2nd PUC Biology Model Question Paper 4 with Answers

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Karnataka 2nd PUC Biology Model Question Paper 4 with Answers

Time: 3.15 Hours
Max Marks: 70

General Instructions:

  1. This question paper consists of four parts A, B, C and D. Part D consists of two parts, Section – I and Section – II.
  2. All the parts are Compulsory.
  3. Draw diagrams wherever necessary. Unlabelled diagrams or illustrations do not attract any marks.

Part – A

I. Answer the following questions in One Word or One Sentence each : (10 × 1 = 10 )

Question 1.
What is implantation of embryo?
The process of embedding or attachment of blastocyst (embryo) to the wall of uterus (endometrium) is called implantation.

Question 2.
What is convergent evolution?
The phenomenon of producing functionally similar structures (analogous organs) by distantly related organisms is called convergent evolution.

Question 3.
Define metastasis.
The property of spreading of cancer cells from one part of the body to other parts is called metastasis.

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Question 4.
Who is called the father of green revolution in India?
Dr. Swaminathan

Question 5.
Name the organism from which cyclosporin is obtained.
Trichoderma polysporum

Question 6.
What is gel electrophoresis?
Electrophoresis is a technique used to separate macromolecules, especially proteins and nucleic acids according to their in size, charge or conformation under electric field.

Question 7.
Human testes are extra abdominal in position. Give reason?
Because they are situated outside the abdominal cavity within a pouch called scrotum as an adaptation to maintain low temperature of the testes, necessary for spermatogenesis.

Question 8.
Give an example for passive immunity.
Transfer of antibodies from mother to child during breast feeding or through placenta during pregnancy.

Question 9.
Water hyacinth (Eichornia crassipes) also called as ‘Bengal Terror is World‘s most problematic aquatic weed‘ give reason?
It is an alien hydrophyte introduced in India. It has become invasive and cause extinction of native species. It grows faster in eutrophic water bodies and changes the dynamics of ecosystem.

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Question 10.
Why do animals like snails enter in to aestivation during summer?
To escape from summer related problems like heat and desssication.

Part – B

II. Answer any FIVE of the following questions in 3 – 5 sentences each, wherever applicable : (5 × 2 = 10 )

Question 11.
What is budding? Explain with an example.
The method of reproduction through bud formation is known as budding.
2nd PUC Biology Model Question Paper 4 with Answers 1
Budding is a common method of asexual reproduction in yeast. when yeast cell matures, it develops an outgrowth called bud, the nucleus of the parent divides into two daughter nuclei by mitosis. One of the nuclei is pushed into the bud, later bud gets detached from the parent by the way of constriction and develops into mature individual.

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Question 12.
What are biodiversity hot spots? Name the biodiversity hot spots of India.
These are regions with very high levels of species richness and endemism. They are the most threatened reservoir of biodiversity on earth.
There are two Biodiversity hotspots in India

  1. Western Ghats
  2. Eastern Himalayas

Question 13.
What is test cross? Mention the uses of test cross.
When offspring with dominant phenotype, whose genotype is not known, is crossed with an individual who is homozygous recessive for the trait is known as test cross

Use of Test Cross:
The test cross is used to find the genotype of an organism.

Question 14.
Distinguish between homologous and analogous organs.
Homologous organs

  • These are structurally similar functionally dissimilar.
  • These are developed by related animals.
  • They show similar developmental pattern.
  • They show divergent evolution.

Analogous organs

  • These are structurally dissimilar but functionally similar.
  • These are developed by unrelated animals.
  • Their developmental pattern is not similar.
  • They show convergent evolution.

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Question 15.
What is biofortification? Mention its importance.
Breeding crops with higher levels of vitamins and minerals or higher protein and healthier fats is known as biofortification.

The objective of bio fortification is to increase quality and improving nutritional status of the plants by improving

  1. Protein content and quality
  2. Oil content and quality
  3. Vitamin content
  4. Micronutrient and mineral content

E.g. Vitamin A enriched carrots, spinach; pumpkin, Vitamin C enriched bitter gourd, calcium enriched spinach, protein enriched beans etc.

Question 16.
What is asexual reproduction? Name the mode of asexual reproduction in the following cases.
a) Yeast b) Amoeba c) Penicillium d) Sponges
a) Yeast – Budding
b) Amoeba – Binary fission
c) Penicillium – Sporulation (conidia)
d) Sponges – Gemmules (internal buds)

Question 17.
Show schematic representation of steps of PCR
2nd PUC Biology Model Question Paper 4 with Answers 2

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Question 18.
What are polindromic sequences? Give an example.
The sequences produced by restriction endonucleases possess the same base sequences in both the strands but in opposite direction i.e. ( 5l – 3l and 3l – 5l ). Therefore, it reads the same but in opposite direction. Such sequences are called palindrome sequences.
2nd PUC Biology Model Question Paper 4 with Answers 3

Part – C

III. Answer any FIVE of the following Questions in 40-80 words each, wherever applicable. (5 × 3 = 15 )

Question 19.
What are homologous organs? What is homology? What do the homologous organs explain as an evidence of organic evolution?
Organs which are similar in origin but perform varied functions are called homologous organs.
Example: mouth parts of insects.

Homology is phenomenon of having similar origin and basic structures in different species due to their common ancestry for the same phenotype. Homologous organs indicate divergent evolution.

Question 20.
Why should we conserve biodiversity?
There are three types of benefits of biodiversity, they are

  1. Economic benefits.
  2. Ecological benefits.
  3. Ethical benefits.

1. Narrow utilitarian reasons for direct or economic benefits
Man derives maximum economic benefits from nature in the form of food (cereals, pulses fruits), fire wood, construction material, industrial products (tannin, resins, gums, latex, perfumes, dyes) and products of medicinal importance (quinine, reserpine, morphine, nimbin, vincristine), more than 25% of the drugs sold in market are derived from plants, more than 85% of the food materials are obtained from just 20 traditional crop species like cereals, millets, pulses etc. Scientists are busy in exploring molecular genetics and species level diversity for products of economic importance this is called biprospecting.

2. Broadly utilitarian reasons for ecological benefits or services
Biodiversity is necessary for maintenance and sustainable utilization of useful products and services from various ecosystems, such as cycling and recycling of nutrients through producers, consumers and decomposers, helps in maintaining climate conditions, soil fertility , pollination of plants, decomposition of waste and services such as purification of air, water mitigating floods and droughts and other environmental disasters.

3. Ethical reasons or benefits
Biodiversity has an ethical role. Every species have an intrinsic right to exist and share the wealth of the planet, therefore, it is our moral duty to ensure the well being of all other organisms and leave the biological legacy to future generations.

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Question 21.
Write short notes on Darwin’s finches.

  • A divergent evolution has occurred in the ground finches of Galapagos Islands situated on the equator, some 900 km west of equator.
  • Good example of adaptive radiation illustrated by Charles Darwin.
  • He differentiated thirteen species of finches and grouped them into six main types.
  • Finches in general possess stout, conical beaks adapted for crushing seeds.
  • But they have undergone great diversification in their feeding habits.
  • Accordingly shape and size of their beak has changed, ancestral finches on reaching different islands occupied all empty ecological niches in absence of competition and evolved into different species.

Question 22.
Name the causative organism, mode of transmission and symptoms of filariasis.
Casual organism
It is caused by two nematode worms Wuchereria bancrofti and Wuchereria malayi.

Mode of transmission
Filarial worms are dimorphic and live in the lymph glands and lymph vessels of the lower limb. A female filarial worm is viviparous, it produces micro filarial larvae, which exhibit nocturnal periodicity. The movement of larvae in the peripheral blood circulation suits the visits of mosquitoes and enters the mosquitoes.

They act as a vector and transmit the micro filarial larvae to the new host, now the larvae penetrate through skin and reach the- lymph vessels of the host, it takes 5-18 months, inside the lymphatic vessels, they increase in the number. This results in blockage and swelling of lymph vessels. The enormous increase in the size of lymph vessels and associated tissue is called filariasis or elephantiasis.

Initial symptoms include inflammation of lymph glands accompanied by filarial fever; in the later stages, it results in blockage of lymph vessels and lymph glands in the legs, arms and other parts.

Question 23.
What is cross pollination. Mention its types. Differentiate geitonogy and xenogamy.
When pollen grains are transferred from anthers of one flower to the stigma of another flower present in the same plant or different plant is called cross pollination or allogamy.

Cross pollination is two types namely geitonogamy and xenogamy.

Geitonogamy Xenogamy
1. It is the cross pollination between the flowers of the same plant. 1. It is the cross pollination between the flowers of different plants.
2. Does not provide opportunity for gametic 2. Provide opportunity for gametic

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Question 24.
Enumerate the major steps of isolation of DNA.
Major steps for isolation of DNA

  1. Cell containing DNA is treated with lysozyme or cellulose or chitinase
  2. DNA along with RNA, Protein, lipid are released
  3. Treatment with RNAase, protease to remove RNA and Protein
  4. Appropriate treatment to remove other impurities
  5. Addition of chilled ethanol to get precipitation of purified DNA
  6. The fine threads of DNA can be collected by centrifugation

Question 25.
A child has blood group O. If the father has blood B and mother has blood group B. Work out the genotypes of the parents and the possible genotypes of the other offspring.
2nd PUC Biology Model Question Paper 4 with Answers 4

2nd PUC Biology Model Question Paper 4 with Answers 5
The genotype of the parents of a child having blood group O will be IAIO for male and IBIO for female in heterozygous condition.

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Question 26.
Explain carbon cycle with a suitable diagram.
The cyclic movement of carbon between the living and non living systems of the environment is called carbon cycle. It is a perfect gaseous cycle. Its reservoir pool is atmosphere, which is used and repleni shed continuously by living organisms through activities like photosynthesis, respiration and decomposition.
2nd PUC Biology Model Question Paper 4 with Answers 6
Sources : Carbon is present in the air in the form of carbon dioxide, its concentration is very low (0.0032%), burning of fossils fuels like petrol, diesel, peat, coal adds large amounts of CO2 into the atmosphere. The decomposition of dead bodies of plants and animals also release CO2 to the atmosphere.

Atmosphere and hydrosphere are the cycling pool,where as lithosphere is the reservoir pool, therefore, a large amount of fixed carbon is used by marine zooplanktons to make calcium carbonate shells, these are not eaten or decomposed easily, they sink to the bottom and form carboniferous rocks (chalk, limestone), about 99% of carbon is stored in this form, therefore, ocean acts as global sink of CO2.

Circulation: The CO2 present in the atmosphere is used by plants for photosynthesis, during this process CO2 is converted into carbohydrates. Some amount of glucose is used by plants during their respiration and the rest is converted into biomass (starch and fats) and stored as reserved food materials. These organic compounds containing carbon enter animals as food which are digested and absorbed. The absorbed organic nutrients are used to build their body mass.

Some amount of organic matter is also used by animals in respiration and CO2 is released to the atmosphere after the death of plants and animals, the bodies are decomposed by decomposers like bacteria and helps in releasing back CO2 to the atmosphere. This cyclic movement of carbon dioxide between plants, animals and back to atmosphere is called carbon cycle.

Part – D

Section – I

IV. Answer any FOUR of the following questions oh 200 – 250 words each, wherever applicable. ( 4 × 5 = 20 )

Question 27.
What are contraceptives? Mention the characters of an ideal contraceptive. Briefly describe the natural methods of birth control.

Question 28.
What is sex determination? Explain XX XY method of sex determination in human beings.
The procedure by which the reason for the development of male and female is known in animals is called sex determination.

Sex determination in human beings is of male: heterogametic type, both male and females have the same number of chromosomes but vary in their gamete production. Females are homogametic with XX chromosomes; they produce ova haying X chromosome which are similar, but males are heterogametic with X and Y chromosomes.

They produce two kinds of sperms X and Y, 50% of the sperms carry X chromosome while the rest 50% carry Y chromosome, such a sex which produces two types of gametes is called heterogametic type.

The sex of the offspring largely depends on the sperm that fertilizes the ovum. When sperm with X chromosome fertilizes the egg having X chromosome, the zygote with XX develops into female on the other hand sperm carrying Y chromosome fertilize the egg having X chromosome develops into male.
2nd PUC Biology Model Question Paper 4 with Answers 11

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Question 29.
What is DNA finger printing? Describe the various steps involved in the technique of DNA fingerprinting.
DNA finger printing is a technique used for determining the nucleotide sequences of certain regions of DNA which are unique.to each individual and distinguishes him or her more exactly from others. Using DNA for distinguishing and identification of individuals is called DNA finger printing. It works on the principle of polymorphism in DNA sequences.

Various steps involved the technique of DNA fingerprinting

  1. The isolation of the desired DNA from small amounts of blood, semen or other cells of body.
  2. The digestion of DNA by restriction endonuclease enzyme.
  3. The blotting of separate DNA fragments to synthetic membrane e.g., nylon or nitrocellulose membranes.
  4. The hybridization by use of labelled VNTR probe (mini satellite).
  5. By autoradiography, the detection of hybridised DNA fragments is done.

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Question 30.
What is noise pollution? Mention its causes, effects and preventive measures.
Noise pollution:
A loud unpleasant or unwanted sound is called noise.

Sources of noise pollution

  • The sonic boom produced by air crafts, Jet plane is the extreme cause of noise pollution.
  • Textile mills and printing presses, agricultural machines, defense equipments, transport vehicles, public address system, use of crackers on festive occasions. Operations such as blasting, crushing, construction work are other sources of noise pollution.

Effects of Noise Pollution

  • It is harmful and causes psychological and physiological disorders in human beings.
  • Exposure to extremely loud noise like explosion, sounds of jet plane or rockets damage ear drums; this may cause permanently impairing hearing ability.
  • It also causes sleeplessness, increased heartbeat, headache, anxiety, stress, etc.

Prevention of noise pollution

  • Use of loud speakers and amplifiers should be restricted to a fixed intensity and fixed hours of the day.
  • Delimitation of horn free zones around hospitals, schools, etc.
  • Noise producing industries, railway stations, aerodromes should be located away from human settlements.
  • Noisy machines should be installed in sound proof chambers.
  • Motor vehicles noise can be reduced by planting many rows of trees.
  • Occupational exposure can be reduced by using ear muffs or cotton plugs.

Question 31.
Explain the structure of T.S of mature anther with a neat labeled diagram.
Stamens are the male reproductive units of a flower. Each stamen is composed of an anther arid filament; Anther consists of microsporangium, pollen grains which contribute male gametes are formed within microsporangium present in anther.

A typical anther consists of column of sterile tissue called connective and anther lobes on either side. Each anther lobe bears two pollen chambers also called microsporangia. Thus, dithecous anther consists of 4 pollen sacs or micro sporanga.

Anther at maturity consists of sporogenous tissue covered by anther wall which is made up of epidermis, endothelium, middle layer and tapetum.

2nd PUC Biology Model Question Paper 4 with Answers 8

Epidermis: It is the outmost covering of the anther wall, single layered and protective in function.

Endothelium: It lies below the epidermis. The cells of the endothelium are radially elongated with fibrous thickenings. These cells are hygroscopic and when they lose water they contract as a result anther dehisces which helps in the release of pollen grains.

Middle layers: Two to three layered cells present below the endothelium constitute middle layers. The cells of the middle layer store food materials.

Tapetum: It is the inner most layer of the anther wall and surrounds the sporogenous tissue. The cells have dense cytoplasm and prominent nuclei. Tapetum is nutritive in function which supplies nutritive materials to developing sporogenous tissue.

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Question 32.
What is apiculture? Mention the types of honey bees in a honey bee colony. Add a note on the economic importance of apiculture.
The practice of rearing honey bees for honey and wax is called apiculture. It is also called Bee keeping.

There are three castes in honey bee colony.

  1. Queen (fertile female)
  2. Drones (fertile males)
  3. Workers (sterile females)

Economic importance

  • Honey collected from honey combs is a good nourishing food, it is a sweet syrup contains sugars like levulose (41%), fructose (38%), glucose (31%), maltose, it contains vitamins like ascorbic acid (vitamin c), niacin (B3), riboflavin (B2), thiamine (B1), and minerals (Fe, Cu, mn, mg, Na, k ca p)
  • Honey is a good antiseptic, laxative expectorant, blood purifier and chief source of energy.
  • Honey is used in the preparation of jellies, Jams, cakes, etc.
  • Bees wax secreted from the abdominal wax glands is used in manufacture of polishes, candle, etc.
  • Bee venom is used in the treatment of disease like rheumatoid arthritis
  • Honey bees are best natural pollinators.

Section – II

Answer any THREE of the following questions in 200 – 250 words each, wherever applicable. (3 × 5 = 15 )

Question 33.
What is biocontrol? Name the principle behind biological method of pest control. Mention examples of bio control agents and their function.
It is the use of micro organisms to control or eliminate insect pests. The micro organisms employed in biological control are called bio control agents.

It is based on prey – predator relationship.

1. Ladybird and Dragon flies useful to get rid of aphids and mosquitoes.

2. Bad llus thuringiensis (Bt) is used to control butterfly caterpillar. Spores available in sachets are mixed with water and sprayed on plants, eaten by insect larva, toxin released in gut kills larvae.
Example: Bt toxin genes are introduced into cotton plants and made resistant to insect pests such as cotton boll worms, stem borer, aphids and beetles.

3. Nucleo polyhedrovirus ( NPV) is a virus suitable for narrow spectrum insecticide applications. It has no negative impacts on plants, mammals, birds, fish or target insects. It is suitable for overall integrated pest Management programme (IPM) in ecologically sensitive areas.

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Question 34.
What is genetic code? Enumerate the characteristics of genetic code.
Genetic code is a sequence of three nucleotides on DNA or mRNA, codes for a specific amino acids for protein synthesis.

Features of Genetic code

  • Genetic code is triplet: Each codon consists of sequence of three nitrogen bases.
  • Genetic code is universal: A particular codon codes for the same amino acid in all organisms.
  • Genetic code is non overlapping: The successive triplet codons are read in order without overlapping and they do not share any base.
  • Genetic code is degenerate: A single amino acid is coded by more than one codon.
    Example : valine is coded by 4 different codons GUA, GUC, GUU and GUG
  • Genetic code is commaless: Codons are without punctuation and written in linear form. There is no signal to indicate the end of one codon or beginning of the next codon.
  • Genetic code is non-ambiguous: Each codon specifies a particular amino acid in all organisms.
    Example : AUG codes for methionine .
  • Initiator codons: Protein synthesis is always initiated by particular codons called initiator codons.
    Example : AUG in eukaryotas, GUG in prokaryotes
  • Terminator codons: Three codons that act as stop signals to terminate protein synthesis are called terminator codons or nonsense codons.
    Example: UAA (Ochre), UGA (Amber) and UGA (Opal).

Question 35.
Explain the role of microbes as biofertlizers.
Biofertilizers are organisms which are used to enhance the fertility of the soil and availability of nutrients like nitrogen and phosphorus to the crops.

There are three types of bio fertilizers

  1. Bacteria, (Rhizobium Azotobacter).
  2. Cyanobacteria or Blue green algae (Anabaena Nostoc).
  3. Fungi (Mycorrhizae like glomus, VAM).

1. Free living nitrogen fixing bacteria
They fix atmospheric nitrogen in the soil and made available to plants.
Example: The best example is Azotobacter.

2. Symbiotic nitrogen fixing bacteria
These bacteria show symbiotic association with the root nodules of leguminous plants. They convert atmospheric nitrogen and made available to plants.
Example : Rhizobium the most important symbiotic nitrogen fixing bacteria.
Frankia, mycelia bacterium (actinomycetes) shows symbiotic association with the root nodules of several non leguminous plants like casurina, rubus etc.

3. Free living nitrogen fixing cyanobacteria
Cyanobacteria are group of autotrophic microbes also called Blue green algae (BGA), they help in nitrogen fixation in paddy fields. These are extremely low cost biofertilizers.
Example: Anabaena, Nostoc.

4. Symbiotic nitrogen fixing cyanobacteria.
These nitrogen fixing cyanobacteria lead symbiotic mode of life with several plants like cycas roots, lichens, liver worts, Azolla (fern)
Example : Anabaena and Nostoc in the corolloid roots of cycas.

5. Mycorrhizae
The symbiotic association of fungus with the roots of higher plants is called mycorrhizae.
Example : Glomus species fix phosphorus in the soil and made available to plants.

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Question 36.
Explain J shaped or Exponential growth curve.
This kind of growth is often observed in bacterial population some bacteria devide once in 22-30 minutes under optimal conditions (2, 4, 8, 16, every 20 minutes.)
2nd PUC Biology Model Question Paper 4 with Answers 9
Exponential growth is a pattern of growth in which the population density after the initial establish ment phase ( lag phase) increases rapidly in an exponential or logarithmic form, but then stops abruptly as environmental resistance (e.g. seasonality) or some other factor suddenly becomes effective. This type of population growth is termed ‘density-independent’ as the regulation of growth rate is not tied to the population density until the final crash; Population numbers typically show great fluctuation as seen in algal blooms resulting in a J-shaped growth curve when population size is plotted over time.
The equation for exponential population growth is dN/dt = rN
dN/dt = rN (with a definite limit on N)
The intrinsic growth rate (r) is the difference between the birth rates (b) and death rates (d) percapita (r = b – d).
N =is the number of individuals in the population,
t = time,
r = is a constant representing the intrinsic rate of increase (biotic potential) of the organism.

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Question 37.
What is oogenesis? Explain oogenesis with a schematic representation.
The process of formation of ovum is called oogenesis.
It occurs in the ovary . Each ovary is lined by germinal epithelium. At the time of gamete formation, some cells of the germinal epithelium will become active and detach from the epithelium and then enters into the cortex start dividing mitotically to produce large number of primordial germ cells (2n). The primordial cells pass through three phases before they transform into the ovum.

1. Multiplication phase
The primordial germ cells undergo repeated mitotic divisions to produce large number of cells; each cell is called oogonia or egg mother cell (2n).
2nd PUC Biology Model Question Paper 4 with Answers 10
2. Growth phase
In this phase egg mother cells grow in size due to synthesis and accumulation of food materials and these enlarged oogonial cells are called primary oocytes (2n).

3. Maturation phase
The primary oocyte undergoes first meiotic division to produce two unequal sized cells, which are haploid (n), a large cell with more amount of cytoplasm is called secondary oocyte and a small cell with negligible amount of cytoplasm is called primary polar body (polocyte).

The secondary oocyte and primary polar body undergo second meiotic division which is also unequal as a result; secondary oocyte produces one large cell and a smaller cell; larger cell is called ootid which develops into ovum. The smaller cell called secondary polar body and primary polar body produces two secondary polar bodies. Thus, in oogenesis, primary oocyte produces one ovum and three polar bodies. The polar bodies disintegrate later.

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