Question 1
Algin and carrageen are hydrocolloids obtained commercially from respectively:
✅ Correct Answer: Brown algae and Red algae
Explanation: According to NCERT, certain marine brown and red algae produce large amounts of hydrocolloids (water-holding substances). Algin is obtained from brown algae, and carrageen is obtained from red algae.
Question 2
Which of the following organisms is correctly matched with its nitrogenous waste and primary excretory structure?
✅ Correct Answer: Cockroach - Uric acid, Malpighian tubules
Explanation: Insects like cockroaches are uricotelic (excrete uric acid) to conserve water, and their primary excretory structures are Malpighian tubules. Frogs are ureotelic, prawns are ammonotelic (green glands), and earthworms are ureotelic/ammonotelic depending on water availability.
Question 3
In which of the following gymnosperms are the specialized coralloid roots associated with nitrogen-fixing cyanobacteria?
✅ Correct Answer: Cycas
Explanation: In Cycas, small specialized roots called coralloid roots are associated with nitrogen-fixing cyanobacteria (like Nostoc and Anabaena). Pinus, on the other hand, has a symbiotic association with fungi in the form of mycorrhiza.
Question 4
Which of the following groups of cell organelles are considered a part of the endomembrane system?
✅ Correct Answer: Endoplasmic reticulum, Golgi complex, Lysosomes, and Vacuoles
Explanation: The endomembrane system includes the endoplasmic reticulum, Golgi complex, lysosomes, and vacuoles because their functions are coordinated. Mitochondria, chloroplasts, and peroxisomes are not coordinated with these components, so they are excluded.
Question 5
Pleiotropy is a phenomenon in which a single gene controls multiple phenotypic traits. Which of the following is a classic example of pleiotropy in humans?
✅ Correct Answer: Phenylketonuria
Explanation: Phenylketonuria (PKU) is a classic example of pleiotropy. A mutation in the gene coding for the enzyme phenylalanine hydroxylase manifests as multiple phenotypic traits: mental retardation, and a reduction in hair and skin pigmentation.
Question 6
During chemiosmosis in mitochondria, the proton gradient essential for ATP synthesis is created across the:
✅ Correct Answer: Inner mitochondrial membrane
Explanation: During oxidative phosphorylation, the electron transport chain actively pumps protons ($H^+$) from the mitochondrial matrix into the intermembrane space across the inner mitochondrial membrane, building the electrochemical gradient required by ATP synthase.
Question 7
If a person gets a snakebite, the immediate medical treatment involves injecting antivenom. This is an example of:
✅ Correct Answer: Artificial passive immunity
Explanation: Antivenom contains preformed antibodies against the snake venom. Because the antibodies are introduced deliberately via injection (artificial) and the patient's own immune system didn't produce them (passive), it is artificial passive immunity.
Question 8
In the C4 pathway, the bundle sheath cells of Kranz anatomy are characterized by having:
✅ Correct Answer: Thick walls, no intercellular spaces, and a large number of chloroplasts
Explanation: In C4 plants (Kranz anatomy), the bundle sheath cells are tightly packed around the vascular bundles. They have thick walls impervious to gaseous exchange, lack intercellular spaces, and contain a large number of chloroplasts (which are agranal).
Question 9
Assertion (A): The Sino-Atrial (SA) node is called the natural pacemaker of the heart.
Reason (R): The SA node is capable of generating the maximum number of action potentials per minute.
✅ Correct Answer: Both A and R are true, and R is the correct explanation of A.
Explanation: The SA node possesses the highest auto-rhythmicity. Because it generates the highest frequency of action potentials (70-75 beats per minute), it sets the pace for the entire heart's contraction, thereby acting as the pacemaker.
Question 10
Assertion (A): Agrobacterium tumefaciens is frequently used as a vector for introducing nematode-specific genes into the host plant.
Reason (R): Agrobacterium is a natural genetic engineer that can infect all species of broad-leaved and narrow-leaved agricultural crops.
✅ Correct Answer: A is true, but R is false.
Explanation: Assertion is true; Agrobacterium vectors are used for nematode resistance (e.g., in tobacco). Reason is false because Agrobacterium tumefaciens primarily infects dicots (broad-leaved). It does not naturally infect all species of crops, especially monocots (narrow-leaved).
Question 11
Consider the following statements about cell division:
Statement I: During Anaphase I of meiosis, homologous chromosomes separate, while sister chromatids remain associated at their centromeres.
Statement II: During Anaphase II of meiosis, the centromeres split, and sister chromatids move towards opposite poles.
✅ Correct Answer: Both Statement I and Statement II are correct.
Explanation: Meiosis I is a reductional division where homologous pairs separate (Anaphase I), but the centromeres do not split. Meiosis II is an equational division where centromeres finally split (Anaphase II), pulling sister chromatids apart.
Question 12
Consider the following statements about restriction enzymes:
Statement I: Restriction endonucleases inspect the length of a DNA sequence and bind to specific palindromic nucleotide sequences.
Statement II: They cut the strand of DNA exactly in the centre of the palindrome sites to produce sticky ends.
✅ Correct Answer: Statement I is correct, Statement II is incorrect.
Explanation: Statement I is completely true per NCERT. Statement II is false because restriction enzymes producing sticky ends cut the DNA strands a little away from the centre of the palindrome sites, but between the same two bases on the opposite strands (e.g., EcoRI).
Question 13
An mRNA sequence contains 999 bases that code for a protein with 333 amino acids. If a deletion mutation occurs precisely at the 901st base, how many codons will be altered?
✅ Correct Answer: 33
Explanation: The mutation happens at base 901. Therefore, the first 900 bases (coding for 300 amino acids) are completely unaffected. The frameshift will alter everything from base 901 to 999. Total altered bases = 999 - 900 = 99 bases. Number of altered codons = $99 / 3 = 33$ codons.
Question 14
In a standard ECG, if a healthy resting person has a heart rate of 72 beats per minute, how many QRS complexes will be recorded on their ECG strip in exactly 10 seconds?
✅ Correct Answer: 12
Explanation: If the heart rate is 72 beats per 60 seconds (1 minute), the number of beats per second is $72 / 60 = 1.2$ beats/sec. In 10 seconds, the number of QRS complexes = $1.2 \times 10 = 12$.
Question 15
In an aquatic food chain, if the concentration of DDT in water is 0.003 ppb, what will be the approximate concentration of DDT in zooplankton and large fish, respectively, due to biomagnification?
✅ Correct Answer: 0.04 ppm and 2 ppm
Explanation: According to the NCERT flowchart on biomagnification: Water (0.003 ppb) → Zooplankton (0.04 ppm) → Small fish (0.5 ppm) → Large fish (2 ppm) → Fish-eating birds (25 ppm). The question asks for Zooplankton and Large fish.
Question 16
Which of the following microbes is used for the commercial production of statins, a blood-cholesterol lowering agent?
✅ Correct Answer: Monascus purpureus
Explanation: Statins are produced by the yeast Monascus purpureus. They act by competitively inhibiting the enzyme responsible for the synthesis of cholesterol.
Question 17
In human females, oogenesis is initiated during the embryonic development stage. Primary oocytes are arrested in which stage of cell division until puberty?
✅ Correct Answer: Prophase I
Explanation: During embryonic development, oogonia start division and enter into prophase I of meiotic division. They get temporarily arrested at this stage and are called primary oocytes. They resume meiosis only upon reaching puberty.
Question 18
A student performs a restriction digestion experiment. Enzyme X has 4 recognition sites on a linear DNA molecule, while Enzyme Y has 4 recognition sites on a circular plasmid. How many DNA fragments will be produced by X and Y respectively?
✅ Correct Answer: 5 and 4
Explanation: When a linear DNA molecule is cut '$n$' times, it produces '$n+1$' fragments. Thus, 4 cuts on linear DNA yield 5 fragments. When a circular DNA molecule is cut '$n$' times, it produces '$n$' fragments. Thus, 4 cuts on a plasmid yield 4 fragments.
Question 19
A patient is diagnosed with an autoimmune disease that continuously destroys their thyroid gland, leading to very low thyroxine levels. Based on hormonal feedback mechanisms, what will be the expected levels of TRH and TSH in their blood?
✅ Correct Answer: Increased TRH, Increased TSH
Explanation: Because the thyroid gland is destroyed, thyroxine (T3/T4) levels are low. This removes the negative feedback on the hypothalamus and anterior pituitary. As a result, the hypothalamus secretes more TRH, and the pituitary secretes more TSH attempting to stimulate the failing thyroid.
Question 20
Which of the following pairs represents homologous organs (divergent evolution)?
✅ Correct Answer: Thorns of Bougainvillea and tendrils of Cucurbita
Explanation: Homologous organs have the same basic structural design but perform different functions. Both thorns of Bougainvillea and tendrils of Cucurbita arise from axillary buds (stem modifications), making them homologous. Pea tendrils are leaf modifications, while pumpkin tendrils are stem modifications, making them analogous.
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