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Part 121 – Biology Previous Year Questions

Q1. Xenobiotics which are inherently resistant to microbial attack are called as:
(a) Biodegradable
(b) Persistent
(c) All of the given options
(d) Recalcitrant
Ans: (d) The compounds that resist biodegradation and thereby persist in the environment are called recalcitrant. The recalcitrant xenobiotic compounds can be grouped into the following six types: (i) halocarbons; (ii) polychlorinated biphenyls; (iii) synthetic polymers; (iv) alkylbenzyl sulphonates; (v) oil mixture and (vi) others.

Q2. In the grass lands, trees do not replace the grasses as a part of an ecological succession because of

(a) Limited sun light and paucity of nutrients
(b) None of the options
(c) Insect and fungi
(d) Water limits and fire
Ans: (d) Grass ecosystems are an early stage of succession in regions where the mature ecosystems are forests. However, grass ecosystems are climax ecosystems in grassland regions, where there is not enough rainfall to support a forest. Due to limiting factors such as water scarcity and forest fire, a grassland ecosystem changes to a desert ecosystem. The ecological succession of grassland is desert. It is, however, notable that the soil of grassland ecosystem is rich in nutrients and organic matters and provides the largest biomass.

Q3. Molybdenum deficiency affects the activity of :

(a) All of the given options
(b) Chlorate reductase
(c) Nitrogenase
(d) Nitrate reductase
Ans: (d) Numerous investigators have shown that nitrate nitrogen accumulates in higher plants and fungi which are deficient in molybdenum. In molybdenum-deficient plants grown in the presence of nitrate, molybdenum is required for the synthesis of nitrate reductase. Molybdenum deficiency results in the decrease of free amino acids in the plants in comparison to normal plants.

Q4. When one gene pair hides the effect of the other unit, the phenomenon is referred to as:

(a) Epistasis
(b) Mutation
(c) None of the options
(d) Dominance
Ans: (a) Epistasis refers to the phenomenon in which one gene hides the effect of the other. In other word, it does not allow the other gene to express itself. This is counterpart of dominance. While dominance works at inter allelic but intragenic level, Epistasis works at inter generic level. Epistasis is of following types: •Due to a recessive allele: A hides the effect of B, •Due to a dominant allele: A hides the effect of B. This may be in one direction only meaning that either A hides the effect of B or vice versa.

Q5. Which among the following is the sweetest sugar?

(a) lacrose (b) fructose
(c) maltos (d) glucose
Ans: (b) There are primarily three types of sugar: glucose, fructose and sucrose. Of the three sugars, fructose is the sweetest and glucose the least sweet, so typically less fructose can be used than table sugar (sucrose) – if sucrose has a sweetness of one, fructose is 1.7 and glucose 0.74. Fructose is known as the fruit sugar as its make source in the diet is fruits and vegetables.

Q6. An eazyme produced by HIV that allows the integration of HIV DNA into the host cell’s DNA is :

(a) Ligase (b) Integrase
(c) Helicase (d) DNA gyrase
Ans: (b) HIV’s enzyme for inserting the DNA version of its genome into the host cell DNA is called its “integrase”. HIV-1 integrase catalyzes the “cut-and-paste” action of clipping the host DNA and joining the proviral genome to the clipped ends. It is also produced by viruses containing double-stranded DNAs for the same purpose.

Q7. Which of the following plant shows chloroplast dimorphism?

(a) Sugar beet (b) Rice
(c) Wheat (d) Sugarcane
Ans: (d) Certain plans which possess the C4 dicarboxylic acid pathway of CO 2 fixations show a structural dimorphism of chloroplast structure. Sugarcane is a common example of C4 plant that has dimorphic chloroplast. The mesophyll cells possess chloroplasts with well developed grana whereas the bundle sheath chloroplasts lack the organization of grana (Agranal chloroplasts). The malic acid is transported to the bundle sheath chloroplast (Transportations). Here it is converted to pyruvic acid and CO 2 by NADP+ malic enzyme (Decarboxylation). The pyruvic acid is then transported to mesophyll chloroplasts (Transportation).

Q8. The gene which exhibites multiple effects is known as :

(a) Pseudogene
(b) Pleiotropic
(c) Complementary
(d) Polygene
Ans: (b) Pleiotropy describes the genetic effect of a single gene on multiple phenotypic traits. The underlying mechanism is that the gene codes for a product that is, for example, used by various cells, or has a signaling function on various targets. A classic example of pleiotropy is phenylketonuria, a human disease that affects multiple systems but is caused by one gene defect.

Q9. The metal ion present in vitamin B12 is :

(a) cobalt (b) zinc
(c) nickel (d) iron
Ans: (a) The structure of B12 is based on a corrin ring, which is similar to the porphyrin ring found in heme, chlorophyll, and cytochrome. It contains the biochemically rare element cobalt sitting in the center of the ring. Also called cobalamin, it is a water-soluble vitamin.

Q10. Microbial degradation of nitrates into atmospheric nitrogen is known as :

(a) Ammonification
(b) Nitrification
(c) Denitrification
(d) Putrefaction
Ans: (c) Denitrification is the biological conversion of nitrate to nitrogen gas, nitric oxide or nitrous oxide. It refers to nitrate reduction by bacterial species such as Pseudomonas and Clostridium, usually in anaerobic conditions that ultimately produces molecular nitrogen (N2). These bacteria use nitrate as an electron acceptor instead of oxygen during respiration.

Q11. The best milch breed in the word is :

(a) Chittagong (b) Sindhi
(c) Deoni
(d) Holstein–Friesian
Ans: (d) Holstein Friesians are a breed of cattle known today as the world’s highest-production dairy animals. The cattle is characterized by good durability, high productivity and high fat and protein levels in milk, making it a cost-effective and highly profitable livestock on farms around the world.

Q12. Pulses are obtained from the family :

(a) Liliaceae (b) Leguminosae
(c) Cycadaceae (d)Fungi
Ans: (b) Pulse, in botany, is a common name for members of the Fabaceae (Leguminosae), a large plant family. Pulses, high in protein, are used as food for humans and other animals. Besides, they play a key role in crop rotation due to their ability to fix nitrogen.

Q13. The substrate of Photorespiration is :

(a) Fructose (b) Pyruvic acid
(c) Glycolate (d) Glucose
Ans: (c) Glycolate is the major substrate for photorespiration. The enzymes of glycolate metabolism, e.g. glycolate oxidase and catalase, are present in substantial quantities in leaf extracts from both high and low capacity plants. Glycolate has been detected in leaves of both types of plants.

Q14. Match the following :
I II
A. Chlorophyll 1. Plant Disease
B. Nostoc 2. Photosynthetic
C. Transpiration 3. Diazotroph
D. Rust of wheat 4. Loss of water from plant surface

(a) A, B, C, D (b) A, B, C, D
(c) A, B, C, D (d) A, B, C, D
Ans: (c) Chlorophyll: green photosynthetic pigment that absorbs sunlight and uses its energy to synthesise carbohydrates from CO2 and water; Nostoc: an example of Diazotroph that fix atmospheric nitrogen gas into a more usable form such as ammonia; Transpiration: evaporation of water from plant leaves; Rust of Wheat: a fungal plant disease that affects wheat, barley and rye stems, leaves and grains.

Q15. B–Diversity is also known as :

(a) Within habitat diversity
(b) Ecosystem diversity
(c) Global diversity
(d) Between habitat diversity
Ans: (b) Biodiversity includes three main types: diversity within species (genetic diversity), between species (species diversity) and between ecosystems (ecosystem diversity). Ecological diversity is the intricate network of different species present in local ecosystems and the dynamic interplay between them.

Q16. Which one of these animals is jawless :

(a) Sphyrna (b) Trygon
(c) Myxine (d) Shark
Ans: (c) Myxine is a species of jawless fish. It is known as Hag fish in Europe. These are generally classified with the lampreys into the superclass Agnatha (jawless vertebrates) within the subphylum Vertebrata. All other living fishes (shark, rays, chimeras and bony fishes) possess true jaws derived from gill arches and are placed in the superclass Gnathostomata.

Q17. Competition for food, light and space is most severe in:

(a) Distantly related species growing in different habitats
(b) Closely related species growing in the same area or niche
(c) Closely related species growing in different habitats
(d) Distantly related species growing in the same habitats
Ans: (b) Competition for food, light and space is most severe in closely related species occupying the same niche or habitat. Since closely related species have the same desire of food, light and space and in the same area than all requirements are found in limited amount of proportion or quota, they have more competition.

Q18. Rotation of crops is essential :

(a) For increasing the quantity of minerals.
(b) For decreasing the quantity of proteins.
(c) For getting different kinds of crops.
(d) For increasing fertility of the soil.

Ans: (d) Crop rotation is the practice of growing a series of dissimilar/different types of crops in the same area in sequenced seasons. It gives various nutrients to the soil, thus, maintaining soil fertility, organic matter levels and soil structure. It also helps in the replenishment of nitrogen through the use of green manure in sequence with cereals and other crops.

Q19. Addition oxcessive amounts of heat to a lake is referred to as :

(a) Refrigeration effect
(b) Green House effect
(c) Thermal pollution
(d) Heat Bloom
Ans: (c) Thermal pollution is defined as the addition of excess of undesirable heat to water thereby making it harmful to man, animal or aquatic life. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. The change in ambient temperature of water decreases oxygen supply and affects ecosystem composition.

Q20. Afla toxins are produced by

(a) Bacteria (b) Algae
(c) Viruses (d) Fungi
Ans: (d) Aflatoxin are naturally occurring mycotoxins that are produced by Aspergillus flavus and Aspergillus parasiticus, species of fungi. They have been associated with various diseases, such as aflatoxicosis, in livestock, domestic animals and humans throughout the world.

Q21. Which one of the following is the infective stage of the Malarial Parasite?

(a) schigozoite (b) trophozoite
(c) sporoblast (d) sporozoite
Ans: (d) When a mosquito sucks the blood of a person who has malaria parasites in his or her blood, the mosquito picks male and female gametocytes where they undergo a series of changes to become sporozoites. The sporozoites are the infective stages of malaria parasites in the mosquito. This process takes about 10 -14 days depending on environmental temperature.

Q22. Ecosystem consists of :

(a) A biotic community and its non–living elements
(b) Population
(c) A population and its non–living elements
(d) A biotic community
Ans: (a) An ecosystem is defined as any community of living and non-living things that work together. Biotic components are the living things that shape an ecosystem. All non-living components of an ecosystem is called abiotic components such as temperature, light, moisture, air currents, etc.

Q23. Linseed is obtained from

(a) Castor (b) Flax
(c) Groundnut (d) Sesame
Ans: (b) Linseed are the seeds of the flax plant, which are the source of linseed oil and linseed cake. Flax is a member of the genus Linum in the family Linaceae. Linseed is one of the most potent sources of omega 3 fatty acids found in nature.

Q24. Which of the following organism possesses characteristics of a plant and an animal?

(a) Euglena (b) Mycoplasma
(c) Paramecium (d) Chlorella
Ans: (a) Most species of Euglena have photosynthesizing chloroplasts within the body of the cell, which enable them to feed by autotrophy (making energy-containing organic molecules from inorganic raw material through the use of an energy source such as sunlight), like plants. However, they can also take nourishment heterotrophically (making use of food that comes from other organisms in the form of fats, carbohydrates, and proteins), like animals. So Euglena have features of both animals and plants.

Q25. Match the following :
I II
A. Anabaena 1. Bacteria
B. Mucor 2. Gymnosperm
C. Pseudomonas 3. Fungi
D. Ephedra 4. Blue–green algae

(a) A–4, B–2, C–3, D–l
(b) A–4, B–3, C–1, D–2
(c) A–3, B–4, C–l, D–2
(d) A–2, B–l, C–4, D–3
Ans: (b) Anabaena: a blue-green algae; Mucor: a filamentous fungus; Pseudomonas: a common Gram-negative bacterium that can cause disease in animals; Ephedra: a genus of gymnosperm shrubs, the only genus in its family, Ephedraceae, and order, Ephedrales.

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