PRAGATI PUBLIC SCHOOL

CLASS : XII

SESSION : 2019-20)

Holidays are always a welcome break from the normal routine and we all look forward to them. It gives us the opportunity to pursue all those activities that we enjoy but never found enough time to indulge in. So encourage yourself to take up a hobby, a sport or learn an instrument in these vacations. Urge yourself to read as “Books are our Best Friends”. Take membership of a library so that you learns to enjoy the company of good books.Another important aspect of a child’s overall development is directly related to the values that he/she embodies. No education can be complete without inculcating values. In today’s materialistic world value system seems to have been relegated to the background. Therefore, we would like to encourage you to spend time with your grand parents/ relatives during these holidays to bring clarity on moral and ethical valuesHoliday homework has been designed in such a way that the students will get a chance to inculcate reading habit as well as engage themselves in meaningful pursuits that will enhance their comprehension and reasoning skills along with honing their aesthetic sense.

We wish you a very happy and a fruitful family time during this vacation.

ENGLISH

Q.1 Make notes with suitable abbreviations of the Chapter, The Interview of Umberto Eco.

Q.2 Draw a flow chart of the incidents of the Chapter ‘Evans Tries o-level’ along with the characters and their characteristics.

Q3. Complete the question banks 3,4 and 5.

PHYSICS

SECTION -A

1. If the temperature of a good conductor decreases, how does the relaxation time of electrons in the conductor change?

2. If potential difference V applied across a conductor is increased to 2V, how will the drift velocity of the electron change?

3. Two electric bulbs A and B are marked 220V, 40 w and 220V, 60 W respectively. Which one has a higher resistance?

4. A Carbon resistor has three strips of red colour and a gold strip. What is thevalue of resistor? What is tolerance?

5. What happens to the resistance of the wire when its length is increased totwice its original length?

6. (a) Why do we prefer potentiometer to measure the emf of cell than a voltmeter?(b) With suitable circuit diagram, show how emfs of a cell can be compared using a potentiometer?

7. State one condition for maximum current to be drawn from the cell ? 8. Two heated wires of same dimensions are first connected in series and then it’s

parallel to a source of supply. What will be the ratio of heat produced in the twocases?

9. Potential difference V is applied across the ends of copper wire of length (l) anddiameter D. What is the effect on drift velocity of electrons ifV is doubled (2) l is doubled (3) D is doubled

10. What is drift velocity? Derive expression for drift velocity of electrons in a good conductor in terms of relaxation time of electrons?

11. In a potentiometer arrangement for determining emf of the cell, the balance point of the cell in open circuit is 350 cm. When the resistance of 9Ω is used in external circuit of the cell, the balance point shifts to 300 cm. determine the internal resistance of the cell.

12. (a) Using the principle of wheat stone bridge describe the method to determine the specific resistance of a wire in the laboratory. Draw the circuit diagram and write the formula used ? (b) In a whetstone bridge experiment, a student by mistake, connects key (k) in place of galvanometer and galvanometer (G) in place of Key (K). What will be the change in the deflection of the bridge.

13. Four resistors of resistance each of 10Ω is connected as given below. Find the equivalent resistance between x and y.

14. A silver wire has a resistance of 2.1Ω at 27.5˚c and a resistance of 2.7Ω at 100˚c. Determine the temperature coeff. of resistivity of silver.

15. The length of a potentiometer wire is 600 cm and it carries a current of 40 mA. For a cell of emf 2 V and internal resistance 10 ohm, the null

a. point is found to be at 500 cm. If voltmeter is connected across the cell, the balancing length is decreased by 10 cm. Find

b. i) the resistance of the whole wire ii) reading of the voltmeter iii) resistance of voltmeter.

16. A potentiometer wire of length 1 m is connected to a driver cell of emf 3 V as shown in the figure. When a cell of 1.5 V emf is used in the secondary circuit, the balance point is found to be 60 cm. On replacing this cell and using a cell of unknown emf, the balance point shifts to 80 cm.

a. Calculate unknown emf of the cell.

b. Explain with reason, whether the circuit works, if the driver cell is replaced with a cell of emf 1V.

17. Two identical cells of emf 1.5 V each joined in parallel provide supply to an external circuit consisting of two resistances of 17 Ω each joined in parallel. A very high resistance voltmeter reads the terminal voltage of cells to be 1.4 V. Calculate the internal resistance of each cell.

18. Two cells of emf 1.5 V and 2.0 V having internal resistances 0.2 Ω and 0.3 Ω respectively are connected in parallel. Calculate the emf and internal resistance of the equivalent cell.

19. Why is a potentiometer preferred over a voltmeter for determining the emf of a cell? Two cells of emf E1 and E2 are connected together in two ways shown in fig. The balance points in a given potentiometer experiment for these two combinations of cells are found to be at 351 cm and 70.2 cm respectively. Calculate the ratio of the emfs of the two cells.

20. In the circuit shown, R1 = 4 Ω, R2 = R3 = 15 Ω, R1 = 30 Ω and E = 10 V. Calculate the equivalent resistance of the circuit and the current in each resistor.

SECTION-B

1. Make an investigatory project as per allotted in your class.2. Complete your activity file.3. Complete your practical file.

CHEMISTRY

1. Write the structures of following halogen compounds(i) 2-chloro-3-methylpentane(ii) 2-(2-chlorophenyl)-1-iodooctane(iii) 1-bromo-4-sec-butyl-2–methylebenzene.(iv) p-bromotoluene.(v) chlorophenylmethane2. Arrange the following in the increasing order of properly indicated :(i) bromomethane, chloromethane, dichloromethane. (Increasing orderof boiling points).(ii) 1-chloropropane, isopropyl chloride, 1-chlorobutane (Increasing orderof boiling point)(iii) dichloromethane, chloroform, carbon terachloride. (Increasing orderof dipole moment.(iv) CH3F, CH3Cl, CH3Br, CH3l (Increasing reactivity towards nucleophilicsubstitution and increasing order of dipole moment)

3. Explain the following reactions with suitable example :(i) Finkelstein reaction.(ii) Swarts reaction.(iii) Wurtz reaction.(iv) Wurtz-Fitting reaction(v) Friedel-Craft’s alkylation reaction.(vi) Friedel-Craft’s acylation reaction(vii) Sandmeyer’s reaction.

4 Write the difference between

(i) enantiomers and diastereomers(ii) retention and inversion of configuration.(iii) electrophilic and nucleophilic substitution reactions

4. Give a chemical test to distinguish between the following pairs ofcompounds:(i) chlorobenzene and cyclohexylchloride.(ii) vinyl chloride and ethyl chloride

5. Give reasons for the following :(i) The bond length of C–Cl bond is larger in haloalkanes than that inhaloarenes.(ii) although alkyl halides are polar in nature but are not soluble in water.(iii) tert-butyl bromide has lower boiling point than n-butyl bromide.(iv) haloalkanes react with KCN to form alkyl cyanide as main productwhile with AgCN alkyl isocyanide is the main product.(v) sulphuric acid is not used in the reaction of alcohol with Kl.(vi) thionyl chloride is the preferred reagent for converting ethanol tochloroethane.

(vii) haloalkanes undergo nucleophilic substitution reaction easily buthaloarenes do not undergo nucleophilic substitution under ordinaryconditions.(viii) chlorobenzene on reaction with fuming sulphuric acid gives orthoand para chlorosulphonic acids.(ix) 2, 4-dinitro chlorobenzene is much more reactive than chlorobenzenetowards hydrolysis reaction with NaOH.(x) Grignard reagent should be prepared under anhydrous conditions.

6. Give one use of each of following :(i) Freon-12 (ii) DDT(iii) Carbon tetrachloride (iv) Iodoform7. An optically active compound having molecular formula C7H15Br reactswith aqueous KOH to give C7H15OH, which is optically inactive. Givemechanism for the reaction.

II) Prepare project report and submit it by 10 .7.19

MATHEMATICS

General instructions:

1- This HHW consists of two parts (a) Complete and revise all six worksheets(already you have) (b) three papers of CBSE board (based on 1st book) 2- All questions are compulsory. 3- This question paper consists of 18 questions divided into four sections A, B, C and D. Section A comprises of 4 questions of 1 mark each, Section B comprises of 4 questions of 2 marks each, Section C comprises of 7 questions of 4 marks each and Section D comprises of 3 questions of 6 marks each.4- There is no overall choice. Those students who have scored less than 60% in PA have to do 3 times.

PAPER – 1

Section A

1. If ∆=|5 3 82 0 11 2 3|, write the minor of the element a23

2. If (2 35 7)( 1 −3

−2 4 )=(−4 6−9 x) ,write the value of x .

3. Simplify : cosθ ( cosθ sin θ−sin θ cosθ)+sin θ( sinθ −cos θ

cos θ sinθ )4. Write the principal values of cos−1

12−2sin−1 ¿¿

Section B

5. Find dydx at t=

2π3 when x=10 ( t−sin t ) and y=12 (1−cos t ) .

6. Show that the function f given by f( x )=tan−1 (sin x+cos x )is decreasing for all

x∈( π4 , π2 ).7. If A and B are square matrices of order 3 such that |A|=−1 ,|B|=3 , then find the

value of |2 AB|.8. The radius r of the base of a right circular cone is decreasing at the rate of 2

cm/min. and its height h is increasing at the rate of 3 cm/min. When r= 3.5 cm

and h= 6 cm, find the rate of change of the volume of the cone. [use π=227 ]

Section C

9. If (cos x ) y= (cos y )x , find dydx

.

10. Ifsin y=x sin (a+ y ) , prove that dydx

=sin2(a+ y )sin a

.

11. If y=( tan−1 x )2 , show that (x2+1 )2 d2 y

d x2+2x (x2+1 ) dy

dx=2

12. Prove the following, using properties of determinants:

|b+c q+r y+zc+a r+ p z+xa+b p+q x+ y| =2|a p x

b q yc r z|

13. Prove that tan−1¿

14. Prove that sin−1 817

+sin−1 35=cos−1 36

85

15. Using elementary operations, find the inverse of the matrix [−1 1 21 2 33 1 1]

Section D

16. Show that the height of a closed right circular cylinder of given surface and maximum volume, is equal to the diameter of its base.

17. Let A=R X R and let ‘¿’ be a binary operation on A defined by (a ,b )∗(c ,d )=(ad+bc ,bd ) foe all (a ,b ) , (c ,d )∈R X R .

(i) show that ¿ is commutative on A.(ii) show that ¿ is associative on A

18. Let A = {1,2,3,…,9} and R be the relation in A X A defined by (a, b) R (c, d) if a + d = b + c for a, b, c, d∈A. Prove that R is an equivalence relation. Also obtain the equivalence class [(2, 5)].

PAPER – 2

Section A

1. A wire of length 34 m is to be cut into two pieces. One of the pieces os to be made onto a square and the other into a rectangle whose length is twice its breadth. What should be the lengths of the two pieces, so that the combined area of the square and the rectangle is minimum ?

1. Write the value of tan(2 tan−1 15).

2. Find the value of aif ( a−b 2a+c2a−b 3c+d)=(−1 5

0 13)3. If |x+1 x−1

x−3 x+2|=|4 −11 3 | , then write thevalue of x .

4. If[ 9 −1 4−2 1 3 ]=A+[1 2 −1

0 4 9 ], then find the matrix A.

Section B

5. Show that all the diagonal elements of a skew symmetric matrix are zero.

6. Find dydx at x=1 , y=

π4 if sin2 y+cos xy=K .

7. The volume of a sphere is increasing at the rate of 3 cubic centimeters per second. Find the rate at of increase of its surface area, when the radius is 2 cm.

8. Show that the function f( x )=4 x3−18 x2+27 x−7 is always increasing on R.

Section C

9. Prove the following : cos−1¿

10. Find the value of tan 12 [sin−1 2 x1+x2

+cos−1 1− y2

1+ y2 ] ,∨x∨¿<1 , y>0∧xy<1.¿

11. Using properties of determinants, prove the following :

|1 x x2

x2 1 xx x2 1 |= (1−x3 )2

12. Differentiate the following function with respect to x: (log x )x+x log x

13. If y=log [ x+√x2+a2 ] , then provethat (x2+a2 ) d2 y

d x2+ x dy

dx=0.

14. Show that the function f(x)=|x-3|, x ϵR, is continuous but not differentiable at x=3.

15. If x=a sint, y=a(cost + logtant2), find d

2 yd x2

.

Section D

16. A school wants to award its students for the values of Honesty, Regularity and Hard work with total cash award of 6,000. Three times the award money for hard₹ work added to that given for Honesty amounts to 11,000. The award money given for₹ Honesty and Hard work together is double the one given for Regularity. Represent the above situation algebraically and find the award money for each value, using matrix method. Apart from these values, namely Honesty, Regularity and Hard work, suggest one more value which the school must include for awards.

17. Show that the height of the cylinder of maximum volume that can be inscribed in

a sphere of radius R is 2R√3 .Also find the maximum volume.

18. Determine whether the relation R defined on the set R of all real numbers as R={(a,b): a,b∈R and a−b+√3 ∈S, where S is the set of all irrational numbers}, is reflexive , symmetric and transitive.

PAPER – 3

Section A

2. Ifsin ¿¿= 1 , then find x.

3. If 2(3 45 x)+(1 y

0 1 )=( 7 010 5) , find (x− y ) .

4. Solve the following matrix equation for x: [x 1][ 1 0−2 0 ]= 0

5. If |2 x 58 x|=|6 −2

7 3 |, then write the value of x.

Section B

6. For the curve y=5 x−2 x3, if x increases at the rate of 2 units/sec, then find the rate of change of the slope of the curve when x=3.

7. If y=sin−1 (6 x√1−9 x2 ) ,− 13√2

<x< 13√2 , then find

dydx .

8. Find the values of x and y from the following matrix equation :

2(x 57 y−3)+(3 −4

1 2 )=( 7 615 14)

9. Find the derivative of log10 sin−1(x2) with respect to x.

Section C

10. Prove that cot−1[ √1+sin x+√1−sin x√1+sin x−√1−sin x

]= x2; x∈(0 , π4 ) .

11. Prove that : 2tan−1 15+sec−1 5√2

7+2 tan−1 1

8=π4

12. Prove the following, using properties of determinants:

| 2 y y−z−x 2 y2 z 2 z z−x− y

x− y−z 2 x 2 x |=( x+ y+z )3

13. Differentiate tan-1 (√1−x2

x) with respect to cos−1 (2x √1−x2) ,when x≠0.

14. If y=x x , prove that d2 yd x2

− 1y ( dydx )

2

− yx=0.

15. Find the intervals in which the following function f(x)=3x4- 4x3 -12x2 +5 is (a) strictly increasing(b) strictly decreasing

16. Find the equations of the tangent and normal to the curve x =a sin3θ , y=acos3θ

at the point where θ =π4 .

Section D

17. Two schools P and Q want to award their selected students on the values of Discipline, Politeness and Punctuality. The school P wants to award x, y and z₹ ₹ ₹ each for the 3 respective values to its 3, 2 and 1 students with total award money of ₹ 1000. School Q wants to spend 1,500 to award its 4, 1 and 3 students on the respective₹ vales (by giving the same award money for the 3 values as before). If the total amount of award for one prize on each value is 600, using matrix method find the award money₹ for each value. 18. Show that semi vertical angle of the cone of the maximum volume and of given

slant height is cos-1 1√3 .

BIOLOGY

(A) Study the chapter notes and answer the questions that follow.(B) Write the history associated with the discovery of genetic material.

Terrestrial ecosystem – forest, grassland , desert etc.

Ecosystem is the functional unit of nature where living organisms interact among themselves and also with the surroundings physical environment.Ecosystem- Structure and FunctionsEcosystem : There are  two basic categories of ecosystem , namely the terrestrial and the aquatic.

Aquatic ecosystem – ponds, lake, river estuary etc.The biotic and abiotic factors of ecosystem work in integrated manner for flow of energy within the components of ecosystem. Interaction of biotic and abiotic components results in a physical structure that is characteristic for each type of ecosystem. The vertical distribution of different species occupying different levels is called stratification.For example, trees occupy top vertical strata or layer of a forest, shrubs the second and herbs and grasses occupy the bottom layers.The components of ecosystem that are seen as functional unit are(i) Productivity(ii) Decomposition(iii) Energy flow(iv) Nutrient cycling.· Productivity- Primary production is defined as the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis. Rate of production of organic matter by producers is also called primary productivity. It is expressed in terms of weight (g –2 ) or energy (kcal m–2 ).The rate of biomass production is called productivity. It is expressed in terms of g –2 yr –1 or (kcal m–2 ) yr –1. It can be divided into gross primary productivity (GPP) and net primary productivity (NPP).

Gross Primary Productivity Net Primary ProductivityRate of production of organic matter during photosynthesis in an ecosystem.

It is the remaining biomass after respiration in an ecosystem. GPP –R = NPPNPP is the available biomass for consumption to heterotrophs

. Secondary productivity is defined as the rate of formation of new organic matter by consumers.Factors affecting primary Productivity:

1. Plant species inhabiting a particular area.2. Avaliability of nutrients: Greater nutrients greater primary

productivity.3. Photosynthetic efficiency : Some plants have more efficiency

to trp sunlight so more productivity.4. Enviromental factors: Sunlight, Temperature and moisture.

More sunlight and more rainfall more productivity.Decomposition- breakdown of complex organic matter into simple inorganic substances like carbon dioxide, water and nutrients is called decomposition. Dead plants remains like leaves, bark, flowers and dead remains of animals constitute detritus, which is raw material for decomposition. Steps of Decomposition - fragmentation, leaching, catabolism, humification and mineralization.1. Fragmentation of Detritus: Break down of detritus into small

particles by detrivores.2. Leaching: Soluble inorganic nutrients dissolve in water -–

percolate through the soil ( go down into soil horizon)—get precipitated as unavailable salts.

3. Catabolism: Decomposers (bacteria, fungi) release enzymes — decompose degraded detritus — into simpler inorganic compounds using enzymes.

4. Humification: Simplified detritus— converted to humus

– Humus is a Dark, Amorphous substance.– Highly resistant to Microbial Action– Undergoes Decomposition very Slowly.– Reservoir of nutrients (due to colloidal nature)

5. Mineralisation: Humus is degraded – releases inorganic nutrients by microbial action.( CO2, H2O etc) and nutrients (Ca2+, Mg2+,K+ etc)Factors affecting rate of Decomposition:1. Chemical composition of detritus– decomposition rate will be slow when detritus is rich in lignin and chitin and rate increases when detritus is rich in nitrogen and water soluble substances like sugars.2. Climatic conditions – warm and moist environment favour decomposition and low temperature and anaerobiosis inhibit decomposition.

Energy Flow-  There is a unidirectional flow of energy from the sun to producers and then to consumers and it never reverts back. Photosynthetically active radiation (PAR) is responsible for synthesis of food by producers which capture 2-10 % of PAR.Energy is transferred in an ecosystem in the form of food.Major part of food energy is lost and very little is stored as biomassOnly 10 % of total available energy is passed on from one trophic level to the next higher trophic level. So energy decreases as it moves from one trophic level to next higher trophic level.

. Animals obtain their food from plants, so they are called consumers. Food Chain:. The transfer of energy from producers to top consumers through a series of organisms is called food chain. Are of two types: Grazing food chain (GFC)-

The detritus food chain begins (DFC) begins with dead organic matter. It is made up of decomposers which are heterotrophic organisms (fungi and bacteria). These are also known as saprotrophs (sapro: to decompose). Decomposers secrete digestive enzymes that breakdown dead and waste materials into simple, inorganic materials, which are subsequently absorbed by them.Natural interconnection of food chain forms the food web.

Energy for GFC comes from sun. Energy for the DFC comes from Detritus/ organic remains.

Trophic Level : Based on source of food, organism occupies a specific place in food chain that is known as trophic level. Each step or level of food chain is called trophic level. Trophic level tells the functional role of organism in food chain. At First trophic level is producers or autotrophs. They fix solar energy by photosynthesis into food.At second trophic level is herbivore or primary consumers. They feed on producers.At second trophic level are carnivores. They feed on primary consumers.At fourth trophic level are top carnivores. They feed on primary or secondary consumers.

Each tropic level has a certain mass of living material at a particular time called as standing crop.

It is measured as biomass of living organism or number in unit area.The number of trophic levels in the grazing food chain is limited as the transfer of energy follows 10 percent law that is only 10 percent of the energy is transferred to each trophic level from the lower trophic level. In GFC, following trophic levels are possible- producer, herbivore, primary carnivore, secondary carnivore.Ecological PyramidsEcological pyramid is the graphical representation of an ecological parameter (number, biomass, energy) sequence wise in various trophic levels of a food chain with producers at the base and herbivores in the middle and carnivores at the top tiers. It can be upright, inverted, or spindle shaped.

Three common ecological pyramids area) Pyramids of number- employs the number of individuals per unit area at various trophic levels with producer at base and various consumers at successively higher levels. It is generally upright.

A pyramid of number in case of a big tree is generally inverted because number of  insects  feeding on that tree generally exceeds in number.b) Pyramids of biomass- The relationship between producers and consumers in an ecosystem can be represented in the form of pyramid , in terms of flow of biomass called pyramid of biomass. It represents biomass at different trophic levels.. A pyramid of biomass is upright except in aquatic food chain involving short lived plankton.A pyramid of biomass in sea is generally inverted because biomass of fishes generally exceeds that of phytoplankton.

c) Pyramids of energy- The relationship between producers and consumers in an ecosystem can be represented in the form of pyramid , in terms of flow of energy called pyramid of energy. Pyramid of energy is always upright, can never be inverted, because when energy flows from a particular trophic level to the next trophic level, some energy is always lost as heat (90%) at each step e.g in feeding, digestion, assimilation and respiration, Only 10 % of available energy at each trophic level gets passed to next higher trophic level, so energy decreases as we move from one trophic level to next higher trophic level.Ecological SuccessionThe sequential, gradual and fairly predictable change in species composition of a given area is called ecological succession. During succession some species colonise an area and their population becomes more numerous whereas population of other species decline and even disappear.· Orderly and sequential change that leads to a community that is near equilibrium is called climax community.· The entire sequence of communities that successively changes in a given area is called sere and individual transitional communities are termed seral stage or seral communities.Pioneer species/ community : The species that invade a bare area.First one to establish on bare area.Climax community: The community that is in near equilibrium with the environment.Last one to establish in any ecological succession .

Ecoloical Succession : Primary succession, Secondary Succession· Primary succession starts in areas where no organism ever existed. Establishment of biotic community is very slow as no soil is available to start with..For example bare rocks, cooled volcano, newly created pond etc. Secondary succession occurs in the area where naturally biotic communities have been destroyed. Since soil is available it is a faster process. Buried or cut forests, abandoned farm lands.Succession of PlantsOn the basis of nature of habitat, succession of plants can be grouped as-o Hydrach succession takes place in wetter area and the successional series progress from hydric to the mesic conditions.o Xerarch succession takes place in dry areas and series progress from xeric to mesic conditions.

Primary succession on rocks ( Xerach):Lichens are pioneer species on bare area. Lichens secrete some acids to dissolve rocks and help in weathering and soil formation. Later some bryophyte invade( replace) and hold that small amount of soil The bryophytes are succeeded by herbs, shurbs and ultimately big trees At last a stable climax forest is formed The xerophytic habitat is converted into a mesophytic one.

Primary succession in water ( Hydrach) · In primary succession in water, the pioneer species are the small phytoplanktons The phytoplanktons are replaced by free floating angiosperms Then rooted angiosperms invade , sedges, grasses and finally the trees At last a stable climax forest is formed An aquatic habitat is converted into a mesic one.

· Primary succession is slow process as soil is not available for pioneer species but secondary succession is comparatively faster

due to availability of soil or other nutrients. A climax community is reached much faster in case of secondary succession.

Nutrient CyclingThe movement of nutrients elements through the various components ( b iotic and abiotic)of an ecosystem is called nutrient cycling. It is also called as biogeochemical cycles. There are two types of nutrient cycles-· Gaseous – Reservoir exist in atmosphere. Comparitively quick or fast, eg. Carbon and nitrogen cycle.· Sedimentary- Reservoir exists in earth crust. Comparitively slow. Eg. Phosphorus and sulphur cycle.

Environmental factors like soil, moisture, pH, temperature regulate the rate of release of nutrients into the atmosphere. The function of reservoir is to meet with the deficit which occurs due to imbalance in the influx and efflux of nutrients. Total amount of nutrients( C, P, Ca) present in soil at any time is called standing state.Carbon CycleCarbon cycling occurs through atmosphere, ocean and through living and dead organisms. Most of carbon is fixed by plants during the process of photosynthesis and returns to atmosphere in form of CO2 during respiration. Burning of wood, forest fire and combustion of organic matter, fossil fuel, and volcanic activity are other sources of releasing CO2 in the atmosphere.

Phosphorus CyclePhosphorus is major constituent of biological membranes, nucleic acids and cellular energy (ATP) transfer systems.The natural reservoir of phosphorus is rock which contains phosphorus in the form of phosphates. On weathering, minute

amount of phosphates dissolve in soil solution and absorbed by the roots of the plants. Herbivores and carnivores obtain phosphorous from plants directly or indirectly. The waste products and dead organisms are decomposed by phosphate solubilising bacteria to release phosphorus. Gaseous exchange between organism and environment is negligible as compared to carbon.

Phosphorus Cycle

Ecosystem ServicesThe products of ecosystem processes are called ecosystem services. The healthy forest ecosystem/ forests provide following ecosystem services, so by keeping ecosystems healthy we can take advantage of ecosystem services: - purify air and water· Mitigates floods and droughts· Cycle nutrients· Generate fertile soil· Provide wildlife habitat · Maintain biodiversity etc.

- Pollinate crops- Provide storage site for carbon- Provide aesthetic , cultural and spiritual values- Provide stable food chain- Provide economically useful forest produce- Provide sustainable biological legacy to future generations

Researchers( Robert Constanza and his colleagues ) have put an average price tag of US $33 trillion a year on these fundamental ecosystems services which are taken granted because they are free although its value is twice the total global gross national product (GNP).      VSA questions:

1. Name the dominant producers in a deep aquatic ecosystem. What other name would you give to a primary consumer?

2. Differentiate between standing crop and standing state in an ecosystem.3. What is the percentage of PAR in the incident solar radiation?4. Which one of the following has second trophic level in a lake ?

Phytoplankton, Zooplankton, Benthos, Fishes

5. How is litter different from detritus?6. Write the equation that helps in deriving the net primary productivity of an ecosystem?7. What is a detritus food chain made up of ? How do they meet their energy and nutritional

requirements?8. Earthworm is called a detrivore while bacteria a decomposer. Why ?9. Mention the role of pioneer species in primary succession on rocks?10. Why green plants are not found beyond a particular depth in ocean?11. Write the difference between net primary productivity and gross primary productivity?12. List any two ways of measuring standing crop of a trophic level?13. All the primary productivity is not available to herbivores. Give one reason.14. What happens to process of decomposition at low temperature?15. What is meant by stratification?

SA questions :1. Why the pyramid of energy is always upright? Explain.2. It is possible that a species may occupy more than one trophic level in the same ecosystem

at the same time. Explain with the help of an example.3. Differentiate between two different types of pyramids of biomass with the help of one

example of each.4. Identify the type of given ecological pyramid and give one example each of pyramid of

numbers and pyramid of biomass in such cases.

5. Explain the function of reservoir in a nutrient cycle. List the two types of nutrient cycles in nature.

6. Explain using examples that how pyramid of numbers and pyramid of biomass can look inverted.

7. Explain standing crop in an ecosystem. Draw a pyramid of biomass , when a small standing cropof phytoplanktons, support a large standing crop of zooplanktons in a sea.

8. Name the type of food chains responsible for the flow of larger fraction of energy in an aquatic and a terrestrial ecosystem, respectively. Mention one difference between the two chains.

9. Global carbon is fixed in the biosphere through photosynthesis. Explain any two ways by which carbon is returned to the atmosphere.

10. State the difference between the first trophic levels of detritus food chain and grazing food chain.

11. Construct a grazing food chain and a detritus food chain using the following with five links in each:Earthworm, bird, vulture, snake, grasshopper, grass, frog, decaying plant matter

12. Rate of decomposition is fast in tropical rain forest, yet the soil are nutrient poor.

LA Questions1. How are productivity, gross primary productivity, net primary productivity and secondary

productivity interrelated?2. The gradual and predictable changes in the species composition of a given area is called

ecological succession. Define the pioneer and climax community in this context.3. Construct an ideal pyramid of energy, where 1,000,000 Joules of sunlight is available. Label

all its trophic levels.4. Name the pioneer community on a bare rock. How do they help in establishing the next

type of vegetation? Mention the type of climax community that will ultimately get established.

5. Construct a pyramid of biomass starting with phytoplanktons. Label three trophic levels.Is the pyramid upright or inverted? Why ?

6. Draw and complete the following model of carbon cycle filling a,b,c,d,e and f.

7. Explain primary productivity and the factors that influence it.8. Explain with the help of flow chart , the recycling of phosphorus in nature.9. Differentiate between primary and secondary succession.

VLA questions

1. (a) Healthy ecosystems are the base of wide range of ecosystem services. Justify.(b) Explain the difference between and the similarities between hydrarch and xerarch succession.

2. (a)

(i) Name the biogeochemical cycle shown above.(ii) Name an activity of living organisms not depicted in the cycle by which this nutrient

is returned to the atmosphere.(iii) How the flow of the nutrient would affected due to large scale deforestation?

Explain giving reasons.(iv) Describe the effect of increased level of this nutrient in the atmosphere on our

environment.3. (a) Explain different steps involved in decomposition of detritus. (b) Describe how do oxygen and chemical composition of detritus affect decomposition?4. (a) Explain how a xerarch succession proceeds from xeric to mesic conditions and forms a

stable climax community. (b) Why is the rate of secondary succession faster than that of primary succession?5. It is often said that pyramid of energy is always upright.On the other hand , the pyramid of

biomass can be both upright and inverted. Explain with the help of examples and sketches.6. Citing lake as an example of simple aquatic ecosystem interpret how various functions of this

ecosystem are carried out. Make a food chain that is functional in this ecosystem.7. (a) Colonisation of a rocky terrain is a natural process. Mention the group of organisms that

will invade this area first. (b) Over the years, it has been observed that some of the lakes are disappearing due to

urbanisation. In absence of human interference, depict by making a flow chart, how do the successional series progress from hydric to mesic conditions.

(c) Identify the climax community of hydrarch and xerarch succession.

COMPUTER SCIENCE

Solve the sample papers given Make a database of programs for the practical file Work on the synopsis for the project work