II Puc Preparatory Examination Biology Question paper with solutions 2023

II Puc Preparatory Examination Biology Question paper with solutions 2023

PART A

I. Select the correct alternative from choices given below 1×15=15

1. Vegetative propagule in agave is:

a. Runner

b. Sucker

c. Offset

d. Bulbil

Answer : option (d)

2. Polyembryony commonly occurs in

a. Coconut

b. Citrus

c. Viola

d. Tomato

Answer : option (b)

3. Which of the following hormone secretion reaches maximum during ovulution?

a. HCG

b. Estrogens

c. Progesterone

d. LH

Answer : option (d)

4. Which is the following is not sexually transmitted disease

a. Trichomoniasis

b. Thalassemia

c. Hepatitis B

d. Gonorrhoea

Answer : option (b)

5. If a genetic disease is transferred from a phenotypically normal but carrier female to only some of the male progeny, the disease is

a. Autosomal dominant

b. Autosomal recessive

c. X-linked recessive

d. X-linked dominant

Answer : option (c)

6. The human chromosome with the highest and least number of genes in them, respectively, are

a. Chromosome 21 and Y

b. Chromosome 1 and X

c. Chromosome 1 and Y

d. Chromosome X and Y

Answer : option (c)

7. Analogous organs arise due to

a. Divergent evolution

b. Artificial section

c. Genetic drift

d. convergent evolution

Answer : option (d)

8. “Smack” is the drug obtained from the

a. latex of papaver somniferum

b. leaves of canabis sativa

c. flowers of datura

d. fruits of Erythroxylum Coca

Answer : option (a)

9. Which one of the following products of epiculture is used in cosmetics and polishes?

a. Honey

b. Oil

c. Wax

d. Royal jelly

Answer : option (c)

10. BOD of water is estimated by measuring the amount of

a. total organic matter

b. biodegradable organic matter

c. oxygen evolution

d. oxygen consumption

Answer : option (d)

11. Which of the following technique is used for separation of DNA fragments?

a. Blotting

b. Annealing

c. Gel electrophorosis

d. centrifugation

Answer : option (c)

12. Golden rice is a transgenic crop of the future with the following improved trait

a. Insect resistance

b. High lysine

c. high protein content

d. high vitamin A content

Answer : option (d)

13. Organisms which tolerate narrow range of salinity are

a. euryhaline

b. stenohaline

c. eurytherms

d. stenotherms

Answer : option (b)

14. The second tropic level in a a lake is

a. phytoplankton

b. zooplankton

c. benthos

d. fishes

Answer : option (b)

15. The highest DDT concentration can occur in

a. phytoplankton

b. zooplankton

c. fishes

d. seagull

Answer : option (d)

II. Fill in the blanks by choosing the appropriate word(s) from given below (fishes, plant, natality, electrostatic precipitator, cucurbits) 1×5=5

16. Cucurbits is monoecious plant producing unisexual flowers.

17. Biolistics or gene gun method is used to introduce alien DNA into plant cells.

18. Natality refers to number of births during given period of time in population.

19. Highest bio-diversity among vertebrates is represented by fishes

20. In thermal power plants electrostatic precipitator is used for removing particulate matter in exhaust.

PART – B

III. Answer any five of the following questions in 3-5 sentences each. 2×5=10

21. Differentiate between the two surgical methods of contraception.

Answer :

a. Vasectomy: It is sterilization procedure in males, in which a small part of vasdeferens is removed or tied through a small incision on the srotum.

b. Tubectomy: It is a sterilization in females, in which a small part of the fallopian tube is removed or tied through a small incision in abdomen or through vagina.

22. Mention any two methods of overcome infertility.

Answer : a. Testube baby

b. GIFT – gamete intra fallopian transfer

23. Differentiate between homozygous and heterozygous condition.

Answer : Individuals carrying two identical alleles (RR or rr) are known as homozygous. While individual organisms bearing different alleles (Rr) are known as heterozygous.

24. How does heterochromatin differ from eurochromatin.

Answer : a. This is the region of the chromatin that is more densely packed.

b. It absorbs more stain and appears dark in colour.

25. Mention any two techniques that help in early diagnosis of a disease in biotechnology.

Answer : a. PCR – Polymerase chain reaction

b. Recombinant DNA technology

26. Pyramid of biomass in sea is generally inverted-why?

Answer : As the tropic level increases, the biomass also increases. Hence pyramid of biomass in sea is generally inverted.

27. Differentiate between two types of nutrient cycles, with an example each.

Answer : a. There are two types of biogeochemical cycles, namely

(i) The gaseous cycle: Example: Nitrogen, carbon cycle

(ii) Sedimentary cycle: Example: Phosphorous, Sulphur cycle.

b. The reservoir of gaseous cycle exists in the atmosphere whereas the reservoir of sedimentary cycle is located in earth crust.

28. How does In-situ conservation differ from Ex-situ conservation.

Answer : It is the conservation of endangered or threatened species are protected within their natural habitat, so that entire ecosystem is protected.

PART – C

IV. Answer any five of the following questions in about 40-80 words each. 3×5=15

29. Mention any three distinct stages of sexual reproduction with events of each stage.

Answer : The three distinct stages of sexual reproduction with events are

a. Pre-fertilization – Gametogenesis and gametransfer

b. Fertilization – Syngamy

c. Post fertilization – The zygote, Embryogenesis

30. Explain the three types of pollination.

Answer : a. Autogamy: Pollination is achieved within the same flower.

b. Geitonogamy: Transfer pollen grains from the anther to the stigma of another flower of the same plant.

c. Xenogamy: Transfer of pollen grains from anther to the stigma of a different flower

31. Name the hormones produced in women only during pregnancy.

Answer : a. Human chrionic gonadotropin (hCG)

b. Human placental lactogen (hPL)

c. Relaxin

32. In humans the genetic makeup of the sperm determines the sex of the child-substantiate.

Answer : Sex determination in human beings is X – Y method. It is of male heterogametic type, in which males produce two kinds of sperms. 50% of the total sperm produce carry the X chromosome and the rest 50% have Y-chromosome besides the autosomes. Females, however produce only one type of ovum which X chromosome. the sex of the offspring depends on the sperm that fertilizes the ovum. When sperm carrying X chromosome fertilizes the egg the zygote with X X chromosome develops into a female. On the other hand sperm with Y chromosome fertilizes the egg the zygote with XY chromosomes develops into a male offsprings.

33. Draw schematic structure of transcription unit

Answer :

34. With respect to cancer explain the terms:

a. contact inhibition

b. Metastasis

c. carcinogens

Answer : a. Contact inhibition: It is the property of normal cells by virtue of which contact with other cells inhibit their uncontrolled growth.

b. Metastasis: The property of malignant tumours spread to other parts through blood and start new tumours wherever they get lodged in body.

c. Carcinogens: thransformation of normal cells into cancerous neoplastic cells may be induced by physical, chemical and biological agents. Those agents are called as carcinogens.

35. continued inbreeding leads to inbreeding depression – Explain the three methodologies to overcome it.

Answer : a. Out breeding: It is the breeding of the unrelated animals which may be between individuals of the same breed but having no common ancestors for 4 to 6 generation.

b. Out crossing: This is the practise of mating of animals within the same breed but having no common ancestors on either side of pedigree upto 4 to 6 generations.

c. cross breeding: In this method superior males of one breed are mated with superior females of another breed.

36. Give a biotechnological application for management of diabetes.

Answer : Human insulin consist of two polypeptide chains A and B, linked by didulphide bonds. The human insulin is synthesised as a prohormone which contains an extra stretch is called C peptide. This C peptide is removed during the maturation of insulin.

In 1983, Eli Lilly an american company prepared insulin by r -DNA technology

Steps in insulin synthesis

a. two genes A and B controlling the synthesis of A and B chains are prepared.

b. These two genes are cloned into two different plasmids of E. coli, to produce A and B insulin chains separately.

c. Bacterial cell having A gene produces A chain and bacteria with B gene produce B chain.

d. The A and B chains are linked by creating disulphide bonds to produce active insulin.

PART – D

V. Answer any three of the following in about 200-250 words each: 5×3=15

37. Explain the process of megasporogenesis from MMC with neat labelled diagram of mature embryosac.

Answer : The process of formation of megaspores from the megaspore mother cell is called megaspororgenesis. Ovules generally differentiate a single megaspore mother cell (MMC) in the micropylar region of the nucellus. It is a large cell containing dense cytoplasm and a prominent nucleus. The MMC undergoes metotic division. Metosis results in the production of four megaspores.

38. Draw a neat labelled diagram of sectional view of mammary glands.

Answer :

39. ABO blood typing involves both the phenomenon of co-dominance and multiple allelism explain.

Answer : ABO blood grouping in human beings is controlled by three alleles namely I A , I B a n d I O . These are basically the three alternative forms (alleles) of the gene I. Hence it is an example for multiple allelism. Among the three alleles I A and I B are dominant over I O /i, which is why this case is also an example for dominance. Further, I A and I B are both expressed and therefore are said to be equally dominant (codominant). Hence it is an example of codominance too.

40. Explain the mechanism of gene regulation in lac-operon in presence and absence of inducer.

Answer : a. Switched off mechanism

In the absence of an inducer (lactose/allolactose), the repressor protein produced by the inhibitor gene binds to the operator region of the operon and prevents RNA polymerase from transcribing lac mRNA, thus switching off the operon. In the presence of an inducer, the repressor is inactivated by interaction with the inducer. This allows RNA polymerase to bind to the promoter, and transcription proceeds, thus switching on operon.

b. switched on mechanism

41. What are homologous organs? Explain the same with one plant and one animal example.

Answer : The organs found in different organisms which have a common origin and same basic structure but differ in the functions they carry out are called homologous organs.

Thorn of bougainvillea and tendrill of cucurbita is an example for plant. They have same origin but perform different function hence homologous organs

Whales, bats, cheetah and human share similarities in the pattern of bones of forelimbs. Though this forelimb perform different functions in this animals the have similar anatomical structure hence homolgous organs.

42. a. What is immunity?

b. Differentiate between innate and acquired immunity

c. differentiate between active and passive immunity.

Answer : a. overall ability of the host to fight the disease-causing organisms, conferred by the immune system is called immunity

b. Innate immunity: It is non specific type of defense, that is present at the time of birth, it consist of four types (i) physical barriers, (ii) physiological barriers, (iii) cellular barriers and (iv) cytokine barriers

acquired immunity: It is a pathogen specific it is characterized by memory.

c. active immunity: It is slow and takes time to give its full effective response. Injecting the microbes deliberately during immunisation or infectious orgnanisms gaining access into body during natural infection induces active immunity.

Passive immunity: When ready made antibodies are directly given to protect the body against foreign agents is called passive immunities.

VI. Answer any two of the following questions in about 200-250 words each: 5×2=10

43. Mention the five important steps involved in diary farm management.

Answer : The following aspects should be kept in mind while setting up a dairy farm:

a. Proper selection of breed.

b. Proper housing facilities for animals.

c. Monitoring and maintaining disease free and hygienic conditions.

d. Availability of sufficient quantity of good quality fodder.

e. Ensuring proper water supply.

f. Proper record keeping regarding the breed of animals, their health, and feeding patterns.

44. To avoid pollution of our environment by use of chemical insecticides and pesticides, how do microbes help as biocontrol agents.

Answer : As chemical insecticides and pesticides are acting as a slow poison, to overcome that biotechnological engineers developed biocontrol agents for example, transgenic plants (BT cotton).

BT cotton is a transgenic plants, which has Bt genes isolated from soil bacterium Bacillus Thuringiensis (Bt) for the production of insecticidal proteins (cry proteins).

The cry proteins have the property of killing certain insect’s larvae such as tobacco budworm, armyworm, beetles and flies.

Hence cry genes have been introduced in cotton plants to produce cyrstal proteins as inactive protoxins. when insects feed on these plants, inactive endotoxins enter their body. Converted to active toxins in alkaline juices of the gun of insects and induce pores in their midgut epithelium swelling and lysis of epithelial cells of midgut, leading to death of the insect larva.

45. Explain the three steps involved in PCR technique with neat labelled diagram.

Answer : The three steps involved in PCR technique are

(i) Denaturation: During this process we heat the DNA strands to separate them into single standed DNA.

(ii) Annealing: During this process primers are added up to initiate the formation of complimentary strand.

(iii) Extension: During this process we add a polymerous known as Taq polymerous which polymerise the complimentary strands of DNA.

46. What is population interaction in which one species A is benefitted and species B is neutral called? explain with 4 examples.

Answer : population interaction in which one species A is benefitted and species B is neutral called is called commensalism.

In commensalism, one organism benefits from the relationship and the other is neither benefited nor harmed–the effect of the relationship on it is neutral.

The four examples are:

(i) Remora and Large Marine Animals

(ii) An orchid growing as an epiphyte on a mango branch

(iii) Barnacles growing on the back of a whale

(iv) Cattle egret and grazing cattle

47. Write a note on

a. Global warming

b. Depletion of ozone

Answer : a. Global warming: The increase level of greenhouse gases has led to considerbale heating of the earth is known as global warming.

Effects: (i) It brings off climatic changes. Example: El Nino effet

(ii) It leads to melting of polar ice caps and himalayan snow caps. This in turn results in a rise in a sea level that can submerge many coastal areas.

Control measure:

(i) Minimising the use of fossil fuels

(ii) Improvising efficiency of energy usage.

(iii) Reducing deforestation

(iv) planting treees and slowing down the growth of huamn population

(v) International initiatives are also being taken to control them emission of greenhouse gases.

b. Depletion of ozone: Effects of ozone hole/ ozone layer depletion:

Due to ozone layer depletion, harmful UV-B radiations reach the earth surface.

(i) It causes aging of skin, damages skin cells and various types of skin cancers.

(ii) Human cornea in eye absorption UV-B radiation and of high dose of UV-B radiations causes inflammation of cornea called snow blindness, cataract, etc. This may permanently damage the cornea.

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