The Union Public Service Commission (UPSC) Preliminary Examination serves as the gateway to one of the most prestigious careers in India’s civil services. Among the varied subjects tested in the Prelims, Biology stands out as a critical domain, encompassing the intricate tapestry of life forms on our planet. Specifically, the segment on “Diversity in Living Organisms” delves into the rich array of life, from microscopic unicellular organisms to the majestic multicellular beings that populate Earth. This section scrutinizes not only the taxonomy and classification of organisms but also their evolutionary adaptations, ecological roles, and significance in maintaining the delicate balance of our ecosystems. Through a series of meticulously crafted topic-wise questions, UPSC evaluates candidates’ understanding of biological principles, their ability to discern patterns in nature, and their aptitude for applying scientific knowledge to real-world scenarios. Delving into this realm offers candidates not just a chance to showcase their grasp of biology but also an opportunity to appreciate the awe-inspiring complexity and diversity of life forms that share our planet.
Q1. The only snake that builds a nest is [1995]
(a) Chain Viper
(b) King cobra
(c) Krait
(d) Saw-scaled viper
Ans. (b)
The King Cobra stands alone among snakes in its nesting behavior, constructing a nest fashioned from leaves and branches. This industrious serpent diligently safeguards its nest until the eggs hatch. The female diligently gathers substantial amounts of fallen leaves and decaying vegetation, creating a suitable environment in which to deposit her clutch of up to 50 eggs. Throughout the entire incubation period, she remains steadfast in her guardianship of the eggs.
Q2. Biologists have so far known, found and identified a large number of species in the plant and kingdom. In terms of number, the largest found and identified so far is from among the (1996)
(a) fungi
(b) plants
(c) insects
(d) bacteria
Ans. (c)
In terms of sheer quantity, the insect class, a subset of the animal kingdom, boasts the largest known species count within the animal and plant kingdoms. Insect biodiversity comprises a significant portion, estimated at around 70% of all animal species. The staggering number of insect species currently identified stands at 1,025,000. However, our understanding of protists, archaea, bacteria, and viruses remains fragmented. Plant species number at approximately 72,000.
Q3. Which one of the following types of microorganisms is most widely used in industries? (1998)
(a) Bacteria
(b) Bacteria and fungi
(c) Bacteria and algse
(d) Bacteria, microalgae and fungi
Ans. (d)
Bacteria, microalgae, and fungi represent the primary macromolecules extensively utilized in industries. For instance, bacteria such as Lactobacillus spp. play a crucial role in yogurt production. Additionally, various other bacterial strains find commercial utility in the creation of a diverse array of products.
Microalgae, notably species like Spirulina, are predominantly employed as single-cell proteins, enriching various food supplements. Moreover, fungi, exemplified by Penicillium notatum, contribute to the synthesis of essential drugs like penicillin. Yeast, a type of fungus, is pivotal in alcohol manufacturing through the fermentation process in industrial settings.
Q4. Which one of the following is a useful functional association between fungi and the roots of higher plants? (1999)
(a) Biofertiliser
(b) Coralloid rool
(c) Lichen
(d) Mycorrhiza
Ans . (d)
Mycorrhizas represent a beneficial functional bond between fungi and the roots of higher plants. This mutual relationship, found in both gymnosperms (naked seed plants) and angiosperms (flowering plants), offers numerous advantages to plants. These include resistance to root-borne pathogens, increased tolerance to salinity and drought, enhanced absorption of phosphorus from the soil, among others. Additionally, mycorrhizas serve as a significant source of biofertilizer.
Q5. Which one of the following is monogamous? (2002)
(a) Wolf
(b) Walrus
(c) Seal
(d) Deer
Ans. (a)
The wolf stands out in the animal kingdom for its inclination towards monogamy, a relationship form where an individual commits to only one partner either for their entire lifetime or at any given time. While monogamy remains rare in the natural world, other examples include beavers and certain species of bats. However, creatures like walruses, seals, and deer typically do not adhere to monogamous relationships, although some deer, like the European roe deer, may sporadically exhibit monogamous tendencies.
Q6. Which one of the following statements is not correct? (2002)
(a) All echinoderms are viviparous
(b) Roundworm has no circulatory system
(c) In bony fishes, swim bladder is usually present
(d) In cartilaginous fishes, fertilisation is internal
Ans. (a)
Statement (a) is inaccurate, as animals belonging to the phylum Echinodermata are oviparous, meaning they lay eggs. Additionally, they possess the remarkable ability of regeneration. Most echinoderms exhibit a star-shaped body structure and feature stinging cells on their surfaces.
Q7. Which one of the following statements is correct?
(a) Prions are the smallest free-living cells
(b) The cell wall of Mycoplarmaris made up of amino sugars
(c) Viruida consist of single-stranded DNA/RNA molecule
(d) Rickettsia lack cell wall
Ans. (c)
The statement given in option (c) is accurate. Viroids are indeed small infectious segments of nucleic acid, typically RNA, and they are independent pathogenic agents found in the environment. They can cause diseases such as potato spindle tuber disease. However, the other statements are incorrect and need correction. Prions are infectious pathogenic agents composed mainly of proteins and devoid of nucleic acid. Mycoplasmas lack a cell wall, while Rickettsias possess one.
Q8. Ticks and mites are actually (2002)
(a) arachnids
(b) crustaceam
(c) insects
(d) mytiapods
Ans. (a)
Ticks and mites, along with scorpions and spiders, belong to the class Arachnida within the phylum Arthropoda. Crustaceans, on the other hand, are a type of small arthropod found in the subphylum Crustacea, which also includes creatures like shrimp and crabs. Myriapods constitute another subphylum of arthropods, encompassing millipedes, centipedes, and related organisms. Insects, forming the largest group within the phylum Arthropoda, are classified under the class Insecta.
Q9. Consider the following statements.
1. Tapeworm is a hermaphrodite.
2. Roundworm has separate sexes.
3. Filaria is caused by a nematode.
4. Guinea worm is an annelid.
Which of these are correct? (2002)
(a) 1 and 2
(c) 3 and 4
(b) 1.2 and
(d) 2, 3 and 4
Ans. (b)
Statements (1), (2), and (3) are accurate. Tapeworms exhibit hermaphroditism, possessing both male and female reproductive organs within a single individual. Roundworms are dioecious, meaning they have separate sexes. Filaria is the result of infection by Wuchereria bancrofti, a parasitic nematode. Statement 4 is inaccurate because Guinea worm, Dracunculus medinensis, is a slender nematode, not an annelid. This parasite causes dracunculiasis or guinea-worm disease, transmitted through the consumption of contaminated water.
Q10. Octopus is (2004)
(a) an arthropod
(b) an echinoderm
(c) a hemichordate
(d) a mollusc
Ans. (d)
The octopus belongs to the phylum Mollusca, making it a member of the animal kingdom. Typically, mollusks possess a protective hard shell encasing their soft bodies. However, certain species like the octopus and oysters have evolved with shells that are scarcely visible. The octopus, characterized by its octopod body structure, boasts several tentacles that serve as flexible limbs or appendages. These limbs are equipped with suction cups, aiding in locomotion and manipulation. As a defense mechanism against predators, the octopus can expel an inky fluid into the water. Additionally, one of its most remarkable abilities is its capability to change body color, allowing it to camouflage and adapt to its surroundings effectively.
Q11. Consider the following statements. (2004)
1. The common blue-green algae, Spirogyra and Ulothris are found in both freshwater ponds and oceans.
2. The Chameleon can look ahead with one eye and t the same time look behind with another.
Which of these statements is/are correct?
(a) Only 1
(b) Only 2
(c) Both 1 and 2
(d) Neither 1 nor 2
Ans. (b)
Statement (2) stands true. This is because Chameleons possess the remarkable ability to simultaneously observe both forward and backward with distinct eyes. Their eyes operate independently, allowing them nearly 360-degree vision. Moreover, they can independently move and focus their eyes, akin to adjusting a camera lens, enhancing their visual acuity. Conversely, Statement (1) is erroneous as Spirogyra and Ulothrix are not classified as blue-green algae; rather, they are members of the Chlorophyceae class, which comprises green algae.
Q12. Among the following, which one lays eggs and does not produce young ones directly? (2008)
(a) Echidna
(b) Kangaroo
(c) Porcupine
(d) Whale
Ans. (a)
Among the mammals provided, the echidna stands out for its unique reproductive method—it lays eggs instead of giving birth to live young. This makes the echidna a rare example of an egg-laying mammal, known as a monotreme. After mating, the female echidna lays a solitary egg with a soft, leathery shell approximately twenty-two days later. This egg is then placed directly into her pouch. Echidnas belong to a classification known as metatherians, serving as a crucial link between prototherian and eutherian mammals in evolutionary terms.
Q13. In which one of the following kinds of organisms is the phenomenon found wherein the female kills the male after copulation? (2008)
(a) Dragon fly
(b) Honeybee
(c) Spider
(d) Pit viper
Ans. (c)
The occurrence where the female spider engages in post-copulatory consumption of the male is observed in arachnids, commonly referred to as sexual cannibalism. This unique behavior involves a female spider killing and consuming a male of the same species after mating. While various forms of cannibalism are prevalent across the animal kingdom, sexual cannibalism stands out as a distinct phenomenon within spiders.
Q14. For which one of the following snakes, the diet mainly composed of other snakes? (2008)
(a) Krait
(b) Russell’s viper
(c) Rattle snake
(d) King cobra
Ans. (a)
The composition of a king cobra’s diet primarily consists of creatures like pythons, rodents, and various venomous snakes. When raised in captivity, they are typically fed a diet of mice, rats, and occasionally other small mammals. If introduced to this diet early on, most king cobras readily accept it, often refusing alternative foods once they reach adulthood.
Q15. The panda belongs to the same family as that of (2009)
(a) bear
(b) cat
(c) dog
(d) rabbit
Ans. (a)
Kip, the Red Panda, commonly referred to as the cat bear or lesser panda, is a member of the bear family. Primarily herbivorous, these adorable creatures are sadly endangered. Red Pandas inhabit temperate climates, favoring deciduous and coniferous forests, often with a dense bamboo understory and hollow trees.
Q16. Which feature of some species of blue-green algae helps to promote them as biofertilisers? (2010)
(a) They convert atmospheric which the crop plants can absorb readily
(b) They induce the crop plants to produce the enzymes that help convert atmospheric nitrogen to nitrates
(c) They have the mechanism to convert atmospheric nitrogen into a form that the crop plants can absorb readily
(d) They induce the roots of the crop plants to absorb the soil having nitrates in longer qunatities
Ans. (c)
Cyanobacteria, commonly known as blue-green algae (BGA), possess a unique ability to convert atmospheric nitrogen into a form readily absorbed by plants. Throughout the crop growth cycle, they proliferate, utilizing atmospheric nitrogen and releasing it through excretion and autolysis, thus making it accessible to the crops. This process is facilitated by specialized cells called heterocysts, which are responsible for nitrogen fixation.
In addition to their role in agriculture, BGA play a crucial part in the marine nitrogen cycle, serving as significant primary producers in various oceanic regions. Moreover, these organisms are not confined solely to marine environments but can also be found in diverse habitats.
Q17. King cobra is the only snake that makes its own nest. Why does it make its nest? (2010)
(a) It is a snake eater and the nest helps attract other snakes
(b) It is a viviparous snake and needs a nest to give birth to its offspring
(c) It is an oviparous snake and lays its eggs in the nest and guards the nest until they are hatched
(d) It is a large, cold blooded animal and needs a nest to hibernate in the cold season
Ans. (c)
The king cobra, an oviparous snake, lays its eggs in a nest and diligently guards them until they hatch. The female king cobra collects ample fallen leaves and decaying vegetation to create a suitable environment for its clutch of approximately 50 eggs. It then safeguards this nest until the eggs undergo complete incubation and hatch.
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