This includes questions from Class 12 Biology chapters.
Q 1: Assertion (A): Apomixis is a form of asexual reproduction that mimics sexual reproduction.
Reason (R): In apomixis, seeds are produced without fertilisation.
Reason (R): In apomixis, seeds are produced without fertilisation.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (4) Both A and R are true and R is the correct explanation of A
▶️ Apomixis is the production of seeds without fertilisation. E.g. Some species of Asteraceae and grasses.
▶️ It is a form of asexual reproduction that mimics sexual reproduction.
▶️ In some species, diploid egg cell is formed without reduction division and develops into the embryo without fertilisation.
Q 2: Assertion (A): Distribution of some bryophytes & pteridophytes is limited.
Reason (R): Bryophytes & pteridophytes need wind for the transport of male gametes and fertilisation.
Reason (R): Bryophytes & pteridophytes need wind for the transport of male gametes and fertilisation.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (2) A is true but R is false
▶️ Distribution of some bryophytes & pteridophytes is limited because they need water for the transport of male gametes and fertilisation.
▶️ Pollination by water is called Hydrophily and pollination by wind is called Anemophily. These are two types of abiotic pollination.
Q 3: Assertion (A): Hymen is a reliable indicator of virginity.
Reason (R): It is often torn during the first coitus.
Reason (R): It is often torn during the first coitus.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (3) A is false but R is true
▶️ Hymen (Maiden head) is a membrane which partially covers the vaginal opening.
▶️ It is often torn during the first coitus. It may also be broken by a sudden fall or jolt, insertion of a vaginal tampon; active participation in some sports items etc. In some women, hymen persists after coitus. So the hymen is not a reliable indicator of virginity or sexual experience.
Q 4: Assertion (A): All copulations do not lead to fertilization & pregnancy.
Reason (R): Fertilization happens only if ovum & sperms are transported simultaneously.
Reason (R): Fertilization happens only if ovum & sperms are transported simultaneously.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (4) Both A and R are true and R is the correct explanation of A
▶️ During copulation, semen is released by the penis into the vagina. It is called insemination.
▶️ Fusion of sperm with ovum is called fertilization. It occurs in Ampullary region of fallopian tube.
▶️ Fertilization happens only if ovum & sperms are transported simultaneously. So all copulations do not lead to fertilization & pregnancy.
Q 5: Assertion (A): Emergency contraceptives are used after unprotected sex.
Reason (R): They can prevent pregnancy if used within a certain period after intercourse.
Reason (R): They can prevent pregnancy if used within a certain period after intercourse.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (4) Both A and R are true and R is the correct explanation of A
▶️ Progestogens or progestogen-oestrogen combinations & IUDs are used as emergency contraceptives within 72 hours of coitus. It avoids pregnancy due to rape or casual intercourse.
Q 6: Assertion (A): Drosophila melanogaster is the suitable material for genetic study.
Reason (R): Drosophila exhibits least hereditary variations and has large sized body.
Reason (R): Drosophila exhibits least hereditary variations and has large sized body.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (2) A is true but R is false
Drosophila melanogaster is the suitable material for genetic study because,
▶️ They can grow on simple synthetic medium.
▶️ Short life cycle (about 2 weeks).
▶️ Hundreds of progenies per mating.
▶️ Male and female flies are easily distinguishable. E.g. Male is smaller than female.
▶️ It has many types of hereditary variations that can be seen with low power microscopes.
Q 7: Assertion (A): In many insects such as grasshopper, total number of chromosomes in the male and female are equal.
Reason (R): Their sex determination mechanism is XX-XY type.
Reason (R): Their sex determination mechanism is XX-XY type.
(1) Both A and R are true and R is the correct explanation of A
(2) Both A and R are true but R is NOT the correct explanation of A
(3) A is true but R is false
(4) Both A and R are false
✅ (4) Both A and R are false
Mechanisms of sex determination
1. XX-XO mechanism: Here, male is heterogametic, i.e. XO (Gametes with X and gametes without X) and female is homogametic, i.e. XX (all gametes are with X-chromosomes). E.g. Many insects such as grasshopper. Here the total number of chromosomes in the male and female are not equal because male has only one X.
2. XX-XY mechanism: Male is heterogametic (X & Y) and female is homogametic (X only). E.g. Human & Drosophila.
3. ZZ-ZW mechanism: Male is homogametic (ZZ) and female is heterogametic (Z & W). E.g. Birds.
Q 8: Assertion (A): During transcription, both strands are not copied.
Reason (R): If two RNA molecules are produced simultaneously, they form a double stranded RNA and prevents translation.
Reason (R): If two RNA molecules are produced simultaneously, they form a double stranded RNA and prevents translation.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (4) Both A and R are true and R is the correct explanation of A
During transcription, both strands are not copied because
1. The code for proteins is different in both strands. This complicates the translation.
2. If 2 RNA molecules are produced simultaneously, this would be complimentary to each other. It forms a double stranded RNA and prevents translation.
Q 9: Assertion (A): In bacteria, transcription and translation can be coupled.
Reason (R): Transcription and translation take place in different compartments.
Reason (R): Transcription and translation take place in different compartments.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (2) A is true but R is false
In bacteria, transcription and translation can be coupled (translation begins before mRNA is fully transcribed) because
1. mRNA requires no processing to become active.
2. Transcription and translation take place in the same compartment (no separation of cytosol and nucleus).
Q 10: Assertion (A): In England, before industrialization (1850s), there were more dark-winged moths on trees than white-winged.
Reason (R): Before industrialization, dark-winged moths survived but white-winged moths were picked out by predators.
Reason (R): Before industrialization, dark-winged moths survived but white-winged moths were picked out by predators.
(1) Both A and R are true and R is the correct explanation of A
(2) Both A and R are true but R is NOT the correct explanation of A
(3) A is true but R is false
(4) Both A and R are false
✅ (4) Both A and R are false
▶️ In England, before industrialization (1850s), there were more white-winged moths on trees than dark winged or melanised moths. After industrialization (1920), more dark-winged moths and less white winged moths were developed.
▶️ Reason:
1. Before industrialization: There was white lichens covered the trees. In that background, white winged moths survived but dark winged moths were picked out by predators.
2. After industrialization: The tree trunks became dark due to industrial smoke and soot. No growth of lichens. So white winged moths did not survive because the predators identified them easily. Dark winged moth survived because of suitable dark background.
Q 11: Assertion (A): Lamarckism (Theory of Inheritance of Acquired characters) is a theory of evolution that has been rejected today.
Reason (R): It is proved that acquired characters will not develop in any organisms.
Reason (R): It is proved that acquired characters will not develop in any organisms.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (2) A is true but R is false
▶️ Lamarckism (Theory of Inheritance of Acquired characters) was proposed by Lamarck.
▶️ It states that evolution of life forms occurred by the inheritance of acquired characters developed by use & disuse of organs. E.g. Long neck of giraffe is due to continuous elongation to forage leaves on trees.
▶️ This theory was eliminated because it is proved that the characters are inherited only through genes.
▶️ Acquired characters will be developed in organisms due to environmental influence. So the Reason (R) is false.
Q 12: Assertion (A): Children in metro cities are more prone to allergies and asthma than those in rural areas.
Reason (R): Modern-day life style & protected environment provided early in life results in low immunity and more sensitivity to allergens.
Reason (R): Modern-day life style & protected environment provided early in life results in low immunity and more sensitivity to allergens.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (4) Both A and R are true and R is the correct explanation of A
▶️ The exaggerated response of the immune system to certain antigens present in the environment is called allergy.
▶️ Modern-day life style & protected environment provided early in life results in low immunity and more sensitivity to allergens. So children in metro cities suffer from allergies and asthma.
Q 13: Assertion (A): Malignant tumours are more dangerous than benign tumour.
Reason (R): Malignant tumours exhibit contact inhibition.
Reason (R): Malignant tumours exhibit contact inhibition.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (2) A is true but R is false
Types of Tumours
1. Benign tumours: Confined to the place of its origin. They do not spread to other parts. Cause little damage.
2. Malignant tumours: Mass of proliferating cells (neoplastic or tumour cells) that grow rapidly, invade and damage the surrounding normal tissues.
▶️ Normal cells show a contact inhibition (contact with the other cells inhibits their uncontrolled growth). Cancer cells do not have this property.
Q 14: Assertion (A): During Swiss cheese making process, large characteristic holes are formed.
Reason (R): As the cheese ferments, Propionibacterium shermanii produce carbon dioxide, which forms bubbles.
Reason (R): As the cheese ferments, Propionibacterium shermanii produce carbon dioxide, which forms bubbles.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (4) Both A and R are true and R is the correct explanation of A
▶️ Bacterial fermentation (anaerobic respiration) in dough is used to make foods such as dosa, idli etc. The puffed-up appearance of dough is due to the production of CO2.
▶️ Baker’s Yeast (Saccharomyces cerevisiae) is used to make bread by fermenting dough.
▶️ Swiss cheese has large holes due to production of CO2 by Propionibacterium sharmanii (a bacterium).
▶️ Roquefort cheese is ripened by growing a fungus (Penicillium roqueforti) on them.
Q 15: Assertion (A): Agrobacterium tumefaciens is commonly used as a vector in plant genetic engineering.
Reason (R): A. tumefaciens naturally transfers DNA into plant cells, making it an effective tool for introducing foreign genes into plants.
Reason (R): A. tumefaciens naturally transfers DNA into plant cells, making it an effective tool for introducing foreign genes into plants.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (4) Both A and R are true and R is the correct explanation of A
▶️ Agrobacterium tumefaciens (a pathogen of many dicot plants) can deliver a piece of DNA (T-DNA) to transform normal plant cells into a tumor. These tumor cells produce the chemicals required by the pathogen.
▶️ The tumor inducing (Ti) plasmid of A. tumefaciens is modified into a cloning vector which is not pathogenic but can use mechanisms to deliver genes of interest into plants.
Q 16: Assertion (A): In Bacillus thuringiensis, there is an insecticidal protein namely Bt toxin which does not harm the Bacillus itself.
Reason (R): Bacillus thuringiensis contains another protein which neutralizes the action of Bt toxin.
Reason (R): Bacillus thuringiensis contains another protein which neutralizes the action of Bt toxin.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (2) A is true but R is false
▶️ Bacillus thuringiensis forms an insecticidal protein (Bt toxin) crystal during a phase of their growth. It does not kill the Bacillus as it exists as inactive protoxins.
▶️ When an insect ingests the toxin, it becomes active due to alkaline pH of the gut which solubilise the crystals. Toxin binds to surface of mid-gut epithelial cells creating pores. It causes cell swelling and lysis and death of the insect.
Q 17: Assertion (A): Removal of the Pisaster starfish from the rocky intertidal communities led to the extinction of over 10 invertebrate species.
Reason (R): The absence of Pisaster intensified interspecific competition among invertebrate species.
Reason (R): The absence of Pisaster intensified interspecific competition among invertebrate species.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (4) Both A and R are true and R is the correct explanation of A
▶️ Predators maintain species diversity in a community by reducing competition among prey species.
▶️ E.g. the predator starfish Pisaster in the rocky intertidal communities of American Pacific Coast. In an experiment, all these starfishes were removed from an enclosed intertidal area. It caused extinction of over 10 invertebrate species within a year, due to interspecific competition.
Q 18: Assertion (A): Competition does not occur if resources are abundant.
Reason (R): Resources are the only factor that influence competition among organisms.
Reason (R): Resources are the only factor that influence competition among organisms.
(1) Both A and R are true and R is the correct explanation of A
(2) Both A and R are true but R is NOT the correct explanation of A
(3) A is true but R is false
(4) Both A and R are false
✅ (4) Both A and R are false
▶️ Competition occurs in abundant resources also.
▶️ E.g. In interference competition, the feeding efficiency of one species is reduced due to the interfering and inhibitory presence of other species, even if resources are abundant.
Q 19: Assertion (A): Pyramid of biomass in sea is inverted.
Reason (R): The biomass of fishes far exceeds that of phytoplankton.
Reason (R): The biomass of fishes far exceeds that of phytoplankton.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (4) Both A and R are true and R is the correct explanation of A
▶️ The representation of a food chain in the form of a pyramid is called ecological pyramid.
▶️ The base of a pyramid represents producers (first trophic level). The apex represents tertiary or top-level consumer.
▶️ Ecological pyramids are 3 types: Pyramid of number, Pyramid of biomass and Pyramid of energy.
Q 20: Assertion (A): Biologists are not sure about total number of species under Kingdom Monera.
Reason (R): Conventional taxonomic methods are not suitable for identifying microbial species.
Reason (R): Conventional taxonomic methods are not suitable for identifying microbial species.
(1) Both A and R are true but R is NOT the correct explanation of A
(2) A is true but R is false
(3) A is false but R is true
(4) Both A and R are true and R is the correct explanation of A
✅ (4) Both A and R are true and R is the correct explanation of A
▶️ Kingdom Monera includes Archaebacteria and Eubacteria. They are prokaryotes.
▶️ Biologists are not sure about total number of prokaryotic species because
1. Conventional taxonomic methods are not suitable for identifying microbial species.
2. In laboratory, many species cannot be cultured.