1st PUC Biology Model Question Paper 1 with Answers

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Karnataka 1st PUC Biology Model Question Paper 1 with Answers

Time: 3.15 Hours
Max Marks: 70

General Instructions:

1. The question paper consists of four parts A, B, C and D
2. All the parts are compulsory.
3. Draw diagrams wherever necessary. Unlabelled diagrams or illustration do not attract any marks.

Part – A

Answer the following questions in one word or one sentence each: ( 1 × 10 = 10 )

Question 1.
Define metabolism
Answer:
Sum total of all the chemical reactions occurring in the cell of an organism.

Question 2.
What are taxonomic aids?
Answer:
The tools or devices or procedures used in the study of taxonomy.

Question 3.
What is venation?
Answer:
The arrangement of veins and veinlets in the leaf lamina.

Question 4.
Why does enzyme activity decrease at high temperature?
Answer:
Due to denaturation of proteins.

Question 5.
How does diffusion differ from active transport?
Answer:
Diffusion differ from active transport as it occurs across the gradient and do not require metabolic energy.

Question 6.
Define apoplast
Answer:
It is a system of adjacent cell walls that is continuous throughout the plant except the casparian strips of the endodermis in the root.

Question 7.
What is transpiration?
Answer:
The evaporative loss of water by plants.

Question 8.
What is nitrogen fixation?
Answer:
The process of conversion of nitrogen to ammonia.

Question 9.
Define the codont
Answer:
Tooth is embedded in the socket of jaw bone.

Question 10.
What is tetany?
Answer:
Rapid spasms in muscle due to calcium in body fluid.

Part – B

Answer any five of the following questions in 3-5 sentences each wherever applicable: ( 2 × 5 = 10 )

Question 11.
What is binomial nomenclature? Mention any two taxonomic categories
Answer:
The system of providing a name with two components is called binomial nomenclature.
Species, genus, family, order, class, division, phylum, kingdom.

Question 12.
Draw a neat labeled diagram of TMV
Answer:

Question 13.
What are bilateral and radial symmetry?
Answer:
Bilateral symmetry – The body can be divided into identical left and right halves in only one plane.

Radial symmetry – The body can be divided into equal halves in any plane passing through the central axis of the body.

Question 14.
Write any two characters of collenchyma
Answer:

1. Cells may be oval, polygonal or spherical
2. Cell wall is thicker due to deposition of cellulose, hemi cellulose and pectin.
3. Inter cellular spaces are absent
4. Cells may have chloroplast

Question 15.
What are radial and conjoint vascular bundles?
Answer:
The xylem and phloem within a vascular bundles are arranged in an alternate manner on different radii is called radial vascular bundle.
The xylem and phloem are situated at the same radius of the vascular bundles is called conjoint.

Question 16.
Write any two features of metaphase
Answer:

1. Spindle fibres are attached to kinetochores of chromosomes.
2. Chromosomes are moved to spindle equator and get aligned along metaphase plate through spindle to both poles.

Question 17.
How are the mycorrhizal association help in absorption of water and minerals in plants?
Answer:
The fungal filaments form a network around the young root or they penetrate the root cells.
The hyphae have a very large surface area that helps in the absorption of water and mineral ions from the soil

Question 18.
Name any two cells of gastric glands and their secretions
Answer:
Peptic or chief cells – pepsinogen
Parietal or oxyntic cells – HCl
Mucus neck cells – mucus

Part – C

Answer any five of the following questions in 100 – 150 words each: ( 3 × 5 = 15 )

Question 19.
Draw a neat labeled diagram of nucleus
Answer:

Question 20.
What are enzymes? Mention any two types
Answer:
Enzymes are the biocatalyst that catalyzes biochemical reactions in the cells.

• Oxido-reductases
• Transferases
• Isomerases
• Ligases
• Lyases
• Hydrolases

Question 21.
Give the diagrammatic view of cell cycle

Question 22.
Define the following terms: a) Antiport b) Plasmolysis c) Imbibition
Answer:
a) Antiport – When both the molecules cross the membrane in the same direction.
b) Plasmolysis – Shrinkage of protoplast due to exosmosis.
c) Imbibition – A specialized type diffusion when water is absorbed by solids -colloids causing them to increase in volume.

Question 23.
Enlist the criteria for essentiality of mineral nutrients in plants
Answer:

• Absolutely necessary
• Specific and not replaceable
• Directly involved in the metabolism

Question 24.
How does haemodialysis help in purifying the blood?
Answer:

• In kidney failure patients’ urea can be removed by a process called hemodialysis.
• Blood drained from a convenient artery is pumped into a dialyzing unit after adding heparin.
• The unit contains coiled cellophane tubes surrounded by dialyzing fluid having the same composition as that of plasma except nitrogenous wastes.
• The porous cellophane membrane of the tube allows the passage of the molecules based on the concentration gradient.
• As nitrogenous wastes are absent in dialyzing fluid, these substances freely move out there by clearing the blood.
• The purified blood is pumped back through a vein after adding anti-heparin to it.

Question 25.
Explain the structure of actin filament
Answer:

• Each actin (thin) filament is made of two ‘F’ (filamentous) actins helically wound to each other. Each ‘F’ actin is a polymer of monomeric ‘G’ (Globular) actins.
• Two filaments of another protein, tropomyosin also run close to the ‘F’ actins throughout its length.
• A complex protein Troponin is distributed at regular intervals on the tropomyosin.

Question 26.
Mention the physiological effects due to:
a) Deficiency of Growth hormone
b) Deficiency of iodine
c) Deficiency of insulin
Answer:
a) Low secretion of growth hormone – Pituitary dwarfism
b) Deficiency of iodine – hypothyroidism/goitre
c) Deficiency of insulin – Diabetes mellitus

Part – D

Section – I

Answer any four of the following questions in 200 – 250 words each wherever applicable: ( 5 × 4 = 20 )

Question 27.
Enumerate any five characteristic features of Gymnosperms
Answer:

• The gymnosperms are naked seeded plants
• Gymnosperms include medium-sized trees or tall trees and shrubs.
• Roots in some genera have fungal association in the form of mycorrhiza (Pinus), while in some others (Cycas) small specialized roots called coralloid roots are associated with N2- fixing cyanobacteria.
• The stems are unbranched (Cycas) or branched (Pinus, Cedrus).
• The leaves may be simple or compound.
• The leaves in gymnosperms are well-adapted to with stand extremes of temperature, humidity and wind.
• In conifers, the needle-like leaves reduce the surface area.
• Their thick cuticle and sunken stomata also help to reduce water loss.
• The gymnosperms are heterosporous; they produce haploid microspores and megaspores.
• The two kinds of spores are produced within sporangia that are borne on sporophylls which are arranged spirally along an axis to form lax or compact strobili or cones.
• The strobili bearing microsporophylls and microsporangia are called microsporangiate or male strobili. The microspores develop into a male gametophytic generation which is highly reduced and is confined to only a limited number of cells.
• The cones bearing megasporophylls with ovules or megasporangia are called macrosporangiate or female strobili.

Question 28.
Draw a neat labeled diagram of male reproductive system of frog
Answer:

Question 29.
a) Write the functions of:
i) Chloroplast ii) Cytoskeleton iii) Centrosome
Answer:
i) Chloroplast – Photosynthesis
ii) Cytoskeleton – Mechanical support/Motility/Maintenance of the cell shape
iii) Centrosome – Spindle apparatus formation during cell division/Basal body of cilia or flagella

b) Enlist the organs involved in endomembrane system.
Answer:

• Endoplasmic reticulum
• Golgi bodies
• Lysosomes
• Vacuole

Question 30.
Explain the stages of Calvin cycle
Answer:
The Calvin cycle can be described under three stages: carboxylation, reduction and regeneration.
1. Carboxylation – Carboxylation is the fixation of CO₂ into a stable organic intermediate. Carboxylation is the most crucial step of the Calvin cycle where CO₂ is utilised for the carboxylation of RuBP.

This reaction is catalysed by the enzyme RuBP carboxylase which results in the formation of two molecules of 3-A. Since this enzyme also has an oxygenation activity it would be more correct to call it RuBP carboxylase-oxygenase or RuBisCO.

2. Reduction – These are a series of reactions that lead to the formation of glucose. The steps involve utilisation of 2 molecules of ATP for phosphorylation and two of NADPH for reduction per CO₂ molecule fixed. The fixation of six molecules of CO₂ and 6 turns of the cycle are required for the removal of one molecule of glucose from the pathway.

3. Regeneration – Regeneration of the CO₂ acceptor molecule RuBP is crucial if the cycle is to continue uninterrupted. The regeneration steps require one ATP for phosphorylation to form RuBP.

Question 31.
a) Classify plants based on photoperiodism
Answer:

• Long day plants – the plants in which the flowering requires the exposure of light for a period exceeding a well defined critical duration
• Short day plants – the flowering in plants require the exposure of light for a period less than a well defined critical duration
• Day-neutral plants – the flower induction occur in these plants irrespective of the critical duration of light exposure

b) Mention any two physiological roles of Gibberellins
Answer:

• Their ability to cause an increase in length of axis is used to increase the length of grapes stalks.
• Gibberellins, cause fruits like apple to elongate and improve its shape.
• They also delay senescence.
• Thus, the fruits can be left on the tree longer so as to extend the market period. GA3 is used to speed up the malting process in brewing industry.
• Spraying sugarcane crop with gibberellins increases the length of the stem, thus increasing the yield by as much as 20 tonnes per acre.
• Spraying juvenile conifers with GAs hastens the maturity period, thus leading to early seed production.
• Gibberellins also promotes bolting (internode elongation just prior to flowering) in beet, cabbages and many plants with rosette habit.

Question 32.
Explain the mechanism of breathing.
Answer:

• Breathing involves two stages : inspiration during which atmospheric air is drawn in and expiration by which the alveolar air is released out.
• The movement of air into and out of the lungs is carried out by creating a pressure gradient between the lungs and the atmosphere.
• Inspiration can occur if the pressure within the lungs (intra-pulmonary pressure) is less than the atmospheric pressure, i.e., there is a negative pressure in the lungs with respect to atmospheric pressure.
• Similarly, expiration takes place when the intra-pulmonary pressure is higher than the atmospheric pressure.
• The diaphragm and a specialised set of muscles – external and internal intercostals between the ribs, help in generation of such gradients.
• Inspiration is initiated by the contraction of diaphragm which increases the volume of thoracic chamber in the antero-posterior axis.
• The contraction of external inter-costal muscles lifts up the ribs and the sternum causing an increase in the volume of the thoracic chamber in the dorso-ventral axis.
• The overall increase in the thoracic volume causes a similar increase in pulmonary volume. An increase in pulmonary volume decreases the intra-pulmonary pressure to less than the atmospheric pressure which forces the air from outside to move into the lungs, i.e., inspiration.
• Relaxation of the diaphragm and the inter-costal muscles returns the diaphragm and sternum to their normal positions and reduce the thoracic volume and thereby the pulmonary volume.
• This leads to an increase in intra-pulmonary pressure to slightly above the atmospheric pressure causing the expulsion of air from the lungs, i.e., expiration .

Part – D

Section – II

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

Question 33.
Write any five differences between chondricthyes and osteichthyes
Answer:
Chondrichthyes:

• They are marine animals with streamlined body
• Cartilaginous endoskeleton.
• Mouth is located ventrally.
• Gill slits are separate and without operculum (gill cover)
• The skin is covered by minute placoid scales.
• Due to the absence of air bladder, they have to swim constantly to avoid sinking.
• They are mostly viviparous
• Fertilization is internal

Osteichthyes:

• It includes both marine and fresh water fishes
• Bony endoskeleton.
• Mouth is mostly terminal.
• The gills are covered by an operculum on each side.
• Skin is covered with cycloid/ctenoid scales.
• Air bladder is present which regulates buoyancy.
• They are mostly oviparous
• Fertilization is external

Question 34.
Mention the types of placentation with an example each

• Marginal – Pea, beans,
• Axile – China rose/tomato/lemon
• Parietal – mustard/Argemone
• Free central – Dianthus/Primrose
• Basal – Sunflower/Marigold

Question 35.
Explain anaerobic respiration
Answer:

• In fermentation, say by yeast, the incomplete oxidation of glucose is achieved under anaerobic conditions by sets of reactions where pyruvic acid is converted to CO2 and ethanol.
• The enzymes, pyruvic acid decarboxylase and alcohol dehydrogenase catalyse these reactions.
• Other organisms like some bacteria produce lactic acid from pyruvic acid.
  In animal cells also, like muscles during exercise, when oxygen is inadequate for cellular respiration pyruvic acid is reduced to lactic acid by lactate dehydrogenase.
• The reducing agent is NADH+H+ which is reoxidised to NAD+ in both the processes.

Question 36.
Draw a neat labeled diagram of section of human heart
Answer:

Question 37.
Explain the pathway of reflex action
Answer:
The sudden withdrawal of a body part which comes in contact with objects that are extremely hot, cold pointed or animals that are scary or poisonous.

The entire process of response to a peripheral nervous stimulation, that occurs involuntarily, i.e., without conscious effort or thought and requires the involvement of a part of the central nervous system is called a reflex action.
The reflex pathway comprises at least one afferent neuron (receptor) and one efferent (effector or excitor) neuron appropriately arranged in a series.

The afferent neuron receives signal from a sensory organ and transmits the impulse via a dorsal nerve root into the CNS (at the level of spinal cord). The efferent nueuron then carries signals from CNS to the effector. The stimulus and response thus forms a reflex arc.