level in the blood increase. As the Blood Glucose level rise, the pancreas will secrete Insulin. This Insulin will signal the cells to take up the blood glucose. Hence The glucose level decrease in the blood. 

There can be two type of feedback. One is called Positive feedback, and other is called negative feedback. The positive feedback stimulates the secretion or production of the hormone. On the counterpart, the negative feedback inhibits the secretion of the hormone.

(i) The water reservoir is a pond in Figure (a) and underground water body in Figure (b).
(ii) Figure (b) has more advantage than Figure (a) because the advantages of water stored in the ground is more than water stored in a pond. For
example:
(a) It does not evaporate.
(b) It spreads out to recharge wells.
(c) Provides moisture for vegetation over a wide area.
(d) It is protected from contamination by animal and human wastes.
(e) It prevents breeding of insects.

Advantages of sexual reproduction

(i) In sexual reproduction, more variations are produced. Thus, it ensures survival of species in a population.

(ii) The new formed individual has characteristics of both the parents.

Asexual reproduction:

(i) Asexual reproduction is the production of progeny from a single parent without involving the fusion of gametes; the reproductive bodies can be somatic cell/tissue or gametes. 

(ii) The absence of gametogenesis and syngamy results in the production of genetically identical offsprings (clones) that lack any genetic variations and thus, do not support evolution.

People should adopt following changes in habit:
(a) Dispose household waste, chemical waste and hospital waste in a landfill.
(b) Broken plastic articles such as buckets, bowls, cups, plates, etc., should be sent to plastic processing factories.

Difference between biodegradable and non-biodegradable substances :

Two methods of disposal of non-biodegradable waste are :
(i) Recycling: The wastes are treated and same value materials are extracted for reuse.
(ii) Incineration: Medical and toxic waste are burnt at high temperature in incineration. Incinerators transform the waste into ashes.

Sexual reproduction promotes diversity of characters in the offsprings. It results in new combination of genes.

(i) Decomposition Reaction: A decomposition reaction is a type of reaction in which a single compound breaks down into two or more element or a new compound.
(ii) Oxidation Reaction: Oxidation is the loss of electrons during a reaction by a molecule, atom or ion.
(iii) Displacement Reaction: A reaction in which the most reactive element displaces the less reactive element from its compound.
(iv) Displacement Reaction: More reactive metal displaces less reactive metal from its salt solution.
(v) Neutralisation Reaction: A neutralization reaction is when an acid and a base react to form water and a salt and involves the combination of H⁺ ions and OH^– ions to generate water.

(i) Specialised tips of some nerve cells which receive information from the surroundings.
Location: Sense organs
Gustatory receptor: detect a taste
Olfactory receptor: detect a smell
(ii) The information acquired at the end of the dendritic tip of a nerve cell sets off a chemical reaction that creates an electrical impulse, which travels to the cell body, then along the axon to its end, releases some chemicals, across the synapses.

Racemic mixture is optically inactive due to the fact that in equimolecular mixture of enantiomeric pairs, the rotation caused by the molecules of one enantiomer is cancelled by the rotation caused by the molecules of other enantiomer.

This type of compensation of optical rotation in a racemic mixture is called as external compensation.

This is the reason why racemic mixture becomes optically inactive.