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4601.

Question : a) What happens if too much of acid is produced in the stomach? What is the remedy for this situation? b) What is water of crystallization? How is plaster of . The fixed numberparis prepared? Write any two uses of plaster ofparis .

Answer»

Solution :(a) If too much of acid is produced in the stomach it causes HYPERACIDITY (Irritation and pain). To get rid of this pain we have to use bases called ANTACIDS. It neutralises excess of acid and gives relief from pain CAUSED by hyperacidity.
(b) the FIXED number of water molecules present in one formula unit of a crystaline salt is called water of crystallisation. 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 . 1/2 H_2O+ 1/2H_2O `
i) it is used to prepare chalks .
II) It is used to make casts and moulds.
Discussion
4602.

Question : a) What is a balanced chemical equation? b) Write the balanced reactions for the following: (i) Potassium Bromide + Barium iodide toPotassium iodide Barium Bromide. (ii) Zinc carbonate + Zinc oxide + carbondioxide

Answer»

SOLUTION :a) An EQUATION in which the number of atoms of each on the two SIDE of an equation is equal is called a BALANCED CHEMICAL equation. ii) ` ZnCO_3 (s) to ZnO(s)+ CO_2(g)`
Discussion
4603.

Question : a) What factors could lead to the rise of a new species. b) Only variations that can have an advantage to an individual organism will survive in a population. Do you agree with this statement why or why not.

Answer»

Solution :a) NATURAL selection, genetic drift and acquisation of TRAITS during the lift-time of an individual can give rise to new species.
b) In species VARIATIONS that offer survival advantage are naturally selected individuals adjust to their environment with the help of those selected are passed on to their progeny evolution of organisms occurs as a result of this natural selection. However there can be some other variations which do not offer any survival advantage of some genes even if they are not important for survival. This ACCIDENTAL change in the frequency of gene in small POPULATION is reffered to as genetic drift. Thus genetic drift provides diversity without any survival advantage.
Discussion
4604.

Question : (a) What does various steps involved in the sexual reproduction in plants (b) Name two plants which reproduce by sexual reproductin method and two plants which reproduce by asexual reproduction methods.

Answer»


SOLUTION :N//A
Discussion
4605.

Question : What do you mean by a precipitation reaction ? Explain by giving examples.

Answer»

Solution :(a) Any rcaction in with an insoluble solid is produced is called a precipitate reaction. For cxample:
`underset ("Choride Sulphate")underset("Barium Sodium")(BaCl_(2aq)+Na_(2)SO_(4aq))overset("Heat")RARR underset("Sulphate") underset("Barium")(BaSO_(4("S")))darrunderset("Choride")underset("Sodium")(2NaCl_((aq)))`
(b) Oxidation : It is defined as process which involves GAIN of oxygen
For exumple :
`underset("Magnesium")2Mg_(("s")) underset("Oxygen")(+O_(2)("g"))rarr underset("Magnesiumoxide")(2MgO_(("s")))`
Reduction : t is defined al process which involver loss of oxygen.
For example :
`underset("oxide")underset("COPPER")(CuO_(("s")))+ underset("hydrogen")(H_(2("g")))overset("Heat")rarrunderset("copper")(Cu_(("s"))+)underset("water")(H_(2)O_(("g")))`
Discussion
4606.

Question : (a) What criteria can be used to decide whether something is alive ? (b) What is meant by life process? Name the basic life processes common to all living organisms which are essential for maintaining life.

Answer»
Discussion
4607.

Question : (a) What changes are seen in girls at the time of puberty ? (b) Name the organs which produce ova (or egg cells) in human females. (c) Draw a labelled diagram of human female reproductive system. With the help of this diagram , explain the working of human female reproductive system. (d) Describe the process of fertilisation in humans and development of embryo briefly.

Answer»


SOLUTION :N//A
Discussion
4608.

Question : a) What are trophic levels ? b) What will happen if we kill all organisms in one tropic level.'

Answer»

Solution :a) Trophic levels are the feeding level in an ecosystem. the trophic level of living beings represent their placement in a food CHAIN it also tell the order of consumption and energy transfer throughout the ecosystem.
b) If we kill all the organisms in one trophic level the following effects will TAKEN place
* The population of organisms in previous TROPIC level will increase.
* The organisms in NEXT trophic level will not be able to GET the food so they will migrate to some other ecosystem or die.
* It will cause an ecological imbalance in the food chain.
Discussion
4609.

Question : (a) What changes are seen in boys at the time of puberty ? (b) Name the organs which produce sperms in human males. (c) Draw a labelled diagram of the human male reproduction system. With the help of this diagram, describe the working of human male reproductive system? (d) What is the role of seminal vesicles ad prostrate gland in human male reproductive system ?

Answer»


SOLUTION :N//A
Discussion
4610.

Question :(a) What are the two important properties of stem cells? (b) Write a short note on two types of stem cells.

Answer»

Solution :(a) PROPERTIES of stem cells:
• It.s ABILITY to divide and give rise to more stem cells by self-renewal.
• It.s ability to give rise to specialised cells with specific functions by the process of differentiation
(b) TYPES of cells:
1. EMBRYONIC stem cells: Embryonic stem cells are derived from the inner cell mass of blastocyst, which can be extracted from the early embryos. These cells can be developed into any cell in the body.
2. Adult stem cell or somatie stem cell: These cells are found in the new born and adults. They have the ability to divide and give rise to specific cell types. Sources of adult stem cells are amnoitic fluid, umbilical cord and bone marrow.
Discussion
4611.

Question : (a) What are the sources of sewage or waste water? (b) Explain the methods which involve in the conventional waste water treatment.

Answer»

Solution :(a) The sources of sewage or waste water involves:
(i) Domestic purpose or house hold activities
(ii)Dye and TEXTILE industries
(iii) Leather industries
(iv) Sugar and breweries industries
(v) Paper and pulp industries
(b) The conventional waste water treatment methods involve the following step:
(i) Pre-screening:
Waste water generated from domestic and industrial activities is screened to remove soil and solid particulates
(ii) AERATION: Screened waste water is pumped to an aeration tank. Here the microbial contaminants are removed by the biological degradation, that OCCURS, in the presence of air.
Sedimentation process:
In this process, the solid particles in suspension form are allowed to settle. The particles that settle out from the suspension is known as sludge.
Sludge removal:
The sludge generated by the degradation process is transferred PERIODICALLY from the tank for safe disposal.
Disinfection:
Chlorination and ultraviolet (UV) radiation of treated water is required to remove any microorganism contamination.
Water RECYCLING:
The water will then be supplied for domestic or industrial purposes.
Discussion
4612.

Question : (a) What are the contents of jar A and jar B ?(b)What is being shown in the given diagram ?(c)Describe the process.

Answer»

SOLUTION :(a) The CONTENTS of jar A is fresh dialysing solution, which is going inside of the tubes MADE of semi-permeable membrane.
Contents of jar B is used dialysing fluid which contains EXCESS urea, salts and metabolic wastes from the blood circulating in the tubes.
(b)The diagram showthe process of dialysis or Hemodialysis.
Discussion
4613.

Question : (a) What are the aims of wild life management?(b) What are the provision of the wild life protection act?

Answer»

Solution :(a) The main aim of wild life conservation are:
• To control and limit EXPLOITATION of species.
• To preserve the plants and animals from extinction.
• Maintenance of THREATENED species and protect species which are on the verge of extinction.
• Preserve the endangered species.
• To study the ecological relationship of the plants and animals in natural habitat.
• Hunting and poaching should be prohibited.
• Establishment of national parks, wild life sanctuaries, protected AREAS and biosphere reserves.
(b) The provisions of the wild life protection act:< br> • Prohibit killing and hunting of specified animals.
• Constitute sanctuaries, national parks and closed areas for wild life conservation.
• Special schemes for preservation of endangered species.
• Constitute central ZOO AUTHORITY and recognition of zoos.
• Restrict, regulate or prohibit trade in wild animals and products obtained from them.
Discussion
4614.

Question : (a) What are sexually transmitted diseases ? Give two examples of sexually transmitted diseases . (b) Which method of contraception prevents fertilised egg from being inplanted in the uterus ?

Answer»


SOLUTION :N//A
Discussion
4615.

Question :a) List any four reasons for adopting contraceptivemethods. b) If a woman is using copper - T will it help in protectingher from sexually transmitted diseases Why?

Answer»

Solution :Advantages of SEXUAL reproduction.
* In sexual reproduction more variations are produced thus it ensures survival of species in a POLLINATION.
* The new formed individual has characteristics of both the parents.
* Variations are more vaible in sexual mode then in asexual one. This is because in asexual reproduction, DNA has to function inside the inherited cellular apparatus.
B) Four reasons for adopting contraceptive methods are
* To increase the gap between TWO children.
* To prevent unwanted pregnancy.
* To prevent transmission of STD.s
* To control populations growth.
c) If a woman is USING copper-T it will not help in protecting her from sexually transmitted diseases. Copper-T prevents only implantation in the uterus.
Discussion
4616.

Question : (a) What are herbivores, carnivores and omnivores ? Give two examples of each (b) Classify the following into herbivores, carnivores and omnivores : Lion, Man, Dog, Goat, Crow, Elephant, Snake, Hawk, Rabbit, Deer (c) Name the five steps which occur in the process of nutrition in animals.

Answer»
Discussion
4617.

Question : a) What are groups and period in the periodic table? b) Two elements M and N belong to group I and II respectively and are in the same period of the periodic table. How do the following properties of M and N vary?1) Sizes of their atoms 2) Their metallic characters. 3) Their valencies informing oxides. 4) Molecular formula of their chlorides.

Answer»

Solution : a) The vertical columns in the periodic table are called group. The horizontal ROWS in the periodic table are called periods. b) 1. M and N belong to the same period but I and II. Therefore N will be smaller than MAS atomic size is decreasing from left to right. 2. M is more METALLIC than N. Metallic character goes on decreasing from left to right as tendency to lose electrons decreases due to decrease in atomic size. 3. Their VALENCIES are 1 and 2 respectively in forming oxides. Valency goes on increasing first and then increases. 4. `MCI, NCI_2`are molecular FORMULAE of their chlorides.
Discussion
4618.

Question : a) What are groups and period in the periodic table? b) Two element M and N belong to group I and II respectively and are in the same period of the periodic table. How do the following properties of M and N vary? 1) Size of their atoms 2) This metallic characters 3) Their valencies informing oxides. 4) Molecular formulae of their chlorides.

Answer»

Solution : a) The vertical columns in the periodic table are called group. The horizontal ROWS in the periodic table are called periods.
b)1. M and N belong to the same period but group I and Ii. Therefore N will be SMALLER than M as a atomic SIZE is decreases from left to right.
2. M is more metallic than N. Metlallic character goes on decreasing from left to right as TENDENCY to lose electrons.
3.Their VALENCIES are 1 and 2 respectively in forming oxides. Valency goes on increasing first and then decreases.
4. MCI, `NCI_2` are molecules formulae of their chlorides.
Discussion
4619.

Question : A very small population of a species faces a greater threat of extinction than a larger population. Provide a suitable genetic explanation.

Answer»

SOLUTION :• The frequency of genes in smaller populations can EASILY be altered due to accidents or unprecedented catastrophic EVENTS even if the genes had survival advantage. This can lead to extinction of the species.
• Smaller populations have fewer variations compared to larger populations as there is EXTENSIVE interbreeding that reduces the appearance of variations. This WOULD be a disadvantage to the population as it would lead to extinction during drastic environmental changes, if any.
Discussion
4620.

Question : A very small population of a species faces a greater threat of extinction than a larger population, Provide a suitable genetic explanation.

Answer»

Solution : Fewer individuals in a species IMPOSE extensive INBREEDING AMONG them. This limits the appearance of variations and puts the species at a disadvantage if there are changes in the ENVIRONMENT. Since the individuals fail to cope up with the environmental changes, they may become extinct.
Discussion
4621.

Question : A very close relationship between flower and pollinating agent is best exhibited by

Answer»

YUCCA
Avena
Salmalia
Pisum

Answer :A
Discussion
4622.

Question : A variegated leaf with green and yellow patches is used for an experimentto prove thatchlorophyll is required for photosynthesis . Before theexperimentthe green portions (A) , and the pale yellow portions (B), are observed. What will be the colour of 'A' justbefore and afterthe starch test ? Also write the equation of photosynthesisand mark, as well as validate from which moleculethe by product is obtained .

Answer»

Solution : The GREEN portions (A) on the variegated leaves have chlorophyll.
Just before the starch TEST, the leaf has been boiled and WASHED in alcohol and water. Hence it will be pale yellow .
Justafter the starch test, it will be blue-black, indicatingpresence of starch.
Reaction :
`O_(2) and H_(2) O`are RELEASED as by-products from splitting of water.
Discussion
4623.

Question : A typical Mendelian dihybrid ratio of F_(2) generation is 3:1

Answer»

Solution :A TYPICAL MENDELIAN DIHYBRID ratio of `F_(2)` generation is 9 :3 :3 1
Discussion
4624.

Question : (a)Transport of food in plants require living tissues and energy. Justify the statement .(b)Namethe componentof food translocated by livingtissues.

Answer»

Solution :(a) Food materials are translocated fromthe region of theirmanufacture or storage, to the region of their utilisation via a complex tissue known as phloem. Phloem comprises of four types of tracheary elements - sieve tubes, COMPANION cell, phloem parenchyma and phloem fibres. Only phloem fibres are dead cells while rest are living.
Food moves into sieve tubes which are the CONDUCTING channels of phloem. They are elongated tubular channels formed by end to end union of numerous sieve tubeelements. The end walls of sieve tubes have PORES and are called as sieve plates. Their functioning is controlled by adjacentnucleated companion cells as it produces the force required for translocation. The direction of translocation can be downward, upward or both.
(b)The bulk of the translocation nutrients consist of SOLUBLE carbohydrate i.e, SUCROSE. Amino acids, organic acids, hormones and other organic solutes are also translocated bysieve tubes.
Discussion
4625.

Question : "A trait may be inherited, but may not be expressed." Justify this statement with the help of suitable example.

Answer»

Solution :A trait may be INHERITED, but if it is recessive, it will not be expressed UNLESS it is HOMOZYGOUS. Eg.,

Hence, genotype Tt with a recessive gene is expressed as PHENOTYPE of TALL. This shows that only dominant gene is expressed as the trait (T) while .t is not expressed.
Discussion
4626.

Question : "A trait may be inherited, but may not be expressed." Justify this statement with the help of a suitable example.

Answer»

Solution :Let us take the following EXAMPLE to justify the above statement.
Mendel crossed TALL pea plants with dwarf pea plants.

Mendel.s Observation
`F_(1)` generation contained all tall plants. When `F_(1)`, c generation underwent selfing, the trait that was unexpressed in F, (dwarf) was observed in some `F_(2)` progeny. Thus, both traits, tall and dwarf, were expressed in `F_(2)` generation in the ratio 3:1.
The above EXPERIMENT indicates that although both the traits of tallness and shortness were inherited in `F_(1)` plants, only the tallness trait was expressed. This shows that traits may not SHOW up in an individual but are passed on to the next generation.
Discussion
4627.

Question : A trait of an offspring is infulenced is by

Answer»

paternal DNA only
MATERNAL DNA only
both maternal and paternal DNA
neither by paternal nor by maternal DNA

ANSWER :C
Discussion
4628.

Question : A tiny animal having tentacles whichreproduces by growing buds on the sides of its body is :

Answer»

PLANARIA
Yeast
Amoeba
Hydra

Solution :N//A
Discussion
4629.

Question : A thickened undergound stem X of a plant which is swollen with storred food has a number of points Y on its surface. When the old steam X is planted in the soil of a filed in the next growing seaosn, then each point Y present on its surface grows into a new plant. (a) What is the general name of the undergound stems like X? (b) Give one exampleof X (c) What are points Y present on Xknown as ? ltbr gt (d) Is it necessary to plant the whole of stem X in the ground to it new plants? Explain your answer (e) What is he name of this method of reprocuction of plants ? (f) What is the advantage of growing new plants from the underground stems like X?

Answer»


SOLUTION :N//A
Discussion
4630.

Question : (a) The yeas cells fall to multiply in water but they multiply rapidly in sugar solution. Give one reason for it. (b) Why dies bread mould grow profusely on a moist slice of breas but not on a dry slice of bread?

Answer»


SOLUTION :N//A
Discussion
4631.

Question : A tall pea plant (Tt) is crossed with a dwarf pea plant (tt). What will be the ratio of tall and dwarf plant in the progeny ?

Answer»

`1:3`
`3:1`
`2:2`
`2:1`

SOLUTION :
2 TALL (TT) and 2 DWARF (tt)
Discussion
4632.

Question : A successful forest conservation strategy should involve...a.protection of animals at the highest trophic level.b.protection of only consumers.c.to stop all the products available from forests.d.comprehensive programme to protect all the physical and biological components.

Answer»

protection of ANIMALS at the highest trophic level.
protection of only consumers.
to stop all the products AVAILABLE from forests.
COMPREHENSIVE programme to protect all the PHYSICAL and biological components.

Solution :comprehensive programme to protect all the physical and biological components.
Discussion
4633.

Question : a] Study the following cross and showing self pollination in FI, fill in the blank and answer the question that follows: [NCERT Exemplar] {:("Parents:" ,R RYY , xx , rryy),(, "Round, yellow", ,"wrinkled, green"),(Fl, Rr Yy , xx , ?),(,"Round, yellow",,):} b] What are the combinations of character in the F_2 progeny? What are their ratios?

Answer»

Solution :a] RrYy (ROUND, yellow]
b] i] Round yellow - 9 ii] Round green - 3
III] Wrinkled yellow - 3 iv] Wrinkled green - 1
Round yellow, round green, wrinkled yellow, wrinkled green in the ratio of 9:3:3:1.
Discussion
4634.

Question : A study found that children with light-coloured eyes are likely to have parents with light coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive ? Why or why not ?

Answer»

SOLUTION :Out of SYLLABUS.
Discussion
4635.

Question : A study found that children with light coloured eyes are likely to have parents with light coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive ? Why or why not ?

Answer»

Solution :No, we cannot SAY anything about whether the light eye colour trait is dominant or RECESSIVE on the basis of given INFORMATION because information REGARDING cross between two traits, i.e., light colour with black eye colour is essential to determine it. In general population light coloured eyes are in much less proportion as compared to DARK eyes. This indicates that it may be recessive trait.
Discussion
4636.

Question : A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?

Answer»

Solution :No because we cannot SAY with certainty whether light eye colour is dominant or RECESSIVE. HOWEVER, since both children and their parents have light eye colour, the POSSIBILITY that light eye colour is recessive trait.
Discussion
4637.

Question :A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?

Answer»

Solution :In this study, light-coloured EYE is DOMINANT TRAIT because children BORN from parents having light-coloured EYES also had light-coloured eyes.
Discussion
4638.

Question : A student, while observing an embryo of a pea seed in the laboratory, listed various parts of the embryo as given below: Testa, Tegmen, Radicle, Plumule, Micropyle, Cotyledon. On examining the list, the teacher remarked that only three parts are correct. Select the three correct parts from the list:

Answer»

TESTA, RADICLE, COTYLEDON
Tegmen, Radicle, Micropyle
Cotyledon, PLUMULE, Testa
Radicle, Cotyledon, Plumule

Answer :D
Discussion
4639.

Question : A student is viewing under a microscope a permanent slide showing various stages of asexual reproduction by budding in yeast. Draw diagrams of what he observes. (in proper sequence).

Answer»

SOLUTION :
Discussion
4640.

Question : A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected

Answer»

Solution :The student is suffering from MYOPIA or short sightdness. The defect can be corrected by the use of convcave LENS of SUITABLE power
Discussion
4641.

Question : a) State the principle of an electric generator b) Write the difference between direct current and alternating current.

Answer»

Solution :a) An electric generation is based on the principle of ELECTROMAGNETIC induction when a rectangular coil is rotated in a UNIFORM magnetic field, an induced voltage is generated between the ends of the coil.
b) Direct current :
* Its magnitude is constant and FLOWS in one direction only.
* The FREQUENCY of DC is zero
Alternating current:* Its magnitude and direction reserves periodically. * The frequency of AC is finite.
Discussion
4642.

Question : (a)State the form in which the following are stored.(i)Unused carbohydrates in plants.(ii)Energy derived from in human .(b)Describe the process of nutrition in amoeba with the help of diagram.

Answer»

Solution :(a) i. As starch in fruits / storage roots tubers etc.
ii. As glycogen.(b)Amoeba is a unicellular eukaryotic organism that exhibits holozoic mode of NUTRITION. FIVE steps are involved in this mode of nutrition NAMELY ingestion. absorption, assimilation andegestion.

Ingestion - Amoeba feeds on microscopic organisms. It takes in food using finger likeprojections CALLED pseudopodia. It encircles the food and ENGULFS or ingests it by a process called phagocytosis. The food comes to lie in a vesicle called phagosome or food vacuole.
Digestion - a lysosome fuseswith phagosome and complex substances are brokendown into simplerones, Such type of digestionwhich occurs within a cell is referred as Intra cellular digestion. The digested food then diffuses into cytoplasm.
Absorption and Assimilation - Thedigested food which has diffused into the cytoplasm are quickly absorbed by the organisma nd comverted into constituents of protoplasm.
Egestion - The undigested food material reaches the rear end of the organism and is thrown out by the process of exocytosis. The membrane of the vesicle fuses with thesurface membrane.
Discussion
4643.

Question : How does the electronic configuration of an atom of an element related to its position in the modern periodic table ? Explain with one example.

Answer»

Solution :"Properties of clements are the periodic fiunction of their atomic number
The position of elements depend upon number of valence electrons which depend upon clectronic configuration those clements wich have same valenee elcctrons OCCUPY same group. Those elements which have one vaience electrons BELONG to group I elements, which have TWO valence CLECTRONS belong to group 2. Period numbers is cqual to the number of shell. Example atonic number of sodium (Na) is 1, so electronic conf+guration will be 2.8,1. Sodium has one valence electron in vaience shell so it belong to group1 as sodium has THREE shells, so it belong to 3rd period.
Discussion
4644.

Question : a) State Mendeleev's periodic law. b) Did Mendeleev have gaps in his perodic table? c) Any three limitations of Mendeleev's classification. d) Does electronic configurations of atoms change in a period with increase in atomic number?

Answer»

SOLUTION :a) Mendeleev.s periodic law states that "the physical and CHEMICAL properties of all elements are the periodic function of their atomic masses"".
b) Gaps were left for UNDISCOVERED element in the Mendeleev.s periodic table.
c).i) Position of hydrogen was not justified II) Increasing order of atomic mass could not be maintained iii) Isotopes have similar chemical properties but different atomic masses, they cannot be given separate places.
d) Number of shells remain the same, number of valence electrons goes on increasing from left to right in a period TILL octet is complete.
Discussion
4645.

Question : (a) State in brief the functions of the following organs in the human female reproductive system: Ovary, Fallopian tube, Uterus (b) What is menstruation? Why does it occur?

Answer»

Solution :(a) Functions of ovary are:
(i) production of female GAMETE.
(II) production of female harmone.
Functions of FALLOPIAN tube are:
(i) It is the site of fertilisation.
(ii) TRANSFER of female gamete from ovary takes place through it.
Functions of uterus are:
(i) implantation of zygote.
(ii) nourishment to the developing embryo.
(B) Menstruation: It is the periodic breakdown of uterine lining and its removal along with blood and mucous in (post pubertal stage of a) human female.
Uterine lining is required to nourish the embryo that is formed if fertilization takes place. In absence of fertilization, the lining is not required and hence is shed in the form of mensuration.
Discussion
4646.

Question : (a) State in brief the functions of the following organs in the human female reproductive system: Ovary, Fallopian tube. (b) What is menstruation? Why does it occur?

Answer»

Solution :Funtion of follopion tube : (i) Producation of female gamete.
(ii) Producation of female hormone
Function of follopian tube:
(i) Site of fertilization
(ii) Transfer of female gamets from ovary
Function of UTERUS:
(i) Iinplantation of zygote fertilizes the egg.
(ii) Nourishment to the DEVELOPING embryo
Menstruation : It is the periodic breakdown of uterine lining and it is removed along with blood & MUCOUS in human female uterine lining is required to nourish the embryo that is formed if fertilization takes PLACE. In ABSENCE of fertilization the lining is not requirea and hence is shed in the from of menstruation.
Discussion
4647.

Question : (a) State any two changes seen in boys at the time of puberty. (b) Define fertilisation and implantation.

Answer»

Solution :(a) (i) Body BECOMES MUSCULAR.
(i) Facial and pubic hair.
(b) Fertilisation - It is the process of UNION of male and female gamete to form zygote.
Implantation - It is the process of attachment of EMBRYO in the uterine wall, with the help of placenta.
Discussion
4648.

Question : (a) Specify the events which occur in the reproductive system of human female: (i) If egg is fertilised. (ii) If egg is not fertilised. (b) Mention the changes that take place in uterus in both the above events.

Answer»

Solution :(a) (i) Pregnancy (ii) Menstruation.
(b) In first case, the lining of uterus BECOMES thick and spongy, richly supplied with blood, helps in implantation of the EMBRYO. In SECOND case, the lining breaks along with blood vessels and comes out through vagina as menstrual flow.
Discussion
4649.

Question : A specific function of light energy in the process of photosynthesis is to

Answer»

ACTIVATE chlorophyll
split water
synthesis glucose
reduce `CO_(2)`

ANSWER :A
Discussion
4650.

Question : A species of Amoeba is called 'proteus' because

Answer»

has abundance of proteins
constantly CHANGES its body shape
does not change its body shape
has PROTOPLASM 

ANSWER :A
Discussion