CBSE Class 12 Biology MCQs

Important CBSE Class 12 Biology MCQs with Answers

1. Reproduction in Organisms

Q1. The period from birth to the natural death of an organism is called:

a) Life span

b) Age

c) Longevity

d) Generation

Ans: a) Life span

Q2. Which of the following organisms reproduces only by asexual method?

a) Amoeba

b) Hydra

c) Paramoecium

d) All of these

Ans: d) All of these

Q3. Oviparous animals are those which:

a) Give birth to young ones

b) Lay eggs

c) Reproduce vegetatively

d) None of these

Ans: b) Lay eggs

Q4. Which is a seasonal breeder?

a) Humans

b) Cow

c) Birds

d) All of these

Ans: c) Birds

Q5. Vegetative propagation in plants is an example of:

a) Sexual reproduction

b) Asexual reproduction

c) Fertilization

d) Pollination

Ans: b) Asexual reproduction

2. Genetics and Evolution

Q1. Law of Segregation was given by:

a) Charles Darwin

b) Gregor Mendel

c) Hugo de Vries

d) T.H. Morgan

Ans: b) Gregor Mendel

Q2. Test cross is used to determine:

a) Genotype of a plant

b) Phenotype of a plant

c) Evolutionary history

d) Type of gametes

Ans: a) Genotype of a plant

Q3. The sudden appearance of new species is explained by:

a) Natural selection

b) Mutation theory

c) Inheritance of acquired characters

d) Lamarckism

Ans: b) Mutation theory

Q4. Which of the following is sex-linked disorder?

a) Hemophilia

b) Sickle-cell anemia

c) Down syndrome

d) Thalassemia

Ans: a) Hemophilia

Q5. Homozygous tall (TT) crossed with dwarf (tt) produces all tall (Tt) progeny in F1. This shows:

a) Dominance

b) Segregation

c) Incomplete dominance

d) Mutation

Ans: a) Dominance

3. Biotechnology

Q1. PCR is used for:

a) Cutting DNA

b) Amplification of DNA

c) Ligation of DNA

d) Sequencing of DNA

Ans: b) Amplification of DNA

Q2. The first recombinant DNA was created by:

a) Paul Berg

b) Watson and Crick

c) Herbert Boyer

d) Stanley Cohen

Ans: a) Paul Berg

Q3. The role of "Agrobacterium tumefaciens" in biotechnology is:

a) Biopesticide

b) Gene transfer

c) Nitrogen fixation

d) DNA sequencing

Ans: b) Gene transfer

Q4. Which enzyme is used to join DNA fragments?

a) Ligase

b) Restriction endonuclease

c) Polymerase

d) Helicase

Ans: a) Ligase

Q5. Which product is obtained from transgenic bacteria?

a) Insulin

b) Vitamin B12

c) ATP

d) RNA

Ans: a) Insulin

4. Ecology

Q1. The pyramid of energy in an ecosystem is always:

a) Upright

b) Inverted

c) Cylindrical

d) Irregular

Ans: a) Upright

Q2. Primary consumers are generally:

a) Carnivores

b) Herbivores

c) Omnivores

d) Decomposers

Ans: b) Herbivores

Q3. The ultimate source of energy for ecosystem is:

a) Green plants

b) Sun

c) Decomposers

d) Soil

Ans: b) Sun

Q4. Which of the following is a secondary succession?

a) Growth of forest on a bare rock

b) Growth of forest on abandoned farmland

c) Colonization of lichens on stones

d) None of these

Ans: b) Growth of forest on abandoned farmland

Q5. Biomagnification refers to:

a) Increase of harmful chemicals in food chain

b) Magnification of DNA

c) Amplification of energy

d) Increase in biomass

Ans: a) Increase of harmful chemicals in food chain

5. Human Health and Disease

Q1. Malaria is caused by:

a) Plasmodium

b) Virus

c) Bacteria

d) Fungi

Ans: a) Plasmodium

Q2. Which disease is caused by deficiency of insulin?

a) Hypertension

b) Diabetes mellitus

c) Jaundice

d) Tuberculosis

Ans: b) Diabetes mellitus

Q3. AIDS is caused by:

a) HBV

b) HIV

c) HCV

d) Influenza virus

Ans: b) HIV

Q4. Which vaccine is given for tuberculosis?

a) Polio

b) BCG

c) DPT

d) MMR

Ans: b) BCG

Q5. Which of the following is not a bacterial disease?

a) Cholera

b) Typhoid

c) Tuberculosis

d) Ringworm

Ans: d) Ringworm

6. Human Reproduction

Q1. Fertilization in humans usually takes place in:

a) Uterus

b) Ovary

c) Fallopian tube

d) Cervix

Ans: c) Fallopian tube

Q2. The hormone responsible for ovulation is:

a) LH

b) FSH

c) Progesterone

d) Oxytocin

Ans: a) LH

Q3. Which part of the sperm provides energy for movement?

a) Acrosome

b) Nucleus

c) Middle piece

d) Tail

Ans: c) Middle piece

Q4. Placenta is formed by:

a) Embryo only

b) Mother only

c) Both embryo and mother

d) Ovary

Ans: c) Both embryo and mother

Q5. Which of the following prevents polyspermy?

a) Cortical reaction

b) Acrosomal reaction

c) Cleavage

d) Ovulation

Ans: a) Cortical reaction

7. Molecular Basis of Inheritance

Q1. The DNA double helix model was proposed by:

a) Hershey and Chase

b) Watson and Crick

c) Meselson and Stahl

d) Wilkins and Franklin

Ans: b) Watson and Crick

Q2. In DNA replication, Okazaki fragments are joined by:

a) Ligase

b) Helicase

c) Polymerase

d) Primase

Ans: a) Ligase

Q3. The length of one complete turn of DNA is:

a) 3.4 nm

b) 34 nm

c) 0.34 nm

d) 2 nm

Ans: a) 3.4 nm

Q4. Which of the following is not a stop codon?

a) UAA

b) UAG

c) UGA

d) AUG

Ans: d) AUG

Q5. Which enzyme unzips the DNA strands during replication?

a) DNA polymerase

b) DNA helicase

c) Ligase

d) RNA polymerase

Ans: b) DNA helicase

8. Human Physiology (Body Fluids & Circulation)

Q1. Which blood group is called universal donor?

a) A

b) B

c) AB

d) O

Ans: d) O

Q2. Pacemaker of the human heart is:

a) AV Node

b) SA Node

c) Purkinje fibres

d) Bundle of His

Ans: b) SA Node

Q3. Normal blood pressure in humans is:

a) 100/60 mmHg

b) 120/80 mmHg

c) 140/100 mmHg

d) 160/120 mmHg

Ans: b) 120/80 mmHg

Q4. Which blood vessels carry oxygenated blood?

a) Veins

b) Arteries

c) Pulmonary vein

d) Both b and c

Ans: d) Both b and c

Q5. Hemoglobin is present in:

a) Plasma

b) WBC

c) RBC

d) Platelets

Ans: c) RBC

9. Microbes in Human Welfare

Q1. Which microorganism is used in production of ethanol?

a) Penicillium

b) Saccharomyces cerevisiae

c) Rhizobium

d) Lactobacillus

Ans: b) Saccharomyces cerevisiae

Q2. Streptococcus is used in production of:

a) Cheese

b) Vinegar

c) Antibiotics

d) Curd

Ans: d) Curd

Q3. Antibiotic Penicillin was discovered by:

a) Alexander Fleming

b) Louis Pasteur

c) Robert Koch

d) Jenner

Ans: a) Alexander Fleming

Q4. Biofertilizer Azospirillum is:

a) Nitrogen-fixing bacteria

b) Fungi

c) Cyanobacteria

d) Virus

Ans: a) Nitrogen-fixing bacteria

Q5. Biogas mainly contains:

a) CO₂

b) CH₄

c) H₂S

d) N₂

Ans: b) CH₄

10. Strategies for Enhancement in Food Production

Q1. The process of crossing superior males and females of the same breed is called:

a) Cross breeding

b) Out breeding

c) Inbreeding

d) Hybridization

Ans: c) Inbreeding

Q2. MOET technology is related to:

a) Animal breeding

b) Crop improvement

c) Tissue culture

d) Hybridization

Ans: a) Animal breeding

Q3. Semi-dwarf varieties of wheat were developed in:

a) India

b) Mexico

c) China

d) USA

Ans: b) Mexico

Q4. Single-cell protein (SCP) is obtained from:

a) Spirulina

b) Mushroom

c) Yeast

d) All of these

Ans: d) All of these

Q5. The term ‘Green Revolution’ is associated with:

a) Animal husbandry

b) Agriculture

c) Sericulture

d) Horticulture

Ans: b) Agriculture

11. Evolution

Q1. The concept of “Natural Selection” was proposed by:

a) Charles Darwin

b) Gregor Mendel

c) Hugo de Vries

d) Lamarck

Ans: a) Charles Darwin

Q2. The idea of inheritance of acquired characters was given by:

a) Darwin

b) Lamarck

c) Wallace

d) Weismann

Ans: b) Lamarck

Q3. Industrial melanism in moths (Biston betularia) is an example of:

a) Adaptive radiation

b) Mutation

c) Natural selection

d) Genetic drift

Ans: c) Natural selection

Q4. Which of the following provides the strongest evidence for evolution?

a) Embryology

b) Fossils

c) Homologous organs

d) Biogeography

Ans: b) Fossils

Q5. Who coined the term “Survival of the fittest”?

a) Darwin

b) Herbert Spencer

c) Huxley

d) Wallace

Ans: b) Herbert Spencer

12. Organisms and Populations

Q1. Commensalism is the relationship in which:

a) Both partners benefit

b) One benefits, the other is unaffected

c) Both are harmed

d) One benefits, the other is harmed

Ans: b) One benefits, the other is unaffected

Q2. Which factor is not abiotic?

a) Light

b) Temperature

c) Water

d) Parasites

Ans: d) Parasites

Q3. The maximum growth rate of a population is called:

a) Natality

b) Mortality

c) Biotic potential

d) Carrying capacity

Ans: c) Biotic potential

Q4. In which biome do animals like reindeer and musk ox occur?

a) Desert

b) Tundra

c) Grassland

d) Savanna

Ans: b) Tundra

Q5. Which of the following is an ectoparasite?

a) Tapeworm

b) Lice

c) Plasmodium

d) Bacteria

Ans: b) Lice

13. Ecosystem

Q1. The functional unit of nature is:

a) Species

b) Population

c) Ecosystem

d) Biome

Ans: c) Ecosystem

Q2. Which process is not involved in ecosystem functioning?

a) Energy flow

b) Nutrient cycling

c) Mutation

d) Decomposition

Ans: c) Mutation

Q3. Which of the following is a detritivore?

a) Lion

b) Earthworm

c) Cow

d) Tiger

Ans: b) Earthworm

Q4. Standing crop in an ecosystem is measured in terms of:

a) Number or biomass per unit area

b) Energy content

c) Productivity

d) Oxygen released

Ans: a) Number or biomass per unit area

Q5. Secondary productivity is defined as:

a) Biomass produced by plants

b) Biomass produced by consumers

c) Biomass consumed by decomposers

d) None of these

Ans: b) Biomass produced by consumers

14. Environmental Issues

Q1. Ozone depletion is mainly caused by:

a) CO₂

b) CFCs

c) Methane

d) NO₂

Ans: b) CFCs

Q2. Minamata disease is caused by:

a) Arsenic pollution

b) Mercury poisoning

c) Lead poisoning

d) Cadmium poisoning

Ans: b) Mercury poisoning

Q3. Eutrophication in lakes is due to:

a) Excess oxygen

b) Excess nutrients

c) Acid rain

d) Thermal pollution

Ans: b) Excess nutrients

Q4. Which protocol was signed to control emission of ozone depleting substances?

a) Kyoto Protocol

b) Montreal Protocol

c) Paris Agreement

d) Geneva Convention

Ans: b) Montreal Protocol

Q5. The chipko movement was related to:

a) Soil conservation

b) Forest conservation

c) Wildlife protection

d) Pollution control

Ans: b) Forest conservation

15. Biotechnology and Its Applications

Q1. Bt cotton is resistant to:

a) Bacterial disease

b) Insect pests

c) Viral disease

d) Herbicides

Ans: b) Insect pests

Q2. Which protein is used in gene therapy?

a) Insulin

b) Interferon

c) ADA enzyme

d) Hemoglobin

Ans: c) ADA enzyme

Q3. Golden rice is enriched with:

a) Vitamin C

b) Vitamin A

c) Iron

d) Protein

Ans: b) Vitamin A

Q4. The first transgenic cow produced human protein in milk was:

a) Rosie

b) Dolly

c) Daisy

d) Bella

Ans: a) Rosie

Q5. Which of the following is a bio-patent product?

a) Bt cotton

b) Golden rice

c) Flavr Savr tomato

d) All of these

Ans: d) All of these

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