Uttarakhand Ubse Class 12 Biology — Real Previous-Year Papers

Multiple choice question (each part carries 1 mark; write the correct option in your answer book): (क) Functional megaspore in a flowering plant develops into- (i) Endosperm (ii) Ovule (iii) Embryo sac (iv) Embryo (ख) The menstrual cycle in females is regulated by which hormones? (i) Estrogen and Progesterone hormones (ii) Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH) (iii) Luteinizing hormone (LH) and Testosterone (iv) Prolactin and Oxytocin (ग) Which generation of Mendalian Cross has a phenotypic ratio of 3:1? (i) F₀ (ii) F₁ (iii) F₂ (iv) F₃ (घ) Which of the following is not a stage in the 'Hershey-Chase experiment'? (i) Infection (ii) Conjugation (iii) Blending (iv) Centrifugation (ङ) Antibody present in Colostrum that protect the newborn baby from disease is- (i) IgA (ii) IgG (iii) IgD (iv) IgE (च) Gene therapy was first used to treat which of the disease? (i) Cancer (ii) AIDS (iii) Cystic fibrosis (iv) To overcome the deficiency of ADA (छ) How many steps are there in the process of decomposition? (i) 10 (ii) 2 (iii) 8 (iv) 5 (ज) What is the impact on the biodiversity of indigenous species when alien species are introduced into an area, either unintentionally or deliberately for any purpose? (i) Decrease in alien species (ii) Increase in habitat (iii) They turn invasive and cause an increase in species. (iv) They turn invasive and cause the decline or extinction of indigenous species. Direction: In the next two parts of Question No. 1, there are two statements labelled as Assertion (A) and Reason (R). From the following options select their correct answer: (i) Both (A) and (R) are correct and (R) is the correct explanation of (A). (ii) Both (A) and (R) are correct but (R) is not the correct explanation of (A). (iii) (A) is correct but (R) is incorrect. (iv) Both (A) and (R) are incorrect. (झ) Assertion (A): Marijuana and Hashish are clinically used as analgesic. Reason (R): Both these drugs suppress brain's functionality. (ञ) Assertion (A): Asexual reproduction is more important with regard to biotechnology. Reason (R): Asexual reproduction preserves the genetic information while sexual reproduction permits variations.

Explain the 8-nucleate mature embryo sac of a typical angiospermic flower with the help of a labelled diagram only.

Mention the location and function of mitochondria in sperm.

'Lactational amenorrhea is a contraceptive method'. Write any two reasons in support of this.

Write the genotype of- (क) An individual who is carrier of Sickle-cell anaemia gene but apparently unaffected. (ख) An individual who is affected with Sickle-cell anaemia disease.

Match the following- (क) Natural Selection (ख) Inheritance of acquired characters (ग) Analogous Structures (घ) Industrial Melanism (i) Convergent evolution (ii) Dark winged and white winged moths (iii) Charles Darwin (iv) Long neck of Giraffe

How is lactic acid bacteria (LAB) beneficial to us other than helping in curding the milk? Write any two benefits. **OR** Mention one use of each of the following- (क) Passive immunisation (ख) Antihistamine

What do 'Eco', 'R' and 'I' represent in enzyme EcoRI?

Write the role of UV light and ethidium bromide during gel electrophoresis of DNA fragments.

Write the functions of Cry I Ab and Cry II Ab.

What will be the effect on decomposition rate if- (क) Detritus is rich in lignin and chitin. (ख) Detritus is rich in nitrogen and sugars. **OR** Write any two differences between in-situ and ex-situ conservation.

How does a mature pollen grain develop from a pollen mother cell? Show the various stages with labelled diagram. **OR** "A fertilized egg is the blueprint of future development." Explain.

Why is Drosophila melanogaster (Fruit fly) used extensively for genetic study?

A molecule that can act as a genetic material must fulfill what criteria?

(क) In which part of the world, the Neanderthal Man lived? (ख) What was the brain capacity of Neanderthal Man? (ग) Mention the advancement which Neanderthal Man showed over Homo erectus.

What three things affect human health? Explain. **OR** Draw a well labelled diagram of an antibody molecule and describe it briefly.

Write any three differences between exonuclease and endonuclease. **OR** Many people are apprehensive of accepting Genetically Modified (GM) Crops. Write any three reasons to convince them to adopt these crops.

What are the basic processes that cause population density to fluctuate in a given habitat over a given period of time? Explain each process.

What do you understand by latitudinal gradient? What could be the possible reasons for diversity between tropic and temperate regions?

(क) Draw a diagramatic labelled sectional view of seminiferous tubule of human. (ख) Describe the spermatogenesis process in human. **OR** What is double fertilisation? In which plants does it occur? Describe the changes that occur after double fertilisation.

Describe the following- (क) Punnet square (ख) Histones **OR** Write any four salient features of the double helix structure of DNA.

Read the following passage carefully and answer the questions given below- Large quantities of waste-water is generated everyday in cities and towns. A major component of this waste water is human excreta. This waste water is also called sewage. It contains large amounts of organic matter and microbes, many of which are pathogenic. This can not be directly discharged into natural water bodies like rivers and streams. Before disposal hence sewage is treated in sewage treatment plants to make it less polluting. This treatment is carried out in two stages. In primary treatment, small and large particles are physically removed from sewage whereas in secondary treatment the primary effluent is passed into large aeration tanks and air is pumped into it. This allows vigorous growth of useful aerobic microbes into flocs. (क) Why is sewage treatment necessary? (ख) What is the difference between primary and secondary treatment of sewage? (ग) What is 'Flocs' and what is their role? (घ) By which method, small and large particles are physically removed from sewage in primary treatment?