Biology

1. What is the causative agent of West Nile fever ?

What is the causative agent of West Nile fever ?

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Bacteria
Virus
Protozoa
Fungus
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UPSC Combined Section Officer – 2024
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West Nile fever is a viral infection transmitted primarily by mosquitoes. The causative agent is the West Nile virus (WNV).
– West Nile fever is caused by a virus.
– The virus is transmitted by mosquitoes.
West Nile virus is a single-stranded RNA virus that belongs to the genus Flavivirus, family Flaviviridae. It is commonly found in Africa, Europe, the Middle East, West Asia, and North America. Most people infected with WNV have no symptoms, but some develop fever, headache, body aches, joint pains, vomiting, diarrhea, or rash. A small percentage develop severe illness affecting the central nervous system.

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2. A disease that is present permanently in a region or population is kno

A disease that is present permanently in a region or population is known as

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pandemic
epidemic
endemic
zoonotic
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A disease that is present permanently in a region or population is known as endemic.
In epidemiology, an endemic disease is one that is constantly maintained at a baseline level in a population within a geographical area without external inputs. This means the disease is regularly found among particular people or in a certain area.
An ‘epidemic’ refers to a sudden increase in the number of cases of a disease above what is normally expected in a population in a given area. A ‘pandemic’ is an epidemic that has spread over several countries or continents, affecting a large number of people. A ‘zoonotic’ disease is an infectious disease that has jumped from a non-human animal to humans.

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3. What is the common name for the Asiatic wild dog that was once found a

What is the common name for the Asiatic wild dog that was once found all over the continent?

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Dhole
Dachshund
Beagle
Mudhol Hound
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The common name for the Asiatic wild dog that was once found all over the continent is Dhole.
The Dhole (Cuon alpinus) is a canid native to South, Southeast, East, and Central Asia. It is also known as the Asian wild dog, Indian wild dog, whistling dog, red dog, and mountain wolf. The Dhole is a highly social animal, living in packs, and is a formidable predator.
Dholes are listed as Endangered on the IUCN Red List, facing threats from habitat loss, depletion of prey base, competition with other predators, and persecution. Dachshund, Beagle, and Mudhol Hound are breeds of domesticated dogs and are not wild species found across the continent.

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4. Rhizobium is a

Rhizobium is a

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biopesticide
biofertilizer
bioherbicide
mycoherbicide
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UPSC CISF-AC-EXE – 2024
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Rhizobium is a genus of bacteria known for forming a symbiotic relationship with the roots of leguminous plants. Within root nodules, these bacteria fix atmospheric nitrogen (Nā‚‚) and convert it into a form usable by plants (ammonia/ammonium), thereby enriching the soil and providing essential nutrients for plant growth. This process makes Rhizobium a type of biofertilizer.
Rhizobium bacteria fix atmospheric nitrogen, acting as a natural fertilizer for plants, especially legumes.
Biofertilizers are substances containing living 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. Biopesticides, bioherbicides, and mycoherbicides are types of pesticides or herbicides derived from natural materials (e.g., bacteria, fungi, plants, minerals) used to control pests or weeds.

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5. Which one of the following human cells is devoid of a nucleus?

Which one of the following human cells is devoid of a nucleus?

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Nerve cell
Bone cell
Red blood cell
White blood cell
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UPSC CISF-AC-EXE – 2024
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Mature mammalian red blood cells (erythrocytes) are unique among human cells in that they lack a nucleus, as well as other organelles like mitochondria, ribosomes, and endoplasmic reticulum. This adaptation allows them to maximize the space available for hemoglobin, the protein responsible for oxygen transport, and also makes them more flexible to squeeze through narrow capillaries.
Mature red blood cells are anucleated, meaning they are devoid of a nucleus.
While mature red blood cells in mammals lack a nucleus, this is not the case for red blood cells in birds, reptiles, amphibians, and fish, which retain their nuclei. Nerve cells, bone cells, and white blood cells are all nucleated cells that perform various functions in the body, such as transmitting electrical signals, providing structural support, and fighting infections, respectively.

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6. The process of degradation of humus by some microorganisms and release

The process of degradation of humus by some microorganisms and release of inorganic nutrients is known as

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eutrophication
mineralization
humification
stratification
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The correct answer is B) mineralization.
Mineralization is the process by which organic matter, such as humus, is decomposed by microorganisms into inorganic nutrients (minerals) like nitrates, phosphates, and sulfates. These inorganic nutrients are then available for uptake by plants.
Humification is the process of formation of humus, a stable form of organic matter, from the decomposition of plant and animal residues. Eutrophication is the enrichment of water bodies with nutrients. Stratification refers to the layering of soil or water bodies. Mineralization is a key part of nutrient cycling in ecosystems.

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7. Fruit formation from the thalamus instead of ovary is known as false f

Fruit formation from the thalamus instead of ovary is known as false fruit. The most common examples are

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orange and mango
mango and banana
apple and strawberry
guava and cherry
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The correct answer is C) apple and strawberry.
A false fruit (or accessory fruit) is one where the fleshy, edible part is developed from tissues other than the ovary, such as the thalamus, petals, or sepals. In apples and strawberries, the edible fleshy part is primarily derived from the receptacle (thalamus).
True fruits develop exclusively from the ovary after fertilization. Examples include mango, orange, tomato, and cherry. Banana is also considered a true fruit, often developing parthenocarpically (without fertilization). Guava is a true fruit.

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8. The arrangement and distribution of flowers over a plant is called

The arrangement and distribution of flowers over a plant is called

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flowering
inflorescence
thalamus
aestivation
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UPSC CISF-AC-EXE – 2024
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The correct answer is B) inflorescence.
The arrangement of flowers on the floral axis of a plant is known as inflorescence. This arrangement can vary widely among different plant species (e.g., spike, raceme, panicle, umbel, capitulum).
Flowering is the process of producing flowers. Thalamus (or receptacle) is the part of the flower stalk from which the floral parts arise. Aestivation refers to the arrangement of petals and sepals within a flower bud before it opens.

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9. Lichens represent the symbiotic relationships between algae and fungi.

Lichens represent the symbiotic relationships between algae and fungi. The algae component present in lichen is best known as

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mycobiont
phycobiont
prion
symbiont
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The correct answer is B) phycobiont.
Lichens are composite organisms resulting from the symbiotic association between a fungus and a photosynthetic partner, usually an alga or cyanobacterium. The fungal component is called the mycobiont, and the photosynthetic algal or cyanobacterial component is called the phycobiont.
In the lichen symbiosis, the fungus typically provides structure, protection, and absorbs water and minerals, while the phycobiont produces food through photosynthesis. This mutualistic relationship allows lichens to survive in harsh environments where neither partner could thrive alone. A prion is a misfolded protein that can cause disease. Symbiont is a general term for an organism involved in a symbiotic relationship.

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10. Consider the following statements about stem cells : 1. Stem cells h

Consider the following statements about stem cells :

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  • 1. Stem cells have the potential for self-renewal via mitotic cell division.
  • 2. In 1908, James Thomas and his colleagues first derived human embryonic stem cells from donated blastocysts through in vitro fertilization.

Which of the statements given above is/are correct?

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1 only
2 only
Both 1 and 2
Neither 1 nor 2
This question was previously asked in
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The correct answer is A) 1 only.
Statement 1 is correct: Stem cells possess the unique ability to divide and renew themselves through mitotic cell division, maintaining the stem cell population. Statement 2 is incorrect: Human embryonic stem cells were first successfully derived in 1998 by James Thomson and his colleagues at the University of Wisconsin-Madison, not in 1908 by James Thomas.
Stem cells are undifferentiated cells that can differentiate into specialized cell types and can self-renew. There are different types, including embryonic stem cells (derived from blastocysts) and adult stem cells (found in various tissues). Their discovery and potential applications in regenerative medicine are significant areas of research.

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