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Karnataka 2nd PUC Biology Previous Year Question Paper March 2017
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)
What are Hermaphrodites?
Bisexual animals that possess both male and female reproductive organs are hermaphrodites.
Mention the asexual reproductive structure in sponges.
What is Euchromatin?
Loosely packed region of chromatin which stains lightly in colour is known as euchromatin.
Why DNA replication is called semiconservative?
After the completion of replication, each DNA molecule would have one parental and one newly synthesised strand. Thus it is termed as semi-conservative DNA replication.
Name the microbe used in the production of citric acid.
What is Micro – Injection
The method of directly injecting recombinant DNA or alien DNA into the nucleus of an animal cell is known as microinjection.
The number of deaths in the population during a given period is known as mortality.
Give an example of the gaseous cycle.
Species confined to one region and not found anywhere else in the world is called as endemic species.
What is Eutrophication?
Eutrophication is the natural ageing of a lake by nutrient enrichment of its water.
Part – B
Answer any five of the following questions in 3 to 5 sentences each: Wherever applicable: (5 × 2 = 10)
List the hormones produced by the placenta during pregnancy.
- Human chorionic gonadotropin (HCG)
- human placental lactogen (HPL)
Write any two simple principles to prevent sexually transmitted diseases.
- Avoid sex with unknown partners/multiple partners.
- Always use condoms during coitus.
Mention four symptoms of Down’s syndrome.
- Short statured with a small round head.
- furrowed tongue and partially open mouth.
- Palm is broad with characteristic palm crease.
- Physical, Psychomotor and mental development is retarded.
What is Incomplete dominance? Give an example.
It is a process where the dominant gene is incompletely dominant over the recessive gene and produces a phenotype which is intermediate to the parental type.
ex: Inheritance of flower colour in snapdragon
Write any two factors affecting the Hardy-Weinberg principle.
- Gene migration or gene flow
- Genetic drift
What is the significance of the selectable marker in the cloning vector?
The selectable marker helps in identifying and eliminating noh transformants and selectively permitting the growth of the transformants.
Codon AUG has a dual function – Justify.
AUG codes for methionine (Met) and it also act as initiator codon.
What are the criteria of DNA to act as genetic material?
- It should be able to generate its replica,
- It should chemically and structurally be stable.
- It should provide the scope for slow changes (mutation) that are required for evolution.
- It should be able to express itself in the form of ‘Mendelian characters’.
Part – C
Answer any five of the following questions in about 40 to 80 words each wherever applicable: (5 × 3 = 15)
Name the types of vegetative propagules in the following points:
- Stem tuber
- Adventitious buds present at margins of leaves.
What is pollination? Mention any four features of wind-pollinated flowers.
Transfer of pollen grains shed from the anther to the stigma of a pistil is termed pollination. Features of wind-pollinated flowers:
- Pollen grains are light and non-sticky so that they can be transported in wind currents.
- They possess well-exposed stamens for easy dispersal in wind currents.
- Posses large often – feathery stigma to easily trap airborne pollen grains.
- Flowers often have a single ovule in each ovary and numerous flowers packed into an inflorescence.
What is infertility? Give reasons for infertility in humans.
Inability to produce children in spite of unprotected sexual cohabitation even after two years of marriage. Reasons for infertility in humans could be:
What are analogous organs? Give any two examples.
The analogy is the relationship among organs of different groups of organisms performing the same function, irrespective of structural or anatomical differences.
Some examples of organs showing analogy are:
- Eyes of octopus and those of mammals.
- Wings of a butterfly (insect) and those of birds.
- Flippers of whales or dolphins and those of penguins.
- Tubers of sweet potato (root modified) and those of potato (stem modified).
The analogy is the result of convergent evolution, i.e., the evolutionary process. where anatomically different structures in different groups of organisms evolve towards the same function. It is the similar habitat conditions that have selected similar adaptive features in different groups of organisms, towards the same function.
Mention the types of carcinogens with an example for each.
Causes of cancer (Carcinogenic agents)
These include physical, chemical and biological agents, which transform normal cells by directly causing changes in the DNA of these cells.
- Physical agents: They include various forms of ionizing radiations. UV radiation is a powerful mutagen for skin cancer. The exposure of the thyroid glands to x – rays have shown to increase the incidence of thyroid cancer.
- Chemical agents: The chemical carcinogens that have been found to be carcinogenic in humans include:
- a. Chemical mixtures like soot (black carbon), tars, cigarette smoke, etc.
- b. Industrial chemicals: Arsenic, nickel compounds, benzidine, etc.
- c. Drugs: Mustard gas, phenacetin.
Write the meaning of the following terms:
- Some clones.
- The explant is any part of a plant taken out arid grown in a test tube.
- Capacity to generate a whole plant from any cell/explant is called Totipotency.
- Genetically identical plants produced through plant tissue culture are known as soma clones.
Draw a neat labelled diagram of simply stirred tank bioreactor.
Mention three causes of biodiversity loss.
- Habitat destruction and fragmentation
- Introduction of Alien species
- Co – extinctions.
Part – D
Section – I
Answer any four of the following questions in about 200 to 250 words each, wherever applicable: (4 × 5 = 20)
Describe the structure of pollen grain of angiosperms.
Structure of pollen grain: Pollen grain is the haploid unicellular, uninucleated spherical shaped body bounded by outer thick, spiny or reticulate callose wall called exine and inner thin, smooth cellulose wall called intine. In the exine, thin areas called germ pores are present. Intine encloses peripheral cytoplasm and central nucleus.
Pollen grain represents the first stage of male gametophyte. Development by pollen grain takes place when it is still present in the anther locule. During the development, it divides unequally into a large vegetative cell and a small generative cell. The generative cell then divides and give rise to two non-motile male gametes. This takes place either in the pollen grain or in the pollen tube after pollination.
- Pollen grains of many species cause severe allergies and chronic respiratory disorders like asthma, bronchitis etc. e.g. parthenium (carrot grass)
- Pollen grains are rich in nutrients. Thus pollen tablets are used as nutrient supplements.
Draw a neat labelled diagram of the human male reproductive system.
Explain Mendel’s experiment to describe the inheritance of one gene with reference to the height of pea plants.
Monohybrid Cross: Mendel selected two plants. One with tall and the other with the dwarf to get F1 generation. To his surprise, he got all tall plants in the F1 generation.
Parents: Tall plant × Dwarf plant
F1 → All tall plants
Thus the tall character appeared in the F1 generation but the dwarf character did not appear. He self crossed the F1 plants and raised the F2 generation. Surprisingly he got both tall and dwarf plants in the ratio of 3 : 1 respectively. This ratio is called the Phenotypic ratio. He repeated the experiment by taking other contrasting characters and got the same results.
F1 → Tall plant × F1 Tall plant.
F2 → Tall plants : Dwarf plants. (3 : 1)
Based on these results, he concluded that the tall character is dominant and the dwarf character is recessive. Then he used appropriate symbols to designate the dominant and recessive factors. He used capital letters for dominant factors and small letters of the same type to denote the recessive alleles. The monohybrid cross can be represented as below.
Number of plants of alleles involved – 1 pair
Base Number – 4
Phenotypic ratio – 3 : 1 (3 tall : 1 dwarf)
Genotypicratio – 1 : 2 : 1
Phenotypic classes – Two (Tall and dwarf only)
Genotypic classes – Three
[1 homozygous tall, 2. heterozygous tall and 3. homozygous dwarf]
List the salient features of the Human Genome.
- The human genome contains 3164.7 million nucleotide bases.
- The average gene consists of 3000 bases.
- The largest known human gene being dystrophin at 2.4 million bases.
- The total number of the gene is estimated at 30,000.
- 99.9 per cent of nucleotide base sequences are the same in all the people.
- The function of 50% of the genes discovered is still unknown.
- Less than 2 per cent of the genome, codes for proteins.
- Repeated sequences make up a very large portion of the human genome.
- Chromosome I has the most genes (2968) and Y has the fewest (231).
- It is identified about 1.4 million locations where single-base DNA differences (SNPs – single nucleotide polymorphism) occur in humans.
Name the diseases caused by the following organisms:
- Rhinovirus. (1)
- Epidermophyton. (1)
- Salmonella typhi. (1)
- Wuchereria malayi. (1)
- Plasmodium vivax. (1)
- Common cold
What is Bee – Keeping? Write any four points for successful Bee – Keeping?
Bee-keeping or Apiculture: Maintenance of hives of honeybees for the production of honey and beeswax is called apiculture.
Honey is used as (i) Food of high nutritive value and (ii) Medicine in Ayurveda.
Beeswax is used in industry for the preparation of cosmetics and polishes.
The most common species of the honeybee is Apis indica.
Bee-keeping can be practised in any area where there are sufficient bee pastures (some wild shrubs, cultivated crops, fruit-orchards, etc.)
Beehives can be kept in any place like courtyard, verandah or on the roof of the house.
Bee-keeping is relatively easy and requires the following considerations:
- Knowledge of the nature and habits of a bee.
- Selection of suitable location of keeping beehives.
- Catching and hiving of swamis.
- Management of beehives during different seasons.
- Handling and .collection of honey and beeswax.
Bees are the pollinators of many crop plants (apple, pear, sunflower, Brassica, etc.) and hence keeping beehives ¡n crop fields during flowering seasons increases pollination efficiency and thereby improves the yield.
Section – II
Answer any three of the following questions in about 200 to 250 words each wherever applicable: (3 × 5 = 15)
Describe the biogas plant with a neat labelled diagram.
Microbes in Production of Biogas: Biogas is a mixture of gases (containing predominantly methane) produced by the microbial activity and which may be used as fuel. Microbes produce different types of gaseous end-products during growth and metabolism. The type of gas produced depends upon the microbes and the organic substrates they utilise. Bacteria, which grow anaerobically on cellulosic material, produce a large amount of methane along with CO2 and H2. These bacteria are collectively called methanogens, and one such common bacterium is methane bacterium. These bacteria are commonly found in the anaerobic sludge during sewage treatment. These bacteria are also present in the rumen (a part of the stomach) of cattle. A lot of cellulosic material present in the food of cattle is also present in the rumen.
Note: In the rumen, these bacteria help in the breakdown of cellulose and play an important role in the nutrition of cattle.
The excreta (dung) of cattle, commonly called gobar, is rich in these bacteria. Dung can be used for the generation of biogas, commonly called gobar gas.
The biogas plant consists of a concrete tank (10 – 15 feet deep) in which bio-wastes are collected and a slurry of dung is fed. A floating cover is placed over the slurry, which keeps on rising as the gas is produced in the tank due to the microbial activity. The biogas plant has an outlet, which is connected to a pipe to supply biogas to nearby houses. The spent slurry is removed through another outlet and may be used as a fertiliser. Cattle dung is available in large quantities in rural areas where cattle are used for a variety of purposes. So, biogas plants are more often built in rural areas. The biogas thus produced is used for cooking and lighting.
(a) What is Biopiracy? (2)
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.
(b) How ADA deficiency cured, by gene therapy? (3)
The first gene therapy experiment involved extraction of T-lymphocytes from the bone marrow of SCID patient. A healthy copy of the ADA gene is introduced into these cells with the help of retrovirus as a vector. These engineered cells are then injected into the bone marrow of the patient where those cells multiply. The altered cells would produce enough adenosine deaminase to relieve the disease symptoms. The lymphocytes have a definite life span, the disease cannot be cured permanently. Repeated injections of modified lymphocytes about three months for the patient are needed to control the disease.
(a) What is Ecological succession? (1)
The gradual and fairly predictable change in the species composition of a given area is called ecological succession.
(b) Write types of plant succession? (2)
Xerarch succession and hydrarch succession
(c) Represent pyramid of number in a grassland ecosystem. (2)
It is a graphic representation of the numerical relationship between successive trophic levels in a food chain. Usually, it is an upright pyramid and it illustrates the decreasing number of individuals at a successive trophic level from producers to consumers. The number of individuals is maximum in producers compared to consumers.
e.g.: Pond food chain.
Explain mutualism with examples.
Mutualisna or symbiosis in which both the species are mutually benefitted but the association is obligatory and they cannot live separately under normal conditions.
e.g., mycorrhizal with the association of fungus (e.g., Boletus) and roots of higher plants. The fungi help the plant in the absorption of water and essential nutrients from the soil while the plant, in turn, provides the fungi with carbohydrates.
Lichens represent an intimate mutualistic relationship between a fungus and photosynthesising
algae or cyanobacteria. Root ñodules of legume plants, Casuarina. Alnus and leaf nodules of Ardisia have symbiotic
association of nitrogen-fixing bacteria – Rhizobium. The plants provide food and shelter to the bacteria and the bacteria fix free atmospheric nitrogen to the plant.
The most interesting example of mutualism is found in plant-animal relationships. Plants take the help of animals for pollinating their flowers and dispersing their seeds. Animals get rewards or fees in the form of pollen and nectar (for pollinators) and juicy and nutritious fruits (for seed dispersals).
In many species of fig trees, there is a tight one-to-one relationship with the pollinator species of wasp. The female wasp uses the fruit not only as an oviposition (egg-laying) site but uses the developing seeds within the fruit for nourishing its larvae. The wasp pollinates the fig inflorescence while searching for suitable egg-laying sites. In return for the favour of pollination, the fig offers the wasp some of its developing seeds as food for the developing wasp larvae.
The Mediterranean orchid ophrys employs sexual deceit to get pollination done by a species of bee. One petal of its flower bears a un carry resemblance to the female of the bee in size, colour and markings. The male bee is attracted to what is perceives as a female, ‘pseudo copulates’ with the flower and during that process is dusted with pollen from the flower. When this same bee pseudoscope lates with another flower, it transfer pollen to it and thus pollinates the flower.
Write a brief account of electrostatic precipitator with a neat labelled 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 thç charged particles.
- The velocity of air between the plates must be low enough to allow the particles to fall on them.