Maximum Marks: 70
Time allowed: Three hours
(Candidates are allowed additional 15 minutes for only reading the paper. They must NOT start writing during this time)
- This paper comprises of TWO PARTS - Part I and Part II.
- Answer all questions.
- Part I contains twenty questions of one mark each.
- Part II consists of Section A, B & C.
- Section A contains seven questions of two marks each
- Section B contains seven questions of three marks each
- Section C contains three questions of five marks each.
- Internal choices have been provided in two questions in Section A, two questions in Section B and in all three questions of Section C.
Answer all questions.
(a) Answer the following questions briefly and to the point: [8×1]
- Name the most common motile spore of fungi.
Answer: Zoospore.
- State the chromosome number in the endosperm of onion.
Answer: The endosperm is triploid (3n). Since the diploid number of onion is 2n = 16, the endosperm has 24 chromosomes.
- Give the use of test cross.
Answer: It is used to determine whether an organism exhibiting a dominant trait is homozygous or heterozygous for that trait.
- Mention the use of Lactobacillus.
Answer: It is used to convert milk into curd by producing lactic acid, which partially digests milk proteins.
- What will happen if a child does not get colostrum in his early childhood?
Answer: The infant will miss out on IgA antibodies, resulting in weaker passive immunity and higher susceptibility to infections.
- What is the shape of the pyramid of number in a single tree ecosystem?
Answer: Inverted.
- What is the biological significance of golden rice production?
Answer: It is genetically modified to produce beta-carotene (provitamin A) to combat Vitamin A deficiency.
- Bt crops are resistant to pests. Name the gene responsible for pest resistance.
Answer: cry gene.
(b) Each of the following questions has four choices. Choose the best option in each case: [4×1]
- Capacitation refers to the process of changes in the:
- (1) Testis
- (2) Sperm
- (3) Ovary
- (4) Ovum
Answer: 49,Answer: (2) Sperm
- MTP is considered to be safe up to how many weeks of pregnancy?
- (1) Six
- (2) Eight
- (3) Twelve
- (4) Eighteen
Answer: 55,Answer: (3) Twelve
- Which of the following is a vestigial organ in humans?
- (1) Pinna
- (2) Coccyx
- (3) Tail
- (4) Molars
Answer: 61,Answer: (2) Coccyx
- Secondary sewage treatment is mainly a:
- (1) Chemical process
- (2) Biological process
- (3) Mechanical process
- (4) Physical process
Answer: 67,Answer: (2) Biological process
(c) Give one significant contribution of each of the following scientists: [4×1]
- Gamow
Answer: Proposed that the genetic code consists of a triplet of nucleotides (codons) that code for 20 amino acids.
- Chargaff
Answer: Formulated Chargaff's rules: in a DNA molecule, the amount of Adenine equals Thymine, and Guanine equals Cytosine (A=T, G=C).
- T.H. Morgan
Answer: Established the chromosomal theory of inheritance through his work on Drosophila melanogaster, demonstrating linkage and crossing over.
- Alec Jeffery
Answer: Developed the technique of DNA fingerprinting.
(d) Define the following: [2×1]
- Life span
Answer: The period from birth to the natural death of an organism.
- Natality
Answer: The number of births during a given period in the population that are added to the initial density.
(e) Give reason: [2×1]
- Retrovirus is considered to be an exception to the central dogma.
Answer: Retroviruses have RNA as their genetic material and synthesize DNA from RNA using the enzyme reverse transcriptase, reversing the standard DNA → RNA information flow.
- The rate of Ozone depletion is greater in Antarctica.
Answer: Unique weather conditions during winter (extremely low temperatures) facilitate the formation of polar stratospheric clouds (PSCs), providing surfaces for reactions that release active ozone-depleting chlorine.
Answer all questions
Question 2 [2]
- (a) Draw a labelled diagram of human ovum.
Answer: (Self-Study Note: Draw a spherical human ovum indicating the corona radiata, zona pellucida, perivitelline space, plasma membrane (vitelline membrane), cytoplasm (ooplasm), and a prominent nucleus (germinal vesicle).)
OR
- (b) Draw a labelled diagram of human sperm.
Answer: (Self-Study Note: Draw a human sperm showing the head (with acrosome and nucleus), neck (containing centrioles), middle piece (with a spiral arrangement of mitochondria), and a long tail (flagellum).)
Question 3 [2]
If phenotype of father is blood group 'O' and genotype of mother is heterozygous 'A', what are the possible genotypes and phenotypes of the offspring?
Answer: Father is 'O' (genotype ii). Mother is heterozygous 'A' (genotype IAi). Possible offspring genotypes: IAi and ii. Phenotypes: Blood group A and Blood group O (in a 1:1 ratio).
Question 4 [2]
Mention four features of pBR322.
Answer: 1. Contains an origin of replication (ori). 2. Possesses selectable marker genes (ampR and tetR). 3. Has multiple unique recognition sites for various restriction endonucleases. 4. Small size, which facilitates easy isolation and introduction into host cells.
Question 5 [2]
State four measures taken by the government to control high level of air pollution in cities.
Answer: 1. Mandating the use of unleaded petrol in vehicles. 2. Implementation of stringent emission norms (like Bharat Stage emission standards). 3. Promoting the use of compressed natural gas (CNG). 4. Phasing out old, highly polluting vehicles.
Question 6 [2]
In recent years, there has been large scale loss of biodiversity. Mention four ways in which humans are responsible for it.
Answer: 1. Habitat destruction and fragmentation (deforestation, urbanization). 2. Over-exploitation of natural resources and poaching. 3. Introduction of invasive alien species. 4. Environmental pollution and contributing to global climate change.
Question 7 [2]
Mention any one symptom of elephantiasis. Name its causative agent.
Answer: Symptom: Abnormal swelling of the lower limbs or genital organs due to chronic inflammation of lymphatic vessels. Causative agent: Wuchereria bancrofti (or W. malayi).
Question 8 [2]
- (a) Mention any two properties of DNA that make it an ideal genetic material.
Answer: 1. It is chemically and structurally stable. 2. It is capable of replicating itself accurately due to complementary base pairing.
OR
- (b) Give two differences between Darwinism and the theory of mutation.
Answer: 1. Darwinism states that evolution occurs through continuous, small, directional variations, whereas mutation theory suggests it occurs through large, sudden, discontinuous, and directionless mutations. 2. Darwin believed natural selection acts on minor variations, while de Vries believed single-step large mutations (saltation) cause speciation.
Answer all questions
Question 9 [3]
- (a) Explain the steps involved in artificial hybridization.
Answer: 1. Emasculation: Removal of anthers from the flower bud of the female parent before dehiscence. 2. Bagging: Covering the emasculated flower to prevent contamination by unwanted pollen. 3. Pollination: Dusting mature, viable pollen from the desired male parent onto the receptive stigma. 4. Re-bagging and tagging: Covering the pollinated flower again and attaching a tag with details.
OR
- (b) What are the main objectives of plant breeding programmes?
Answer: 1. To produce crops with higher yields and improved nutritional quality. 2. To develop varieties with increased tolerance to environmental stresses (salinity, extreme temperatures, drought). 3. To breed plants resistant to various pathogens and insect pests.
Question 10 [3]
Differentiate between infectious diseases and non-infectious diseases. Give two examples of each.
Answer: Infectious diseases are caused by pathogenic microorganisms and can be transmitted from one person to another (e.g., Malaria, Common Cold). Non-infectious diseases are not caused by pathogens and cannot be transmitted; they arise from genetic, lifestyle, or environmental factors (e.g., Cancer, Diabetes).
Question 11 [3]
Define:
Answer: An interaction between two different species where both species mutually benefit from the association.
Answer: An interaction where one species benefits while the other is neither harmed nor benefited.
Answer: An interaction between two species where one is harmed or destroyed while the other remains unaffected.
Question 12 [3]
Define species-area relationship. What is the significance of the slope of regression? Show with the help of a graph.
Answer: Species-area relationship states that within a region, species richness increases with explored area, but only up to a limit (S=cAz). Significance of slope (z): It indicates the rate at which species richness increases with area (usually 0.1 to 0.2 for local regions, but steeper for continents). (Self-Study Note: Draw a graph with 'Area' on the x-axis and 'Species richness' on the y-axis, plotting a curve for S=cAz and a straight line for logS=logC+zlogA.)
Question 13 [3]
Give six features of genetic code.
Answer: 1. Triplet nature (codon consists of three bases). 2. Unambiguous and specific (one codon codes for one amino acid). 3. Degenerate (some amino acids are coded by more than one codon). 4. Commaless (read in a continuous fashion). 5. Universal (almost identical across all organisms). 6. Non-overlapping.
Question 14 [3]
State the measures to be taken by the owner of a dairy farm to improve the quality of milk and the quantity of its production.
Answer: 1. Selection of high-yielding, disease-resistant breeds. 2. Providing proper housing with adequate ventilation, space, and water. 3. Scientific feeding with a balanced diet of fodder and concentrates. 4. Maintaining strict hygiene during milking and storage. 5. Regular veterinary checks and vaccinations.
Question 15 [3]
- (a) Draw a labelled diagram of the T.S of anther.
Answer: (Self-Study Note: Draw the Transverse Section of a young anther showing the tetrasporangiate structure. Label epidermis, endothecium, middle layers, tapetum, and sporogenous tissue, along with the connective tissue.)
OR
- (b) Draw a labelled diagram of the LS of anatropous ovule.
Answer: (Self-Study Note: Draw the Longitudinal Section of an anatropous ovule. Label the funicle, hilum, outer and inner integuments, micropyle, chalaza, nucellus, and the embryo sac containing egg apparatus, polar nuclei, and antipodal cells.)
Answer all questions
Question 16 [5]
- (a) How has biotechnology been useful in controlling nematode infection in plants? Explain the technique involved in this process.
Answer: Biotechnology controls nematode infections (e.g., in tobacco) using RNA interference (RNAi). Nematode-specific genes are introduced into the host plant via Agrobacterium vectors, producing both sense and anti-sense RNA. These form double-stranded RNA (dsRNA) which initiates RNAi. When the nematode feeds on the plant, dsRNA gets cleaved into siRNAs that silence the specific nematode mRNA, preventing translation of essential proteins and causing the nematode to die.
OR
- (b) Answer the following:
- What are molecular scissors? What is their role in rDT?
Answer: Molecular scissors are restriction endonucleases that cut DNA at specific recognition sequences. In rDT, they cut both source and vector DNA to produce compatible ends, allowing the foreign gene to be ligated into the vector.
- Explain the steps involved in downstream processing, in biotechnology.
Answer: Downstream processing involves separation and purification of a product before marketing. Steps include: 1. Separation from the cell culture broth. 2. Purification to remove impurities. 3. Formulation with preservatives. 4. Rigorous quality control and clinical trials (for drugs).
Question 17 [5]
- (a) Expand the following terms and explain them briefly:
- GIFT
Answer: Gamete Intra-Fallopian Transfer: An ART method where retrieved ovum and sperms are transferred into the fallopian tube for in vivo fertilization.
- ZIFT
Answer: Zygote Intra-Fallopian Transfer: A technique where in vitro fertilization produces an early zygote (up to 8 blastomeres) which is then transferred into the fallopian tube.
- RCH
Answer: Reproductive and Child Health Care Programmes: Government initiatives aimed at creating awareness about reproduction-related aspects and building a reproductively healthy society.
- ICSI
Answer: Intracytoplasmic Sperm Injection: A specialized IVF procedure where a single sperm is directly injected into the cytoplasm of an ovum.
- IVF
Answer: In Vitro Fertilization: A procedure where fertilization occurs outside the body in a laboratory setting, followed by embryo transfer.
OR
- (b) Classify the methods of contraception. Write short notes on any two of the methods mentioned by you.
Answer: Contraceptive methods are classified into: 1. Natural/Traditional, 2. Barrier methods, 3. IUDs, 4. Oral Contraceptives, 5. Injectables/Implants, 6. Surgical methods.
Barrier Methods: Prevent physical meeting of sperm and ovum. Examples include condoms, diaphragms, and cervical caps.
Surgical Methods: Terminal methods blocking gamete transport, e.g., vasectomy in males (cutting/tying vas deferens) and tubectomy in females (cutting/tying fallopian tubes).
Question 18 [5]
- (a) Answer the following questions:
- If 10000 K cal energy is available at the level of producers, calculate the amount of energy at the level of secondary consumer.
Answer: According to Lindeman's 10% law, primary consumers get 1,000 Kcal (10% of 10,000). Secondary consumers receive 10% of 1,000 Kcal, which is 100 Kcal.
- A snapdragon plant with red flowers was crossed with a plant with white flowers. It produced pink progeny in the F1 generation. Explain the principle of inheritance involved with the help of Punnett square.
Answer: The principle involved is Incomplete Dominance, where neither allele is completely dominant, resulting in an intermediate phenotype (pink). (Self-Study Note: Draw a Punnett square showing RR (Red) x rr (White) -> all Rr (Pink) F1. Selfing F1 (Rr x Rr) gives F2 ratio of 1 RR : 2 Rr : 1 rr.)
OR
- (b) Describe the process of DNA replication in prokaryotes.
Answer: DNA replication in prokaryotes occurs in the cytoplasm:
- Initiation: Replication begins at the Origin of Replication (ori). Helicase unwinds the double helix, Topoisomerase relieves supercoiling, and SSBPs stabilize unwound strands.
- Primer Synthesis: Primase synthesizes short RNA primers.
- Elongation: DNA Polymerase III adds complementary nucleotides to the 3' end. The Leading strand is synthesized continuously, while the Lagging strand is synthesized discontinuously as Okazaki fragments.
- Maturation/Ligation: DNA Polymerase I removes RNA primers and fills gaps; DNA Ligase joins the Okazaki fragments.
