Chapter-Wise MCQs for CBSE Class 12 Biology (Exam Oriented)

(NCERT-Based | Chapter-Wise Coverage | With Answers & Concept-Clearing Explanations)

Chapter 1: Reproduction in Organisms & Human Reproduction (10 MCQs)

Q1. The fusion of male and female gametes is called:
A. Pollination
B. Fertilization
C. Germination
D. Implantation

Answer: B. Fertilization
Explanation: Fertilization involves fusion of haploid gametes to form a diploid zygote.

Q2. The hormone responsible for ovulation is:
A. FSH
B. Estrogen
C. LH
D. Progesterone

Answer: C. LH
Explanation: LH surge causes rupture of Graafian follicle and ovulation.

Q3. Binary fission is commonly seen in:
A. Hydra
B. Amoeba
C. Yeast
D. Spirogyra

Answer: B. Amoeba
Explanation: Amoeba reproduces asexually by simple binary fission.

Q4. Which structure prevents polyspermy in humans?
A. Acrosome
B. Zona pellucida
C. Corona radiata
D. Vitelline membrane

Answer: B. Zona pellucida
Explanation: It undergoes changes after fertilization to block additional sperms.

Q5. The site of fertilization in humans is:
A. Ovary
B. Uterus
C. Cervix
D. Fallopian tube

Answer: D. Fallopian tube
Explanation: Fertilization occurs in the ampullary region.

Q6. Apomixis leads to formation of:
A. Fruits without seeds
B. Seeds without fertilization
C. Sterile plants
D. Hybrid seeds only

Answer: B. Seeds without fertilization
Explanation: Apomixis is a type of asexual reproduction via seeds.

Q7. Menarche refers to:
A. First ovulation
B. First menstruation
C. Menopause
D. Ovulatory cycle

Answer: B. First menstruation
Explanation: It marks the beginning of reproductive life in females.

Q8. Which hormone maintains pregnancy?
A. Estrogen
B. Oxytocin
C. Progesterone
D. Prolactin

Answer: C. Progesterone
Explanation: Progesterone maintains uterine lining during pregnancy.

Q9. The edible part of coconut is:
A. Embryo
B. Cotyledon
C. Endosperm
D. Pericarp

Answer: C. Endosperm
Explanation: Coconut water and kernel are forms of endosperm.

Q10. Vegetative propagation is a form of:
A. Sexual reproduction
B. Asexual reproduction
C. Apomixis
D. Amphimixis

Answer: B. Asexual reproduction
Explanation: New plants are produced without gamete fusion.

Chapter 2: Principles of Inheritance & Evolution (10 MCQs)

Q11. Mendel’s Law of Segregation is based on:
A. Monohybrid cross
B. Dihybrid cross
C. Test cross
D. Back cross

Answer: A. Monohybrid cross
Explanation: It explains separation of alleles during gamete formation.

Q12. A carrier female for haemophilia has genotype:
A. XʰXʰ
B. XHXH
C. XHXʰ
D. XʰY

Answer: C. XHXʰ
Explanation: One normal and one affected allele.

Q13. Crossing over occurs during:
A. Leptotene
B. Zygotene
C. Pachytene
D. Diplotene

Answer: C. Pachytene
Explanation: Exchange of genetic material occurs at this stage.

Q14. The start codon is:
A. UAA
B. UGA
C. UAG
D. AUG

Answer: D. AUG
Explanation: AUG codes for methionine and initiates translation.

Q15. The unit of evolution is:
A. Individual
B. Species
C. Population
D. Community

Answer: C. Population
Explanation: Evolution involves changes in allele frequency in populations.

Q16. Homologous organs indicate:
A. Convergent evolution
B. Parallel evolution
C. Divergent evolution
D. Coevolution

Answer: C. Divergent evolution
Explanation: Same origin but different functions.

Q17. DNA replication is:
A. Conservative
B. Dispersive
C. Semiconservative
D. Random

Answer: C. Semiconservative
Explanation: Each new DNA has one parental strand.

Q18. Genetic drift is more prominent in:
A. Large populations
B. Small populations
C. Stable populations
D. Migrating populations

Answer: B. Small populations
Explanation: Random changes affect small populations more.

Q19. RNA polymerase is involved in:
A. Replication
B. Translation
C. Transcription
D. Mutation

Answer: C. Transcription
Explanation: It synthesizes RNA from DNA template.

Q20. Darwin’s finches show:
A. Convergent evolution
B. Genetic drift
C. Adaptive radiation
D. Parallel evolution

Answer: C. Adaptive radiation
Explanation: Species diversified from a common ancestor.

Chapter 3: Biology in Human Welfare (10 MCQs)

Q21. Curd formation involves:
A. Yeast
B. Lactobacillus
C. Rhizobium
D. Penicillium

Answer: B. Lactobacillus
Explanation: It converts lactose into lactic acid.

Q22. Malaria is caused by:
A. Virus
B. Bacteria
C. Protozoan
D. Fungus

Answer: C. Protozoan
Explanation: Caused by Plasmodium.

Q23. Antibiotics are ineffective against:
A. Bacteria
B. Protozoa
C. Viruses
D. Fungi

Answer: C. Viruses
Explanation: Viruses lack metabolic machinery.

Q24. SCP stands for:
A. Single Cell Protein
B. Secondary Crop Production
C. Synthetic Cell Product
D. Stored Cell Protein

Answer: A. Single Cell Protein
Explanation: Microbial protein used as food supplement.

Q25. Which disease is sexually transmitted?
A. Typhoid
B. Malaria
C. AIDS
D. Cholera

Answer: C. AIDS
Explanation: Caused by HIV.

Q26. Biogas mainly contains:
A. CO₂
B. Methane
C. Nitrogen
D. Hydrogen

Answer: B. Methane
Explanation: Methane is the major fuel component.

Q27. Which organism fixes nitrogen in legumes?
A. Azotobacter
B. Nostoc
C. Rhizobium
D. Anabaena

Answer: C. Rhizobium
Explanation: Symbiotic nitrogen fixer.

Q28. Penicillin is obtained from:
A. Bacteria
B. Virus
C. Algae
D. Fungus

Answer: D. Fungus
Explanation: Produced by Penicillium.

Q29. Sewage treatment uses mainly:
A. Algae
B. Fungi
C. Bacteria
D. Protozoa

Answer: C. Bacteria
Explanation: Bacteria decompose organic matter.

Q30. Rabies spreads through:
A. Water
B. Air
C. Animal bite
D. Food

Answer: C. Animal bite
Explanation: Virus is transmitted via saliva.

Chapter 4: Biotechnology – Principles & Processes (10 MCQs)

Q31. Restriction enzymes are called:
A. Molecular glue
B. Molecular scissors
C. Vectors
D. Markers

Answer: B. Molecular scissors
Explanation: They cut DNA at specific sequences.

Q32. PCR amplifies:
A. RNA
B. Protein
C. DNA
D. Lipids

Answer: C. DNA
Explanation: Makes multiple copies of DNA.

Q33. Heat-stable enzyme used in PCR is:
A. DNA ligase
B. Taq polymerase
C. RNA polymerase
D. Primase

Answer: B. Taq polymerase
Explanation: Isolated from Thermus aquaticus.

Q34. Vector commonly used in cloning is:
A. Ribosome
B. Chromosome
C. Plasmid
D. mRNA

Answer: C. Plasmid
Explanation: Plasmids replicate independently.

Q35. Bt cotton resists:
A. Viruses
B. Fungi
C. Insects
D. Weeds

Answer: C. Insects
Explanation: Bt toxin kills insect larvae.

Q36. ELISA is used for:
A. Gene cloning
B. Disease diagnosis
C. PCR
D. DNA sequencing

Answer: B. Disease diagnosis
Explanation: Detects antigen–antibody reaction.

Q37. Insulin is produced using:
A. Yeast
B. Virus
C. E. coli
D. Algae

Answer: C. E. coli
Explanation: Recombinant bacteria produce insulin.

Q38. RNA interference is used to:
A. Amplify genes
B. Silence genes
C. Mutate DNA
D. Translate mRNA

Answer: B. Silence genes
Explanation: Prevents mRNA translation.

Q39. A bioreactor provides:
A. Antibiotics
B. Enzymes
C. Optimal growth conditions
D. DNA

Answer: C. Optimal growth conditions
Explanation: Controls pH, oxygen and temperature.

Q40. Selectable markers help in:
A. DNA cutting
B. Identifying recombinants
C. Replication
D. Transcription

Answer: B. Identifying recombinants
Explanation: Marker genes identify transformed cells.

Chapter 5: Ecology & Environment (10 MCQs)

Q41. Main source of energy in ecosystem is:
A. Producers
B. Consumers
C. Decomposers
D. Sun

Answer: D. Sun
Explanation: Solar energy drives ecosystem processes.

Q42. Pyramid of energy is always:
A. Inverted
B. Upright
C. Spindle-shaped
D. Irregular

Answer: B. Upright
Explanation: Energy decreases at higher trophic levels.

Q43. Which cycle lacks gaseous phase?
A. Carbon
B. Nitrogen
C. Water
D. Phosphorus

Answer: D. Phosphorus
Explanation: Phosphorus cycle has no gaseous stage.

Q44. Lichens are indicators of:
A. Water pollution
B. Soil fertility
C. Air pollution
D. Radiation

Answer: C. Air pollution
Explanation: Sensitive to SO₂.

Q45. Major cause of biodiversity loss is:
A. Climate change
B. Overpopulation
C. Habitat loss
D. Pollution

Answer: C. Habitat loss
Explanation: Destruction of natural habitats.

Q46. Biological magnification refers to:
A. Energy loss
B. Population increase
C. Toxin accumulation
D. Nutrient recycling

Answer: C. Toxin accumulation
Explanation: Increase of toxins at higher trophic levels.

Q47. Eutrophication is due to excess:
A. Oxygen
B. Nutrients
C. Salts
D. Heat

Answer: B. Nutrients
Explanation: Excess nitrates and phosphates.

Q48. In-situ conservation includes:
A. Zoo
B. Botanical garden
C. Seed bank
D. National park

Answer: D. National park
Explanation: Conservation in natural habitat.

Q49. Ex-situ conservation includes:
A. Wildlife sanctuary
B. Biosphere reserve
C. Zoological park
D. National park

Answer: C. Zoological park
Explanation: Conservation outside natural habitat.

Q50. The term ecosystem was coined by:
A. Odum
B. Clements
C. Darwin
D. Tansley

Answer: D. Tansley
Explanation: A.G. Tansley introduced the concept.

✅ This chapter-wise, NCERT-aligned MCQ set is ideal for systematic CBSE Class 12 Biology board exam preparation.