NIOS Class 12 Biology April 2019 Set B (58/OSS/1)

NIOS Question Paper April 2019 Set B Solved

1 MARK QUESTIONS

1. Which of the following enzymes is called “Joining Enzyme”?

A) Plasmids

B) DNA ligase

C) Protease

D) Amylase

2. Which of the following bacteria causes cholera?

A) Vibrio cholerae

B) Rhizobium

C) Azotobacter

D) Lactobacillus

3. One of the macronutrients given below plays a key role in food production and normal growth of the plant.

A) Boron

B) Copper

C) Carbon

D) Uranium

4. Which one of the following is a Criss-Cross nerve fibre connecting two cerebral hemispheres?

A) grey matter

B) white matter

C) meninges

D) corpus callosum

5. With reference to organisation of life, Rana tigrina comes into which category?

A) Community

B) Species

C) Organism

D) Biome

6. Choose the plant hormone which induces “Parthenocarpy”.

A) Auxin 

B) Gibberelins

C) Ethylene 

D) Lactic acid

7. Identify the following figure:

A) Sac 

B) Leaf

C) Embryo 

D) Seed Coat

8. Name the complex tissue which function as a unit to conduct water and minerals upward from root to leaves.

A) Phloem

B) Parenchyma

C) Xylem

D) Sclerenchyma

2 MARKS QUESTIONS

9. Give an example for each of the following:

a) Aerobic bacteria which fix nitrogen

b) Anaerobic bacteria which fix nitrogen

c) Cyanobacteria which fix nitrogen

d) Photosynthetic non-sulphur bacteria which fix nitrogen

Ans: 

1. Azotobacter
2. Clostridium
3. Anabaena
4. Rhodospirillum

10. Define the term inflorescence. What are the major types of inflorescence in flowering plants?

Ans: Inflorescence is the arrangement of flowers on the floral axis called the peduncle. The two major types of inflorescence are racemose and cymose. 

11. What is the importance of balanced diet? Reason out the special diet recommendation to pregnant and lactating women?

Ans: A balanced diet contains all essential nutrients in suitable proportions and amounts to provide necessary energy and keep the body in a healthy state. A pregnant woman has to feed the developing embryo; therefore, she has a special need for extra nutrients. Similarly, nursing mothers (who breastfeed their babies) also need a special diet to take care of their additional requirements of lactation (milk formation). So their diet should contain more protein, calcium and vitamins.

12. How is the phenotypic ratio of F2-generation in dihybrid cross is different from monohybrid cross?

Ans: Crosses involving plants differing in the inheritance of one contrasting feature only are called monohybrid crosses. Crosses involving two contrasting features are termed dihybrid crosses.

In a monohybrid cross, tallness and dwarfness were involved, TT x tt, 

The F1 was all tall with a genotype of Tt, as the gene for tallness is dominant over that for dwarfness. 

In the F2, Tt x Tt, the results will be 

Gametes	T	t
T	TT	Tt
t	Tt	tt

The phenotype of F2 here is 3 Tall: 1 dwarf.

In a dihybrid cross, two contrasting characters are taken into consideration- height and colour of the flower. 

In a cross between a tall red plant with a dwarf red, 

Parents: TTRR x ttrr

Gametes: T, T, R, R x t, t, r, and r

F1: TtRr. 

When F1 is selfed, 

Gametes	TR	Tr	tR	tr
TR	TTRRTall red	TTRrTall red	TtRRTall red	TtRrTall red
Tr	TTRrTall red	TTrrTall white	TTRrTall red	TtrrTall white
tR	TtRRTall red	TtRrTall red	ttRRDwarf red	ttRrDwarf red
tr	TtRrTall red	TtrrTall white	ttRrDwarf red	TtrrDwarf white

Thus, F2 shows 9 Tall red, 3 Tall white, 3 Dwarf red, and 1 dwarf white.

13. Observe the diagrams and answer the following:

a) Are these types of stomata found in monocots or dicots?

b) Mention their main function.

Ans: 

1. Stomata in dicots.
2. Stomata help in gaseous exchange and allow the loss of water vapour during transpiration.

14. Answer the following:

a) Which phase of growth curve shows rapid and maximum growth?

b) What is the term used for inducing early flowering in plants at low temperatures?

c) Name the specially designed equipment used to measure the rate of growth of shoot length of plants.

d) What is the hypothetical plant hormone which is responsible for initiation of flowering in plants?

Ans: 

1. Log phase
2. Vernalisation
3. Auxanometer
4. Florigen

15. Draw a neat diagram of human lung and label the Larynx and trachea parts:

Ans: 

16. Write the functions of the following:

a) Oxytocin

b) Prostate gland

Ans: 

1. The hormone Oxytocin from the posterior pituitary is responsible for uterine contractions during childbirth.
2. The prostate gland secretes an alkaline fluid, discharged into the urethra, that keeps the sperm alive and helps them to swim vigorously.

17. Write any four advantages of Bio-diesel.

Ans: Bio-diesel has several advantages; some of them are given below- (any four)

• It is an agriculture-based fuel substitute.
• It can be made from both vegetable oil and animal fats.
• It can be used without major modifications in engines.
• It does not need a separate infrastructure for storage and delivery.
• Handling biodiesel is safer.
• Planting of Jatropha curcus will utilise wasteland in our country.
• Its combustion emits less carbon monoxide, sulphates, unburnt hydrocarbons and particulate matter, thus reducing air pollution.

18. Where does spinal cord is located in human beings? Mention its main function.

Ans: The spinal cord extends from the medulla of the brain downward almost the whole length of the backbone. Its main function is to carry out reflexes below the neck and conduct both sensory impulses and motor responses to and from the brain.

19. Give reasons:

a) Habitat is called an address of the organism.

b) Fins are an adaptation of fish to aquatic life.

Ans: 

1. Habitat is the physical environment in which an organism lives and is thus considered its address.
2. An adaptation is the appearance, behaviour, structure or mode of life of an organism that allows it to survive in a particular environment. The presence of gills and fins are example of adaptation of fish to an aquatic habitat.

20. A person is suffering from softening of bones and pain in bones which tend to fracture easily.

a) What is this condition?

b) How to prevent it?

Ans: 

1. Osteomalacia due to a deficiency of vitamin D.
2. Osteomalacia can be prevented by giving a diet rich in calcium, like milk, cod liver oil, egg yolk, and green leafy vegetables.

4 MARK QUESTIONS

21. Differentiate between “Sapwood” and “Heartwood”.

Ans: The outer part of wood, which is functional and consists of recently formed secondary xylem having some living cells, is called sapwood. As the plant ages in the central part of the stem, the inner cells of sap wood that become non-functional and dark in colour constitute heartwood.

Sapwood	Heart wood
It is the outer light coloured wood of an old stem	It is the central dark colored wood of an old stem
Light coloured	Dark coloured due to the presence of gums, resins, oils, tannin, etc.
Contains living cells	Living cells are absent
Vessels not plugged help in the upward movement of water and minerals	Vessels are plugged with tyloses
Wood is lighter in weight	Heavier in weight
Less durable because of susceptibility to attack by pathogens	More durable, resistant to the attack of pathogens
Commercially less valuable	Commercially more valuable

22. A man with ‘A’ blood group married a woman with blood group ‘B’. Work out a cross to show possible blood groups that can be expected in their offspring.

Ans: 

Parents: A x B

Genotype: I^AI^A x I^BI^B  

Gametes	IB	IB
IA	IAIB	IAIB
IA	IAIB	IAIB

All their offspring will have the AB blood group. 

23. Write short notes on:

a) Mode of nutrition in Yeast.

b) Sexual recombination in Bacteria.

Ans: 

1. Yeast is saprotrophic. It can directly absorb simple sugar (glucose), but for obtaining sucrose (cane sugar), it gives out the enzyme invertase or sucrase, which breaks down sucrose into simple sugars. The simple sugars are then simply absorbed into the cell.
2. Some bacteria show a primitive mode of sexual reproduction. It is different from sexual reproduction in higher forms. The steps are:
   1. Two conjugating (lie very close for the transfer of genes) bacteria are held together by pili.
   2. A segment of a DNA strand is transferred from one bacterium to another bacterium.

24. Draw a schematic diagram of “Carbon Cycle”.

Ans: 

25. Explain the process of translocation.

Ans: Movement of organic and inorganic solutes from one part of the plant to another is known as translocation, e.g. Transport of sugar in sieve tubes of leaves to the stem or fruit.

Mechanism of translocation

• Sugar solution in the phloem sieve tube moves along the water potential gradient created between the source (leaf) and sink (storage) cells
• Here we find a mass movement of sugar solution from the leaf mesophyll to the sieve tubes of the leaf, and then to all parts of the plant.

26. Give reasons: 

a) Sino-atrial node is called pacemaker of the heart.

b) Person with blood group ‘O’ called Universal donor.

Ans: 

1. Since the Sinu-atrial Node initiates and regularises the heartbeat, it is also called the pacemaker. The pacemaker is influenced by nerves, hormones, CO₂ and O₂ content of blood, and heat.
2. Blood groups of O type can be given to all groups. It is thus the Universal Donor. This is because there are no antigens in the blood of Group O.

6 MARKS QUESTIONS

27. a) Name the scientist who discovered C3 cycle.

b) Draw a neat schematic diagram of C3 cycle in plants.

c) Justify your answer why C4 plants are most efficient than C3 plants?

Ans: 

1. Melvin Calvin
2. Calvin Cycle

3. C4 plants are more efficient than C3 plants because C4 plants have no photorespiration and thus there is no loss of additional carbon dioxide, due to breakdown of RuBP to Glycolate and CO₂.

28. a) Write the various steps involved in obtaining wine from grapes by fermentation of yeast, along with the diagram.

b) Write any two types of alcohols produced by same method.

Ans: 

1. Wine is obtained by fermentation of grapes. Grapes are fermented by S. cerevisiae, and their soluble sugars (glucose and fructose) are converted into CO₂ and ethyl alcohol. Steps taken for fermentation
   1. The fermenter or tank and the nutrient medium are sterilised by steam under pressure (autoclave).
   2. The correct strain of yeast is selected.
   3. The yeast is inoculated into the medium. Inoculation can be done in two ways:
      1. (a) Yeast can be grown as a layer on the surface of the nutrient medium. This is called a support growth system.
      2. (b) Cells or mycelia are suspended in a liquid medium. This is called a suspended growth system.
   4. Care is taken to maintain the right temperature, pH, oxygen and carbon dioxide concentration.
   5. The medium is stirred and left to ferment.
   6. The sugar in the medium gets fermented by enzymes released by yeast.
   7. (vii) The fermented product is taken out

2. Some alcohols manufactured by yeast fermentation are: Ethyl alcohol, butanol and glycerol.

29. a) What is “Criss-Cross inheritance”?

b) Why is red-green colour blindness more common in males than females?

c) How is colour blindness inherited? Explain with the help of flow chart.

Ans: 

1. The type of inheritance of a recessive sex linked character from father to daughter and then from the daughter to her sons is known as criss-cross inheritance or sex linked or X-linked inheritance.
2. The defective gene for red-green colour blindness is located on the X chromosome. In males, a single defective gene causes the disease, while in females, it requires the presence of two defective genes. This is why this disease is more common in males than in females.
3. In males, the single X chromosome is received from the mother. Hence, a defective gene for colour blindness on the  X chromosome of the mother is passed on to the son and expressed as a defect. The daughter who receives the defective gene becomes a carrier.

Parents: XX^C x XY

Gametes: X, X^C, and X, Y

Gametes	X	Y
X	XX Normal daughter	XYNormal son
XC	XCXCarrier daughter	XCYColour blind son

30. a) Write any four salient features of Class-Aves with two examples.

b) Define “Alteration of generation”, with one example.

Ans: 

1. Features of Class Aves (any four)
   1. The body is covered with feathers, and scales are present only on the hind limbs
   2. The body is divisible into three parts: head, neck and trunk.
   3. Jaws with a horny beak, no teeth.
   4. Hind limbs with four digits adapted for perching, walking or swimming
   5. Bones with air spaces to make the skeleton light (pneumatic bones).
   6. Forelimbs modified into wings for flight.
2. The alternation between two phases in the life cycle between a gametophytic and a sporophytic generation is called alternation of generations.  Eg. The main body of bryophytes is the gametophyte, and the diploid zygote is the only sporophyte in their lives.

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