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3201.

Question : How many Chambers are presentin our body?

Answer»

2
4
3
1

Answer :B
Discussion
3202.

Question : How many cells are present in young globular embryo of dicots ?

Answer»

SOLUTION :SIXTEEN
Discussion
3203.

Question : How many cells are present in suspensor ?

Answer»

SOLUTION :SIX to TEN CELLS
Discussion
3204.

Question : How many biodiversity spots are reported all over the World ?

Answer»

30
34
35
40

Solution :34
Discussion
3205.

Question : Write a note on Von Helmont's experiment focusing on how he concluded that water was important for growth in plant body mass?

Answer»

SOLUTION :1) A Belgian scientist Jan Baptist Von Helmont (1648) conducted an experiment that CONTINUED for five YEARS .
2) Von Helmont took a small willow tree and planted it in a large pot with soil.
3) Before he did this, he carefully measured the mass of the dry soil and mass of the tree.
4) He covered the soil with a lid so that nothing could fall on to the SURFACE of the soil and add to its mass.
5) There were holes in the lid so that the tree could grow out of the soil and that air and water could reach the roots.
6) Von Helmont left the tree for five years, giving it only rain water to absorb.
7) At the end of five years he measured the mass of the tree and the mass of the drysoil for a second time.
8) The results of this expe f iment are shown below .

9) This experiment changed the belief of hundreds of years . This is because Von Helmont arrived at a result that
a) The substances needed for the growth of a plant do not come from the soil only .
b) The plant grow because of the water it gets.
Discussion
3206.

Question : How is variation necessary for existence of each species ? Explain with example.

Answer»

Solution :The population of organisms fill niches in the ecosystem, using their ability to reproduce. During reproduction the consistency of DNA copying is important for the maintenance of body design. This allow the organism to use that particular niche. Thus, the stability of populations of species in particular niches are maintained by the process of reproduction.
There are CHANCES that niches can CHANGE due to reasons beyond the control of organisms. The changes may be in form of fluctuations in temperature of the earth, varying water level, METEORITE hits or any other ecological imbalance.
Under such conditions any alteration in the particular kind of niche is surely going to hit the population of reproducing organisms. The affected population may be wiped out due to this. Few individuals of this population, with some variations in their DNA may survive.
Example: A population of bacteria LIVING in water with moderate temperature. Because of global warming the temperature of water may be increased, many bacteria may DIE, but few temperature resistant bacteria may survive and grow further.
Thus, variation is useful for the survival of species.
Discussion
3207.

Question : How is the structure of DNA organized? What is the biological significance of DNA?

Answer»

Solution :DNA is the heridetary material, as it contains the genetic information. It is a large molecule consisting of millions of nucleotides, so it is called a polynucleotide. Each nucleotide consists of three components.
(a) A sugar molecule - Deoxyribose sugar
(b) A nitrogenous base - There are TWO types of nitrogenous base in DNA they are
(i) purines (Adenine and Guanine)
(ii) Pyrimidines (Cytosine and Thymine)
(c ) A phosphate group - The poly nucleotide chains from a double helix, Nitrogenous bases in the centre are linked to sugar-phosphate units, which FORM the backbone of the DNA. Pairing between the nitrogenous bases is very specific and is always between PURINE and pyrimidine, linked by hydrogen bonds.
Adenine (A) links Thymine (T) with two hydrogen bonds [A=T]. Cytosine (C ) links Guanine (G) with three hydrogen bonds `(C-=G)`. The hydrogen bonds between the nitrogenous bases make the DNA molecule stable. The nucleotides in a helix are joined together by PHOSPHODIESTER bonds.
Biological significance of DNA:
(i) It is responsible for the transmission of heredity information from one generation to next generation.
(ii) It contains information required for the formation of proteins.
(III) It controls the developmental process and life activities of an organism.
Discussion
3208.

Question : How is the small intestine designed to absorb digested food?

Answer»

Solution :The SMALL intestine is the MAIN region for the absorption of digested FOOD. The inner LINING of small intestine has millions of tiny finger-like projections called villi. The presence of villi gives the inner walls of the small intestine a very large SURFACE area for absorption of digested food. The villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body.
Discussion
3209.

Question : How is the sperm genetically different from the egg?

Answer»

Solution :Sperms contain EITHER X or Y chromosome WHEREAS an egg will ALWAYS have an X chromosome.
Discussion
3210.

Question : How is the small intesting designed to absorb digested food ?

Answer»

Solution :The inner lining of the small intestinghas numerous finger-likeprojections called villi which increases the surface area for ABSORPTION of DIGESTED food. The villi are richly suppliedwith blood vesselswhich transport theabsorbed food to each and every CELL of the body where it is utilised for OBTAINING, buliding up NEW tissues and the repair of the old tissues .
Discussion
3211.

Question : How is the sex of the child determined in human beings?

Answer»

Solution :In HUMAN BEINGS, sex of the child DEPENDS UPON which kind of male gamete fertilises the female gamete. If sperm carrying X CHROMOSOME fertilises the ovum carrying X chromosome, then the child born will be a girl. If a sperm carrying Y chromosome fertilises the ovum which carries X chromosome, then the child born will be a boy.
Discussion
3212.

Question : How is the sex of the child determined in human beings ?

Answer»

Solution :HUMAN beings have 22 pairs of autosomes and one pair of SEX chromosome. This pair is XX in females and XY in males. Thus, if parents are

This CROSS shows that females produce all similar gametes, carrying X chromosome. While males produce two types of gametes 50% with X and 50% with Y chromosome. Hence, when a female gamete fuses with SPERM with X chromosome, a female CHILD is produced and when it fuses with sperm with Y chromosome, a male child is produced. So, it is male that determines the sex of the child.
Discussion
3213.

Question : How is the sex of child determined in human beings ?

Answer»

Solution :Determination of the sex of child. Sex chromosomes determine sex in HUMAN beings. In males, there are `44 + XY` chromosomes, WHEREAS, in female there are `44 + XX` chromosomes. Here, X and Y chromosomes determine sex in the human beings.
TWO types of gametes are formed in male, one type is having `50%`, X-chromosome, whereas the other type is having Y-chromosome. In female, gametes are of one type and contain X-chromosome. The females are homogametic. If male gamete having Y-chromosome (androsperm) undergoes fusion with female gamete having X-chromosome the zygote will have XY chromosomes and this gives rise to male child.
If the male gamete having X-chromosome undergoes fusion with female gamete having X-chromosome, the zygote will be having XX-chromosome and this gives rise to female child.
Discussion
3214.

Question : How is the sex of child determined in human beings?

Answer»

SOLUTION :
Discussion
3215.

Question : How is the process of pollination different from fertilization?

Answer»

SOLUTION :POLLINATION is the transfer of pollen grains from anther to stigma whereas FERTILISATION is the FUSION of male and FEMALE gamete.
Discussion
3216.

Question : How is the process of pollination different from fertilisation?

Answer»

SOLUTION :Pollination is the transfer of pollen grains from the anther of a stamen to the stigma of a carpel. The pollen grains are transferred by agents, such as insects, birds, man, wind and water. It occurs only in plants. However, fertilisation in plants is the fusion of pollen grains, nuclei (male gamete with the egg cell) and SECONDARY nucleus of embryo sac to forin DIPLOID zygote and TRIPLOID endosperm nucleus, respectively. Fertilisation in animals is defined as the fusion of a male gamete (sperm) with a female gamete (ova) to form a zygote during sexual reproduction.
Discussion
3217.

Question : How is the process of pollination different from fertilisation ?

Answer»

SOLUTION :DISTINCTION between POLLINATION and FERTILISATION :
Discussion
3218.

Question : How is the process of making variants be speed up through the sexual mode of reproduction ? Explain.

Answer»

Solution :The single cell divides to form two cells and it involves copying of DNA as well as of the cellular apparatus. The mechanism of DNA copying is not absolutely accurate. Sexual REPRODUCTION involves fusion of male and female gametes. The variation GENERATED due to DNA copying during gamete formation moves on to the next GENERATION.
Each new variation is made in a DNA COPY that already has variations accumulated from PREVIOUS generations. Thus, two different individuals in a population would have quite different patterns of accumulated variations. Combining variations from two or more individuals would thus create new combinations of variants.
The sexual mode of reproduction incorporates such a process of combining DNA from two different individuals during reproduction.
Discussion
3219.

Question : How is the number of chromosomes and the DNA content maintained constant generation after generation sexually reproducing organisms ?

Answer»

Solution :For sexually reproducing organisms, each NEW generation is the combination of the DNA copies from two parents. So, each new generation gets twice the amount of DNA from parents.
But this does not happen because, for sexually reproducing organisms gamete producing cells undergo MEIOSIS and hence chromosome NUMBER is reduced to half. Thus, there is half the amount of DNA as compared to the non-reproductive cells of body. Meiosis a type of cell division plays an important role for this. Thus, when two haploid germ cells from two INDIVIDUALS combine during sexual REPRODUCTION they form diploid zygote making number of chromosomes and the DNA content in the new generation same again.
Discussion
3220.

Question : How is the movement of leaves of the sensitive plant different form the movement of a shoot toward light ?

Answer»

Solution :Movement of leaves of SENSITIVE plant are nastic MOVEMENTS that OCCUR DUE to TURGOR change while movement of shoot towards light is trophic movement.
Discussion
3221.

Question : How is the equal genetic contribution of male and female parents ensured in the progeny?

Answer»

Solution :In human beings, every somatic cell of the body contain 23 pairs are known as autosomes and the remaining one pair is known as SEX chromosomes repesented as XandY Female have two X chromosomes and males have one Xand Y chromosome each. The GAMETE RECEIVES half of the chromosome. There fore the male gametes have 22 autosomes and EITHER X or Y chromosomeThe female gamete, on the other hand, has 22autosomes and X chromosome During reproduction the male and female gametes fuse and thus PROGENCY receives 22 autosomes and one X or Y chromosomes from male parent and 22 autosomes and one X chromosomes from the female parent
Discussion
3222.

Question : How is the equal genetic contribution of male and female parents ensured in the progeny ?

Answer»

Solution :
In this cross, while the F1 expresses dominant trait of both the parents, the F2 expresses all FOUR traits. These traits from two different parents are inherited independent of each other. Thus, it proves that both parents CONTRIBUTE equal genetic MATERIAL.
Discussion
3223.

Question : How is the entry of food prevented in the respiratory tract ?

Answer»

SOLUTION :During swallowing a cartilaginous flap like structure called EPIGLOTTIS covers the GLOTTIS and PREVENTS the entry of FOOD into respiratory tract.
Discussion
3224.

Question : How is the digestive system of rabbit suited for herbivorous mode of feeding?

Answer»

Solution :Caecum is a THIN walled SAC present at the JUNCTION of small INTESTINE and large intestine. It contains bacteria, that helps in digestion of cellulose. So the digestive system of RABBIT is suited for herbivorous mode of feeding.
Discussion
3225.

Question : How is the circulatory system designed in leech to compensate the heart structure?

Answer»

Solution :The circulation in Leech is Haemocoelic system. There are no true blood vessels. The blood vessels are replaced by channels called Haemocoelic channels or canals, filled with blood like fluid. The coelomic fluid contains Haemoglobin.
There are four LONGITUDINAL channels. One channel lies above (dorsal) to the Alimentary canal be helow (ventral) to the Alimentary canal. The other TWO channels lie on EITHER (lateral) SIDE of the Alimentary canal, which serves as a heart and have inner valves. All the four channels are connected together posteriorly in the `26^(th)` segment. Thus the circulatory system is DESIGNED in Leech to compensate the heart structure.
Discussion
3226.

Question : How is the amount of urine produced regulated?

Answer»

Solution :The AMOUNT of urine produced depends on how much of excess water there is in the body, and on how much of dissolved waste there is to be EXCRETED. More water and dissolved waste in the body will produce more urine and on the other HAND, less water and less dissolved waste will therefore, produce less urine.
Discussion
3227.

Question : How is the amountof urine produced regulated ?

Answer»

SOLUTION :Total urine excreted PER DAY is about 1.6 - 1.8 litres . The quantity increases withlargeintake offluids and decreases withlesser intakethe them. If the amountof water anddissolved wastes in bodyare more thanprescribed limit the amountof urinewill be more and if water and dissolved wastes are less in BODY, the amount of urine willbe less.
Discussion
3228.

Question : The acid formed when CO_2 is dissolved in water-

Answer»

Solution :1) There are two major phases found in photosynthesis. They are light reaction and dark reaction.
2) Light reaction : The light reaction takes place in chlorophyll containing thylakoids called grana of chloroplasts .
3) The chlorophyll on exposure to light energy becomes activated by absorbing photons.
4) The energy is used in splitting the water molecule into its two component ions.
`H_2O to H^(+)+OH^(-)`
This is known as photolysis of water.
5) `OH^(-)` ions through a series of steps PRODUCE water and oxygen. 6) ATP and NADPH are FORMED at the end of the light reaction are called assimilatory powers.
7) Dark reaction : Dark reactions do not depend on light. These reactions occur in stroma of chloroplast.
8) `H^(+)` ions produced in photolysis are immediately picked up by SPECIAL compound NADP to form NADPH.
9) In the dark phase , the hydrogen of the NADPH is used to combine it with `CO_2`. by utilising ATP energy and to ultimately produce glucose.
10) The synthesis of glucose OCCURS in number of steps using certain special intermediate compounds (mainly ribulose biphosphate) and enzymes.
11) Finally the glucose is converted to starch.
Discussion
3229.

Question : How is small intestine designed to absorb digested food ?

Answer»

Solution :Small intesine is a LONG tubular structure . The inner WALL of small intestine is THROWN into folds called villi. The absorptive cells have numerous FINGER -like processes called microvilli. They INCREASE the surface area for absorption of food.
Discussion
3230.

Question : How is sexual reproduction different from asexual reproduction ? State the limitations of asexual mode of reproduction.

Answer»

Solution :When new GENERATIONS are to be created from a single individual without gametes then it is known as asexual reproduction. WHEREAS the mode of reproduction involving both male and female sexes to produce new generation is called sexual reproduction.
LIMITATIONS of asexual mode of reproduction are as follows:
`rarr` It hinders diversity.
`rarr` Organisms reproduce very quickly, as a result number of offsprings increase leading to INCREASED competition.
`rarr` Inheritance is possible from only single parent.
`rarr` POPULATION cannot be controlled.
`rarr` Organisms cannot adapt easily.
`rarr` The niche gets filled up quickly.
Discussion
3231.

Question : How is reproduction to be achieved a single type, if the organism itself from consists of many cell types ?

Answer»

Solution :ORGANISM may contain many CELLS but only SPECIALIZED cells are able to perform REPRODUCTION.
Discussion
3232.

Question : How is respiration different from breathing ?

Answer»

Solution :Slow OXIDATION of food to release energy is called RESPIRATION while BREATHING is a biophysical PROCESS which is the FIRST step of respiration.
Discussion
3233.

Question : How is reproduction in Hydra different from the reproduction in Amoeba ?

Answer»

SOLUTION :
Discussion
3234.

Question : How is process of pollination different from fertilisation ?

Answer»

SOLUTION :DIFFERENCES between POLLINATION and FERTILIZATION :
Discussion
3235.

Question : How is pollination brought about in maize?

Answer»

by insects
by BATS
by wind
by water

Answer :C
Discussion
3236.

Question : How is plaster of paris prepared?

Answer»

Solution :Plaster of paris is prepared by heating GYPSUM to a temperature of `100 ^(@) C`. The following REACTION takes place:
`CaSO_(4). 2H_(2)O to CaSO_(4). (1)/(2) H_(2)+ 1(1)/(2)H_(2)`
On mixing with water it retracts to a hard mass to form gypsum again i.e., the reverse reaction takes place.
B) * Bases possess a bitter taste
* Bases are slippery to touch.
*Bases turn red litmus blue Bases turn phenolpthalein solution pink
*Strong base LIKE caustic soda (NaoH) caustic POTASH (KOH) are corrosive in nature and produce burning sensation on the skin
*Solution of bases in water conduct electricity
*Bases react with acid, neutralise them.
*Producing salt and water.
Discussion
3237.

Question : How is Plaster of Paris prepared? What reaction takes place when it sets to a hard mass?

Answer»

Solution :Plaster of PARIS is PREPARED by heating gypsum to a temperature of `100^@C` . The following reaction takes place
` CaSO_4. 2H_2O overset(100^@C)(to) CaSO_(4) 1/2H_2O+ 1(1)/(2) H_2O`
: On mixing with water, it react to a hard mass to form gypsum again i.e, the REVERSE reaction takes place.
Discussion
3238.

Question : How is oxygen and CO_2 transported in human beings ?

Answer»

Solution :1. Transport of oxygen . It is transported from respiratory ORGANS to body cells .
(i) Haemoglobin helps in the transport of oxygen. In the alveoli of the lungs , the haemoglobin oxygen. In the alveoli of the lungs , the haemoglobin (Hb) PRESENT in red blood corpuscles combines with oxygen to form oxyhaemoglobin . When the blood reaches the tissue , oxygen is released from the oxyhaemoglobin for the consumption by the tissues .
`Hb + O_(2) to HbO_2`
(ii) Some of `O_2` is transported in the solution form by plasma of blood.
2. Transport of `CO_2` .
1 `CO_(2)` diffuses into blood plasma to form PHYSICAL solution .
2. `CO_2` forms unstable carbonic ACID with WATER and is transported as such .
3 `CO_(2)` is also transported from tissue to lungs as bicarbonates.
Discussion
3239.

Question : How is oxygen and carbon dioxide transported in human beings?

Answer»

Solution :During inhalation, oxygen comes into alveoli of the lungs. The alveoli is surrounded by very thin blood VESSELS called capillaries. So, the oxygen diffuses out from the alveoli walls to the blood in capillaries. The oxygen is carried by blood to all the parts of body by binding it with haemoglobin present in blood.
The blood passes through the tissues of the body and the oxygen present in it diffuses into the CELLS (due to its higher CONCENTRATION in the blood). This oxygen combines with the DIGESTED FOOD present in the cells to release energy. Carbon dioxide is produced as a waste product during respiration in the cells of the body tissues. This `CO_(2)`diffuses into the blood (due to its higher concentration in body tissues). Blood carries the back to the lungs where it diffuses into the alveoli of the lungs into the trachea, nostrils and then out of the body into air. `CO_(2)`is more soluble in water than oxygen and hence mostly transported in the dissolved form in our blood
Discussion
3240.

Question : Howis oxygen and carbon dioxide transported in human beings ?

Answer»

Solution :Oxygen and carbon dioxide are two metabolic gases. Oxygen is required by everylivingcell for cellular respiration whereas `CO_(2)`is formed as a by-product and has to be eliminated from the body. In human beings, a pigment HAEMOGLOBINIS present in red blood corpuscles which has a strong affinity for oxygen, takesup the oxygen from the air in the LUNGS and CARRY it to tissues whichare deficient in oxygen.Some`O_(2)`istransported in DISSOLVED state in blood plasms. Carbon dioxide whichis more SOLUBLE in water than oxygen is mostly transported in the dissolved state in our blood. Some `CO_(2)`is transported by haemoglobin as carbaminohaemoglobin .
Discussion
3241.

Question : How is leafy stage formed in mosses ? How is it different from protonema ?

Answer»

SOLUTION :Leaf stage develops from secondary protonema as a lateral bud. Protonema is creeping, GREE, branched frequently filamentous stage whereas leafy stage is upright WIT spirally arranged leaves.
Discussion
3242.

Question : How is food transported in plants?

Answer»

Solution :The food manufactured by the leaves of a plant is transported to its other parts through a kind of tube system CALLED phloem. The TRANSPORT of food from the leaves to other parts of the plant is called translocation. The movement of material through phloem depends on the action of living cells called sieve tubes. Food molecules enter the phloem elements or cells from mesophyll cells of the leaf. Once they enter phloem, they can be transported upwards or downwards to all parts of a plant, including roots. This food is transported to different parts of plant in the form of solution through sieve tubes. The end walls of sieve tubes are connected with each other by perforated sieve plates, forming a continuous passage from root tips to stem tips through which DISSOLVED food substances move freely. The translocation in phloem is achieved by utilising energy. Material like sucrose is transferred into phloem tissue using energy from ATP. This INCREASES the osmotic pressure of the tissue causing water to move into it. This pressure moves the material in the phloem to tissues which have less pressure. This allows the phloem to move material according to plant’s NEEDS.
Discussion
3243.

Question : Howis food transported in plants ?

Answer»

Solution :Foodis transported in plants through phloem which consists of sieve tubes,cells phloem parenchyma andcompanion cells. This transportof solubleproducts of photosynthesis is called translocation. Besidesthe products of photosynthesis , thephloem TRANSPORTS amino acids and other substances. These substances are DELIVERED to the storage organsof roots, fruitsand seedsand to GROWING organs. The translocation of food and othersubstances takes place in the sieve tubeswith the help of adjacentcompanion cells both in upward and downward direction.
The translocation in phloemis achieved by utilising energy. Material like sucrose in transferred into phloemtissue energy from ATP. Thisincreases the osmotic pressure of the tissuecausing water to move into it .This pressure moves the materials in the phloem to TISSUES which have less pressure. Thisallows the phloem to move material according to theplant.s needs. For example, in the spring, sugar stored in root or stem tissue wouldbe transported to thebubs which needenergy to grow .
Discussion
3244.

Question : How is food transported in plants ?

Answer»

SOLUTION :Phloem transports food materials from the LEAVES to different parts of the PLANT body. The transportation of food in phloem is achived by utilizing energy from ATP. As a result of this, the osmotic PRESSURE in the tissues increases CAUSING water to move into it, this pressure moves the material in the phloem to the tissues which have less pressure. This is helpful in moving materials according to the needs of the plant. For example, the food material such as sucrose, is transported into the phloem tissues using ATP energy.
Discussion
3245.

Question : How is equal genetic contribution of male and female parents ensured in the progeny ?

Answer»

Solution :MALE and female parents produce male gametes (SPERMS) and egg cells (Ovum) respectively through a process of MEIOSIS. It REDUCES the number of chromosomes and amount of DNA to HALF in gametes.
Such germ cells from two individuals, i.e., male and female parents are fused to form zygote. This ensures the equal genetic contribution of male and female parents in the progeny that develop from zygote.
Discussion
3246.

Question : How is diastema formed in rabbit?

Answer»

SOLUTION :The DIASTEMA is FORMED in Rabbit, as a gap between the incisors and PREMOLARS.
Discussion
3247.

Question : How is caustic soda obtained? Mention its uses.

Answer»

Solution :CAUSTIC Soda (NaOH) is manufactured by electrolysis of aqueous solution of sodium CHLORIDE (Brine). This method is called chloroalkali process.
`2NaCl (aq) + 2H_2O (l) to 2NaOH(aq) + Cl_2 + H_2`
Sodium hydroxide is USED in making soaps and DETERGENTS, degreasing metals, paper making and ARTIFICIAL fibers like rayon
Discussion
3248.

Question : How brain is protected inside a human body?

Answer»

SOLUTION :The brain is situated in the cavity of a bonyt BOX called skull. The brain is CONTAINED in a fluid-filled balloon which PROVIDES further shock ABSORPTION.
Discussion
3249.

Question : How is body of mother designed to undertake the development of the child ?

Answer»

SOLUTION :The UTERUS in MOTHER prepares itself every month to receive and nurture the GROWING embryo.
Discussion
3250.

Question : How is asexual reproduction different from sexual reproduction?

Answer»

Solution :REPRODUCTION TAKING place by the fusion of male and FEMALE gametes is called sexual reproduction. Two PARENTS ofopposite sex are involved in sexual reproduction. Offsprings are genetically not identical to parents or to each other.
Reproduction taking place by the help of asexual parts (without fusion of gametes) is called asexual reproduction. Asexual reproduction involves only a single PARENT. Offsprings produced are genetically identical to the mother and to each other offsprings.
Discussion