Explanation: The three smallest bones in the human body are the ossicles, located in the middle ear: the malleus (hammer), incus (anvil), and stapes (stirrup). Of these three, the stapes is the smallest. The femur (thigh bone) is the largest and strongest bone in the body

The instrument with which atmospheric pressure is measured is the (c) barometer.

• Explanation:

  • A barometer measures atmospheric pressure.

  • A wind vane indicates the direction of the wind.

  • A hydrometer measures the relative density (specific gravity) of liquids.

  • A hygrometer measures humidity (the amount of water vapor in the air).

• Correct Option: (b) amphibians

• Explanation: Cutaneous respiration is the process of breathing through the skin. This method is prominent in amphibians (like frogs), whose moist, permeable skin is rich in blood capillaries, allowing for efficient gas exchange to supplement their lungs.

• Correct Option: (b) stomach

• Explanation: The stomach secretes hydrochloric acid (HCl), creating a highly acidic environment (pH 1.5-3.5) that kills pathogens and activates digestive enzymes like pepsin. The mouth is slightly alkaline, and the duodenum is alkaline due to secretions from the pancreas and bile from the liver.

• Correct Option: (a) morphological variation

• Explanation: Morphological variation refers to differences in the physical form and structure of organisms. Height, skin color, and weight are all observable physical traits. They are also examples of continuous variation, as they show a wide range of intermediate values.

• Correct Option: (b) dominant

• Explanation: A dominant allele masks the effect of a recessive allele. It expresses its trait when present in either a homozygous state (e.g., TT) or a heterozygous state (e.g., Tt). A recessive allele is only expressed in the homozygous state (e.g., tt).

• Correct Option: (c) B1

• Explanation: Beriberi is a disease caused by a deficiency of Vitamin B1 (Thiamine). Deficiency of Vitamin A causes night blindness, Vitamin K causes poor blood clotting, and Vitamin C causes scurvy.

• Correct Option: (d) rabbit

• Explanation: A diastema is a natural gap between the incisors and premolars. It is a common feature in herbivores like rabbits and rodents, which lack canine teeth. The gap allows them to manipulate food within the mouth.

• Correct Option: (d) ethylene

• Explanation: Ethylene is a gaseous plant hormone that plays a crucial role in the ripening of fruits, as well as in the aging (senescence) of plant parts.

• Correct Option: (c) AB

• Explanation: Blood type AB has both A and B antigens on its red blood cells. To avoid self-destruction, its plasma contains neither Anti-A nor Anti-B antibodies. This is why people with AB blood are known as "universal recipients."

• Correct Option: (b) nitrogen-fixing bacteria

• Explanation: Nitrogen-fixing bacteria convert unusable atmospheric nitrogen gas (N₂) into ammonia (NH₃), which is then converted into nitrates that plants can absorb and use. Denitrifying bacteria do the opposite, converting nitrates back to nitrogen gas.

• Correct Option: (c) earthworm

• Explanation: Diffusion is only efficient for gas exchange in small organisms with a large surface-area-to-volume ratio and a short diffusion path. An earthworm's long, thin, moist body is perfectly suited for this. Larger animals like rats and lizards require complex respiratory systems (lungs).

• Correct Option: (a) mitochondrion

• Explanation: The mitochondrion is known as the "powerhouse of the cell" because it is the primary site of cellular respiration, the process that generates ATP (the cell's energy currency).

• Correct Option: (c) beef

• Explanation: Taenia saginata is the beef tapeworm, which humans can get by eating undercooked, infected beef. Taenia solium is the pork tapeworm.

• Correct Option: (c) genotype

• Explanation: The genotype refers to the specific combination of alleles (genes) an organism possesses for a particular trait. The phenotype is the observable physical expression of that genotype

• Correct Option: (c) cerebrum

• Explanation: The cerebrum is the largest part of the brain and is responsible for higher cognitive functions such as intelligence, memory, reasoning, consciousness, and voluntary actions.

• Correct Option: (d) population dynamics

• Explanation: Population dynamics is the field of study concerned with the factors that influence the size, density, distribution, and age structure of populations over time.

• Correct Option: (a) virus

• Explanation: Viruses are often considered to be on the borderline of life. They are inert and non-living when outside a host cell but can replicate and carry out life processes by hijacking the machinery of a living cell they infect.

• Correct Option: (d) chromatophore

• Explanation: Chromatophores are specialized pigment-containing cells that can expand and contract to change the color and pattern of an animal's skin. Chameleons use these cells for camouflage and communication.

• Correct Option: (b) urethra

• Explanation: In males, the urethra is the tube that transports urine from the bladder out of the body. It also serves as the channel through which semen is ejaculated during reproduction.

• Correct Option: (a) detoxification

• Explanation: The three key processes in urine formation within the kidney's nephrons are ultrafiltration, selective re-absorption, and secretion. Detoxification is primarily a function of the liver, which breaks down toxins in the blood.

• Correct Option: (c) evaporation and condensation

• Explanation: The water cycle is driven by the sun. Evaporation turns liquid water into vapor, and condensation turns that vapor back into liquid, forming clouds. These two processes are the primary engines of the global water cycle, leading to precipitation.

• Correct Option: (c) saprophytism

• Explanation: Predation, commensalism, and mutualism are all relationships between two or more living organisms. Saprophytism is a mode of nutrition where one living organism (like a fungus) feeds on dead and decaying organic matter.

• Correct Option: (a) interspecific

• Explanation: Interspecific competition occurs between individuals of different species competing for the same limited resources. Since P. Aurelia and P. caudatum are different species, their competition is interspecific.

• Correct Option: (a) Jean Lamarck

• Explanation: Jean-Baptiste Lamarck proposed the theory of evolution based on the inheritance of acquired characteristics, which included the principle of "use and disuse" (organs become stronger with use and weaker with disuse).

• Correct Option: (b) 46 & 23

• Explanation: A human cheek cell is a somatic (body) cell and is diploid (2n), containing 46 chromosomes. A sperm cell is a gamete (sex cell) and is haploid (n), containing half the number, which is 23 chromosomes.

• Correct Option: (d) warning colouration

• Explanation: These large "eyespots" serve as startle or warning coloration. When flashed, they can surprise a predator by resembling the eyes of a larger animal, giving the moth a chance to escape.

• Correct Option: (a) ¼

• Explanation: In a monohybrid cross between two heterozygous parents (e.g., Tt x Tt), the resulting offspring genotypes have a ratio of 1 TT : 2 Tt : 1 tt. The recessive phenotype is only expressed by the tt genotype, which has a probability of 1 in 4, or ¼.

• Correct Option: (a) Ulna

• Explanation: The axial skeleton forms the central axis of the body and includes the skull, vertebral column, ribs, and sternum. The ulna is a bone in the forearm, which is part of the appendicular skeleton (limbs and girdles).

• Correct Option: (b) streamlined body

• Explanation: A streamlined body shape, which is tapered at both ends, significantly reduces water resistance (drag). This allows the fish to move through the water with maximum efficiency and minimal energy expenditure.

C: This is arch fingerprint. Arch fingerprints have ridges that form a hill.
NB: i. Loops are the most common type of fingerprints. They constitute about 65% of the encountered fingerprints
ii. Arches are the least common, they constitute about 5% of all fingerprints.

A: Fingerprints show morphological variation

B: Since no two persons can have exactly the same fingerprint, fingerprints can be used in crime detection.

• Correct Option: (c) hepatic portal vein

• Explanation: This describes a portal venous system. The hepatic portal vein is formed by the capillaries from the digestive system and ends in the capillary-like sinusoids of the liver. This allows the liver to process absorbed nutrients directly from the gut.

• Correct Option: (d) bile

• Explanation: Bile is a substance produced by the liver that aids in digestion by emulsifying fats (breaking large fat globules into smaller ones). It is not an enzyme. Erepsin, lipase, and trypsin are all enzymes that chemically break down proteins and fats.

• Correct Option: (b) mammalia

• Explanation: Mammals exhibit the most extensive and complex parental care, which includes feeding their young with milk (lactation), protection, and teaching essential survival skills over a prolonged period.

• Correct Option: (a) enamel

• Explanation: Tooth enamel, the outer layer of the teeth, is the hardest substance in the human body due to its high concentration of minerals, primarily hydroxyapatite. It is even harder than bone.

• Correct Option: (c) cycad

• Explanation: Plants with "naked seeds" (seeds not enclosed in an ovary/fruit) are called gymnosperms. Cycads are a group of gymnosperms. Mango is an angiosperm (seeds in a fruit), while mosses and ferns are non-seed plants that reproduce with spores.