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12th Biology question paper with answers in english

12th Biology question paper with answers
Biology questiom paper

Biology (set-2)

Short answers questions (with answers)     2-Marks

For class 12th                                      Number of questions-26

1. Differentiate between linkage and crossing over.
Ans:-
Linkage
Crossing over
1. Linkage keeps the genes of a chromosome together
1. Crossing over separates the genes of a chromosome, forming new recombinations
2. Linkage strength increases due to closeness of genes
2. Frequency of crossing over decreases between nearby genes
3. It maintains the parental characters in the offsprings
3. It changes the parental characters in the offsprings
4.  Linkage prevents the formation of new varieties of organisms by geneticists
4.  It helps in the formation of new varieties of organisms by geneticists


2. What do you understand by parthenogenesis?
Ans:- Parthenogenesis is a process in which the female gamete of some organisms like rotifers, honeybee and birds (Turkey), undergoes development to form new organisms without fertilization.

3. Write principles of Biotechnology.
Ans:- Principles of Biotechnology is based on two main techniques– 
(i)  Genetic engineering – It is the science of manipulation of genes. In a strict sense it involves alterations in the chemistry of genetic material, introduction of the same into host and thereby changing the phenotype of host.
 (ii) Biochemical engineering processes devoted for the growth of desired microbe or eukaryotic cell in large quantities in a culture medium in aseptic conditions for the manufacture and multiplication of biotechnological products, such as antibiotics, vaccines, enzymes etc.

4. Give difference between Interferons and Antibodies.
Ans:-
Interferons
Antibodies
1. These are produced by any microbe- infected cells.
1. These are produced only by plasma -cells.
2.  These are quick in action but gives a temporary protection against microbes
2. These are slow in action but give a long lasting protection against antigens.
3. These act inside the cells.
3. These act outside the cells.
4.  Form the body’s second line of defence.
4.  Form the body’s third line of defence.

5. Name the hormones involved in regulation of spermatogenesis.
Ans:- The hormones involve in the regulation of spermatogenesis one follicle stimulating hormones (F.S.H.) and Lutenizing hormones (L.S.H.) which are secreted by pituitary gland under the influence of gonadotropin releasing hormones from the hypothalamus.
 
6. Differentiate between gametogenesis and embryogenesis?
Ans:-
           Gametogenesis
          Embryogenesis
1. Gametogenesis refers to the process of formation of the two types of gametes, male and female.
1. Embryogenesis refers to the process of development of embryo from the zygote.
2. It involves the formation of haploid male and female gametes from diploid meiocytes through the process of meiosis.
2. It involves the development of the embryo from the repeated mitotic divisions of the diploid zygote.



7. Differentiate between Innate and Acquired Immunity?
Ans:- Innate immunity is a kind of non-specific protection of the body which persist from the birth whereas acquired immunity is pathogen-specific in which primary and secondary responses occur which depend upon memory of the primary responses.

8. What is significance of double fertilization?
Ans:- Significance of double fertilization:–
(i) Double fertilization is very important in angiospermic plants. If only syngamy occurs in plants and triple fusion does not occur, only 3 zygote will be formed. Endosperm will not be formed and this will result seed with undeveloped embryo or seed without embryo.
(ii) Endosperm is formed due to double fertilization this provides nutrition to embryo and it contains maternal and paternal chromosome. A body shows physiological aggressiveness due to hybrid vigour in inner endospermic cells.


9. What is co-dominance? Explain
Ans:- In co-dominance both dominant alleles of a gene express themselves equally in F1 hybrids. The phenotypic ratio matches with genotypic ratio i.e., 1: 2: 1 in F2 generation of offspring.

10. What is Bt cotton?
Ans:- Bt cotton: – Bt is a type of toxin, which is obtained from Bacillus thuringiensis. It is called Bt in short form. Bt toxin gene has been cloned from the bacteria and expressed in plants to provide resistance from insects without the requirement of insecticide. Bt toxin genes were isolated from Bacillus thuringiensis and incorporated into the several crop plants such as cotton.

11. What is radio-active pollution? What are the sources of radio-active pollution?
Ans:- Radioactive Pollution – Certain elements such as Radium, Thorium, Uranium emit protons (Alpha particles) electrons (Beta particles) and Gamma particles bydisintrigration of atomic nuclei. This phenomenon is called radioactivity and these elements are known as radioactive.   When the radioactive radiations contaminate to water, air, soil and food materials it is called radioactive pollution.

12. Write the effects of Acid Rain.
Ans:- Effects of Acid Rain:–
(i) Acid rain damages a number of heritage monuments due to deposition of acids eg. Statue of Liberty, Taj Mahal etc.
(ii) Acid rain kills the useful soil microbial community thus disturbing terrestrial ecosystems. (iii) In the aquatic ecosystem acid rain below 5 pH causes death of planktons, molluses and fish, therefore it disturb the food chain.

13. Explain contact inhibition?
Ans:- Uncontrolled cell division and prolifezation growth & multiplication is sign of cancer cells & cancer disease, cancerous cells are called malignant neoplasm, which develop on neighbouring cells (by taking nutritive elements from them) grow and multiply. At last these cancerous cell kill the neighbouring cell. These concerns cell when come in contact with normal cell, they inhibit the growth and dynamic of these cells. This property of cancer cells are called contact inhibition.

14. What is IUDs ? How does it work ?
Ans:- Intra Uterine Devices (IUDs) are inserted by doctors or expert nurses in the uterus through vagina. These are of different types for example (1) non medicated IUDs (eg. Lippes loop), (2) Copper releasing IUDs (Cu-T, Cu-T Multiload 375) and (3) the hormone releasing IUDs (Progestasert, LNG-20). IUDs increase phagocytosis of sperms within the uterus and the Cu ions released suppress sperm motility and the fertilizing capacity of sperms. The hormone releasing IUDs in addition, make the uterus unsuitable for implantation and cervix hostile to the sperms. IUDs are ideal contraceptives for the females who want to delay pregnancy an/or space children.

15. What are the main features of Cancer cells? Explain.
Ans:- The main features of cancer cell are following– (a) Cancer cells have their own unchangeable plasma membrane, but sometimes formation of mucopolysachharides on cell surface are seen. (b) Cytoplasm of cancer cells contain various types of cell inclusions. (c) Swollen mitochondrion in cancer cells are observed. (d) Nucleus shows its increased  shape. The outer membrane is irregular. (e) Chromatin granules in the nucleus are irregularily distributed.

16. What is Tranquilizers ? Explain it with examples.
Ans:- Drugs which are used in patients having mental tension & worries are called tranquilizers.  For example:– (i) Benzodiazepins – Used in case of mental patient and given mental peace to them. (ii) Phenothiazines – It stimulate the patient and given mental peace through eradicating mental worriness. (iii) Reserpine – It is obtained from Rauvolfia serpentina and very effective in mental tension and worriness.

17. How does killer T-cells act ?
Ans:- T-cells attack directly and destroy antigens. In the process, these cells move to the site of invasion and produce chemicals that attract phagocytes and stimulate them so that they can feed more vigorously on antigens. They also produce substances that attract other T-cells.

18. What do you mean by Drug. Describe its two types with example ?
Ans:- Those substance which are useful in prevention, diagnosis and test of physical trouble and disease condition of men are called drug.
            On the basis of effect on the body drugs are of two types–
(a) Psychotropic Drug – These drugs directly affect the brain and caused changes in nature. Therefore these drugs are called as mood alternating drug. For example- Cafine, Cocain, Aphim, Morphin and Heroin etc.
(b) Psychedelic drug – These drugs affect the central nervous system and cause hallucination. For example- LSD, Bhang, Ganza, Charas etc.

19. What are the hormones secreted by placenta ?
Ans:- The hormones secreted by placenta are–
(a) Human chorionic gonadotropin (HCG)
(b) Human placental lactogen (HPL)
(c) Estrogen
(d) Progestogens etc.


20. What is lactation?
Ans:- The mammary glands of the female undergo differentation during pregnancy and start producing milk towards the end of pregnancy by the process called lactation.


21. What was the place of origin & two main features of Australopithecine man? 
Ans:- About two million years ago, australopithecine man originated in grassland of East Africa. The two important features were–
(a) They used stone made arms in hunting.
(b) They were frugivorous.

22. What is Homologous organs and Analogous organs?
Ans:- Homologous organ – The organs which have the same fundamental structure but different in functions are called homologous organs. These organs follow the same basic plan of organisation during their development. Ex-forelimbs of frog, lizard, pigeon and whale have the same basic structural plan but the fore limbs of these animals have different shape and function.
Analogous organ –The organs which have similar function but different in their structural details and origin are called analogous organs. Ex- the basic structure of the wings of an insect is different from wings of a bird, bat and pterodactyl however, their functions are similar.

23. The theroy of lamarck is based upon which facts? Write it.
Ans:- The theory of Lamarck are based upon following facts–
(a) Tendency to increase in size.
(b) Direct influence of environment.
(c) Effect of use and disuse of organs.
(d) Inheritance of acquired characters.


24. Define external fertilization. Mention its disadvantages.
Ans:- External Fertilization is defined as fusion of sperm with ovum outside the body of female. Usually it takes place in water as in frogs. 
Disadvantages:-
(a) Offsprings are extremely vulnerable to predators thus threatning their survival upto adulthood.
(b) Development of embryo in the external environment like water is endangered due to unfavourable change in climatic conditions like temp., rainfall etc.


25. What is BOD?
Ans:- Biological Oxygen Demand (BOD) represents the amount of dissolved oxygen required to oxidise the organic matter in one litre of water by micro-organism. Whenever untreated sewage are disposed into natural waters such as rivers etc the normal amount of dissolved oxygen present in water, gets quickly utilized by microorganism. High value of BOD is an indicator of highly polluted water by organic matter. Low value of BOD means the water is comparatively less polluted.


26. Name the three important components of biodiversity.
Ans:- Three important components of biodiversity are:-
(a) Genetic Biodiversity
(b) Species Biodiversity
(c) Ecological Biodiversity
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