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TN State Board 12th Biology Model Question Paper 2 English Medium

General Instructions:

    1. The question paper comprises of four parts. Questions for Botany and Zoology are asked separately.
    2. You are to attempt all the parts. An internal choice of questions is provided wherever applicable.
    3. All questions of Part I, II, III and IV are to be attempted separately.
    4. Question numbers 1 to 8 in Part I are Multiple Choice Questions of one mark each. These are to be answered by choosing the most suitable answer from the given four alternatives and writing the option code and the corresponding answer.
    5. Question numbers 9 to 14 in Part II are two-marks questions. These are to be answered in about one or two sentences.
    6. Question numbers 15 to 19 in Part III are three-marks questions. These are to be answered in about three to five short sentences.
    7. Question numbers 20 and 21 in Part IV are five-marks questions. These are to be answered in detail. Draw diagrams wherever necessary.

Time: 2.30 Hours
Maximum Marks: 70

Bio-Botany [Maximum Marks: 35]

Part – I

Choose the correct answer. [8 × 1 = 8]

Question 1.
How many different kinds of gametes will be produced by a plant having the genotype AABbCC?
(a) Three
(b) Four
(c) Nine
(d) Two
Answer:
(d) Two

Question 2.
pBR 322, BR stands for ________.
(a) Plasmid Bacterial Recombination
(b) Plasmid Bacterial Replication
(c) Plasmid Boliver and Rodriguez
(d) Plasmid Baltimore and Rodriguez
Answer:
(c) Plasmid Boliver and Rodriguez

Question 3.
Which of the given plant produces cardiac glycosides?
(a) Calotropis
(b) Acacia
(c) Nepenthes
(d) Utricularia
Answer:
(a) Calotropis

Question 4.
Methane is _______ times as effective as CO2 at trapping heat.
(a) 5
(b) 10
(c) 20
(d) 100
Answer:
(c) 20

Tamil Nadu 12th Biology Model Question Paper 2 English Medium

Question 5.
Statement 1: Arachis hypogea belongs to Fabaceae
Statement 2: It is a native of Brazil.
(a) Statement 1 is correct and Statement 2 is incorrect
(b) Statement 1 is incorrect and Statement 2 is correct
(c) Both the Statements are correct
(d) Both the Statements are incorrect
Answer:
(c) Both the Statements are correct

Question 6.
Which of the following scientist developed world’s first cotton hybrid?
(a) Dr. B.P. Pal
(b) C.T. Patel
(c) Dr. K. Ramiah
(d) N.G.P. Rao
Answer:
(b) C.T. Patel

Question 7.
Ecosystem is the structural and functional unit of ecology. This statement was given by _______.
(a) Tansley
(b) Odum
(c) Charles Elton
(d) Edwin
Answer:
(b) Odum

Tamil Nadu 12th Biology Model Question Paper 2 English Medium

Question 8.
Name the scientist(s) who rediscovered the Mendelian work? .
(i) Hugo de Vries (ii) Carl Correns (iii) Tschermak (iv) T.H. Morgan
(a) (i), (ii)and (iv) (b) (i), (ii)and (iii) (iii) ii, iii, iv (d) i, iii and iv
Answer:
(b) (i), (ii)and (iii)

Part – II

Answer any four of the following questions. [4 × 2 = 8]

Question 9.
Detached leaf of Bryophyllum produces new plants. How?
Answer:
In Bryophyllum, the leaf is succulent and notched on its margin. Adventious buds develop at these notches and are called epiphyllous buds. They develop into new plants forming a root system and become independent plants when the leaf gets decayed.

Question 10.
Crossing over occurs only in germinal cells. Yes or No? Support your answer.
Answer:
No. Though crossing over is a common process in germinal cells rarely it also occurs in somatic cells during mitosis. Such crossing over is called mitotic crossing over or somatic crossing over.

Tamil Nadu 12th Biology Model Question Paper 2 English Medium

Question 11.
Why do we use cryoprotectants in conservation process? Name any two cryoprotectant.
Answer:
Cryoprotectants are the protective agents that are used to protect the cells or tissues from the stress of freezing temperature. E.g: Sucrose, dimethyl sulphoxide.

Question 12.
What is Eltonian pyramid?
Answer:
Eltonian pyramid or Ecological pyramid is a graphic representation of the trophic structure and function at successive trophic levels of an ecosystem.

Question 13.
What do you understand by the term good ozone and bad ozone?
Answer:
The ozone layer of troposphere is called bad ozone.
The ozone layer of stratosphere is called good ozone because the layer acts as an shield for absorbing UV rays coming from sun which is harmful for living organisms causing ONA damage.

Tamil Nadu 12th Biology Model Question Paper 2 English Medium

Question 14.
A person got irritation while applying chemical dye. What would be your suggestion for alternative?
Answer:
If a grey haired person is allergic on using chemical dyes then he can go for natural dyes like Henna. Henna is an organic dye obtained from leaves and young shoots of Lawsonia inermis. The principal colouring matter is Tacosone’ which is harmless and causes no irritation on skin.

Part – III

Answer any three questions in which question number 19 is compulsory. [3 × 3 = 9]

Question 15.
Differentiate between incomplete dominance and codominance.
Answer:
Incomplete Dominance:

  • In incomplete dominance, neither of the allele is not completely dominant to another allele rather combine and produce new trait.
  • New phenotype is formed due to character blending (not alleles)
  • Example : Pink flowers of Mirabilis Jalapa

Co-dominance:

  • In co-dominance, both the alleles in heterozygote are dominant and the traits are equally expressed (joint expression)
  • No formation of new phenotype rather both dominant traits are expressed, conjointly.
  • Example : Red and white flowers of camellia.

Question 16.
What are the features that a vector must possess to facilitate cloning?
Answer:
The following are the features that are required to facilitate cloning into a vector.

  • Origin of replication (ori): This is a sequence from where replication starts and piece of DNA when linked to this sequence can be made to replicate within the host cells.
  • Selectable marker: In addition to ori the vector requires a selectable marker, which helps in identifying and eliminating non-transformants and selectively permitting the growth of the transformants.
  • Cloning sites: In order to link the alien DNA, the vector needs to have very few, preferably single, recognition sites for the commonly used restriction enzymes.

Question 17.
Define somatic embryogenesis? Give any two of its applications.
Answer:
Somatic embryogenesis is the formation of embryos from the callus tissue directly and these embryos are called Embryoids.

Applications:

  • Somatic embryogenesis provides potential plantlets which after hardening period can establish into plants.
  • Somatic embryoids can be used for the production of synthetic seeds.

Question 18.
What is TSM? How it is classified and what does it focuses on?
Answer:
TSM stands for Traditional Systems of Medicines India has a rich medicinal heritage. A number of Traditional Systems of Medicine (TSM) are practiced in India some of which come from outside India. TSM in India can be broadly classified into institutionalized or documented and non-institutionalized or oral traditions. Institutionalized Indian systems include Siddha and Ayurveda which are practiced for about two thousand years.

These systems have prescribed texts in which the symptoms, disease diagnosis, drugs to cure, preparation of drugs, dosage and diet regimes, daily and seasonal regimens. Non-institutional systems, whereas, do not have such records and or practiced by rural and tribal peoples across India. The knowledge is mostly held in oral form. The TSM focus on healthy lifestyle and healthy diet for maintaining good health and disease reversal

Tamil Nadu 12th Biology Model Question Paper 2 English Medium

Question 19.
How do sacred groves help in the conservation of biodiversity?
Answer:
These are the patches or grove of cultivated trees which are community protected and are based on strong religious belief systems which usually have a significant religious connotation for protecting community. Each grove is an abode of a deity mostly village God Or Goddesses like Aiyanar or Amman. 448 grooves were documented throughout Tamil Nadu, of which 6 groves (Banagudi shola, Thirukurungudi and Udaiyankudikadu, Sittannnavasal, Puthupet and Devadanam) were taken up for detailed floristic and faunistic studies.

These groves provide a number of ecosystem services to the neighbourhood like protecting watershed, fodder, medicinal plants and micro climate control.

Part – IV

Answer all the questions. [2 × 5 = 10]

Question 20.
(a) Draw a flow chart depicting the various types of ploidy.
Answer:
Tamil Nadu 12th Biology Model Question Paper 2 English Medium 1

[OR]

(b) Mention the application of biotechnology.
Answer:

  • Biotechnology is one of the most important applied interdisciplinary sciences of the 21st century. It is the trusted area that enables us to find the beneficial way of life.
  • Biotechnology has wide applications in various sectors like agriculture, medicine, environment and commercial industries.
  • This science has an invaluable outcome like transgenic varieties of plants e.g. transgenic cotton (Bt-cotton), rice, tomato, tobacco, cauliflower, potato and banana.
  • The development of transgenics as pesticide resistant, stress resistant and disease resistant varieties of agricultural crops is the immense outcome of biotechnology.
  • The synthesis of human insulin and blood protein in E.coli and utilized for insulin deficiency disorder in human is a breakthrough in biotech industries in medicine.
  • The synthesis of vaccines, enzymes, antibiotics, dairy products and beverages are the products of biotech industries.
  • Biochip based biological computer is one of the successes of biotechnology.
  • Genetic engineering involves genetic manipulation, tissue culture involves aseptic cultivation of totipotent plant cell into plant clones under controlled atmospheric conditions.
  • Single cell protein from Spirulina is utilized in food industries.
  • Production of secondary metabolites, biofertilizers, biopesticides and enzymes.
  • Biomass energy, biofuel, bioremediation and phytoremediation for environmental biotechnology.

Tamil Nadu 12th Biology Model Question Paper 2 English Medium

Question 21.
(a) Differentiate Primary succession and Secondary succession.
Answer:
Primary succession:

  • Developing in an barren area.
  • Initiated due to a biological or any other external factors.
  • No soil, while primary succession starts
  • Pioneer species come from outside environment.
  • It takes more time to complete.

Secondary succession:

  • Developing in disturbed area.
  • Starts due to external factors only.
  • It starts where soil covers is already present.
  • Pioneer species develop from existing environment.
  • It takes comparatively less time to complete.

(b) Enumerate the characters of anemophilous flowers
Answer:
Anemophilous plants have the following characteristic features:

  • The flowers are produced in pendulous, catkin-like or spike inflorescence.
  • The axis of inflorescence elongates so that the flowers are brought well above the leaves.
  • The perianth is absent or highly reduced.
  • The flowers are small, inconspicuous, colourless, not scented, do not secrete nectar.
  • The stamens are numerous, filaments are long, exerted and versatile.
  • Anthers produce enormous quantities of pollen grains compared to number of ovules available for pollination. They are minute, light and dry so that they can be carried to long distances by wind.
  • In some plants anthers burst violently and release the pollen into the air. Example: Urtica.
  • Stigmas are comparatively large, protruding, sometimes branched and feathery, adapted to catch the pollen grains. Generally single ovule is present.
  • Plant produces flowers before the new leaves appear, so the pollen can be carried without hindrance of leaves.

Bio-Zoology [Maximum Marks: 35]

Part – I

Choose the correct answer. [8 × 1 = 8]

Question 1.
Which one of the following groups includes sexually transmitted diseases caused by bacteria only?
(a) Syphilis, gonorrhoea and candidiasis
(b) Syphilis, chlamydiasis and gonorrhoea
(c) Syphilis, gonorrhoea and trichomoniasis
(d) Syphilis, trichomoniasis and pediculosis
Answer:
(b) Syphilis, chlamydiasis and gonorrhoea

Question 2.
ABO blood group in man is controlled by __________.
(a) Multiple alleles
(b) Lethal genes
(c) Sex linked genes
(d) Y-linked genes
Answer:
(a) Multiple alleles

Question 3.
Hershey and Chase experiment with bacteriophage showed that ____________.
(a) Protein gets into the bacterial cells
(b) DNA is the genetic material
(c) DNA contains radioactive sulphur
(d) Viruses undergo transformation
Answer:
(b) DNA is the genetic material

Tamil Nadu 12th Biology Model Question Paper 2 English Medium

Question 4.
Modern man belongs to which period?
(a) Quaternary
(b) Cretaceous
(c) Silurian
(d) Cambrian
Answer:
(a) Quaternary

Question 5.
Allergy involves _______.
(a) IgE
(b) IgG
(c) IgA
(d) IgM
Answer:
(a) IgE

Question 6.
Recombinant Factor VIII is produced in the ______ of the Chinese Hamster.
(a) Liver cells
(b) blood cells
(c) ovarian cells
(d) brain cells
Answer:
(c) ovarian cells

Question 7.
Match with correct pair
Tamil Nadu 12th Biology Model Question Paper 2 English Medium 2
(a) A – ii, B – iv, C – i, D – iii
(b) A – ii, B – iii, C – i, D – iv
(d) A – iii, B – i, C – iv, D – ii
(d) A – iv, B – ii, C – i, D – iii
Answer:
(b) A – ii, B – iii, C – i, D – iv

Question 8.
Assertion (A): Snake is a stenotherm.
Reason (R): Organism can tolerate narrow temperature fluctuations.
(a) Both A and R are correct R explain A
(b) A is correct R is incorrect
(c) A and R are correct, R doesn’t explains A
(d) Both A and R are incorrect
Answer:
(a) Both A and R are correct R explain A

PART – II

Answer any four of the following questions. [4 × 2 = 8]

Question 9.
Mention the differences between spermiogenesis and spermatogenesis.
Answer:
Spermiogenesis:
Transformation of spermatids into mature sperm.

Spermatogenesis:
Spermatogenesis is the sequence of events in the seminiferous tubules of testes that produces male gametes, the sperms.

Tamil Nadu 12th Biology Model Question Paper 2 English Medium

Question 10.
Draw and label a gemmule of sponge.
Answer:
Tamil Nadu 12th Biology Model Question Paper 2 English Medium 3

Question 11.
State Wiener’s Hypothesis on Rh-factor.
Answer:
Wiener proposed the existence of eight alleles (R1, R2, R0, RZ, r, r1, r11, ry) at a single Rh locus. All genotypes carrying a dominant ‘R allele’ (R1, R2, R0, Rz) will produce ‘Rh-positive’ phenotype and double recessive genotypes (rr, rr1, rr11, rry) will give rise to Rh-negative phenotype.

Question 12.
Why t-RNA is called an adapter molecule?
Answer:
The transfer RNA (t-RNA) molecule of a cell acts as a vehicle that picks up the amino acids scattered through the cytoplasm and also reads specific codes of mRNA molecules. Hence it is called as adapter molecule. This term was postulated by Francis Crick.

Question 13.
Why Red list is prepared periodically?
Answer:
The purpose of preparation of Red List are:

  • To create awareness on the degree of threat to biodiversity
  • Identification and documentation of species at high risk of extinction
  • Provide global index on declining biodiversity .
  • Preparing conservation priorities and help in conservation of action
  • Information on international agreements on conservation of biological diversity

Tamil Nadu 12th Biology Model Question Paper 2 English Medium

Question 14.
Write notes on (a) Eutrophication (b) Algal Bloom
Answer:
Eutrophication refers to the nutrient enrichment in water bodies leading to lack of oxygen and will end up in the death of aquatic organisms.
Algal Bloom is an excess growth of algae due to abundant excess nutrients imparting distinct color to water.

Part – III

Answer any three questions in which question number 19 is compulsory. [3 × 3 = 9]

Question 15.
Explain Foetal-ejection reflex.
Answer:
As the pregnancy progresses, increase in the oestrogen concentration promotes uterine contractions. These uterine contractions facilitate moulding of the foetus and downward movement of the foetus. The descent of the foetus causes dilation of cervix of the uterus and vaginal canal resulting in a neurohumoral reflex called Foetal ejection reflex or Ferguson reflex.

This initiates the secretion of oxytocin from the neurohypophysis which in turn brings about the powerful contraction of the uterine muscles and leads to the expulsion of the baby through the birth canal.

Question 16.
Role of Y- chromosome is crucial for maleness – Justify.
Answer:
Current analysis of Y chromosomes has revealed numerous genes and regions with potential genetic function; some genes with or without homologous counterparts are seen on the X. Present at both ends of the Y chromosome are the pseudoautosomal regions (PARs) that are similar with regions on the X chromosome which synapse and recombine during meiosis. The remaining 95% of the Y chromosome is referred as the Non-combining Region of the Y (NRY).

The NRY is divided equally into functional genes (euchromatic) and non-functional genes (heterochromatic). Within the euchromatin regions, is a gene called Sex determining region Y (SRY). In humans, absence of Y chromosome inevitably leads to female development and this SRY gene is absent in X chromosome. The gene product of SRY is the testes determining factor (TDF) present in the adult male testis.

Tamil Nadu 12th Biology Model Question Paper 2 English Medium

Question 17.
State immunological surveillance theory.
Answer:
The concept of immunological surveillance postulates that the primary function of the immune system is to “seek and destroy” malignant cells that arise by somatic mutation. The efficiency of the surveillance mechanism reduces either as a result of ageing or due to congenital or acquired immuno deficiencies, leads to increased incidence of cancer. Thus, if immunological surveillance is effective, cancer should not occur. The development of tumour represents a lapse in surveillance.

Question 18.
Write a short note on Pathaneer.
Answer:
In some parts of South India, a traditional drink called pathaneer is obtained from fermenting sap of palms and coconut trees. A common source is tapping of unopened spadices of coconut. It is a refreshing drink, which on boiling produces jaggery or palm sugar. When pathaneer is left undisturbed for few hours it gets fermented to form toddy with the help of naturally occurring yeast, to form a beverage that contains 4 percent alcohol. After 24 hours toddy becomes unpalatable and is used for the production of vinegar.

Question 19.
Elucidate the methodology of ELISA test.
Answer:
During diagnosis the sample suspected to contain the antigen is immobilized on the surface of an ELISA plate. The antibody specific to this antigen is added and allowed to react with the immobilized antigen. The anti-antibody is linked to an appropriate enzyme like peroxidase.

The unreacted anti-antibody is washed away and the substrate of the enzyme (hydrogen peroxidase) is added with certain reagents such as 4-chloronaphthol. The activity of the enzyme yields a coloured product indicating the presence of the antigen.

Part – IV

Answer all the questions. [2 × 5 = 10]

Question 20.
(a) What are IUD’s? Explain its way of functioning. Also describe their types.
Answer:
Intrauterine Devices (IUDs) are inserted by medical experts in the uterus through the vagina. These devices are available as copper releasing IUDs, hormone releasing IUDs and nonmedicated IUDs. IUDs increase phagocytosis of sperm within the uterus. IUDs are the ideal contraceptives for females who want to delay pregnancy. It is one of the popular methods of contraception in India and has a success rate of 95 to 99%.

Copper releasing IUDs differ from each other by the amount of copper. Copper IUDs such as Cu T-380 A, Nova T, Cu 7, Cu T 380 Ag, Multiload 375, etc. release free copper and copper salts into the uterus and suppress sperm motility. They can remain in the uterus for five to ten years.

Hormone-releasing IUDs such as Progestasert and LNG – 20 are often called as intrauterine systems (IUS). They increase the viscosity of the cervical mucus and thereby prevent sperms from entering the cervix.

Non-medicated IUDs are made of plastic or stainless steel. Lippes loop is a double S-shaped plastic device.

[OR]

(b) Explain how Urey – Miller’s experiment supports the origin of life?
Answer:
Tamil Nadu 12th Biology Model Question Paper 2 English Medium 4
Urey and Miller (1953), paved way for understanding the possible synthesis of organic compounds that led to the appearance of living organisms is depicted in the Figure In their experiment, a mixture of gases was allowed to circulate over electric discharge from an tungsten electrode.

A small flask was kept boiling and the steam emanating from it was made to mix with the mixture of gases (ammonia, methane and hydrogen) in the large chamber that was connected to the boiling water. The steam condensed to form water which ran down the ‘U’ Diagrammatic representation of Urey-Miller’s experiment tube. Experiment was conducted continuously for a week and the liquid was analysed. Glycine, alanine, beta alanine and aspartic acid were identified.

Thus Miller’s experiments had an insight as to the possibility of abiogenetic synthesis of large amount of variety of organic compounds in nature from a mixture of sample gases in which the only source of carbon was methane. Later in similar experiments, formation of all types of amino acids, and nitrogen bases were noticed.

Tamil Nadu 12th Biology Model Question Paper 2 English Medium

Question 21.
(a) Discuss any two Allosomal abnormalities in human beings.
Answer:
Allosomal abnormalities in human beings:
Mitotic or meiotic non-disjunction of sex chromosomes causes allosomal abnormalities.
Several sex chromosomal abnormalities have been detected. E.g. Klinefelter’s syndrome and
Turner’s syndrome.

1. Klinefelter’s Syndrome (XXY Males):
This genetic disorder is due to the presence of an additional copy of the X chromosome resulting in a karyotype of 47, XXY. Persons with this syndrome have 47 chromosomes (44AA+XXY). They are usually sterile males, tall, obese, with long limbs, high pitched voice, under developed genetalia and have feeble breast (gynaecomastia) development.

2. Turner’s Syndrome (XO Females):
This genetic disorder is due to the loss of a X chromosome resulting in a karyotype of 45 ,X. Persons with this syndrome have 45 chromosomes (44 autosomes and one X chromosome) (44AA+XO) and are sterile females. Low stature, webbed neck, under developed breast, rudimentary gonads lack of menstrual cycle during puberty, are the main symptoms of this syndrome:

[OR]

(b) Explain in detail about various types of extinctions.
Answer:
There are three types of Extinctions
1. Natural extinction: It is a slow process of replacement of existing species with better adapted species due to changes in environmental conditions, evolutionary changes, predators and diseases. A small population can get extinct sooner than the large population due to inbreeding depression (less adaptivity and variation)

2. Mass extinction: The Earth has experienced quite a few mass extinctions due to environmental catastrophes. A mass extinction occurred about 225 million years ago during the Permian, where 90% of shallow water marine invertebrates disappeared.

3. Anthropogenic extinctions: These are abetted by human activities like hunting, habitat destruction, over exploitation, urbanization and industrialization. Some examples of extinctions are Dodo of Mauritius and Steller’s sea cow of Russia. Amphibians seem to be at higher risk of extinction because of habitat destruction.

The most serious aspect of the loss of biodiversity is the extinction of species. The unique information contained in its genetic material (DNA) and the niche it possesses are lost forever.

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