Biology

121. With reference to the food chains in ecosystems, which of the followin

With reference to the food chains in ecosystems, which of the following kinds of organism is/are known as decomposer organism/organisms?

  1. Virus
  2. Fungi
  3. Bacteria

Select the correct answer using the codes given below.

[amp_mcq option1=”1 only” option2=”2 and 3 only” option3=”1 and 3 only” option4=”1, 2 and 3″ correct=”option2″]

This question was previously asked in
UPSC IAS – 2013
Download PDFAttempt Online
Fungi and Bacteria are the primary decomposers in most ecosystems. They break down dead organic matter, returning nutrients to the environment. Viruses are not decomposers; they are parasitic and reproduce within host cells.
Decomposers are organisms that break down dead or decaying organisms, and in doing so, they carry out the natural process of decomposition. They play a vital role in nutrient cycling, making essential nutrients available to producers (plants).
Decomposition is a critical part of the food web. While fungi and bacteria are the main decomposers, detritivores (like earthworms, beetles, and millipedes) also contribute by physically breaking down organic matter, which increases the surface area for fungi and bacteria to act upon.

122. Consider the following minerals : 1. Calcium 2. Iron 3. Sodium Wh

Consider the following minerals :

  • 1. Calcium
  • 2. Iron
  • 3. Sodium

Which of the minerals given above is/are required by human body for the contraction of muscles?

[amp_mcq option1=”1 only” option2=”2 and 3 only” option3=”1 and 3 only” option4=”1, 2 and 3″ correct=”option3″]

This question was previously asked in
UPSC IAS – 2013
Download PDFAttempt Online
Calcium and Sodium are minerals required by the human body for the contraction of muscles.
– **Calcium:** Calcium ions (Ca²⁺) are essential for initiating muscle contraction. In skeletal muscle, the release of calcium from the sarcoplasmic reticulum triggers the binding of myosin to actin filaments, leading to the sliding filament mechanism of contraction.
– **Sodium:** Sodium ions (Na⁺) play a critical role in the electrical signaling that initiates muscle contraction. An action potential, involving the influx of sodium ions across the muscle cell membrane, causes depolarization, which in turn leads to the release of calcium ions. Potassium ions (K⁺) are also crucial for repolarization and maintaining the membrane potential.
– **Iron:** Iron is vital for overall muscle function, primarily because it is a component of myoglobin, which stores oxygen in muscle cells, and enzymes involved in energy metabolism. However, it is not directly involved in the biochemical process of muscle fiber contraction itself in the same way calcium and sodium are.
Muscle contraction is a complex physiological process involving nerve impulses, changes in membrane potential, release of neurotransmitters, and the interaction of contractile proteins (actin and myosin) mediated by calcium ions. Electrolytes like sodium, potassium, calcium, and magnesium are all important for proper muscle and nerve function.

123. Which of the following diseases can be transmitted from one person to

Which of the following diseases can be transmitted from one person to another through tattooing?

  • 1. Chikungunya
  • 2. Hepatitis B
  • 3. HIV-AIDS

Select the correct answer using the codes given below.

[amp_mcq option1=”1 only” option2=”2 and 3 only” option3=”1 and 3 only” option4=”1, 2 and 3″ correct=”option2″]

This question was previously asked in
UPSC IAS – 2013
Download PDFAttempt Online
Hepatitis B and HIV-AIDS can be transmitted from one person to another through tattooing if contaminated equipment is used.
Tattooing involves piercing the skin. If needles or other instruments used for tattooing are not properly sterilized and have been contaminated with infected blood, blood-borne viruses can be transmitted.
1. Chikungunya is a viral disease transmitted by mosquitoes, not through blood-to-blood contact via needles.
2. Hepatitis B is a blood-borne virus that can be transmitted through contaminated needles, syringes, or other sharp instruments.
3. HIV-AIDS is caused by the Human Immunodeficiency Virus (HIV), which is primarily transmitted through blood, semen, vaginal fluids, and breast milk. Sharing contaminated needles is a known risk factor for HIV transmission.
Other infections that can potentially be transmitted through unsterile tattooing practices include Hepatitis C, tetanus, and various bacterial infections. Proper sterilization techniques and single-use needles are crucial for preventing the spread of diseases during tattooing.

124. Consider the following organisms : 1. Agaricus 2. Nostoc 3. Spirog

Consider the following organisms :

  • 1. Agaricus
  • 2. Nostoc
  • 3. Spirogyra

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

[amp_mcq option1=”1 and 2″ option2=”2 only” option3=”2 and 3″ option4=”3 only” correct=”option2″]

This question was previously asked in
UPSC IAS – 2013
Download PDFAttempt Online
Nostoc is used as a biofertilizer. Agaricus and Spirogyra are not typically used as biofertilizers.
1. Agaricus is a genus of fungi (mushrooms) and is not generally used as a biofertilizer. Some fungi like mycorrhizal fungi are used as biofertilizers as they enhance nutrient uptake, but Agaricus is not primarily used for this purpose.
2. Nostoc is a genus of cyanobacteria (blue-green algae) known for its ability to fix atmospheric nitrogen. It is widely used as a biofertilizer, especially in paddy fields.
3. Spirogyra is a genus of filamentous green algae. It is photosynthetic but does not fix nitrogen and is not used as a biofertilizer.
Biofertilizers are substances containing live microorganisms which, when applied to seed, plant surfaces, or soil, colonize the rhizosphere or the interior of the plant and promote growth by increasing the supply or availability of primary nutrients to the host plant. Examples include nitrogen-fixing bacteria (Rhizobium, Azotobacter), cyanobacteria (Anabaena, Nostoc), and phosphorus-solubilizing microorganisms.

125. Improper handling and storage of cereal grains and oilseeds result in

Improper handling and storage of cereal grains and oilseeds result in the production of toxins known as aflatoxins which are not generally destroyed by normal cooking process. Aflatoxins are produced by

[amp_mcq option1=”bacteria” option2=”protozoa” option3=”moulds” option4=”viruses” correct=”option3″]

This question was previously asked in
UPSC IAS – 2013
Download PDFAttempt Online
The correct answer is C) moulds.
Aflatoxins are naturally occurring mycotoxins that are produced by certain molds, specifically species of *Aspergillus*, most notably *Aspergillus flavus* and *Aspergillus parasiticus*. These molds grow on various food crops, such as maize, peanuts, cottonseed, and tree nuts, often under conditions of high humidity and temperature and improper storage. Aflatoxins are highly toxic and carcinogenic, and are not typically destroyed by normal cooking temperatures.
Aflatoxin contamination is a significant concern for food safety, particularly in tropical and subtropical regions. Exposure to aflatoxins can cause acute liver damage and is a major risk factor for liver cancer. Regulatory limits for aflatoxins in food and feed are set by many countries to protect public health.

126. Consider the following animals: 1. Sea cow 2. Sea horse 3. Sea lio

Consider the following animals:

  • 1. Sea cow
  • 2. Sea horse
  • 3. Sea lion

Which of the above is/are mammal/mammals?

[amp_mcq option1=”1 only” option2=”1 and 3 only” option3=”2 and 3 only” option4=”1, 2 and 3″ correct=”option2″]

This question was previously asked in
UPSC IAS – 2013
Download PDFAttempt Online
The correct option is B, meaning that Sea cow and Sea lion are mammals, while Sea horse is not.
– Sea cows (which include manatees and dugongs) are aquatic mammals belonging to the order Sirenia.
– Sea horses are small marine fish belonging to the genus Hippocampus. They are a type of fish, not a mammal.
– Sea lions are marine mammals characterized by external ear flaps, long foreflippers, the ability to walk on all four flippers on land, and short, thick hair. They belong to the family Otariidae.
Mammals are characterized by features such as having mammary glands (producing milk for young), being warm-blooded, having hair or fur, and typically giving birth to live young. Fish are aquatic vertebrates characterized by gills, fins, and usually scales, and they are cold-blooded.

127. Recombinant DNA technology (Genetic Engineering) allows genes to be tr

Recombinant DNA technology (Genetic Engineering) allows genes to be transferred

  • 1. across different species of plants
  • 2. from animals to plants
  • 3. from microorganisms to higher organisms

Select the correct answer using the codes given below.

[amp_mcq option1=”1 only” option2=”2 and 3 only” option3=”1 and 3 only” option4=”1, 2 and 3″ correct=”option4″]

This question was previously asked in
UPSC IAS – 2013
Download PDFAttempt Online
Recombinant DNA technology allows genes to be transferred across different species and even kingdoms. All three statements describe possible applications of this technology.
1. Transfer across different species of plants: Yes, this is common in developing Genetically Modified (GM) crops, for example, transferring herbicide resistance genes between plant species or varieties.
2. From animals to plants: Yes, while perhaps not as common as plant-to-plant or microorganism-to-plant transfers for agricultural purposes, it is technically possible to transfer genes from animals to plants using genetic engineering techniques. This has been explored in research for various purposes.
3. From microorganisms to higher organisms: Yes, this is a very common application. For instance, transferring genes from bacteria (like the Bt gene) to plants for pest resistance (e.g., Bt cotton), or inserting genes from humans into bacteria or yeast for the production of therapeutic proteins like insulin.
Recombinant DNA technology involves techniques like gene cloning and transformation, allowing scientists to isolate a gene from one organism and introduce it into another organism, often unrelated, to express a desired trait or produce a specific product. This technology has vast applications in agriculture, medicine, and industry.

128. Which one of the following structure is NOT found in prokaryotes ?

Which one of the following structure is NOT found in prokaryotes ?

[amp_mcq option1=”Nuclear envelope” option2=”Cell membrane” option3=”Ribosome” option4=”Cell wall” correct=”option1″]

This question was previously asked in
UPSC CAPF – 2024
Download PDFAttempt Online
The correct option is A. The nuclear envelope is a structure that is NOT found in prokaryotes.
– Prokaryotic cells (like bacteria and archaea) lack a true nucleus and other membrane-bound organelles.
– The genetic material (DNA) in prokaryotes is located in a region called the nucleoid, which is not enclosed by a membrane.
– The nuclear envelope is the double membrane that surrounds the nucleus in eukaryotic cells.
Cell membranes are present in all cells, prokaryotic and eukaryotic, as they define the cell boundary. Ribosomes, responsible for protein synthesis, are also present in both prokaryotes and eukaryotes, although they differ slightly in size (70S in prokaryotes, 80S in eukaryotes). Cell walls are present in most prokaryotes (like bacteria) and some eukaryotes (like plants and fungi), but not in animal cells.

129. Which one of the following is the correct chronology of invention/ dis

Which one of the following is the correct chronology of invention/ discovery in the field of Bio-technology ?

[amp_mcq option1=”Discovery of Plasmid, Double Helical structure of DNA, DNA fingerprinting, cloning of Dolly” option2=”Double Helical structure of DNA, Discovery of Plasmid, DNA fingerprinting, cloning of Dolly” option3=”DNA fingerprinting, cloning of Dolly, Double Helical structure of DNA, Discovery of Plasmid” option4=”Double Helical structure of DNA, DNA fingerprinting, Discovery of Plasmid, cloning of Dolly” correct=”option1″]

This question was previously asked in
UPSC CAPF – 2024
Download PDFAttempt Online
The correct option is A. The correct chronological order of the listed events in the field of biotechnology is: Discovery of Plasmid, Double Helical structure of DNA, DNA fingerprinting, cloning of Dolly.
– Discovery of Plasmid: Although observed earlier, the term “plasmid” was coined by Joshua Lederberg in 1952.
– Double Helical structure of DNA: Watson and Crick published their model of the DNA double helix in 1953.
– DNA fingerprinting: Developed by Sir Alec Jeffreys in 1984.
– Cloning of Dolly: Dolly the sheep was born in July 1996, and her birth was announced in 1997.
This sequence reflects the foundational molecular biology discoveries in the 1950s paving the way for later applied technologies like DNA fingerprinting and cloning in the 1980s and 1990s.

130. In what form excess of glucose is stored in human body ?

In what form excess of glucose is stored in human body ?

[amp_mcq option1=”Fructose” option2=”Glycogen” option3=”Glucose” option4=”Starch” correct=”option2″]

This question was previously asked in
UPSC CAPF – 2024
Download PDFAttempt Online
The correct option is B. In the human body, excess glucose is stored primarily in the liver and muscles in the form of glycogen.
– Glycogen is a complex polysaccharide, a branched polymer of glucose.
– This process of glucose storage as glycogen is called glycogenesis.
– Glycogen serves as a readily available energy reserve.
Fructose is a different type of sugar. Glucose is the circulating form of sugar in the blood, used for immediate energy. Starch is the primary storage form of glucose in plants, not in animals or humans.
Page 1Page 2Page 3Page 4Page 5