Free Class 12 Biology MCQs – NCERT-Based Practice
Free Class 12 Biology MCQs - Online Practice — Practice Questions
1. Which of the following is NOT a method of artificial vegetative propagation?
- (A) Layering
- (B) Grafting
- (C) Budding
- (D) Fragmentation
Answer: (D) Fragmentation
Fragmentation is a natural method of asexual reproduction, whereas layering, grafting and budding are artificial methods.
2. In angiosperms, one male gamete fuses with the egg cell while the other fuses with:
- (A) Antipodal cells
- (B) Synergids
- (C) Polar nuclei
- (D) Integuments
Answer: (C) Polar nuclei
The second male gamete fuses with the two polar nuclei to form the primary endosperm nucleus during triple fusion.
3. Which hormone is administered to induce ovulation in infertile women?
- (A) Estrogen
- (B) Progesterone
- (C) FSH
- (D) Oxytocin
Answer: (C) FSH
FSH stimulates follicular development and is used during assisted reproductive techniques.
4. During PCR, which step involves the synthesis of new DNA strands?
- (A) Denaturation
- (B) Annealing
- (C) Extension
- (D) Ligation
Answer: (C) Extension
During extension, Taq DNA polymerase synthesizes the new DNA strand.
5. Which bacterium is widely used for producing human insulin through genetic engineering?
- (A) Rhizobium
- (B) Agrobacterium tumefaciens
- (C) Escherichia coli
- (D) Bacillus subtilis
Answer: (C) Escherichia coli
Recombinant human insulin is commonly produced using genetically modified E. coli.
6. Which of the following acts as the first line of defence in the human immune system?
- (A) Antibodies
- (B) Skin
- (C) B-lymphocytes
- (D) T-lymphocytes
Answer: (B) Skin
Skin and mucous membranes form the body's first line of defence against pathogens.
7. Which sexually transmitted disease is caused by a virus?
- (A) Gonorrhoea
- (B) Syphilis
- (C) AIDS
- (D) Chlamydia
Answer: (C) AIDS
AIDS is caused by Human Immunodeficiency Virus (HIV).
8. The transfer of pollen grains from the anther to the stigma of the same flower is called:
- (A) Xenogamy
- (B) Geitonogamy
- (C) Autogamy
- (D) Hybridization
Answer: (C) Autogamy
Autogamy is self-pollination within the same flower.
9. Which restriction enzyme recognizes palindromic DNA sequences?
- (A) DNA polymerase
- (B) DNA ligase
- (C) EcoRI
- (D) Primase
Answer: (C) EcoRI
EcoRI is a restriction endonuclease that recognizes a specific palindromic DNA sequence.
10. The hormone responsible for milk ejection is:
- (A) Prolactin
- (B) Oxytocin
- (C) Estrogen
- (D) Progesterone
Answer: (B) Oxytocin
Oxytocin stimulates contraction of myoepithelial cells, resulting in milk ejection.
11. The process by which foreign DNA is introduced into a bacterial cell is known as:
- (A) Translation
- (B) Transformation
- (C) Transduction
- (D) Conjugation
Answer: (B) Transformation
Transformation is the uptake of foreign DNA by bacterial cells.
12. Which organism is commonly used as a biofertilizer in paddy fields?
- (A) Rhizobium
- (B) Nostoc
- (C) Azospirillum
- (D) Frankia
Answer: (B) Nostoc
Nostoc, a cyanobacterium, fixes atmospheric nitrogen and is used in paddy fields.
13. The maximum biodiversity on Earth is found in:
- (A) Temperate forests
- (B) Tropical rainforests
- (C) Grasslands
- (D) Deserts
Answer: (B) Tropical rainforests
Tropical rainforests have the highest species richness due to climatic stability and long evolutionary history.
14. Which one is an example of ex situ conservation?
- (A) Wildlife sanctuary
- (B) National park
- (C) Botanical garden
- (D) Biosphere reserve
Answer: (C) Botanical garden
Botanical gardens conserve plants outside their natural habitats.
15. Bt cotton is resistant to:
- (A) Whitefly
- (B) Bollworm
- (C) Aphids
- (D) Grasshopper
Answer: (B) Bollworm
Bt cotton produces Cry proteins that are toxic to bollworms.
16. Which enzyme joins DNA fragments during recombinant DNA technology?
- (A) DNA polymerase
- (B) Restriction endonuclease
- (C) DNA ligase
- (D) Reverse transcriptase
Answer: (C) DNA ligase
DNA ligase seals phosphodiester bonds between DNA fragments.
17. Which category of biodiversity represents variation within a species?
- (A) Species diversity
- (B) Ecosystem diversity
- (C) Genetic diversity
- (D) Community diversity
Answer: (C) Genetic diversity
Genetic diversity refers to variation in genes among individuals of the same species.
18. Which component of an ecosystem receives maximum solar energy?
- (A) Primary consumers
- (B) Secondary consumers
- (C) Producers
- (D) Decomposers
Answer: (C) Producers
Producers capture solar energy through photosynthesis.
19. Which of the following is NOT a barrier method of contraception?
- (A) Condom
- (B) Diaphragm
- (C) Copper-T
- (D) Cervical cap
Answer: (C) Copper-T
Copper-T is an intrauterine device (IUD), not a barrier contraceptive.
20. According to NCERT, biological oxygen demand (BOD) is an indicator of:
- (A) Soil fertility
- (B) Air pollution
- (C) Water pollution
- (D) Greenhouse effect
Answer: (C) Water pollution
Higher BOD indicates greater organic pollution in water due to increased microbial activity.