Biology (Part-I) (UPSC)

Total Questions: 50

11. Which one of the following organisms can serve as a biofertilizer for rice crop? [2000]

Correct Answer: (a) Blue-green algae
Solution:Blue green algae is used as a biofertilizer in rice crop. Blue green algae has the nitrogen fixing ability which enhances the production of rice.
Blue-Green Algae are a type of photosynthetic bacteria consisting either of single cells or colonies which is also known as the Cyanobacteria. Cyanobacteria contain only one type of chlorophyll, Chlorophyll a, a green pigment. In addition, they also contain pigments such as carotenoids, phycobilin.
These bacteria grow naturally in marine and freshwater systems. They thrive in dams, rivers, reservoirs, lakes and even in hot springs. These bacteria normally look green and sometimes turns blue when scum are dying. Almost all species of these bacteria are buoyant and float on the water surface and forms floating mats.
The accumulation of these algae is termed as ‘blooms’. These blooms discolour the water and produce unpleasant taste and odour. They affect the fish population and reduces water quality. The decomposition of these blooms deplete the oxygen and triggers the killing of fish.
Examples of cyanobacteria: Nostoc, Oscillatoria, Spirulina, Microcystis, Anabaena.

12. Phytotron is a facility to : [2000]

Correct Answer: (c) grow plants under controlled conditions
Solution:

Phytotrons are the chambers having controlled environmental conditions. These are immensely helpful in investigating the growth of plants under various experimental set ups. These are most commonly found in the majority of botanical laboratories. It provides them with environmental control at a small and limited level. Thus, the interaction between plants and its environmental conditions could be effectively studied in these phytotrons. This will provide the account of the effect of several environmental elements on the growth and development of plants.
Phytotron chambers consist of the controlled environment spaces that can be lit both naturally as well as artificially. Besides, this chambers are well equipped with incubators, refrigerators, photoperiod rooms, rosettes and seed germination chambers as well. These provide diverse environmental conditions. They also provide opportunities to carry out various biochemical studies under stable and reproducible conditions. Research based on simulation modeling for which an extensive range of numerous environmental aspects are needed can also be carried out in phytotrons.

13. Soft drinks such as colas contain significant quantities of: [2000]

Correct Answer: (a) caffeine
Solution:Cocoa contains caffeine, carbonated water, glucose-fructose, kola extract and caramel colour.
• Caffeine is a natural stimulant of the central nervous system (CNS) most frequently found in tea, coffee, and cocoa plants.
• It works by activating the central nervous system and brain, keeping you alert and delaying the onset of fatigue.
• It is used to improve cognitive function by raising alertness and attentional capacity.
• By preventing adenosine from attaching to the adenosine A1 receptor, caffeine increases the release of the neurotransmitter acetylcholine.
• Additionally, caffeine raises levels of cyclic AMP by nonselectively inhibiting phosphodiesterase.

14. Canola refers to special type of oil seed mustard varieties bred for human consumption. The main characteristic of these varieties is that the : [2000]

Correct Answer: (b) oil is rich in unsaturated fatty acids
Solution:Canola refers to both an edible oil (also known as canola oil) produced from the seed of any of several varieties of the Brassicaceae family of plants, and to those plants, namely a cultivar of Brassica napus L., Brassica rapa subsp. oleifera, syn. B. campestris L. or Brassica juncea. To be called canola, it must contain less than 2% erucic acid and less than 30 micromoles glucosinolates.

15. Which organelle in the cell, other than nucleus contains DNA? [2001]

Correct Answer: (d) Mitochondrion
Solution:DNA is also found in mitochondria other than nucleus. The DNA is called mitochondrial DNA.
Deoxyribonucleic Acid (DNA) is the molecule that carries the genetic information for an organism’s development and function. DNA is made up of two linked strands that wind around each other to form a twisted ladder shape known as a double helix. The majority of DNA is found in the cell nucleus (referred to as nuclear DNA), but a small amount can also be found in the mitochondria. DNA is essential in all living things for inheritance, protein-coding, and providing instructions for life and its processes.

16. "Athlete's Foot" is a disease' caused by : [2001]

Correct Answer: (b) Fungus
Solution:Athlete's Foot disease is caused by parasitic fungus of genus Trichophyton. Scaling, flaking and itching of affected areas are the symptoms of this disease. This disease transmitted in moist areas where people walk bare foot.
Types of Athlete’s Foot Infection
Toe web
The most prevalent form, a toe web infection, affects the skin between the fourth and fifth toes. Individuals may observe changes in skin colour, cracking, peeling, or flaking in this region.
Moccasin
This variant impacts the soles, heels, and edges of the feet. Initial symptoms include soreness, followed by thickening and cracking of the skin on the soles. In rare cases, toenails may become infected, leading to thickening, fragmentation, and eventual loss.
Vesicular
Commonly affecting the soles but potentially appearing anywhere on the feet, a vesicular-type infection is characterised by the presence of bumps or fluid-filled blisters (vesicles).
Ulcerative
The rarest type, an ulcerative infection, is marked by open sores (ulcers) that often appear between the toes and may also manifest on the soles of the feet. Open sores are a distinctive feature of this uncommon form of athlete’s foot.

17. Epiphytes are plants which depend on other plants for : [2001]

Correct Answer: (b) mechanical support
Solution:An epiphyte is a plant normally grows on another plant for support. It is non parasitic, but uses the host plant for support. A plant such as tropical orchid or staghorn fern, that grows on another plant upon which it depends for mechanical support but not for nutrients.

18. In a bisexual flower, if androecium and gynoecium mature at different times, the phenomenon is known as : [2002]

Correct Answer: (a) dichogamy
Solution:In bisexual flower, the male and female flowers (androecium and gynoecium) mature at different times to avoid self-fertilization. It is called dichogamy.
Dichogamy is the process of maturation of the anthers and the stigma of a flower. The maturation occurs at different times in different plants. Protandry is when the anthers are the first to mature in the flowers of the plant. Protogyny is when the stamens are the first to mature in the flowers of the plant. This process takes place only in the bisexual flowers. In the case of unisexual flowers, it takes place in monoecious and dioecious plants. The process is said to be complete if the stigmas get matured after the wilting of stamens or if the stamens get matured after the wilting of stigmas. If one of the plants attain sexual maturity and the other has not then dichogamy is said to be incomplete.
For example Cruciferae, Rosaceae, Ranunculaceae, etc shows dichogamy
Protandry occurs in the flowers of Jasmine, Sunflower, etc.
Protogyny occurs in the flower of Rose, Ashoka, etc.
Dichogamy or dichogyny was discovered by Sprengel in the late 1790s. He designates hermaphrodite flower whose sex organs mature at different intervals of time. The same condition was first described by Kolreuter but it was further recognized by Sprengel. He named the male-female sequence as dichogamy androgyny and the female-male sequence as dichogamy gynandry. These sequences are further known as protandry and protogyny. Scientists find it more desirable to call all dichogamy as heterodichogamy which is the condition where both protandry and protogyny exists among the individuals of the species. A scientist named Delpino called dichogamy as a general law of cross-pollination. He meant that all morphological or physiological adaptations are for cross-fertilization. But the final theory confirmed was of Sprengel which was the maturation of stamen and pistil at different intervals of time.

19. Consider the following plants : [2003]

1. Bougainvillea

2. Carnations

3. Cocoa

4. Grapes

Which of these plants are propagated by stem cuttings?

Correct Answer: (d) 1, 2, 3 and 4
Solution:Propagation by stem cuttings is a common method of asexual reproduction in plants, where a portion of the stem with at least one node and one or more leaves is cut from the parent plant and rooted to form a new individual plant. The new plant will have the same genetic makeup as the parent plant and will exhibit similar characteristics, making this method useful for maintaining desirable traits of a plant. Bougainvillea, carnations, grapes, and cocoa are all plants that can be propagated by stem cuttings.

20. Consider the following statements: [2003]

1. The common blue green algae, Spirogyra and Ulothrix, are found in both fresh water ponds and oceans.

2. The Chameleon can look ahead with one eye, and at the same time look behind with another.

Which of these statements is/are correct?

Correct Answer: (c) Both 1 and 2
Solution:The common blue green algae Spirogyra and Ulothrix are found in both fresh water ponds and oceans. Algae species like Spirogyra and Ulothrix are generally found in fresh water environments.

However, the statement declares they are found in oceans as well, and without specific supporting evidence, this claim is debatable. But the answer assumes it as true.

The chameleon can look ahead with one eye, and at the same time look behind with another. This is accurate, as chameleons have unique eyes that can swivel independently, allowing them to look in two completely different directions at once.