Tamil Nadu 12th Biology Model Question Paper 5 English Medium

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TN State Board 12th Biology Model Question Paper 5 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

Answer all the questions. [8 × 1 = 8]
Choose the most suitable answer from the given four alternatives and write the option code with the corresponding answer.

Question 1.
Size of pollen grain in Myosotis is _______ micrometer.
(a) 10
(b) 20
(c) 200
(d) 2000
Answer:
(a) 10

Question 2.
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 3.
EcoRI cleaves DNA at ________.
(a) AGGGTT
(b) GTATAC
(c) GAATTC
(d) TATAGC
Answer:
(c) GAATTC

Question 4.
Choose the correct match from the following.


Answer:
1 – C, 2 – A, 3 – D, 4 – B

Question 5.
Photo synthetically active radiation wave length between the range of ________.
(a) 200-700nm
(b) 300-700nm
(c) 400-700 nm
(d) 500-700nm
Answer:
(c) 400-700 nm

Question 6.
For the given statements with respect to Eichhomia select the suitable answer.
Statement A: It drains of oxygen from water and is seen growing in standing water.
Statement B: It is an indogeneous species of our country.
(a) Statement A is correct and statement B is wrong.
(b) Both the statement A and B are correct.
(c) Statement A is wrong and statement B is correct.
(d) Both the statement A and Bare wrong.
Answer:
(d) Both the statement A and Bare wrong.

Question 7.
Which of the following is incorrectly paired?
(a) Wheat – Himgiri
(b) Milch breed – Sahiwal
(c) Rice – Ratna
(d) Pusa Komal – Brassica
Answer:
(d) Pusa Komal – Brassica

Question 8.
Find out the correctly matched pair:
(a) Rubber – Shora robusta
(b) Dye – Lawsonia inermis
(c) Timber – Cypress papyrus
(d) Pulp – Hevea brasiliensis
Answer:
(b) Dye – Lawsonia inermis

Part – II

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

Question 9.
The endosperm of Angiosperm is different from Gymnosperm. Do you agree? Justify your answer.
Answer:
Yes, the endosperm of Angiosperm is different from Gymnosperm because in Angiosperm, the endosperm develops from primary endosperm nucleus which is formed after double fertilization whereas in Gymnosperms the endosperm is developed before the fertilization process.

Question 10.
Who are rediscovered Mendel’s experimental works?
Answer:
Hugo de Vries of Holland, Carl Corren’s of Germany, Erich von Tschermak of Austria.

Question 11.
Multiple Alleles-Define.
Answer:
Two or more alternate forms of single gene occupying the same locus in a chromosome are called as Multiple Alleles.

Question 12.
Differentiate Somaclonal variation, Gametoclonal variation.
Answer:

Somaclonal variation	Gametoclonal variation
Somatic variations found in plants is regenerated in vitro (i.e. variations found in leaf, stem, root, tuber or propagule).	Gametophytic variations found in plants is regenerated in vitro gametic origin (i.e. variations found in gametes and gametophytes)

Question 13.
What is called Phytoremediation?
Answer:
The process in which the plants can be used to remove toxic substances like cadmium from contaminated soils is known as Phytoremediation.

Soya bean and tomato tolerate cadmium poisoning by isolating cadmium and storing in few group of cells and prevent from affecting other cells.

Question 14.
What is ozone hole?
Answer:
The decline in the thickness of the ozone layer over restricted area is called ozone hole.

Part – III

Answer three from the following questions. Question No. 19 is compulsory. [3 × 3 = 9]

Question 15.
Differentiate continuous variation with discontinuous variations.
Answer:
1. Discontinuous Variation: Within a population there are some characteristics which show a limited form of variation. Example: Style length in Primula, plant height of garden pea. In discontinuous variation, the characteristics are controlled by one or two major genes which may have two or more allelic forms. These variations are genetically determined by inheritance factors.

Individuals produced by this variation show differences without any intermediate form between them and there is no overlapping between the two phenotypes. The phenotypic expression is unaffected by environmental conditions. This is also called as qualitative inheritance.

2. Continuous Variation: This variation may be due to the combining effects of environmental and genetic factors. In a population most of the characteristics exhibit a complete gradation, from one extreme to the other without any break.

Inheritance of phenotype is determined by the combined effects of many genes, (polygenes) and environmental factors. This is also known as quantitative inheritance. Example: Human height and skin color.

Question 16.
What is gene mapping? Mention its uses.
Answer:
Genetic Map: The diagrammatic representation of the portion of genes and related distance between the adjacent genes in called Genetic mapping.
Use: Gene map provides clues about the where the genes lies on that chromosome.

Question 17.
Lichen is considered as a good example of an obligate mutualism. Explain.
Answer:
Lichen is considered as a good example of obligate mutualism, because in Lichen, the algae (cyano bacteria) and fungi lives in a mutual relationship i.e., the algae being a autotroph synthesizes its food and provides the fungus and in turn the fungus helps the algae in absorption of water and nutrients and also protects form bacterial or other fungal infections.

Question 18.
Draw a pyramid from following details and explain. The quantities of organisms are given: Hawks 25 and plants-500 rabbit and mouse-125+125 snake and lizard- 50+25 respectively.
Answer:

The pyramid represents pyramid of numbers in grassland ecosystem.
The pyramid of numbers in grassland ecosystem is always upright because there is a gradual decrease in the number of organisms in each trophic level form producers to consumers and then to secondary consumers and finally to tertiary consumers.

Question 19.
What do you know about the objectives of plant breeding?
Answer:

• To increase yield, vigour and fertility of the crop.
• To increase tolerance to environmental condition, salinity, temperature and drought.
• To prevent the premature falling of buds and fruits, etc.
• To improve synchronous maturity.
• To develop resistance to pathogens and pests.
• To develop photosensitive and thermos-sensitive varieties.

Part – IV

Answer all questions. [2 × 5 = 10]

Question 20.
(a) With a suitable diagram explain the structure of an ovule.
Answer:

Ovule is also called megasporangium and is protected by one or two covering called integuments.

• A mature ovule consists of a stalk and a body.
• The stalk or the funiculus is present at the base and it attaches the ovule to the placenta.
• The point of attachment of fiinicle to the body of the ovule is known as hilum. It is a junction between ovule and fiinicle.
• In an inverted ovule, the funicle is adnate to the body of the ovule forming a ridge called raphe.
• The body of the ovule has a central mass of parenchymatous tissue called nucellus which has large reserve food materials.
• The nucellus is covered by integuments completely except at the top and forms a pore called micropyle.
• The ovule with one or two integuments are called unitegmic or bitegmic ovules respectively.
• The basal of the ovule where the nucellus, the integument and the funicle meet is called chalaza.
• Inside the nucellus, toward micropylar end there is a large, oval sack like structure called embryo sac or female gametophyte.
• The embryo sac develops from the functional megaspore.
• In some species, the inner integument perform the nutritive function for the embryo sac and is called as endothelium or integumentary tapetum (Example : Asteraceae).
• Group of cells found at the base of the ovule between chalaza and embryo sac is called Hypostase.
• The thick walled cells found above micropylar end and embryo sac is called epistase.
• There are two types of ovules based on the position of sporogenous.
  (a) Tenuinucellate ovule: Ovules with hypodermal sporogerous cell with single layer of nucellus around it is called tenuinucellate. They have very small nucellus
  (b) Crassinucellate ovule: Ovule with subhypodermal sporogenous cell is called crassinucellate ovule. They have large nucellus.
• The thick walled cells found above micropylar end and embryo sac is called epistase.

[OR]

(b) What is single cell protein. Mention its application.
Answer:
Single Cell Protein (SCP) are dried cells of microorganisms that are used as protein supplement in foods or animal feeds.

Organism used in SCP production:
Bacteria – Methylophilus methylotrophus, Cellulomonas, Alcaligenes
Fungi – Agaricus campestris , Saccharomyces cerevisiae, Candida utilis
Algae – Spirulina, Chlorella and Chlamydomonas

Substrates for SCP production: Straw, molasses, animal manure, sewage, waste water from potato processing plants with starch.

Uses:

• SCP offers an unconventional but possible solution to protein deficiency faced buy human beings.
• SCP forms an important food source because of their protein content, carbohydrates, fats, vitamins and minerals.
• It is used by Astronauts and Antarctica expedition scientists.
• Since SCP can be grown even in sewage water, it also reduces environmental pollution.
• 250 gms of Methylophilus methylotrophus as its high rate of biomass production and growth can yield 25 tonnes of proteins.

Disadvantage of SCP: Although SCP has high nutritive value due to high content of protein, vitamin, lipid and amino acids, there are doubts on whether it could replace conventional protein source due to high nucleic acid content and slower in digestibility.

Question 21.
(a) Suggest a solution to water crises and explain its advantages.
Answer:
Rainwater harvesting is the accumulation and storage of rain water for reuse in-site rather than allowing it to run off. Rainwater can be collected from rivers, roof tops and the water collected is directed to a deep pit. The water percolates and gets stored in the pit. RWH is a sustainable water management practice implemented not only in urban area but also in agricultural fields, which is an important economical cost effective method for the future.

Environmental benefits of Rain Water Harvesting:

• Promotes adequacy of underground water and water conservation.
• Mitigates the effect of drought.
• Reduces soil erosion as surface run-off is reduced.
• Reduces flood hazards.
• Improves groundwater quality and water table / decreases salinity.
• No land is wasted for storage purpose and no population displacement is involved.
• Storing water underground is an eco-friendly measure and a part of sustainable water storage strategy for local communities.

[OR]

(b) What are millets? What are its types? Give example for each type.
Answer:
Millets: (Siru Thaniyangal)

• Millets is the term applied to a variety of very small seeds originally cultivated by ancient Africans and Asians.
• They are gulten free and have less glycemic index.

Types of Millets:

1. Major millets
2. Minor millets.

Example for Major millets:

• Finger millets – Ragi (Eleusine coracana)
• Sorghum – Sorghum vulgare

Example for Minor millets:

• Foxtail millet – (Setaria italica)
• Kodo millet – Paspalum scrobiculatum

Bio-Zoology [Maximum Marks: 35]

Part – I

Answer all the questions. [8 × 1 = 8]
Choose the most suitable answer from the given four alternatives and write the option code with the corresponding answer.

Question 1.
Which among the following animals exhibit ovoviviparity?
(a) frog
(b) shark
(c) sheep
(d) hen
Answer:
(b) shark

Question 2.
21^st trisomy is observed in ________.
(a) Down’s syndrome
(b) Patau’s syndrome
(c) Turner’s syndrome
(d) Klinefelter’s syndrome
Answer:
(a) Down’s syndrome

Question 3.
Which among the codon codes for methionine?
(a) AUG
(b) UAA
(c) UUU
(d) AUC
Answer:
(a) AUG

Question 4.
The disease caused by Wuchereria bancrofti is ________.
(a) Malaria
(b) Filariasis
(c) Kala-azar
(d) Sleeping sickness
Answer:
(b) Filariasis

Question 5.
Which of the following pair is correctly matched? [Wrong question]
(a) Trichoderma polysporum – clot buster
(b) Aspergillus niger – butric acid
(c) Clostridium butyricum – cyclosporine A
(d) Streptococcus – citric acid

Question 6.
The first clinical gene therapy was done for the treatment of _______.
(a) SCID
(b) cancer
(c) AIDS
(d) cystic fibrosis
Answer:
(a) SCID

Question 7.
Given below are some examples for population interactions. Which among the following shows mutualism?
(a) Lion and deer
(b) Man and tape worm
(c) Hermit crab and sea-anemone
(d) Sucker fish and shark
Answer:
(c) Hermit crab and sea-anemone

Question 8.
The most abundant green house gas is ______.
(a) Carbon-dioxide
(b) Methane
(c) Sulphur-dioxide
(d) Nitrous oxide
Answer:
(a) Carbon-dioxide

Part – II

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

Question 9.
Describe the structure of the head of a human sperm.
Answer:
The head comprises of two parts namely acrosome and nucleus. Acrosome is a small cap like pointed structure present at the tip of the nucleus and made of Golgi body of the spermatid. It contains hyaluronidase (sperm cysin) a proteolytic enzyme which helps to penetrate the ovum during fertilisation. The nucleus is flat and oval.

Question 10.
Mention any four salient features of Human Genome Project.
Answer:
The main goals of Human Genome Project are as follows:

• Identify all the genes (approximately 30000) in human DNA.
• Determine the sequence of the three billion chemical base pairs that makeup the human DNA.
• To store this information in databases.
• Improve tools for data analysis.

Question 11.
Name an opioid drug and its plant source. How does the drug affect Human body?
Answer:
Morphine is an opioid drug obtained from flowers of the poppy plants.
It is used as a strong pain killer during surgery.

Question 12.
How does the transgenic cow Rosie’s milk differ from normal cow’s Milk?
Answer:
Rosie was the first transgenic cow. It produced human protein enriched milk, which contained the human alpha lactalbumin (2.4 gm/litre). This milk was a nutritionally balanced food for infants than the normal milk of cows.

Question 13.
Differentiate natality from mortality.
Answer:

Question 14.
What is ozone depletion? How is it caused?
Answer:
Thinning of the stratospheric ozone layer is known as ozone depletion. Such depletion causes the ‘ozone hole’, resulting in poor screening of the harmful UV rays and increase in incidences of skin cancer. Ozone depression is due to certain gases like CFC’s.

Part – III

Write any three of the following in which question No.19 is compulsory. [3 x 3 = 9]

Question 15.
Explain multiple fission in Plasmodium with a diagram.
Answer:
In Multiple fission of plasmodium, the oocyte or schizont divides into many similar daughter cells simultaneously. Nucleus undergoes repeated mitosis producing many nuclei without the division of cytoplasm. Later the cytoplasm divides and encircles each nucleus forming many daughter cells oocyte undergoes sporogony forming sporozoites. Schizont undergoes schizogony forming merozoites.

Question 16.
Write the causes and the differences between Haemophilia and Thalassemia.
Answer:
Causes for Haemophilia: Haemophilia is also called bleeder’s disease is caused by a recessive X-linked gene. A person with a recessive gene for haemophilia lacks a normal clotting substance in blood, hence minor injuries cause continuous bleeding, leading to death.

Causes for Thalassemia: Thalassemia is an autosomal recessive disorder caused by.gene mutation resulting in excessive destruction of RBC’s due to the formation of abnormal haemoglobin molecules.

Haemophilia	Thalassemia
1. It is a X-linked recessive gene inheritance	1. It is a autosomal recessive gene inheritance
2. It follows criss-cross pattern of inheritance	2. It follows Mendelian pattern of inheritance

Question 17.
Explain the secondary treatment of waste water.
Answer:
Secondary treatment or biological treatment: The primary effluent is passed into large aeration tanks where it is constantly agitated mechanically and air is pumped into it. This allows vigorous growth of useful aerobic microbes into floe (masses of bacteria associated with fungal filaments to form mesh like structures). While growing, these microbes consume the major part of the organic matter in the effluent. This significantly reduces the BOD (Biochemical oxygen demand or Biological oxygen demand).

BOD refers to the amount of the oxygen that would be consumed, if all the organic matter in one litre of water were oxidized by bacteria. The sewage water is treated till the BOD is reduced. The greater the BOD of the waste water more is its polluting potential. Once the BOD of sewage water is reduced significantly, the effluent is then passed into a settling tank where the bacterial “floes” are allowed to sediment. This sediment is called activated sludge. A small part of activated sludge is pumped back into the aeration tank to serve as the inoculum.

The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters. Here, the bacteria which grow anaerobically, digest the bacteria and the fungi in the sludge. During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and CO2.
These gases form biogas and can be used as a source of energy.

Question 18.
Explain the steps involved in the preparation of human insulin artificially.
Answer:
Production of insulin by recombinant DNA technology started in the late 1970s. This technique involved the insertion of human insulin gene on the plasmids of E.coli. The polypeptide chains are synthesized as a precursor called pre-pro insulin, which contains A and B segments linked by a third chain (C) and preceded by a leader sequence. The leader sequence is removed after translation and the C chain is excised, leaving the A and B polypeptide chains.

Question 19.
Differentiate in-situ and ex-situ conservation by sighting examples for each.
Answer:
In-situ conservation:
Conservation of plants and animals in theimatural habitat.
Eg., Sacred Groves
A sacred grove or sacred woods are any grove of trees that are of special religious importance to a particular culture. Sacred groves feature in various cultures throughout the world.

Ex-situ conservation:
Conservation of selected or rare plants or animals in place outside their natural habitat.
E.g., Gene banks
Gene banks are a type of biorepository which preserve genetic materials. Seeds of different genetic strains of commercially important plants can be stored for long periods in seed banks, gametes of threatened species can be preserved in viable and fertile condition for long periods using ervopreservation techniques.

Part – IV

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

Question 20.
(a) Explain any five techniques of Assisted Reproductive Technology (ART).
Answer:
Intra-uterine insemination (IUI): This is a procedure to treat infertile men with low sperm count. The semen is collected either from the husband or from a healthy donor and is introduced into the uterus through the vagina by a catheter after stimulating the ovaries to produce more ova. The sperms swim towards the fallopian tubes to fertilize the egg, resulting in normal pregnancy.

Zygote intra-failopian transfer (ZIFT): As in IVF, the zygote upto 8 blastomere stage is transferred to the fallopian tube by laparoscopy. The zygote continues its natural divisions and migrates towards the uterus where it gets implanted.

Intra uterine transfer (IUT): Embryo with more than 8 blastomeres is inserted into uterus to complete its further development.

Gamete intra-failopian transfer (GIFT): Transfer of an ovum collected from a donor into the fallopian tube. In this the eggs are collected from the ovaries and placed with the sperms in one of the fallopian tubes. The zygote travels toward the uterus and gets implanted in the inner lining of the uterus.

Intra-cytoplasmic sperm injection (ICSI): In this method only one sperm is injected into the focal point of the egg to fertilize. The sperm is carefully injected into the cytoplasm of the egg. Fertilization occurs in 75 – 85% of eggs injected with the sperms. The zygote is allowed to divide to form an 8 celled blastomere and then transferred to the uterus to develop a protective pregnancy.

[OR]

(b) (i) Differentiate divergent and convergent evolution with examples.
(ii) What are the various objections to Darwinism?
Answer:
(i) Divergent Evolution:
Divergent evolution is a result of homology. E.g: The wings of bird and the forelimbs of human both are homologous structures modified according to functions. In birds, it is used for flight and in humans used for writing and other purposes.

Convergent Evolution:
Convergent evolution is a result of analogy. E.g: Root modification in sweet potato, and stem modification in potato are analogous structures both performing same function i.e., storage.

(ii) Some objections raised against Darwinism were,

• Darwin failed to explain the mechanism of variation.
• Darwinism explains the survival of the fittest but not the arrival of the fittest.
• He focused on small fluctuating variations that are mostly non-heritable.
• He did not distinguish between somatic and germinal variations.
• He could not explain the occurrence of vestigial organs, over specialization of some organs like large tusks in extinct mammoths and oversized antlers in the extinct Irish deer, etc.

Question 21.
(a) Explain the life cycle of Plasmodium.
Answer:
Plasmodium vivax is a digenic parasite, involving two hosts, man as the secondary host and female Anopheles mosquito as the primary host. The life cycle of Plasmodium involves three phases namely schizogony, gamogony and sporogony.

The parasite first enters the human blood stream through the bite of an infected female Anopheles mosquito. As it feeds, the mosquito injects the saliva containing the sporozoites. The sporozoite within the blood stream immediately enters the hepatic cells of the liver. Further in the liver they undergo multiple asexual fission (schizogony) and produce merozoites. After being released from liver cells, the merozoites penetrate the RBC’s.

Inside the RBC, the merozoite begins to develop as unicellular trophozoites. The trophozoite grows in size and a central vacuole develops pushing them to one side of cytoplasm and becomes the signet ring stage. The trophozoite nucleus then divides asexually to produce the schizont. The large schizont shows yellowish – brown pigmented granules called Schuffners granules. The schizont divides and produces mononucleated merozoites.

Eventually the erythrocyte lyses, releasing the merozoites and haemozoin toxin into the blood stream to infect other erythrocytes. Lysis of red blood cells results in cycles of fever and other symptoms. This erythrocytic stage is cyclic and repeats itself approximately every 48 to 72 hours or longer depending on the species of Plasmodium involved. The sudden release of merozoites triggers an attack on the RBCs.

Occasionally, merozoites differentiate into macro gametocytes and micro gametocytes. When these are ingested by a mosquito, they develop into male and female gametes, respectively. In the mosquito’s gut, the infected erythrocytes lyse and male and female gametes fertilize to form a diploid zygote called ookinete. The ookinete migrates to the mosquito’s gut wall and develop into an oocyte.

The oocyte undergoes meiosis by a process called sporogony to form sporozoites. These sporozoites migrate to the salivary glands of the mosquito. The cycle is now completed and when the mosquito bites another human host, the sporozoites are injected and the cycle begins a new.

The pathological changes caused by malaria, affects not only the erythrocytes but also the spleen and other visceral organs. Incubation period of malaria is about 12 days. The early symptoms of malaria are headache, nausea and muscular pain. The classic symptoms first develop with the synchronized release of merozoites, haemozoin toxin and erythrocyte debris into the blood stream resulting in malarial paroxysms – shivering chills, high fever followed by sweating. Fever and chills are caused partly by malarial toxins that induce macrophages to release tumour-necrosis factor (TNF-α) and interleukin.

[OR]

(b) Mention the reasons for the richness of biodiversity in the tropics.
Answer:
The reasons for the richness of biodiversity in the Tropics are,

• Warm tropical regions between the tropic of Cancer and Capricorn on either side of equator possess congenial habitats for living organisms.
• Environmental conditions of the tropics are favourable not only for speciation but also for supporting both variety and number of organisms.
• The temperatures vary between 25°C to 35°C, a range in which most metabolic activities of living organisms occur with ease and efficiency.
• The average rainfall is often more than 200 mm per year.
• Climate, seasons, temperature, humidity, photo periods are more or less stable and encourage both variety and numbers.
• Rich resource and nutrient availability.