JKBOSE class 12th Biology Paper 2025 Download with Solution
JKBOSE Class 12 Zoology Paper 2025 – Complete Solutions
Section A: Very Very Short Answer Type (1 Mark Each)
1. Which one is found in males only?
The Y-chromosome is found only in males. It determines male sex characteristics and is inherited from the father. Females have two X-chromosomes (XX), while males have one X and one Y-chromosome (XY).
2. Name the evolutionary stage of man with brain capacity 900 C.C.
The evolutionary stage of humans with a brain capacity of 900 C.C. is Homo erectus. This species lived approximately 1.9 million to 110,000 years ago and is known for its upright posture and use of tools.
3. Trisomic condition is represented as:
The trisomic condition is represented as 2X + 1. This means an individual has an extra chromosome in one of the pairs, resulting in a total of 47 chromosomes instead of the usual 46. An example is Down syndrome, where there is an extra chromosome 21.
4. Causative agent of Filariasis:
The causative agent of filariasis is Wuchereria bancrofti, a parasitic worm transmitted through mosquito bites. It affects the lymphatic system, leading to swelling in limbs and other body parts, a condition known as elephantiasis.
5. Providing a functional gene to overcome a defective gene:
Providing a functional gene to overcome a defective gene is known as gene therapy. This technique involves inserting a healthy gene into the patient’s cells to replace or compensate for the defective gene, potentially curing genetic disorders like cystic fibrosis or sickle cell anemia.
Section B: Very Short Answer Type (2 Marks Each)
6. Functions of oxytocin in human females:
Oxytocin, often called the “love hormone,” plays two key roles in human females. First, it stimulates uterine contractions during childbirth, helping in the delivery of the baby. Second, it triggers the ejection of milk from mammary glands during lactation, facilitating breastfeeding.
7. Adaptive radiation:
Adaptive radiation refers to the evolution of diverse species from a common ancestor to occupy different ecological niches. This process occurs when organisms adapt to various environments, leading to the development of unique traits. A classic example is Darwin’s finches in the Galápagos Islands, which evolved different beak shapes to exploit various food sources.
8. How is sex determined in human beings?
Sex in humans is determined by the presence of sex chromosomes. Females have two X-chromosomes (XX), while males have one X and one Y-chromosome (XY). During fertilization, if a sperm carrying an X-chromosome fertilizes the egg, the offspring will be female (XX). If a sperm carrying a Y-chromosome fertilizes the egg, the offspring will be male (XY).
9. What do you mean by Biosafety issues?
Biosafety issues refer to the potential risks associated with the use of genetically modified organisms (GMOs) and biotechnology. These include environmental risks (e.g., unintended spread of GMOs), health risks (e.g., allergic reactions), and ethical concerns (e.g., misuse of genetic engineering). Proper regulations and containment measures are necessary to address these issues.
10. Applications of genetically engineered insulin:
Genetically engineered insulin, also known as recombinant insulin, is used to treat diabetes. It is produced by inserting the human insulin gene into bacteria or yeast, which then produce insulin. This method is safer and more efficient than extracting insulin from animal sources, as it reduces the risk of allergic reactions and ensures a steady supply.
Section C: Short Answer Type (3 Marks Each)
11. Microscopic anatomy of Testis:
The testis is composed of numerous seminiferous tubules, which are the site of sperm production. These tubules are lined with three types of cells: spermatogonia (germ cells that divide to form sperm), Sertoli cells (which provide nourishment to developing sperm), and Leydig cells (which produce testosterone). The interstitial space between the tubules contains blood vessels and connective tissue. A diagram would show the lobules, seminiferous tubules, and interstitial cells, highlighting their roles in spermatogenesis and hormone production.
12. Gene flow and Genetic drift:
Gene flow refers to the transfer of genetic material from one population to another through migration. It increases genetic diversity and reduces differences between populations. Genetic drift, on the other hand, is the random change in allele frequencies in a small population due to chance events. It can lead to the loss of genetic variation and is more significant in smaller populations.
13. Turner’s Syndrome:
Turner’s syndrome is a genetic disorder in females caused by the absence or partial absence of one X-chromosome (45,X). Symptoms include short stature, webbed neck, and underdeveloped ovaries, leading to infertility. Hormone therapy and growth hormone treatments are often used to manage the condition.
14. Drug abuse:
Drug abuse refers to the excessive and harmful use of substances like alcohol, nicotine, and illegal drugs. It leads to physical and psychological dependence, affecting an individual’s health, relationships, and social life. Prevention involves education, counseling, and strict enforcement of drug laws.
15. How can sexually transmitted diseases be prevented?
Sexually transmitted diseases (STDs) can be prevented by:
- Using condoms during sexual intercourse.
- Avoiding multiple sexual partners.
- Getting vaccinated for diseases like HPV and hepatitis B.
- Regular health check-ups and early treatment of infections.
Section D: Long Answer Type (5 Marks)
16. Explain the need for Reproductive Health. Also, add a note on medical termination of pregnancy.
Need for Reproductive Health:
Reproductive health is essential for overall well-being and societal development. It ensures individuals have access to information and services related to family planning, safe pregnancy, and prevention of sexually transmitted diseases (STDs). By promoting reproductive health, we can reduce maternal and infant mortality rates, control population growth, and improve the quality of life. Awareness programs and access to contraceptives play a crucial role in achieving these goals.
Medical Termination of Pregnancy (MTP):
Medical Termination of Pregnancy (MTP) refers to the safe and legal termination of pregnancy under specific conditions. In India, the MTP Act of 1971 (amended in 2021) allows abortion up to 24 weeks in special cases, such as rape, fetal abnormalities, or risk to the mother’s life. The procedure must be performed by a registered medical practitioner in a recognized facility to ensure safety. MTP is a critical component of reproductive health, providing women with the right to make informed choices about their bodies and health.
Or: Describe the human male reproductive system with the help of a diagram.
The human male reproductive system consists of the following organs:
- Testes: Produce sperm and testosterone.
- Epididymis: Stores and matures sperm.
- Vas deferens: Transports sperm to the urethra.
- Seminal vesicles, prostate gland, and bulbourethral glands: Produce seminal fluid.
- Penis: Delivers sperm during ejaculation.
A diagram would show the location and connection of these organs, highlighting their roles in sperm production, storage, and delivery.
Class 12th JKBOSE Botany 2025 Paper with solution
JKBOSE Class 12 Botany Paper 2025 – Complete Solutions
Section A: Multiple Choice Questions (1 Mark Each)
1. Which of the following is wrongly matched?
Answer: (C) AUG, GUA – Initiation Codons
Explanation:
– AUG is the initiation codon for methionine, and GUG can also act as an initiation codon for valine in some cases.
– However, GUA is not an initiation codon; it codes for valine during elongation.
Why other options are correct:
– (A) AUG and GUG are correctly matched with methionine and valine.
– (B) UAA, UAG, and UGA are correctly matched with stop codons (Ochre, Amber, Opal).
– (D) UAA, UAG, and UGA are correctly identified as stop codons.
2. Bt-toxin kills:
Answer: (A) Insects
Explanation:
– Bt-toxin is produced by the bacterium Bacillus thuringiensis.
– It specifically targets insect larvae by binding to their gut lining, causing cell lysis and death.
Why other options are incorrect:
– (B) Weeds: Bt-toxin does not affect weeds; herbicides are used for weed control.
– (C) Rodents: Bt-toxin is not toxic to rodents.
– (D) None of these: Incorrect, as Bt-toxin does kill insects.
3. Biogas production is carried out by:
Answer: (D) Methanogens
Explanation:
– Methanogens, such as Methanobacterium, are anaerobic archaea that decompose organic matter to produce methane (CH4), the primary component of biogas.
Why other options are incorrect:
– (A) Halophiles: These thrive in high-salt environments and are not involved in biogas production.
– (B) Thermoacidophiles: These thrive in high-temperature and acidic environments and are not involved in biogas production.
– (C) Luminescent bacteria: These produce light (bioluminescence) and are unrelated to biogas production.
4. The flow of energy in an ecosystem is:
Answer: (A) Unidirectional
Explanation:
– Energy flows from producers (plants) to consumers (herbivores, carnivores) and is lost as heat at each trophic level.
– It does not cycle back, making the flow unidirectional.
Why other options are incorrect:
– (B) Bidirectional: Energy does not flow back to the sun or producers.
– (C) Multidirectional: Energy flow is not random or multidirectional.
– (D) No specific direction: Energy flow follows a specific, unidirectional path.
5. Which one of the following is not a hotspot of biodiversity in India?
Answer: (A) Eastern Ghats
Explanation:
– India’s biodiversity hotspots are the Western Ghats, Indo-Burma Region, and Sundaland.
– The Eastern Ghats are not recognized as a biodiversity hotspot.
Why other options are correct:
– (B) Western Ghats: A recognized hotspot with high endemism.
– (C) Indo-Burma Region: A hotspot spanning Northeast India and Southeast Asia.
– (D) Sundaland: Includes the Andaman and Nicobar Islands, part of India’s biodiversity hotspots.
Section B: Short Answer Type (2 Marks Each)
6. Define Polyembryony. Differentiate between simple and adventive polyembryony.
Polyembryony: Formation of multiple embryos from a single fertilized egg or ovule.
Simple Polyembryony: Multiple embryos arise from the same zygote (e.g., Citrus).
Adventive Polyembryony: Embryos develop from nucellus or integuments (e.g., Mango).
7. What is Cellular Totipotency?
Cellular Totipotency: The ability of a single plant cell to regenerate into a whole plant under suitable conditions. Demonstrated by Haberlandt and applied in tissue culture techniques.
8. Differentiate between Mutualism and Competition.
Mutualism: Both species benefit (e.g., lichens: algae + fungi).
Competition: Species compete for limited resources (e.g., plants competing for light).
9. Define Pyramid of Energy. Why is it always upright?
Pyramid of Energy: Graphical representation of energy flow across trophic levels.
Upright: Energy decreases at each level due to metabolic losses (10% law), making it impossible to invert.
10. Name outbreeding devices. Describe one.
Devices: Dichogamy, herkogamy, self-incompatibility, unisexuality.
Dichogamy: Anthers and stigma mature at different times to prevent self-pollination (e.g., Sunflower).
Section C: Descriptive Answer Type (3 Marks Each)
11. Microspore development into male gametes:
Microspore undergoes mitosis to form:
1. Vegetative Cell: Larger cell for pollen tube growth.
2. Generative Cell: Divides into two male gametes.
The process occurs within the pollen sac, and a labeled diagram would show the pollen grain structure.
12. Pleiotropic Gene with examples:
Pleiotropic Gene: A single gene influencing multiple traits.
Plant Example: LEAFY gene in Arabidopsis (affects flowering time and leaf development).
Animal Example: Sickle cell gene (causes anemia and malaria resistance).
13. Applications of Plant Tissue Culture:
- Micropropagation of elite plants
- Production of disease-free plants
- Somatic hybridization (e.g., pomato)
- Conservation of endangered species
14. Processes in Decomposition:
(i) Fragmentation: Breaking down of detritus into smaller particles by decomposers.
(ii) Catabolism: Enzymatic breakdown of complex molecules into simpler ones.
(iii) Leaching: Water-soluble nutrients percolate into soil.
15. Ramsar Sites:
Definition: Wetlands of international importance under the Ramsar Convention.
Importance: Conservation of migratory birds and aquatic biodiversity.
Indian Sites: Chilika Lake, Keoladeo National Park, Loktak Lake.
Section D: Long Answer Type (5 Marks)
16. Operon and Inducible Operon:
Operon: A cluster of genes regulated by a single promoter (e.g., lac operon in E. coli).
Inducible Operon: Normally inactive, activated by an inducer. In the lac operon:
1. Repressor binds to operator in absence of lactose.
2. Lactose acts as inducer, inactivates repressor.
3. RNA polymerase transcribes genes for lactose metabolism.
Or: Independent Assortment with dihybrid cross:
Principle: Alleles for different traits segregate independently during gamete formation.
Example: Mendel’s dihybrid cross (Round/Yellow vs Wrinkled/Green peas). F2 ratio: 9:3:3:1.
Exception: Linked genes (e.g., Drosophila eye color and wing size).
