Biology (Part-I) (UPSC)

Total Questions: 50

1. Most of the desert plants bloom during night time because : [1995]

Correct Answer: (d) the desert insects are active during night time
Solution:Plant and animal activity happens at night in deserts due to high temperature. The desert insect pollinates flowers in night.
Desert Vegetation
• The predominant vegetation of both hot and mid-latitude deserts is xerophytic or drought-resistant.
• This includes the cacti, thorny bushes, long-rooted wiry grasses and scattered dwarf acacias.
• Trees are rare except where there is abundant ground water to support clusters of date palms.
• Along the western coastal deserts washed by cold currents as in the Atacama Desert, support a thin cover of vegetation.
• Intense evaporation increases the salinity of the soil so that the dissolved salts tend to accumulate on the surface forming hard pans (Bajada, Palaya).
• Absence of moisture retards the rate of decomposition and desert soils are very deficient in humus.
• Most desert shrubs have long roots and are well spaced out to gather moisture, and search for ground water. Plants have few or no leaves and the foliage is either waxy, leathery, hairy or needle-shaped to reduce the loss of water through transpiration.
• The seeds of many species of grasses and herbs have thick, tough skins to protect them while they lie dormant.

2. Living organisms require at least 27 elements, of which 15 are metals. Among these, those required in major quantities, include : [1996]

Correct Answer: (c) potassium, sodium, magnesium and calcium
Solution:Living organism require about 27 elements of which 15 are metals. K, Mg, Na and Ca are required in major quantities. Minor quantity of Mn, Fe, Co, Cu, Zn and Mo and trace amount of V, Cr, Sn, Ni and Al are required by some organisms. Calcium, magnesium and phosphorus are essential parts of the bones and teeth. Calcium is necessary for blood clotting. Sodium helps in muscle activity and transmission of nerve.

3. It is possible to produce seedless tomato fruits by : [1996]

Correct Answer: (c) spraying hormones on flowers
Solution:

Hormone auxin is responsible to produce seedless tomato fruits.
Auxins are a group of naturally occurring and artificially synthesised plant hormones. They play an important role in the regulation of plant growth. Auxins were initially isolated from human urine. Auxin means to “enlarge” or “increase”. They induce cell division, differentiation and elongation.
Mechanism of Action of Auxin
• Auxin is mostly produced in the apical meristem of shoots, young leaves and seeds
• Movement of auxin is unidirectional or polar, it moves downwards from its site of production
• Polar transport results in an auxin concentration gradient, which stimulates specific responses
• Auxin specific transport proteins in the plasma membrane control the movement of auxin out of the cell
• Plant hormones act by signal transduction, eliciting more than one cellular responses
• Auxin binds to enzyme-linked receptors, which promotes catalysis of a reaction
• When auxin binds to a receptor, it initiates binding of a repressor protein for certain genes (auxin response gene) to ubiquitin, resulting in degradation of repressor protein and the transcription of auxin response genes progresses leading to cellular growth and development

4. Match List-I (Physiological processes) with List-II (Cell organelles) and select the correct answer by using the codes given below: [1996]

List-I List-II 
A. Photosynthesis1. Plasma membrane
B. Mineral uptake2. Chloroplast
C. Respiration3. Mitochondria
D. Protein synthesis4. Ribosomes

Codes:

ABCD
(a)1234
(b)1243
(c)2134
(d)2142
Correct Answer: (c)
Solution:Photosynthesis occurs in green plants by the help of chloroplast. Plasma membrane helps in transport of minerals. Cellular respiration is related to mitochondria, by which energy releases. Ribosome helps in protein synthesis.
• Photosynthesis takes place in the chloroplast organelle of plant cells. It is a double-membrane organelle having its own DNA, mitochondria, and ribosomes. It also contains a third inner membrane, called thylakoid.
• Thylakoid membranes: They look like stacks of coins. It contains chlorophyll.
• The membrane system is responsible for trapping the light energy for the synthesis of ATP and NADPH.
• Stroma: The space between the thylakoid and the chloroplast membranes is called the stroma.
• Within the stroma, enzymatic reactions occur to synthesize sugar, subsequently leading to the formation of starch.

5. Which one of the following is a modified stem? [1996]

Correct Answer: (d) Potato
Solution:Potato tuber bears buds in small pits known as eyes. Buds develops to branches. Some of the branches become green, erect and leafy stems that grow horizontally under ground.
Potato is mostly cultivated by planting tubers. Purity of the cultivars and healthy seed tubers are the primary requirements for a successful crop. However, seed tuber is the costliest input in potato cultivation. The tuber seed should be disease free, well-sprouted and 30-40 g each in weight. It is advisable to use the entire seed tuber for planting. Hill tuber seeds are split into pieces and planted later in winter when they do not decay due to mild temperatures. The main objectives of cutting large size tubers are to reduce the cost of seed and to obtain uniform sprouting. Tubers should be cut longitudinally through the crown eye and the weight of the cut piece should be around 30-40 g. Usually the seed tubers are cut with a knife just and treated with fungicide before planting. Before cutting the seed tuber, the knife should be disinfected with Potassium Permanganate solution. The shortage of good quality seed tubers, high seed cost, transportation of bulky potato seed, and virus infiltration in seed tubers are some of the important problems associated with use of seed tubers as planting material.

6. Which one of the following type of micro organisms is most widely used in industries? [1998]

Correct Answer: (d) Bacteria, microalgae and fungi
Solution:Bacteria, microalgae and fungi is most widely used in industries. Bacteria like Lactobacillus sp. is used in manufacturing of vinegar and alcohol by fementation process.

Most of algae are used as single cell protein (1.e. Spirulina). Different drugs like penicillin is manufactured from fungi Penicillium notatum.

7. Match List-I with List-II and select the correct answer by using the codes given below the lists [1998]

List-I List-II 
A. Fruit1. Ovule
B. Seed2. Leaf
C. Wood3. Stem
D. Starch4. Ovary

Codes:

ABCD
(a)2134
(b)4132
(c)2314
(d)4312
Correct Answer: (b)
Solution:After the pollination of ovary, fruit develops gradually from it Stem of tree develops to wood. Seed develops from fertilized ovule. Leaf produces starch at the time of photosynthesis.
• The development of a fruit is a sequence of steps involved after the pollination and fertilization process in a flower. It involves multiple stages and a series of developmental and physiological changes. Parts of a flower:
• Stamen: Male reproductive organ of a flower, it consists of anther and filament. The anther produces pollen grains.
• Pistil/Carpel: Female reproductive organ of the flower, consisting of the stigma, style, and ovary. The ovary contains one or multiple ovules.
• Petal: Usually brightly colored to attract insects.
• Sepal: These protect flower bud.
• Ovule: This is contained within the ovary and, upon fertilization, will become a seed.

8. Which one of the following statements regarding starch and cellulose is not correct? [1998]

Correct Answer: (c) Both of them give colour with iodine
Solution:Starch and cellulose both are plant origin. Starch deposits in plant cells, whereas cellulose is most important constituent of plant cell wall. Both starch and cellulose are polymers. Starch is branched polymer of a-D-glucose unit linked by a-1,4 glycosidic bond. Cellulose is a linear polymer of B D-glucose unit. Glucose molecules are present in both starch and cellulose.

Amylose in starch is responsible for the formation of deep blue colour in the presence of iodine but cellulose does not give any colour at the treatment with iodine, because amylose is absent in cellulose.

9. Ergotism is due to consumption of : [1998]

Correct Answer: (a) contaminated grains
Solution:Ergotism is the effect of long term ergot poisoning, due to ingestion of alkaloids produced by fungus Claviceps purpurea which is found in infected cereals and ryes.

• Gangrenous Ergotism ("St. Anthony's Fire"):
  • Burning pain, numbness, cold, pale limbs.
  • Blisters, dry skin, blue/black discoloration.
  • Gangrene, tissue death, and sloughing of digits.
• Convulsive Ergotism:
  • Muscle spasms, twitching, convulsions, tremors.
  • Hallucinations, confusion, delirium, psychosis.
  • Nausea, vomiting, diarrhea, excessive sweating, headaches.

10. Which one of the following is a useful functional association between fungi and the roots of higher plants? [1999]

Correct Answer: (d) Mycorrhiza
Solution:• Mycorrhiza are symbiotic associations between plant roots and certain soil fungi which play a key role in nutrient cycling in the ecosystem and also protect plants against environmental and cultural stress.
• The plant makes organic molecules by photosynthesis and supplies them to the fungus in the form of sugars or lipids, while the fungus supplies the plant with water and mineral nutrients, such as phosphorus, taken from the soil.
• Mycorrhizas are located in the roots of vascular plants, but mycorrhiza-like associations also occur in bryophytes.
• They greatly increase the efficiency of nutrient and water uptake, enhance resistance to pathogens, and buffer plant species against several environmental stresses and drought resistance. Mycorrhizae also improve plant growth and survival in soils contaminated by heavy metals.
• Mycorrhizae acting as a bio-fertilizer and help in maintaining soil biology and chemistry. These are of 2 types:
• Endo mycorrhizae – Example with orchids.
• Ecto mycorrhizae – Example with pines, mushrooms, etc.