Assertion-Reasoning Type Questions

Assertion. Human red blood cells are circular and biconcave.

Reason. This shape prevents the easy passage of these cells through blood capillaries.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
The disc like shape of red blood cells i.e., circular and biconcave shape helps it to easily pass through the blood capillaries.

Assertion. Nucleolus does not produce ribosomes.

Reason. Nucleolus participates in protein synthesis by forming and storing R.N.A.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
The nucleolus is primarily responsible for producing and assembling ribosomes. It contains the genes that encode ribosomal RNA (rRNA). The ribosomes serve as site of protein synthesis.

Assertion. Iodine solution makes the nucleus more distinct.

Reason. Nucleus contains starch which becomes blue-black upon absorbing the iodine solution.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False

Explanation
Iodine solution is a common stain used in microscopy to enhance the visibility of certain cellular structures, including the nucleus.
The enhanced visibility of the nucleus with iodine staining is not due to the presence of starch. Instead, iodine binds to various cellular components, including nucleic acids, making the nucleus more visible under a microscope.

Assertion. Cell membrane is freely permeable.

Reason. Cell membrane permits free movement of the solutions across the membrane when two solutions of different tonicity are separated through it.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

Both A and R are False.

Explanation
A cell membrane is semi-permeable. It selectively allows the passage of some molecules while preventing others. Solutions of different tonicity will result in osmotic movement of water, but not necessarily the free movement of solutes across the membrane.

Assertion. Scattered Golgi body in animal cells are called as 'dictyosomes'.

Reason. Plant cells have dictyosomes because the entire central space is occupied by a large vacuole.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Scattered Golgi body in plant cells are called as 'dictyosomes'. Plant cells have dictyosomes because the entire central space is occupied by a large vacuole. They play a role in cell plate formation during cell division.

Assertion. The basic structural unit of DNA is nucleotide.

Reason. DNA is composed of repeating nucleosome which are made up of three components - pentose sugar, phosphate group and nitrogenous bases.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
DNA is composed of repeating nucleosome which are made up of nucleotide and histone proteins. Nucleotide are composed of pentose sugar, phosphate group and nitrogenous bases.

Assertion. Centrosome is the point of attachment of two chromatids of a chromosome.

Reason. Centrosome initiates and regulates the process of cell division as it helps in the formation of spindle fibres.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Centromere is the point of attachment of two chromatids of a chromosome. Centrosomes or centrioles are structures present in cell that initiate and regulate cell division.

Assertion. Meiosis is the kind of cell-division which occurs during gamete formation in the gonads.

Reason. During meiosis, chromosome number remains the same in parent cell and daughter cells which is very significant to maintain the identity of the organism.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
During meiosis, chromosome number is halved. During fertilisation, two haploid gametes/cells fuse to restore normal chromosome count.

Assertion. Heredity is the basic fundamental unit of Genetics.

Reason. Genes carry hereditary information from the offsprings to their parents.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
Genes do not carry hereditary information from offspring to parents. Instead, genes are the carriers of hereditary information from parents to offspring.

Assertion. Karyotype is the division of nucleus during cell-division.

Reason. Karyon means nucleus and type explains the number, shape and size of the chromosome.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Karyokinesis is the division of nucleus during cell-division. Karyotype is a picture showing all chromosome pairs arranged according to their size and shape.

Assertion. Dominant alleles can express themselves only in homozygous condition.

Reason. Dominant alleles support recessive alleles and allow them to express, even in heterozygous condition.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

Both A and R are False.

Explanation
Dominant alleles can express themselves in homozygous as well as in heterozygous condition. Dominant alleles suppress recessive alleles and do not allow them to express in heterozygous condition.

Assertion. Genotype is the genetic make up of a cell.

Reason. Phenotype is the set of genes present in the cells of an organism that expresses internal characters.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
The phenotype refers to the observable characteristics or traits of an organism.

Assertion. A daughter can resemble only her mother and not her father.

Reason. Sex chromosomes of the daughter (XX) are received from both the parents.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
A daughter can resemble her mother as well as her father because she receives genes from both the parents.

Assertion. Roots absorb water and mineral nutrients from the soil.

Reason. Soil is the storehouse of all the essential minerals for photosynthesis that are absorbed by the plant through the roots of the plant by the process of diffusion.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
Soil is the storehouse of different essential minerals but for photosynthesis, plant absorb Carbon dioxide from air.

Assertion. Diffusion is the process of free movement of liquid molecules only. It does not occur in gaseous state.

Reason. The main condition which regulates the process of diffusion is the concentration gradient and not the state of matter. It always occurs from higher to lower concentration.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Diffusion is the process of free movement of liquid as well as gas molecules.

Assertion. Translocation of prepared food material in plants always occurs through the phloem tissue in an upward direction.

Reason. Phloem is a kind of a complex permanent tissue in plants which surrounds the xylem tissue. It is present all throughout the plant-root, stem or leaves.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Translocation of prepared food material in plants always occurs through the phloem tissue in both upward and downward directions.

Assertion. Active transport does not occur through a non-living semi-permeable membrane.

Reason. Active transport is in a direction opposite to that of diffusion, i.e., from a region of lower concentration to higher concentration.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

Both A and R are True.

Explanation
Active transport does not occur through a non-living semi-permeable membrane because it requires energy (ATP) which can only be provided by living membrane.
Active transport moves molecules against their concentration gradient, from an area of lower concentration to an area of higher concentration, which requires energy input.

Assertion. Lenticels allow diffusion of gases for respiration.

Reason. Lenticels are located on the surface of older woody stems. They close during night time and open during the day for the process of transpiration.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False

Explanation
Lenticels are located on the surface of older woody stems. They remain open as they have no opening and closing mechanism like stomata.

Assertion. Transpiration decreases the amount of moisture in the atmosphere.

Reason. Forests contribute in bringing rain because of transpiration.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Transpiration increases the amount of moisture in the atmosphere. Increased moisture in atmosphere helps in rain.

Assertion. Nerium leaves have sunken stomata covered by trichomes.

Reason. Nerium is a hydrophytic plant which gets rid of excessive water through the process of transpiration.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
Nerium is adapted to dry environments and has sunken stomata and trichomes to reduce water loss. Nerium is not a hydrophytic plant (which lives in water-rich environments); it is actually a xerophytic plant adapted to arid conditions. The adaptations such as sunken stomata and trichomes help in minimizing water loss, not getting rid of excess water.

Assertion. Transpiration helps in the descent of sap by producing a suction force acting from the top of a plant.

Reason. Transpiration is the evaporative loss of water through the aerial parts (leaves, stems) of a plant. However, this loss holds much significance for the plant.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Transpiration helps in the ascent of sap by producing a suction force acting from the top of a plant.

Assertion. Photosynthesis occurs in all parts of a green plant.

Reason. Chlorophyll is the green pigment which traps solar energy during daytime.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Photosynthesis only occurs in green parts of the plant. For example, roots and non-green tissues do not perform photosynthesis.
Chlorophyll is the pigment responsible for absorbing light energy from the sun, which is then used to drive the process of photosynthesis.

Assertion. Guard cells regulate the opening and closing of the stomatal aperture.

Reason. Guard cells contain chloroplasts and are mostly located on the lower surface of the leaves. Other cells of the lower epidermis do not contain chloroplasts.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

Both A and R are True.

Explanation
Guard cells are found in the lower portion of leaf and their function is to close and open the stomata as per need. They contain chloroplasts and carry out photosynthesis.

Assertion. Palisade cells of mesophyll are loosely arranged towards the lower epidermis of a dorsiventral leaf.

Reason. Palisade cells contain the maximum amount of chlorophyll, trap solar energy and help in the process of photosynthesis.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Palisade cells of mesophyll are loosely arranged towards the upper epidermis of a dorsiventral leaf. They along with spongy tissues are engaged in photosynthesis.

Assertion. Phosphorylation occurs in all organisms only during the process of respiration.

Reason. Photophosphorylation is the process during which ADP combines with inorganic phosphate (iP) and produces ATP.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Phosphorylation, the process of adding a phosphate group to a molecule (like ADP to form ATP), occurs during both respiration and photosynthesis. In respiration, this process is called oxidative phosphorylation, while in photosynthesis, it is called photophosphorylation.

Assertion. Plants do not have sense organs but they can still respond against different stimuli.

Reason. Plants have well-developed nervous and hormonal systems which enable them to respond against sunlight, gravity and water, etc.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
Plants do not have well-developed nervous and hormonal systems which enable them to respond against sunlight, gravity and water, etc. but their remarkable ability to respond to stimuli through hormones and other mechanisms ensures their survival and adaptation to changing environments.

Assertion. Parthenocarpic fruits contain a large number of smaller seeds.

Reason. The process of development of fruits without fertilization is termed as parthenocarpy.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Parthenocarpic fruits do not contain seeds as they are formed without fertilization.

Assertion. Auxin is a growth-retarding plant hormone.

Reason. Auxins are mainly synthesized in shoot apical meristems and young leaves.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Auxin is a growth-promoting plant hormone. Auxins are mainly synthesized in shoot apical meristems, root apical meristem and young leaves.

Assertion. Ethylene is the only hormone which is a gas at ordinary temperature.

Reason. It helps in the ripening of fruits and is produced in the roots.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
Ethylene is produced in various tissues of plants, especially in fruits, leaves, and flowers, rather than specifically in the roots.

Assertion. Human beings have an open blood vascular system.

Reason. Blood is contained in the heart and openly flows all throughout the body via three kinds of blood vessels — arteries, veins and capillaries.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True

Explanation
Human beings have a closed blood vascular system i.e., the blood circulates in the body through blood vessels.

Assertion. The wall of left ventricle is thicker than the wall of right ventricle.

Reason. The left ventricle must generate enough force to pump oxygenated blood to the entire body, so it has thicker muscular walls compared to the right ventricle, which pumps blood to the lungs.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

Both A and R are True.

Explanation
The left ventricle needs to generate more force during contraction because it must pump blood to distant body tissues. In contrast, the right ventricle only pumps blood to the nearby lungs.

Assertion. The respiratory pigment haemoglobin (Hb) is formed of RBCs and albumin.

Reason. Haemoglobin contains an iron-containing part called haemin. It is richly found in erythrocytes.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
The respiratory pigment haemoglobin (Hb) is formed of globin protein and iron containing part called haemin.

Assertion. Lymphocytes produce antibodies and are the smallest of WBCs with a single large nucleus.

Reason. Lymphocytes contain granules in the cytoplasm. Lymphocytes release histamine.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
Basophils contain granules in the cytoplasm and release histamine.

Assertion Thrombin is the inactive form of prothrombin which is produced during blood coagulation.

Reason Vitamin K, a fat-soluble vitamin, is essential for the production of prothrombin.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False
4. A is False and R is True

Answer

A is False and R is True

Explanation
Prothrombin is the inactive form of thrombin which is produced during an injury for the purpose of blood clotting.

Assertion. Blood group 'AB' does not contain any antibody but contains both the antigens 'A' and 'B'.

Reason. In humans, WBCs have specific proteins on their surfaces. These proteins are called antibodies.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
In humans, RBCs have specific proteins on their surfaces. These proteins are called antigens.

Assertion. Kidneys eliminate urea and water only during excretion.

Reason. Urea is the most poisonous, nitrogenous waste of the body, so it must be excreted out as early as possible.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Kidneys eliminate urea and water continuously. 1-2 litres of blood passes through kidney per minute.

Assertion. Renal artery carries deoxygenated blood full of nitrogenous wastes.

Reason. Most of the arteries carry oxygenated blood, but there are exceptions.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
The renal artery carries oxygenated blood from the heart to the kidneys.
Most arteries carry oxygenated blood away from the heart, but there are exceptions such as the pulmonary artery, which carries deoxygenated blood from the heart to the lungs.

Assertion. Efferent arteriole is wider than the afferent arteriole.

Reason. The difference in the size of the diameter of these arterioles creates a high pressure known as hydrostatic pressure. This pressure helps in the process of ultrafiltration through the glomerulus.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True

Explanation
Efferent arteriole is narrower than the afferent arteriole. The difference in the size of the diameter of these arterioles creates a high pressure known as hydrostatic pressure. This pressure helps in the process of ultrafiltration through the glomerulus.

Assertion. Haematuria is the condition in which the blood passes with urine due to some infection in the urinary tract, kidney stones or tumour.

Reason. An excessive number of RBCs and haemoglobin is produced in the bone marrow. So these are excreted out through the urine.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False

Explanation
Haematuria occurs due to infection and not due to excessive production of RBCs and haemoglobin.

Assertion. Effectors are the part of our body which, on receiving stimulus, set up waves of impulses towards the central nervous system.

Reason. The specialized epithelial cells of certain organs are capable of receiving stimuli which can be light, sound, heat, pain, hunger, etc.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Effectors are muscles or gland that responds to motor nerve impulse.

Assertion. The aggregates of the cell bodies or perikaryons of neurons form the synapse.

Reason. Ganglia are the structures from which the nerve fibres may arise or enter into, whereas the synapse connects two neurons with a small gap in between.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False
4. A is False and R is True

Answer

A is False and R is True

Explanation
A synapse is a junction that allows communication between neurons (nerve cells) or between a neuron and a muscle cell or gland. The term perikaryon refers to the cell body of a neuron (or nerve cell).

Assertion. The cerebellum is the largest portion of the brain.

Reason. Cerebellum is located just at the base of the cerebrum. It maintains body balance. Cerebrum is the seat of intelligence, consciousness and will power.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True

Explanation
The cerebrum is the largest portion of the brain, not the cerebellum.
The cerebellum is located at the base of the cerebrum and plays a crucial role in maintaining body balance and coordination. The cerebrum is responsible for higher brain functions, including intelligence, consciousness, and will power.

Assertion. The protective membranous covering of the brain and spinal cord are the same, whereas the bony coverings of these are cranium and vertebral column respectively.

Reason. Since both are very delicate and sensitive organs of our body, they are protected by a three-layered membrane known as meninges.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

Both A and R are True.

Explanation
The meninges are three layers of membranes that envelop and protect the brain and spinal cord.

Assertion. The arrangement of white and gray matter is the same in both brain and spinal cord.

Reason. Gray matter consists of cell bodies of the neuron, whereas white matter contains the axons of the nerve cells. One region is termed as the cortex and the other is medulla.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True

Explanation
In the brain, the outer portion of cerebrum contains the gray matter and the inner portion of cerebrum contains the white matter. In the spinal cord, the arrangement is reversed. The gray matter lies on the inner side and the white matter on the outer side.

Assertion. The sympathetic nervous system is stimulated by the hormone thyroxine which is secreted by the thyroid gland.

Reason. Sympathetic nervous system prepares the body for violent action against abnormal conditions. Adrenaline is termed as emergency hormone.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
The sympathetic nervous system is stimulated by the hormone adrenalin which is secreted by the adrenal gland.

Assertion. Reflexes are involuntary but all involuntary actions are not reflexes.

Reason. Reflexes and involuntary actions of our body are controlled by medulla oblongata and spinal cord respectively.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
Reflexes are controlled by spinal cord and involuntary actions are controlled by medulla oblongata respectively.

Assertion. Lacrimal gland is a kind of endocrine gland which secretes an enzyme called thrombokinase.

Reason. Lacrimal gland is located in the upper outer portion of the orbit of the eye. Tears act as a lubricant and also have antiseptic property.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
The lacrimal gland is an exocrine gland located above the eyeball. It secretes lacrimal fluid (tear fluid), a watery fluid isotonic to plasma, onto the surface of the eyeball. These tears help clean, lubricate, nourish, and maintain eye health.

Assertion. Choroid layer provides nourishment to the eye and also prevents light rays form reflecting and scattering inside the eye.

Reason. Choroid layer is the outermost layer of the eyeball which surrounds the sclerotic layer. This layer contains two types of pigments-Rhodopsin and Iodopsin.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False

Explanation
Choroid layer lies between the retina and the sclera. The choroid plays a crucial role in maintaining eye health by supplying nutrients to the retina.

Assertion. The image formed on the retina is straight and real.

Reason. Images from the retina are transmitted to the brain through the optic nerve. Then brain interprets it in an upright position. Both the eyes form two images but the brain interprets them as one due to the overlapping of the images.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
The image formed on the retina is actually inverted (upside down) and real.
The brain receives inverted images from the retina through the optic nerve and then processes and interprets these images as upright. Additionally, the brain merges the two slightly different images from each eye into a single cohesive image due to the overlapping visual fields.

Assertion. Myopia is caused due to the shortening of the eyeball from front to back.

Reason. Myopia can be corrected by using suitable convex (converging) lens and the power of the glasses used is mentioned in plus "+".

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

Both A and R are False.

Explanation
Myopia is caused due to the lengthening of the eyeball from front to back or if the lens is too curved. It can be corrected by suitable concave (diverging) lens and the power of the glasses used is mentioned in minus "-".

Assertion. Semi-circular canals are present in the middle ear and they contain sensory cells responsible for the static balance of the body.

Reason. One end of each of the three semi-circular canals is widened to form an ampulla which contains the sensory cells for dynamic balance.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True

Explanation
Semi-circular canals are present in the inner ear and they contain sensory cells responsible for the dynamic balance of the body.

Assertion. The tube/canal which transmits the air currents from the pinna to tympanum is termed as eustachian tube.

Reason. The eustachian tube equalizes the air pressure on either side of the ear drum allowing it to vibrate freely.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True

Explanation
Eustachian tube connects the cavity of the middle ear with the throat.

Assertion. The human ear is responsible for hearing, dynamic equilibrium and also static balance.

Reason. Cochlea, semi-circular canals and vestibule (utriculus and sacculus) are responsible for hearing, dynamic balance and static balance respectively.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

Both A and R are True.

Explanation
The inner ear contains the vestibular apparatus, which includes the vestibule and semicircular canals. These structures help maintain postural equilibrium.

Assertion. Hormones are the secretions from some glandular parts of the body which regulate certain physiological processes by chemical means.

Reason. Hormones are directly poured into the target organs which are usually very close to the source/gland secreting the hormones.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
Hormones are directly poured into the blood. The blood transports it to the target organ.

Assertion. Adrenal medulla secretes glucocorticoids which regulate glucose levels of the blood.

Reason. Glucocorticoids, a kind of cortisone, stimulate the deposition of extra glucose in blood as glycogen in the liver and muscles. The roles of insulin and glucocorticoids are the same.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

Both A and R are False.

Explanation
Adrenal cortex secretes glucocorticoids which regulate glucose levels of the blood. Glucocorticoids help regulate blood glucose levels by promoting gluconeogenesis.

Assertion. Oversecretion of insulin causes hyperglycemia or diabetes mellitus.

Reason. Oversecretion of insulin can lead to hypoglycemia by casuing excessive uptake of glucose from the blood into the cells, which in turn can lead to increased insulin resistance and ultimately result in hyperglycemia or diabetes mellitus.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True

Explanation
Under-secretion of insulin causes hyperglycemia or diabetes mellitus.

Assertion. Cretinism is a condition which affects adults causing dwarfism and mental retardation.

Reason. Cretinism is a kind of hypothyroidism. This disease occurs due to the defective development, or early atrophy (degeneration), of the thyroid.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Cretinism is a condition which affects children causing dwarfism and mental retardation. The thyroid gland degenerates in early childhood.

Assertion. The placenta is a vital organ during pregnancy, responsible for providing nutrients and oxygen to the developing foetus.

Reason. The placenta develops from the fusion of the zygote and the endometrial lining, forming a specialized tissue structure that facilitates the exchange of substances between the maternal and foetal bloodstreams.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

Both A and R are True.

Explanation
The placenta begins developing from the blastocyst shortly after implantation. The placenta connects to the fetus via the umbilical cord.

Assertion. Leydig cells produce oestrogen and progesterone.

Reason. Leydig cells are also called as interstitial cells which are located as packing tissues between the coils of seminiferous tubules.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Leydig cells, also known as interstitial cells, primarily produce testosterone, not oestrogen and progesterone. Oestrogen and progesterone are mainly produced by the ovaries in females.

Assertion. Prostate gland pours an alkaline secretion which neutralizes the acidic pH of the vagina.

Reason. Prostate gland is a lobulated gland located between the posterior surface of the urinary bladder and the rectum.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
Prostate gland is a bilobed gland located below the bladder and surrounds the urethra.

Assertion. Fertilization of the ovum and sperm occurs in the sperm duct of the female reproductive system.

Reason. Vas deferens carries sperms from the epididymis to the urethra of the male reproductive system.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Fertilization of the ovum and sperm occurs in the fallopian tube of the female reproductive system.

Assertion. Lamarck's theory of inheritance of acquired characters is mainly based on "survival of the fittest".

Reason. Lamarck has explained his principle of 'use and disuse' with the example of Giraffe's neck.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
"Survival of the fittest" is a concept associated with Darwin's theory of natural selection, not Lamarck's theory. Lamarck's theory is based on the idea that characteristics acquired during an organism's lifetime can be passed on to its offspring.
Lamarck used the example of the giraffe's neck to illustrate his principle of 'use and disuse,' suggesting that giraffes stretched their necks to reach higher leaves, and this trait was then passed on to their offspring.

Assertion. The analogous organ to the vermiform appendix in herbivorous mammals is quite helpful in digesting cellulose. But it is considered a vestigial organ in humans.

Reason. Vermiform appendix is a wide worm-like tubular structure, projecting from the blind part of the colon (a part of large intestine). Its function is the same as that of the colon, i.e., absorption of water and some remnants of digested food.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
Vermiform appendix is a small and narrow worm-like tubular structure, projecting from the blind part of the colon. It is a vestigial organ in humans having no function.

Assertion. The theory of natural selection, proposed by Charles Darwin, is a fundamental mechanism driving human evolution.

Reason. Natural selection operates through the preservation of favourable variations that enhance an organism's ability to survive and reproduce, leading to the gradual adaptation of populations to their environments over time.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

Both A and R are True.

Explanation
Natural selection is the differential survival and reproduction of individuals due to differences in their phenotypes (observable traits). It is a crucial mechanism of evolution, leading to changes in inheritable traits within populations over generations.

Assertion. Population density is the number of individuals in an area of 100 square kilometers per year.

Reason. Population density gives us an idea of all the living organisms of different species in a particular area every year.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

Both A and R are False.

Explanation
Population density is the number of individuals per square kilometer. It gives an idea of average number of individuals of a species living in an area.

Assertion. Tubectomy is a temporary method of contraception for males in which the sperm ducts are cut and ligated with a nylon thread.

Reason. Tubectomy closes the passage of the sperms. The sperm duct is also known as vas deferens, which stores the sperms for some days during which they mature and become motile.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

Both A and R are False.

Explanation
Tubectomy, also known as female sterilization, is a surgical procedure that involves blocking or sealing a woman’s fallopian tubes to prevent the eggs from reaching the uterus. It is a permanent method of contraception.

Assertion. Fossil fuels are renewable and non-conventional sources of energy.

Reason. The underground reserves of coal and petroleum are depleting fast. People should look at other non-conventional sources of energy like solar energy, tidal energy, etc. for their use.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is False and R is True.

Explanation
Fossil fuels are non-renewable or conventional sources of energy. They are limited in amount.

Assertion. Pesticides are the chemical substances used in agriculture to destroy pests.

Reason. DDT is an example of a pesticide which is widely used all over India. Pests are the enemies of crop.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
DDT was banned for agricultural use in India in 1972.
Currently, the sole consumer of DDT in India is the Ministry of Health and Family Welfare, which utilizes it to control vector-borne diseases by spraying it on walls in houses and buildings affected by malaria in both rural and urban areas.

Assertion. Ozone layer is a sort of sunscreen present high up in the atmosphere which prevents the harmful ultra-violet rays of the sun from harming us.

Reason. Ozone is an allotropic form of carbon which is formed in the atmosphere due to the release of chloroflurocarbons.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

A is True and R is False.

Explanation
Ozone is an allotropic form of oxygen. Chloroflurocarbons damage the ozone layer.

Assertion. The greenhouse effect is exacerbated by the presence of nitrogen oxides and sulphur oxides in the atmosphere, intensifying the absorption of heat and contributing to global warming.

Reason. Oxides of nitrogen and sulphur, primarily released through industrial activities and combustion processes, amplify the greenhouse effect by enhancing the heat-trapping capacities of the atmosphere, leading to an increase in the average global temperatures.

1. Both A and R are True.
2. Both A and R are False.
3. A is True and R is False.
4. A is False and R is True.

Answer

Both A and R are False.

Explanation
While nitrogen oxides and sulphur oxides contribute to air pollution and have various environmental impacts such as acid rain, they are not significant greenhouse gases. The primary greenhouse gases responsible for the greenhouse effect and global warming are carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O).