Class 12 Biology

4. What is the primary function of the cambium in the perennial dicot vascular plants?

   A) To produce lateral roots

  B) To provide structural support

  C) To produce new xylem and phloem

  D) To regulate transpiration

Describe the internal structure of a monocot root with diagramatic figure.

5. How does plasmolysis alter the osmotic process across the cell membrane?

A) Alters solute equilibrium, promoting water withdrawal from the cell

 B) Blocks water exit, causing water accumulation within the cell

C) Disturbs solute balance, causing water to enter the cell D) Increases solute diffusion across the membrane, leading to osmotic equilibrium

 In which cross, the genotypic and phenotypic ratio are same? Explain it with reference to Mirabilis jalapa plant. 

                                    OR

  Apply your understanding of various processes involved in the ascent of sap in cohesion tension theory for the maximum uptake of water in plants. 

What is called the process in which the shrinkage of protoplasm of fresh plant cell kept in hypertonic solution?

 A) Deplasmolysis    B) Endosmosis     C) Imbibition     D) Plasmolysis

A gardener removes the apical bud of a coffee plant to promote lateral branching. Which hormonal change best explains this effect?

A) Reduced auxins allows lateral buds to grow

B) Increased gibberellin causes stem elongation

C) Increased auxin induces dormancy

D) Increased auxins stimulates lateral buds

Which of the following tissue of a leaf helps in photosynthesis?

 A) Aerenchyma   B) Xylem    C) Mesophyll    D) Sclerenchyma

Dark reaction or Black man’s reaction of photosynthesis occurs in absence of light inside stroma region of chloroplast. It uses ATP and NADP and reduce to \( \text{CO}_2 \) to form sugar. Provide the flow chart for \( \text{C}_3 \) Cycle highlighting 3 major steps, and explain it. Write the chemical equation of photosynthesis. 

 How does aerobic respiration differ from anaerobic respiration? Describe the cycle that involves breakdown of two carbon compound Acetyl CoA in aerobic respiration with necessary diagram. 

 What causes cell elongation in the internodal regions of plants?

    A) Indole acetic acid            B) Gibberellins

    C) Abscisic acid                  D) Cytokinins

Which of the following describes the transmission of an X-linked trait from a father to his grandson through his normal carrier daughter?

A) Co-dominance    B) Maternal inheritance    C) Y-Linked inheritance  D) Criss-cross inheritance

A plant species has \( 2\text{n}=14 \) chromosomes. A mutant plant is found to have \( 2\text{n}+1(15) \) chromosomes. Identify the type of chromosomal mutation and, on this basis, differentiate between aneuploidy and euploidy. 

OR

Glycolysis involves partial oxidation of glucose to pyruvate with release of energy. Write the flow chart of major phases of EMP pathway and state the net gain of ATP and $\text{NADH}$ per molecule of glucose in it. 

'DNA is known as the universal genetic material, where as RNA is not'. Justify this statement. Describe DNA with reference to its chemical composition, Watson and Crick's model with labelled diagram and function.

OR

 Describe the process of crossing over during prophase - I of Meiosis - I with the help of labelled diagrams. Explain how the absence of crossing over would affect genetic variation of offspring.

 "Genes are inherited in new combination due to crossing over in the gametes". Interpret this statement with its mechanism and necessary diagrams. Write the significance also. 

                                  OR

 Briefly discuss the Watson and Crick's model of DNA with the help of neat and labelled diagram. Give three points of differences between DNA and RNA in their structure, composition and function.

 Which of the following genotypes represents monosomy, a type of aneuploidy?

   A) 2n - 2                              B) 2n - 1

  C) 2n + 1                             D) 2n + 1 + 1

1.  Which of the following type of artificial vegetative propagation in which root is induced while it is still attached to the parent plant and it is particularly suitable for plants having soft branches lying near to soil?             

              A) Air layering            B) Grafting   

             C) Soil layering            D) Cutting

What is the substance sampled during amniocentesis?

 A) Placental cells    B) Amniotic fluid

 C) Maternal blood   D) Umbilical cord tissue

What is the specific term used for the part of the plant that provides the root system?

A) Propagule

B) Stock

C) Callus

D) Scion

Although plant tissue culture has the potential to reduce global hunger, it is often considered expensive for developing countries. Briefly analyze its limitations and suggest some suitable measures for effective implementation in Nepal.

What is blastula? How is blastula formed during development of frog? Why micromeres divide faster than the macromeres? 

            OR

 Explain the basic steps involved in IVF. Mention any two potential risks or complications associated with IVF. 

Study the given figure and answer the following questions.

i) Identify the given figure and name the parts label by A and B.                                                                                         

ii) Explain the development of this structure from a microspore with the help of labelled diagrams. 

 Which of the following epithelium forms the inner lining of vagina?

 A) Columnar                                 B) Cuboidal 

 C) Stratified keratinized squamous  D) Stratified non-keratinized squamous

Compare and contrast between simple and compound epithelium

Tendons connect muscles to bones. Why are they less elastic in nature?
A) They contain more elastin fibres
B) They contain more collagen fibres
C) They contain less collagen fibres
D) They contain more reticular fibres

Compare and contrast bone and cartilage.

Which is the correct sequence in embryonic development of frog?

A) Morula, blastula, gastrula

 B) Blastula, morula, gastrula

C) Morula, gastrula, blastula

 D) Blastula, gastrula, morula

Describe the process of oogenesis, with the help of schematic diagram. 

OR

Discuss the advantages and disadvantages of organ transplantation.

What is the space between the somatic and visceral layer of mesoderm called in the embryonic development of frog?
A) Blastocoel    B) Archenteron    C) Coelom     D) Neurocoe

 Draw a labelled diagram of T.S. of a typical dicot stem and mention any two anatomical characteristics of its vascular bundles.

Look at the figure related to the sexual reproduction of angiosperms and answer the following questions:

     a) What is the figure about, and why is it important? [1]

     b) Label the parts marked as A and B. [1]                                                                                                  

     c) Describe the different phases of female gametophyte development using labelled diagrams. [2]

Study the given figure carefully and answer the following questions.

 i) Label the parts A and B. .                                                                          

ii) Why is part B called mixed gland?             

 iii) What is the function of part A and C ? 

 iv) Name the sphincter located at the Ampulla of Vater or hepato-pancreatic ampulla. 

 What would happen, if the oxyntic cells of gastric glands becomes non-functional due to some reasons?

A) Lipase enzyme becomes more active

B) Protein digestion does not take place

C) pH of stomach falls

D) Pepsin is not secreted

Coronary sinus collect deoxygenated blood from myocardium (muscles) of heart. It drains blood into which chamber?
A) Left atrium    B) Right atrium    C) Left ventricle     D) Right ventricle

Show the correct path for the flow of urine.

A) Renal pelvis, ureter, urinary bladder, urethra

B) Renal pelvis, ureter, urethra, urinary bladder

C) Renal pelvis, urinary bladder, urethra, ureter

 D) Renal pelvis, urethra, ureter, urinary bladder

Study the given figure and answer the following questions.

       i) Label the parts C and D.

      ii) What is the difference between the parts A and B? (any two) 

      iii) Mention the function of part C.

Sympathetic and parasympathetic nervous system have opposing functions and controls involuntary activities of the body. Differentiate between sympathetic and parasympathetic nervous system. Draw a well labelled diagram of human brain and give short account on brain ventricles. 

OR

Adrenal glands also known as suprarenals are located above the kidneys and have outer cortex and inner medulla region. Name the different groups of hormones secreted by the different regions of adrenal cortex. Mention specific functions of each. Describe the disorders of hormones secreted by adrenal cortex.

Human alimentary canal is a complete tube designed for ingestion, digestion, absorption, assimilation and egestion process. Draw a labelled diagram of human digestive system and explain the parts of alimentary canal. What would happen if the bile duct becomes blocked? 

    OR

Human ear is concerned with hearing and equilibrium. With the help of a labelled diagram, explain the structure of human ear. What would happen, if the opening of Eustachian tube becomes blocked?

A 17-year old student can read books comfortably but cannot clearly see the letters on black or white board. What could be the defect and its cause?
A) Hypermetropia due to short eyeball
B) Myopia due to increased focal length
C) Myopia due to elongated eyeball
D) Presbyopia due to weak ciliary muscles

If the person has puffy appearance, moon face, low body temperature and is intolerance to cold. What do you think he is suffering from?

A) Grave's disease      B) Conn's disease

C) Myxoedema             D) Hashimoto's disease

 How do organic fertilizers contribute to sustainable agricultural practices compared to chemical fertilizers, and why is prioritizing their use advantageous? 

 Name the causative agent of AIDS. Mention its mode of transmission, symptoms and preventive measures. Why is it prevalence among intravenous drug users?

Which vaccine is prepared using DNA-recombinant technology and contains only a specific antigen, reducing adverse reactions ?
A) BCG   B) OPV    C) Hepatitis B     D) Rabies

Candidiasis also known as moniliasis is an infection which affect immune compromised people. Describe its causative agent, mode of transmission, symptoms and preventive measures. Why is candidiasis common in diabetic patients?

"Tobacco smoking is injurious to health." Identify some of the health hazards of tobacco smoking and suggest some preventive measures of smoking.

Which of the following are psychotropic drugs?
A) Opiates    B) Antihistamines    C) Mescaline    D) Bhang

Respiratory disorders occur when there is problem in any part of the respiratory system. Identify any four respiratory disorders prevalent in your community. Also, suggest some methods of prevention.