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CSS MCQs

Civil Superior Services β€” Complete MCQ Bank

31 Questions
Exam Preparation Guide

How to prepare for CSS

CSS is Pakistan’s premier federal competitive examination. Strong preparation requires conceptual clarity, broad general knowledge and consistent practice across compulsory and optional areas.

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1
Biology Medium

Which chromosomal disorder is caused by the presence of an extra chromosome 21?

  • ATurner syndrome
  • BDown syndrome
  • CKlinefelter syndrome
  • DPatau syndrome
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Correct Answer: Option B β€” Down syndrome
Explanation: Down syndrome also called trisomy 21 is caused by the presence of an extra copy of chromosome 21 resulting in intellectual disability and characteristic physical features.
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2
Biology Hard

What is the term for the complete set of chromosomes in a cell of an organism?

  • AGenome
  • BKaryotype
  • CPhenotype
  • DGenotype
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Correct Answer: Option B β€” Karyotype
Explanation: A karyotype is the complete set of chromosomes in a cell of an organism arranged and displayed in homologous pairs and used to diagnose chromosomal disorders.
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3
Biology Medium

Which type of RNA brings amino acids to the ribosome during protein synthesis?

  • AmRNA
  • BrRNA
  • CtRNA
  • DsnRNA
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Correct Answer: Option C β€” tRNA
Explanation: Transfer RNA or tRNA is responsible for bringing specific amino acids to the ribosome during translation each tRNA has an anticodon that matches a codon on the mRNA.
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4
Biology Hard

What is the process by which organisms survive extreme heat and drought by entering a dormant state?

  • AAestivation
  • BHibernation
  • CMigration
  • DDormancy only
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Correct Answer: Option A β€” Aestivation
Explanation: Aestivation is a state of dormancy similar to hibernation but entered during hot and dry summer conditions by animals like lungfish snails and some amphibians to prevent dehydration.
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5
Biology Hard

What is the broadest level of biological classification?

  • ADomain
  • BOrder
  • CFamily
  • DKingdom
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Correct Answer: Option A β€” Domain
Explanation: Domain is the broadest level in the modern biological classification system above kingdom and includes three domains Bacteria Archaea and Eukarya.
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6
Biology Medium

What is the two-part Latin naming system for organisms called?

  • APhylogenetic classification
  • BBinomial nomenclature
  • CCladistics
  • DLinnaean classification
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Correct Answer: Option B β€” Binomial nomenclature
Explanation: Binomial nomenclature is the formal system of naming organisms using two Latin words the genus name and the species name developed by Carl Linnaeus in the 18th century.
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7
Biology Medium

What is the term for the gradual process of change in the species composition of an ecosystem over time?

  • AEvolution
  • BAdaptation
  • CMigration
  • DEcological succession
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Correct Answer: Option D β€” Ecological succession
Explanation: Ecological succession is the gradual and predictable process of change in species composition and community structure in an ecosystem over time toward a stable climax community.
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8
Biology Hard

Which type of ecological succession begins on bare rock or sand where no soil exists?

  • ASecondary succession
  • BAllogenic succession
  • CBiotic succession
  • DPrimary succession
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Correct Answer: Option D β€” Primary succession
Explanation: Primary succession occurs on bare substrates like bare rock lava fields or sand dunes where no soil or previous living community exists starting from pioneer species like lichens.
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9
Biology Medium

What is the term for the variety of different species present in a given habitat?

  • AGenetic diversity
  • BSpecies diversity
  • CEcosystem diversity
  • DBiodiversity
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Correct Answer: Option B β€” Species diversity
Explanation: Species diversity refers to the number and relative abundance of different species present in a given habitat and is an important measure of the biodiversity of an ecosystem.
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10
Biology Medium

What is the function of lysosomes in animal cells?

  • AProtein synthesis
  • BDigestion of waste materials and cellular debris
  • CEnergy production
  • DDNA storage
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Correct Answer: Option B β€” Digestion of waste materials and cellular debris
Explanation: Lysosomes are membrane-bound organelles containing digestive enzymes that break down waste materials damaged organelles and foreign substances through a process called autophagy.
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