This includes questions from Class 12 Biology chapters.
Q 1: Correct sequence of layers of anther from outer to inner is
(1) Epidermis → Tapetum → Middle layers → Endothecium
(2) Tapetum → Endothecium → Epidermis → Middle layers
(3) Epidermis → Endothecium → Middle layers → Tapetum
(4) Endothecium → Epidermis → Middle layers → Tapetum
✅ (3) Epidermis → Endothecium → Middle layers → Tapetum
▶️ A typical microsporangium is surrounded by 4 wall layers: epidermis, endothecium, middle layers & tapetum.
▶️ The outer 3 layers give protection and help in dehiscence of anther to release the pollen.
▶️ The tapetum nourishes the developing pollen grains.
Q 2: Select the wrong statement.
(1) Ovum produces estrogen and progesterone
(2) Ovary contains many groups of ovarian follicles
(3) Glans penis is covered by prepuce
(4) Outer wall of uterus is perimetrium
✅ (1) Ovum produces estrogen and progesterone
▶️ Mature ovarian follicles especially Graafian follicles secrete estrogen.
▶️ After ovulation, ruptured Graafian follicles become corpus luteum. It secretes progesterone.
▶️ Prepuce is also called foreskin.
▶️ Uterine wall has 3 layers: Outer perimetrium, middle myometrium and inner endometrium.
Q 3: Select the statement which is not correct about Coitus interruptus.
(1) It is a natural method of contraception.
(2) It is the pull-out method in which penis is withdrawn from the vagina just before ejaculation.
(3) It protects the user from STDs and AIDS.
(4) Ovum and sperms meeting is avoided.
✅ (3) It protects the user from STDs and AIDS.
3 types of Natural method of contraception:
▶️ Periodic abstinence: Avoid coitus from day 10 to 17 of menstrual cycle.
▶️ Coitus interruptus (withdrawal): Withdraw penis from vagina just before ejaculation.
▶️ Lactational amenorrhea method (LAM): It relies on exclusive breastfeeding to suppress ovulation and prevent pregnancy in the postpartum period.
Q 4: How many types of gametes will be produced by individuals of AABbcc
genotype?
(1) 2
(2) 4
(3) 6
(4) 9
✅ (1) 2
▶️ AABbcc genotype produces 2 types of gametes- ABc and Abc.
▶️ In this genotype, only Bb is heterozygous condition. AA and cc are homozygous.
Q 5: Alleles of a gene are found on
(1) Same chromosome
(2) Homologous chromosomes
(3) Non-homologous chromosomes
(4) Any chromosomes
✅ (2) Homologous chromosomes
▶️ Homologous chromosomes are a pair of chromosomes that have the same genes at the same locations but may have different alleles (variants or versions) of those genes.
▶️ In sexually reproducing organisms, individuals inherit one set of chromosomes from each parent. Each parent contributes one chromosome to each pair of homologous chromosomes.
Q 6: Correct combination that can form an RNA nucleotide is
(1) Adenine + deoxyribose + phosphate
(2) Thymine + ribose + phosphate
(3) Uracil + deoxyribose + phosphate
(4) Uracil + ribose + phosphate
✅ (4) Uracil + ribose + phosphate
A nucleotide has 3 components:
▶️ A nitrogenous base.
▶️ A pentose sugar (ribose in RNA & deoxyribose in DNA).
▶️ A phosphate group.
Nitrogen bases are 2 types:
🔹Purines: It includes Adenine (A) and Guanine (G).
🔹Pyrimidines: It includes Cytosine (C), Thymine (T) & Uracil (U). Thymine is present only in DNA and Uracil only in RNA.
Q 7: DNA double helix model is proposed based on X-ray diffraction data produced by
(1) Friedrich Miescher
(2) Watson & Crick
(3) Wilkins & Franklin
(4) Erwin Chargaff
✅ (3) Wilkins & Franklin
▶️ Friedrich Miescher (1869) identified DNA and named it Nuclein.
▶️ James Watson & Francis Crick (1953) proposed double helix model of DNA. It was based on X-ray diffraction data produced by Maurice Wilkins & Rosalind Franklin.
▶️ Erwin Chargaff proposed that in DNA, the ratio of A to T and the ratio of G to C are equal.
Q 8: Analogy is due to
(1) Becoming of unrelated species more similar to adapt in similar environmental conditions.
(2) Becoming of related species dissimilar to adapt in similar environmental conditions.
(3) Becoming of unrelated species more similar to adapt in different environmental conditions.
(4) Becoming of related species less similar to adapt in different environmental conditions.
✅ (1) Becoming of unrelated species more similar to adapt in similar environmental conditions.
▶️ Analogous organs are the organs having similar function but different structure & origin.
▶️ Analogy is due to Convergent evolution (different structures evolve for the same function and hence become similar).
▶️ Homologous organs are the organs having fundamentally similar structure and origin but different functions.
▶️ Homology is due to Divergent evolution (same structure evolve in different directions due to adaptations to different needs).
Q 9: Select the false statement.
(1) Widal test is used for confirmation of typhoid.
(2) Malaria is transmitted through Culex mosquito.
(3) Mary Mallon (Typhoid Mary) was a typhoid carrier who spread typhoid for several years.
(4) Plasmodium releases haemozoin.
✅ (2) Malaria is transmitted through Culex mosquito.
▶️ Malaria is transmitted through Female Anopheles mosquito. Pathogen is Plasmodium species.
▶️ Culex female mosquito transmits the disease Filariasis.
▶️ Filariasis is caused by a helminth called Wuchereria bancrofti and Wuchereria malayi.
Q 10: Primary lymphoid organs are
(1) Bone marrow & thyroid
(2) Thymus & spleen
(3) Thymus & bone marrow
(4) Tonsils & thymus
✅ (3) Thymus & bone marrow
▶️ Primary lymphoid organs: The organs where lymphocytes are matured & differentiated to antigen-sensitive lymphocytes. It includes thymus and bone marrow.
▶️ Secondary lymphoid organs: The organs, to which matured lymphocytes migrate from primary lymphoid organs, interact with antigens and then proliferate to become effector cells. E.g. Spleen, lymph nodes, tonsils, Peyer’s patches, appendix etc.
Q 11: Propionibacterium sharmanii and Penicillium roqueforti are concerned
with
(1) Cheese
(2) Clot buster
(3) Statin
(4) Sewage treatment
✅ (1) Cheese
▶️ Swiss cheese has large holes due to production of CO2 by Propionibacterium sharmanii.
▶️ Roquefort cheese is ripened by growing a fungus (Penicillium roqueforti) on them.
▶️ Streptokinase: Produced by Streptococcus. Used as a ‘clot buster’ to remove clots from the blood vessels of patients who have myocardial infarction.
▶️ Statins: Produced by Monascus purpureus (a yeast). Used as blood-cholesterol lowering agents.
Q 12: The two core techniques of modern biotechnology are
(1) Genetic engineering and Maintenance of sterile ambience.
(2) IVF and Preparation of DNA vaccine.
(3) Gene therapy and IVF.
(4) Microbe-mediated processes and Preparation of DNA vaccine.
✅ (1) Genetic engineering and Maintenance of sterile ambience.
▶️ Genetic engineering: The technique in which genetic material (DNA & RNA) is chemically altered and introduced into host organisms to change the phenotype.
▶️ Bioprocess engineering: Maintenance of sterile ambience in chemical engineering processes for growing desired microbe/eukaryotic cell for the manufacture of antibiotics, vaccines, enzymes etc.
Q 13: A group of enzymes which cut DNA at specific sites into fragments are called
(1) Proteolytic enzymes
(2) Restriction enzymes
(3) Hydrolytic enzymes
(4) Regulatory enzymes
✅ (2) Restriction enzymes
▶️ Restriction Enzymes (‘molecular scissors’) are the enzymes that cut DNA at specific sites into fragments. They belong to a class of enzymes called nucleases.
▶️ Hydrolytic enzymes (Hydrolases): The enzymes that catalyse the hydrolysis of many molecules.
▶️ Proteolytic enzymes (proteases): The enzymes that break down protein.
▶️ Regulatory enzymes: They are enzymes in a biochemical pathway that regulate the activity of the pathway. E.g., regulatory enzymes of the TCA cycle are citrate synthase, isocitrate dehydrogenase, and α-ketoglutarate dehydrogenase.
Q 14: Proteins encoded by the genes cryIAc & cryIIAb control
(1) Cotton bollworms
(2) Corn borer
(3) Bud worms
(4) Butterflies
✅ (1) Cotton bollworms
▶️ Bt toxin genes are the genes isolated from a bacterium called Bacillus thuringiensis and incorporated into crop plants such as cotton.
▶️ Most Bt toxins are insect-group specific. They are coded by cry genes.
▶️ E.g. proteins encoded by cryIAc & cryIIAb genes control cotton bollworms. Protein of cryIAb gene controls corn borer.
Q 15: The first human hormone produced by recombinant DNA technology is
(1) Oestrogen
(2) Progesterone
(3) Thyroxin
(4) Insulin
✅ (4) Insulin
▶️ In 1983, Eli Lilly (an American company) prepared two DNA sequences corresponding to A & B chains of human insulin and introduced them in plasmids of E. coli to produce insulin chains. Chains A & B were combined by creating disulfide bonds to form human insulin (Humulin).
Q 16: In a pond, there were 48 lotus plants last year and through
reproduction 18 new plants are added. Then the birth rate is
(1) 0.375 offspring per lotus per year
(2) 0.17 offspring per lotus per year
(3) 0.775 offspring per lotus per year
(4) 0.3 offspring per lotus per year
✅ (1) 0.375 offspring per lotus per year
▶️ Birth rates: Refer to per capita births. It is calculated by dividing the total number of births by the total population and expressing the result on a per person basis.
▶️ Here, there are 48 lotus plants last year and through reproduction 18 new plants are added.
▶️ So the birth rate = 18/48 = 0.375 offspring per lotus per year.
Q 17: Which of the following relations is correct regarding GPP and NPP of an ecosystem?
(1) NPP = R – GPP
(2) NPP = GPP – R
(3) GPP = NPP – R
(4) GPP = R – NPP
✅ (2) NPP = GPP – R
▶️ The rate of biomass production is called productivity.
▶️ It is divided into GPP and NPP.
▶️ Gross primary productivity (GPP): It is the rate of production of organic matter during photosynthesis. A considerable amount of GPP is used by plants in respiration (Respiration loss, R).
▶️ Net primary productivity (NPP): It is the available biomass for the consumption to heterotrophs.
i.e., NPP = GPP – R
Q 18: The set of processes which occur simultaneously is
(1) Fragmentation, Leaching, Catabolism
(2) Fragmentation, Humification, Mineralization
(3) Catabolism, Humification, Mineralization
(4) Leaching, catabolism, Humification
✅ (1) Fragmentation, Leaching, Catabolism
Steps of decomposition
▶️ Fragmentation: Breakdown of detritus into smaller particles by detritivores (e.g. earthworm).
▶️ Leaching: Water soluble inorganic nutrients go down into soil horizon and precipitate as unavailable salts.
▶️ Catabolism: Degradation of detritus into simpler inorganic substances by bacterial and fungal enzymes.
▶️ Humification: Accumulation of humus (dark amorphous substance) in soil.
▶️ Mineralization: Release of inorganic nutrients due to the degradation of humus by some microbes.
Q 19: Who popularized the term ‘biodiversity’?
(1) Robert May
(2) Edward Wilson
(3) Humboldt
(4) David Tilman
✅ (2) Edward Wilson
▶️ According to Robert May’s Global estimate, about 7 million species would have on earth. (i.e. only 22% of the total species have been recorded so far).
▶️ According to the study of Alexander von Humboldt in South American jungles, within a region, species richness increases with increasing explored area, but only up to a limit.
▶️ According to David Tilman, plots with more species shows less year-to-year variation in total biomass.
Q 20: Choose the right one which denotes genetic diversity in correct sequence.
(1) Chromosomes → Nucleotides → Genes → Individuals → Populations
(2) Populations → Individuals → Chromosomes → Nucleotides → Genes
(3) Genes → Nucleotides → Chromosomes → Individuals → Populations
(4) Nucleotides → Genes → Chromosomes → Individuals → Populations
✅ (4) Nucleotides → Genes → Chromosomes → Individuals → Populations
The sequence should be from smallest level to highest.
Levels of Biodiversity
▶️ Genetic diversity: Diversity shown by a single species at genetic level.
▶️ Species diversity: Diversity at species level.
▶️ Ecological diversity: Diversity at ecosystem level.