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Karnataka 2nd PUC Biology Previous Year Question Paper March 2016
Time: 3 hrs 15 min
Max. Marks: 70
- This question paper consists of four parts A, B, C and D. Part – D consists of two sections. Section – I and Section – II.
- All the parts are compulsory.
- Draw diagrams wherever necessary. Unlabelled diagrams or illustrations do not attract any marks.
Part – A
Answer the following questions in one word or one sentence each. (10 × 1 = 10)
Name the molecular scissors used in recombinant DNA (rDNA) technology.
REN (Restriction Endonuclease).
What are some clones?
Genetically identical plants produced through plant tissue culture.
Reforestation is the process of restoring a forest that once existed but was removed at some point of time in the past.
Name the enzyme by which the HIV genome replicates in the host cell.
What is menarche?
The first menstruation begins at puberty and is called menarche.
Name the disease diagnosed by the Widal test.
Ovulation takes place on the 14th day of the menstrual cycle. Why?
Rapid secretion of LH leading to its maximum level on 14th day of a menstrual cycle called LH surge which induces rupture of Graafian follicle and thereby release of an ovum (ovulation).
What is Colostrum?
The milk produced during the initial few days of lactation is called colostrum which contains several antibodies absolutely essential to develop resistance to the newborn babies.
How do some species of insects and frogs avoid being detected easily by the predators?
Some species of insects and frogs are cryptically coloured (camouflaged) to avoid being detected easily by the predator.
Mention the use of statin.
Statins are used as blood cholesterol-lowering agents.
Part – B
Answer any five of the following questions in 3 to 5 sentences each: Wherever applicable: (5 × 2 = 10)
What is inbreeding depression? How is it controlled?
Continuous inbreeding causes inbreeding depression that reduces vigour, fertility and even productivity. It can be controlled by outbreeding or interspecific hybridisation.
Define biodiversity Write any two types of biodiversity.
The combined diversity at all the levels of biological organisation is biodiversity.
- Genetic diversity
- Species diversity
Why has T.H. Morgan selected fruit flies for his genetical experiments?
Morgan selected fruit flies for his genetical experiments for the following reasons:
- They could be grown on simple synthetic medium in the laboratory.
- They complete their life cycle in about two weeks and a single mating could produce a large number of progeny flies.
- There was a clear differentiation of the sexes – the male and female flies.
- It has many types of hereditary variations that can be seen with low power microscopes.
Differentiate seasonal breeders from continuous breeders.
Non-primates are reproductively active only in favourable seasons (oestrus period). They are known as seasonal breeders. Primates like monkeys and humans are reproductively active throughout the year. They are continuous breeders.
What are analogous organs? Give an example.
The organs which are different in their ground plan and structures but perform similar functions are known as analogous organs. Eg: wings of birds and insects, the tuber of potato and sweet potato.
Draw a neat labelled diagram of an antibody molecule.
Name any four recent extinct organisms as per IUCN Red List.
Dodo, Quagga, Steller’s sea cow, Thylacine.
Draw a neat labelled diagram of a. typical agarose gel electrophoresis.
Part – C
Answer any five of the following questions in about 40 to 80 words each wherever applicable: (5 × 3 = 15)
Explain in brief the separation and isolation of DNA fragments.
(a) Isolation of genetic material (DNA): In recombinant DNA technology, it is essential to isolate DNA in the pure form free from other macromolecules. Since the DNA molecule is enclosed with the membrane in the cell. we have to break open the cell to release DNA along with other macromolecules like RNA, proteins, polysaccharides and lipids. This is carried out in bacterial cells, plant and animal cells with certain enzymes.
The other macromolecules can be removed by appropriate treatment with specific enzymes. Finally, the purified DNA molecules are precipitated out after the addition of chilled ethanol and this can be seen as a collection of fine threads ¡n the suspension.
(b) Cutting of DNA at specific locations: The isolated purified DNA molecule is cut (cleaved) with the help of a suitable enzyme called restriction endonuclease, into segments with sticky ends.
(c) Gel electrophoresis: The cut DNA fragments are separated by gel electrophoresis using an agarose gel. DNA is a negatively charged molecule, hence it moves towards the positive electrode (anode).
Mention any three characteristics of a cancer cell?
Characteristics of cancer cells:
Anaplastic or undifferentiated cells: The cancer cells lack normal cell cycle where the daughter cells.
Immortality: These cells do not age normally and continue dividing indefinitely.
Change in the structure of cell: There is disorganization of the cytoskeleton which alters the shape of the cell.
Mitochondria swell and lack cristae. Cancer cells also show large, irregularly shaped nuclei and prominent nucleoli. There is an increase in the number of rough ER and ribosomes and further, the permeability of the plasma membrane also gets altered.
Invasiveness: Cancer cells grow by progressive infiltration, penetration and destruction of the surrounding tissues.
What is ecological succession? Distinguish primary succession from the secondary succession.
It is the fairly and gradual replacement of species composition in an area.
Primary succession is also referred as ‘preserve’ and is a type of biotic succession that occurs on a substratum devoid of any previous life like bare rock, sand dunes, new islands exposed out of the sea etc. where there was previously no life.
Secondary succession is the biotic succession that occurs in an area, which had an existing biotic community and has become bare due to destruction by fire, landslide, earthquake etc.
What is parthenogenesis? Give two examples.
The phenomenon where female gametes develop into new organisms without fertilisation is known as parthenogenesis.
Eg: honeybees, rotifers.
State Hardy-Weinberg principle. Mention any two factors that affect Hardy-Weinberg equilibrium.
Hardy Weinberg Law or Hardy Weinberg Equilibrium: This law was proposed by British Mathematician Hardy and German Physicist E. Weinberg. The Law states that “Gene frequency of a Mendelian population remains constant through generations unless there are chromosomal aberrations, mutation etc to alter the genetic equilibrium”.
This law describes that when the population is in equilibrium there is no evolution. Evolution occurs only when the equilibrium is altered. The mendelian population is a closely interbreeding group of organisms sharing a common gene pool.
Evolutionary factors like mutation, migration, genetic drift, gene flow, and sexual reproduction are factors affecting the equilibrium of a population.
What is artificial hybridisation? By which technique is it achieved?
Crossing different species and genera to combine desirable characters to produce commercially superior varieties is artificial hybridisation. This is achieved by emasculation and bagging techniques.
With reference to ecological succession define the following terms.
- Climax community
- Pioneer species
- The plant community that is in near equilibrium with the environment is called a climax community.
- The entire sequence of communities that successively change in a given area is called seres.
- The species that invade a bare area are called pioneer species.
Write the karyotype of the following syndromes:
- Down’s syndrome
- Klinefelter’s syndrome
- Turner’s syndrome.
- Down’s syndrome: 45AA + XX & 45AA + XY
- Klinefelter’s syndrome: 44AA + XXY
- Turner’s syndrome: 44AA + XO
Part – D
Section – I
IV. Answer any four of the following questions in about 200 to 250 words each, wherever applicable: (4 × 5 = 20)
Enumerate the salient features of the Human Genome Project (HGP).
Achievements of HGP:
HGP got success in the following aspects.
- This project identified nearly 30,000 to 35,000 genes of human DNA.
- They identified 3164.7 million nitrogen bases in the human genome
- They identified the size and number of bases in genes. The average gene has 3000 bases and the largest human gene. dystrophin has 2.4 million bases.
- They identified the fact that all human beings are 99.9% identical with each other and only 0.1 % are different.
- They identified that the chromosome-1 has a maximum number of genes ie 2968 genes and y chromosome has the lowest number of genes i.e. 231.
- They identified that only 2% of the genome codes for protein and the remaining 98% of DNA remains functionless. This non-functional DNA is called Junk DNA.
Explain the process of translation in protein synthesis.
The translation is the second step during protein synthesis in which using genetic information on mRNA in nucleotide language, protein synthesis takes place on the ribosome in the amino acid lineage. mRNA carrying a coded message for the synthesis of protein will be released into the cytoplasm. With the help of this mRNA translation occurs in four steps.
- Activation and selection of Amino acids
- Chain initiation
- Chain elongation
- Chain termination.
1. Activation and selection of amino acids: In this step, amino acid combines with ATP in the presence of amino acid synthetase and forms activated amino acid and this process is known as activation. The activated amino acid thus will be picked up by specific + RNA molecule and form amino acid + RNA.
Amino acid + ATP → Activated amino acid.
Activated amino acid + +RNA → Amino acid +RNA
2. Chain ¡nidation: During this process, initially mRNA attaches to smaller ribosomal subunit. Then +RNA carrying methionine attaches to the initiator codon (AUG) of mRNA. Now larger ribosomal subunit attaches to mRNA, such that the +RNA with ämino acid coincides at P-Site. Soon after this, another +RNA with a second amino acid attaches to A-site peptide bond is formed, between the first amino acid occupying A-site. Chain initiation needs ATP and proteins called initiation factors.
3. Chain elongation: Soon after chain initiation, ribosomal subunits slide along mRNA. This shifts the +RNA occupying A-site automatically to the P-site. Now to the emptied A-site, +RNA carrying third amino acid gets attached. With this peptide bond is established between second and third amino acids. This results in the growing of polypeptide chain referred to as chain elongation. Chain elongation requires GTP, elongation factors and Mg+2 ions.
4. Chain termination: As soon as the sliding ribosomal subunits arrive at the terminator codons, the protein synthesis is stopped with the association of releasing factors to the larger subunit of the ribosome. This is known as chain termination. Soon after chain termination, newly formed polypeptide chain undergoes processing and attains specific structure.
Draw a neat labelled diagram of a sectional view of the human female reproductive system.
(a) What are multiple alleles? Give an example.
When a gene expresses itself in more than 2 allelic forms, then the alleles are called multiple alleles.
e.g: The gene ‘I’ controls the human blood group. It exists in 3 different allelic forms i.e., IA, IB, and i, and is responsible for the four human blood groups viz, A, B, O and AB.
(b) Write the symptoms of Klinefelter’s syndrome.
- Small penis
- Diminished pubic, axillary, and facial hair
- Enlarged breast tissue (called gynecomastia)
- Learning disabilities
- Simian crease (a single crease in the palm)
- Abnormal body proportions (long legs, short trunk)
- Small firm testicles
- Sexual dysfunction
- Tall Stature
- Personality impairment
Note: The severity of symptoms may vary.
Tests may include:
- Karyotyping showing 47 chromosomes with XXY
- Semen exam showing low sperm count
- Decreased serum testosterone level
- Increased serum luteinizing hormone and increased serum follicle-stimulating hormone.
What is infertility? How is infertility treated by assisted reproductive technologies like GIFT and ICSI?
A woman who is unable to conceive is called infertile. This infertility is caused due to defects in men or women or both.
Causes of Infertility of Men:
- Deficiency of FSH and ICSH lead to diminished production of sperms.
- To maintain fertility, there must be 20 millions of sperms in 1 ml of semen but sterility is caused due to less number of sperms i.e., less than 10 million in 1 ml of semen and it is called oligospermia.
- Due to infections caused by a virus, bacteria and diseases like T-8 may affect the spermatogenesis. Some times, there will be no production of sperms in the semen, called Azoospermia.
- In some cases, when the testis remains in the abdomen and does not descend into the scrotal sacs, it is called cryptorchidism. This causes more temperature in the body and affects spermatogenesis.
- Inflammation of prostate gland and seminal vesicle.
- Impotence: It is the inability of the male to attain or hold an erection of the penis long enough for normal intercourse.
- Defective epididymis and vas deference.
Causes of infertility in women:
- Deficiency of FSH and LH of pituitary
- Blockage of the fallopian tube leads to infertility.
- When the uterus is very small and such a congenital defect may lead to sterility.
- Improper development of uterus leads to sterility.
- Injury or diseases of ovary leads to sterility.
- Deficiency of vaginal fluid (Mucous) leads to sterility.
- Non-canalization of the vagina.
Gamete Ultra Fallopian Transfer(GIFT): Here both ova and sperms are transferred into the fallopian tube of the mother when her both ovaries are defective. This leads to in-vitro fertilization (natural). Here failure of fertilization and pregnancy may happen.
Intracytoplasmic sperm injection (ICSI): It is a technique in which a single healthy sperm is injected into each mature egg directly. ICSI increases the chance of fertilisation for men who have low sperm count or poor sperm quality.
Explain the structure of megasporangium.
Structure of Mature Anatropous Ovule: Ovule represents the megasporangium. The anatropous ovule is an inverted ovule (due to 1800 turn) in which funicle and micropyle lie close to each other. It shows the following parts.
1. Funicle: It is the stalk of the ovule by which ovule is attached to placenta in the ovary.
2. Hilum: It is the region at which ovule is attached to the funicle.
3. Raphae: It is the extended part of the funicle beyond the hilum.
4. Chalaza: It is the basal part of the ovule at which integuments originate.
5. Integuments: These are outer protective coverings of the ovule. These completely enclose the nucellus except for the region at the apex called the micropyle.
6. Nucellus: It is the female gametophyte present in the nucleus towards the micropylar end. It consists of three antipodal cells towards the chalazal end, secondary nucleus at the centre and egg apparatus towards the micropylar end. Egg apparatus consists of a central egg cell and two lateral synergid cells.
7. Embryosac: It is the female gametophyte present in the nucleus towards the micropylar end. It çonsists of three antipodal cells towards the chalazal end, secondary nucleus at the centre and egg apparatus towards the inicroph lar end. Egg apparatus consists of a central egg cell and two lateral synergid cells.
Section – II
Answer any three of the following questions in about 200 to 250 words each wherever applicable: (3 × 5 = 15)
Write a brief account of the functioning of ‘Electrostatic Precipitator’ with diagram.
- It is the most widely used method for removal of particulate matter; about 99% of particulate pollutants are removed from the exhaust of thermal power plant.
- It has electrode wires and a stage of collecting plates.
- The electrode wires are maintained at several thousand volts, which produce a corona that releases electrons.
- These electrons get attached to them (dust) particles and give them a net negative charge within a very small fraction of a second.
- The collecting plates are grounded and hence attract the charged particles.
- The velocity of air between the plates must be low enough to allow the particles to fall on them.
(a) What is Gene therapy? Give an example.
The technique of curing genetic diseases by replacing the defective genes by normal genes is called gene therapy. eg. SCID
(b) Write a note on biopiracy with reference to ‘Basmati Rice’.
Biopiracy: It is a term used to refer to the use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned without compensatory payment.
e.g.: Basmati rice grown in India is distinct for its unique flavour and aroma, but an American company got patent rights on Basmati through the US patent and trademark office. The new variety of Basmati has been developed by this company by crossing an Indian variety with the semi-dwarf varieties.
What is inbreeding? Mention the significance of inbreeding,
Microbes in Industrial Products: A number of industrial products valuable to human beings are produced with the help of microbes. The two common ones are alcoholic beverages and antibiotics.
Alcoholic Fermentation: Microbes especially yeasts have been used for the production of alcoholic beverages from time immemorial. Yeast species used in alcoholic fermentation are Saccharomyces cerevisiae (Brewer’s yeast). S. ellipsoids (wine yeast), S. cake (sake yeast) and S. piriformis (Ginger Beer/Ale yeast).
Substrates containing starch juice from sugar cane or molasses or sugar beet are the common substrates for the production of ethanol. Ethanol is produced by continuous fermentation. The process is carried out in large fermenters. Fermentation is carried out at pH5, at a temperature of 35°C. but the cultures and culture conditions are different. Varieties of alcoholic drinks are made from the same microorganism using different substrates. Starch from barley grains is used in the preparation of beer. Wine is produced from the sugar in grapes.
Note: After fermentation is over, the cells are separated to get biomass of yeast cells which are used as SCP (Single Cell Protein) for animal feed.
Depending upon the raw material and the type of processing, the alcoholic drinks are of two types:
- Without Distillation: Wine and beer are produced without distillation. Beer is an undistilled product of grain mash fermentation, white wine is produced from fruit juice without distillation.
- With Distillation: Whisky, brandy and rum are produced by distillation of the fermented broth.
- Antibiotics are chemical substances, which are produced by some microbes and can kill or retard the growth of other (disease-causing) microbes.
- The term antibiotics were coined by Waksman (1942).
- An antibiotic may be broad-spectrum i.e., it can kill or destroy a number of pathogens that belong to different groups with different structure and wall composition, or specific i.e., effective against only one type of pathogen.
- Most of them are produced by actinomycetes, especially the genus Streptomyces and filamentous fungi.
- Production of Antibiotics: For commercial production of antibiotics, the sterilized nutrient medium is inoculated with a suitable strain of the micro-organism. The nutrient medium is provided with optimum pH, aeration, temperature, antifoaming agent and antibiotic pre-cursor.
The microorganism grows and secretes antibiotics in the medium. When sufficient antibiotic has diffused into the medium, the microorganism is separated and the antibiotic is extracted from the medium by precipitation, absorption or solvent. It ¡s purified, concentrated and bioassayed before packing.
Chemicals, Enzymes and other Bioactive Molecules:
1. Aspergillus niger (a fungus) is used in the production of citric acid, Acetobacter Araceli (a bacterium) for acetic acid; Clostridium bretylium (a bacterium) for butyric acid and Lactobacillus (a bacterium) for lactic acid.
2. Yeast (Saccharomyces cerevisiae) is used for the commercial production of ethanol.
3. Microbes are also used for the production of enzymes. Lipases are used in detergent formulations and are helpful in removing oily stains from the laundry.
Bottled juices are clarified by the use of pectinases and proteases. Streptokinase produced by the bacterium streptococcus and modified by genetic engineering is used as a ‘clot buster’ for removing clots from the blood vessels of patients who. have undergone myocardial infarction leading to a heart attack.
4. Another bioactive molecule, cyclosporin A, that is used as an immunosuppressive agent in organ transplant patients, is produced by the fungus Trichoderniapolysporum.
5. Statins produced by the yeast Monascus pupureus have been commercialised as blood cholesterol-lowering agents. They act by competitively inhibiting the enzyme responsible for the synthesis of cholesterol.
Explain the role of microbes in ‘Industrial products’
Effects of ozone depletion:
Thinning of the ozone layer and development of ozone holes increases the amount of UV-B radiations reaching the earth’s surface. A 5% ozone depletion increases UV-B radiations by 10%. Increased incidence of UV-B radiations on earth will have the following adverse effects.
Skin Cancers: There is an increase in the incidence of skin cancers. 1% fall in ozone concentration increase Uy load of the earth by 2% that causes the addition of 50,000 cases of skin cancer. In Australia which lies near the area of the ozone hole, every second middle-aged person suffers from skin cancer while ¡n old persons the incidence is nearly 100%.
Blinding: Many land animals would lose their eyesight and become blind. In human beings, the cases of photo-burning, cataract and dimming of eyesight are on the increase. 1% fall of ozone concentration in the stratosphere will blind another 1 lakh persons. Immune System: It is partially suppressed. Incidence of herpes and other immune system-related diseases are likely to increase.
Larval Stages: More larvae and young ones of aquatic animals will die.
Photosynthesis: Photosynthetic machinery is impaired. Photosynthesis decreases by 10-25%. There is a corresponding fall in the yield of crops.
Nucleic Acids: Uy radiation damages nucleic acids by forming diners. Incidence of harmful mutations increases.
Phytoplankton: Both photosynthetic activity, as well as the function of phytoplankton, are disturbed by UV-radiations. 6-22% fall in productivity will occur.
Global Warming: Decreased primary productivity over land and inside oceans will increase carbon dioxide concentration resulting in global warming, despite a reduction in CO2 emissions from industries and automobiles.
(a) What is Adaptation?
Any attribute of the organism (morphological, physiological or behavioural) that enables the organism to survive and reproduce in its habitat is called adaptation.
(b) Write the causes and symptoms of ‘Altitude sickness’.
Low atmospheric pressure at high altitudes causes altitude sickness.
Symptoms include fatigue, nausea and heart palpitations.
(c) What is ‘Brood Parasitism’? Give an example.
Brood parasitism in birds is a fascinating example of parasitism in which the parasitic bird lays its eggs in the nest of its host and lets the host incubate them. During the course of evolution, the eggs of the parasitic bird have evolved to resemble the host’s egg in size and colour to reduce the chances of the host bird detecting the foreign eggs and ejecting them from the nest. Eg: cuckoo lays eggs in the nest of crow.