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Q1
short answer
2 marks
(a) (i) Why are crop fields considered as artificial ecosystems?
(ii) Write a common food chain of four steps operating in a terrestrial ecosystem.
Solution
(i) Crop fields are considered artificial ecosystems because they are man-made and maintained by humans. They do not occur naturally; humans decide the crop to be grown, add water, manure/fertilisers and control pests and weeds.
(ii) A common four-step food chain in a terrestrial ecosystem is:
Grass → Grasshopper → Frog → Snake
Q1
short answer
2 marks
(b) (i) Why should biodegradable and non-biodegradable wastes be discarded separately?
(ii) What destructive effect do chlorofluorocarbons bring about in the atmosphere and to the mankind?
Solution
(i) Biodegradable and non-biodegradable wastes should be discarded separately so that biodegradable waste can be decomposed by microorganisms and used for composting, while non-biodegradable waste can be safely recycled or disposed of without causing pollution.
(ii) Chlorofluorocarbons (CFCs) destroy the ozone layer in the atmosphere. The depletion of ozone increases the entry of harmful ultraviolet rays into the Earth, which can cause skin cancer, eye damage, and harm to living organisms.
Q2
short answer
2 marks
(a) (i) A magnetic compass shows a deflection when placed near a current carrying wire. How will the deflection of the compass get affected if the current in the wire is increased? What does it indicate?
(ii) State Right hand thumb rule.
Solution
(i) If the current in the wire is increased, the deflection of the compass increases. This indicates that the magnetic field produced by a current-carrying conductor becomes stronger when the current is larger.
(ii) Right-hand thumb rule: If a straight current-carrying conductor is held in the right hand with the thumb pointing in the direction of current, then the curled fingers show the direction of the magnetic field lines around the conductor.
Q2
short answer
2 marks
(b) List two factors on which the strength of magnetic field at a point due to a current carrying straight conductor depends. State the rule that determines the direction of magnetic field produced in this case.
Solution
The strength of the magnetic field at a point due to a current-carrying straight conductor depends on:
1. The magnitude of current flowing in the conductor.
2. The distance of the point from the conductor.
The direction of the magnetic field is determined by the Right-hand thumb rule.
Q3
short answer
2 marks
(a) ... respectively. Statistical probability of getting either a male or a ...
Solution
The probability of getting either a male or a female child is equal, i.e. 50% each.
This is because the male parent produces two types of sperms, one carrying X chromosome and the other carrying Y chromosome, while the female parent produces only X-bearing eggs. Therefore, the chance of XX (female) and XY (male) offspring is equal.
Q3
short answer
2 marks
(b) If we cross a tall plant (Tt) with a short plant (tt), what ratio of $(Tt)$ and $(tt)$ plants shall we obtain in F$_2$ generation? Show with the help of a diagram (flow chart) only.
Q4
short answer
2 marks
The number of chromosomes in the progeny of sexually
Q4
short answer
2 marks
The number of chromosomes in the progeny of sexually reproducing organisms is restored. Comment.
Q5
short answer
2 marks
Write the names of the following:
(a)
(b)
(c) Gamete
(d) Ovary
(e) Seed
Q5
short answer
2 marks
Mention the changes that occur in the following after fertilisation in a flower :
(a) Petals
(b) Zygote
(c) Ovary
(d) Ovule
Q6
mcq
2 marks
Consider the following four elements of the third period of the Modern Periodic Table:
(i) Si, (ii) Na, (iii) Cl, and (iv) Ar
Which of these elements
-
A.
(a) is most metallic
-
B.
(b) is a noble gas
-
C.
(c) is most electropositive, and
-
D.
(d) is a metalloid?
Q6
short answer
2 marks
Consider the four elements of the 3rd period of the Modern Periodic Table as given below :
(i) Si, (ii) Na, (iii) Cl, and (iv) Ar
Which of these is
(a) most metallic,
(b) a noble gas,
(c) most electronegative, and
(d) a metalloid ?
Q7
short answer
2 marks
Consider the following carbon compounds:
I II
(a) Write the name of the functional group present in these compounds.
(b) Write the general formula of the compounds of this functional group.
Q8
short answer
3 marks
Give reasons for the following :
(a) The existence of decomposers is essential in a biosphere.
(b) Flow of energy is unidirectional in a food chain.
(c) A food chain generally consists of only three or four trophic levels.
Q9
long answer
3 marks
Define the term electric power. An electric device of resistance $R$ when connected across an electric source of voltage $V$ draws a current $I$. Derive an expression for the power in terms of resistance $R$ and voltage $V$. What is the power of a device of resistance $400$ operating at $200$ V ?
Q10
short answer
3 marks
(a) The values of current $I$ flowing through a resistor for the corresponding values of potential difference $V$ across it are given below :
$V$ (volts) 1·5 3·0 6·0 9·0
$I$ (amperes) 0·5 1·0 2·0 3·0
(i) Plot a graph between $V$ and $I$.
(ii) Why should this graph pass through the origin ?
(iii) Name and state the law which is represented by the graph.
Q10
short answer
3 marks
(b) Find the equivalent resistance of the following combinations of resistors :
Q11
short answer
3 marks
(a) Explain the surgical method of contraception used by (i) males, and (ii) females to prevent fertilisation.
(b) Write the role of oral pills taken by women as a contracepti
Q12
short answer
3 marks
(a) (i) In the given below compound H H | | H C C O H | | H H identify (I) the heteroatom, and (II) the functional group. (ii) Write the structural formula of butane (C4H10). (iii) Draw the complete structure of the molecule of (I) Cyclohexane, and (II) Benzene. Which of the two is unsaturated ?
Q12
short answer
3 marks
OR (b) (i) A compound with molecular formula C3H6O has two isomers. (I) Draw the structures of both the isomers. (II) Write their functional group. (ii) Why are the compounds of carbon exceptionally stable ?
Q13
short answer
3 marks
(a) Explain the basis of classification of Dobereiner’s triads. (b) Which of the elements (i) X2O3 and (ii) YH2 should be placed in Mendeleev’s periodic table?
Q14
long answer
4 marks
Take two different coils of copper wire having large number of turns, say 50 and 100 turns respectively. Insert them over a non-conducting roll as shown in the given figure. Connect the Coil-1, having large number of turns, in series with a battery and a plug key. Also connect the other Coil-2 with a galvanometer. (a) State what is observed in the galvanometer, when (i) the key is closed. (ii) the key is opened. (b) Define the phenomenon involved in this case. (c) (i) Explain the reason for the current which is responsible for the deflection in the galvanometer. OR (ii) A coil AB of copper wire is connected to a galvanometer as shown in the figure. What is observed when N-pole of a strong bar magnet is (I) pushed into the coil, and (II) held stationary inside the coil ? State the reason for each observation.
Q15
long answer
4 marks
A student crossed pea plants having round and yellow seeds with pea plants having wrinkled and green seeds. He found that only one type of seeds were produced in the F1 generation. When these F1 generation pea plants were self-pollinated with each other, then in addition to the seed type of F1 generation, some new types of seed combinations were also obtained in the F2 generation. (a) Mention the dominant traits observed in F1 generation. (b) Write any two contrasting visible characters other than the ones shown above, taken by Mendel for his experiment. (c) (i) Give reason why F1 × F2 ? In this case, write the ratio of different types of seeds obtained in F2. OR (ii) What is meant by (I) dominant, and (II) recessive ? Explain.
Q15
short answer
A student crossed pea plants having round and yellow seeds with pea plants having wrinkled and green seeds. He found that only one type of seeds were produced in the $F_1$ generation. When these $F_1$ generation pea plants were self-pollinated with each other, then in addition to the seed type of $F_1$ generation, some new types of seed combinations were also obtained in the $F_2$ generation.
(a) Mention the dominant traits observed in $F_1$ generation.
(b) Write any two contrasting visible characters other than the ones shown above, taken by Mendel for his experiment.
Q24
short answer
4 marks
Explain the reason for the current which is responsible for the deflection in the galvanometer.
Q25
short answer
4 marks
A coil AB of copper wire is connected to a galvanometer as shown in the figure. What is observed when N-pole of a strong bar magnet is (I) pushed into the coil, and (II) held stationary inside the coil? State the reason for each observation.
