Biology (Part-I) (UPSC)

Total Questions: 50

31. Some species of plants are insectivorous. Why? [2010]

Correct Answer: (b) They are adapted to grow in nitrogen deficient soils and thus depend on insects for sufficient nitrogenous nutrition
Solution:Insectivorous plants prey insects because most of the insectivorous plants grow in those area where there is deficiet of nitrogen in nutrients so they catch insect to fulfil its need of nutrients.
• These plants are usually associated with rain-washed, nutrient-poor soils, or wet and acidic areas that are ill-drained.
• Such wetlands are acidic due to anaerobic conditions, which cause partial decomposition of organic matter releasing acidic compounds into the surroundings.
• As a result, microorganisms necessary for complete decomposition of organic matter cannot survive in such poorly oxygenated conditions.
• Normal plants find it difficult to survive in such nutrient poor habitats.
• The hunter plants are successful in such places because they supplement their photosynthetic food production by trapping insects and digesting their nitrogen rich bodies.

32. Mon 863 is a variety of maize. It was in the news for the following reason. [2010]

Correct Answer: (b) It is a genetically modified variety which is pest resistant
Solution:Mon 863 is genetically modified variety of maize, which is resistant of corn root worm.
Genetic modification (GM) is a technology that involves inserting DNA into a host organism’s genome. Plant genetic modification entails inserting a specific stretch of DNA into the plant’s genome to confer new or different characteristics such as making it resistant to a specific disease. The most widely grown GM crops worldwide are cotton, soybeans, maize, and canola with herbicide tolerance and insect resistance.
USA, Brazil, Argentina, India, and Canada are the five top GM-growing countries, together accounting for approximately 90% of area of the GM cultivation.

33. Other than Jatropha curcas, why is Pongamia pinnata also considered a good option for the production of bio-diesel in India? [2010]

1. Pongamia pinnata grows naturally in most of the arid regions of India.

2. The seeds of Pongamia pinnata are rich in lipid content of which nearly half is oleic acid.

Which of the statements given above is/ are correct?

Correct Answer: (c) Both 1 and 2
Solution:Pongamia Pinnata is adaptable to arid zones, and has a varied habitat distribution and able to grow in a variety of soils, it is native to humid and subtropical environment and grows naturally along coasts and river banks of India and Myanmar. It is nitrogen-fixing trees.

34. When the bark of a tree is removed in a circular fashion all around near its base, it gradually dries up and dies because? [2011-1]

Correct Answer: (b) Roots are starved of energy.
Solution:Phloem layer of tissue just below the bark is responsible for carrying food from leave to roots.

35. Consider the following kinds of organisms: [2013-1]

1. Bacteria

2. Fungi

3. Flowering plants

Some species of which of the above kinds of organisms are employed as biopesticides?

Correct Answer: (d) 1, 2 and 3
Solution:All of them are employed as Biopesticides. Biopesticides, derived from natural materials like bacteria and fungi, offer an eco-friendly pest control alternative.

Examples include Bacillus thuringiensis for insects and Trichoderma species for plant diseases. While some plants produce pesticidal compounds, they're less common in pest management.

36. Consider the following organisms: [2013-1]

1. Agaricus

2. Nostoc

3. Spirogyra

Which of the above is/are used as biofertilizer/biofertilizers?

Correct Answer: (b) 2 only
Solution:Nostoc fix atmospheric nitrogen and are used as inoculations for paddy crop.
• For a sustainable agriculture system, it is essential to use renewable inputs (fertilizer, pesticides, water etc.) which can benefit the plant and cause no or minimal damage to the environment.
• One of the energy efficient and pollution free method to exploit the ability of certain microorganisms like bacteria, algae and fungi to fix atmospheric nitrogen, solubilize phosphorus, decompose organic material or oxidize sulphur in the soil.
• When they are applied in soil, they enhance growth and yield of crops, improve soil fertility and reduce pollution. They are known as “bio-fertilizers”.
• Thus bio-fertilizers are living or biologically active products or microbial inoculants of bacteria, algae and fungi (separately or in combination) which are able to enrich the soil with nitrogen, phosphorus, organic matter etc.
• Following are some of the important types of bio fertilizers which can be considered for agro based industries.

37. Fruits stored in a cold chamber exhibit longer storage life because : [2013-1]

Correct Answer: (c) rate of respiration is decreased
Solution:Fruits respire. They give out ethylene which helps in
ripening. When fruits are kept in cold storage the rate of ethylene production can be controlled and shelf life of fruits can be increased.
The term “cold chain” refers to a temperature-controlled supply chain for cold storage and delivery, whereby fresh agricultural food is kept and its shelf life is increased. In addition to agricultural products, the cold chain is required for horticulture, floriculture, dairy, fisheries, pharmaceuticals, industrial chemicals, poultry processing, and meat processing. The Cold Supply Chain Scheme has been in place since 2008 in India.

38. Many transplanted seedling do not grow because : [2013-1]

Correct Answer: (c) most of the root hairs are lost during transplantation
Solution:During a transplant the fine roots are destroyed due to the jostling during the uprooting process. These root hairs come under a shock. The plant which has been transplanted either takes time to readjust to the new soil or dries up and dies due to the root hair loss.

39. Which of the following leaf modifications occurs/occur in desert areas to inhibit water loss? [2013-1]

1. Hard and waxy leaves

2. Tiny leaves or no leaves

3. Thorns instead of leaves

Select the correct answer using the codes given below :

Correct Answer: (d) 1, 2 and 3
Solution:To inhibit water loss or to conserve water most of the desert species have waxy leaves that keep them water proof when stomata are closed. Water is further conserved by reducing surface area so most succulents have few leaves or no leaves. Some desert plants have thorns instead of leaves. Thorns do not let the water go out.

40. Which one of the following is the process involved in photosynthesis? [2014-1]

Correct Answer: (b) Free energy is converted into potential energy and stored
Solution:In photosynthesis the free energy is converted into potential energy and stored.
Photosynthesis – Food Making Process In Plants
• Carbon dioxide from air is taken in through the tiny pores present on the surface of the leaves. These pores are surrounded by ‘guard cells’. Such pores are called stomata.
• Water and minerals are transported to the leaves by the vessels which run like pipes throughout the root, stem, the branches and the leaves. They form a continuous path or passage for the nutrients to reach the leaf.
• The leaves have a green pigment called chlorophyll. It helps leaves to capture the energy of the sunlight. This energy is used to synthesize (prepare) food from carbon dioxide and water. Since the synthesis of food occurs in the presence of sunlight, it is called photosynthesis (Photo: light; synthesis: to combine).
• So we find that chlorophyll, sunlight, carbon dioxide and water are necessary to carry out the process of photosynthesis. Thus, sun is the ultimate source of energy for all living organisms.
• Besides leaves, photosynthesis also takes place in other green parts of the plants such as green branches.
• The desert plants have scale or spine-like leaves to reduce loss of water by transpiration. These plants have green stems which carry out photosynthesis.
• During photosynthesis, chlorophyll containing cells of leaves, in the presence of sunlight, use carbon dioxide and water to synthesise carbohydrates. The carbohydrates ultimately get converted into starch.
• The leaves other than green also have chlorophyll. The large amount of red, brown and other pigments mask the green colour. Photosynthesis takes place in these leaves also.