1. The critical checkpoint in the cell cycle that determines if a cell will commit to division is the:
কোষ চক্রের কোন চেকপয়েন্টটি কোষ বিভাজনের সিদ্ধান্ত গ্রহণের জন্য সবচেয়ে গুরুত্বপূর্ণ?
Correct Answer: (A) G1 checkpoint
Explanation: The G1 checkpoint, also known as the restriction point, is the most crucial. At this point, the cell assesses factors like size, nutrients, and growth factors to decide whether to proceed with division or enter a dormant (G0) phase.
2. The Sodium-Potassium pump (Na+/K+ pump) which maintains the resting potential of a neuron is an example of:
নিউরনের রেস্টিং পটেনশিয়াল বজায় রাখা সোডিয়াম-পটাশিয়াম পাম্প (Na+/K+ pump) কিসের উদাহরণ?
Correct Answer: (D) Active Transport (সক্রিয় পরিবহন)
Explanation: Active transport is the movement of substances against their concentration gradient, which requires energy (ATP). The Na+/K+ pump uses ATP to pump 3 Na+ ions out of the cell and 2 K+ ions into the cell, both against their concentration gradients.
3. During protein synthesis, the specific sequence on a tRNA molecule that pairs with a codon on mRNA is called the:
প্রোটিন সংশ্লেষের সময়, tRNA অণুর যে নির্দিষ্ট অংশটি mRNA-এর কোডনের সাথে যুক্ত হয়, তাকে কী বলে?
Correct Answer: (B) Anticodon (অ্যান্টিকোডন)
Explanation: A codon is a three-nucleotide sequence on mRNA. The anticodon is the complementary three-nucleotide sequence on the tRNA molecule that recognizes and binds to the codon, ensuring the correct amino acid is added to the growing polypeptide chain.
4. The increasing concentration of a toxic substance like DDT in the tissues of organisms at successively higher levels in a food chain is known as:
খাদ্যশৃঙ্খলের উচ্চতর স্তরের জীবের দেহে DDT-এর মতো বিষাক্ত পদার্থের ঘনত্ব ক্রমশ বৃদ্ধি পাওয়ার ঘটনাকে কী বলা হয়?
Correct Answer: (B) Biomagnification (জৈববিবর্ধন)
Explanation: Biomagnification (or bioamplification) is the process where the concentration of non-biodegradable toxins increases as they move up the food chain, becoming most concentrated in the top predators.
5. Which of the following correctly describes the path of blood in human double circulation?
নিম্নলিখিত কোনটি মানুষের দ্বিসংবহন তন্ত্রে রক্তের সঠিক গতিপথ বর্ণনা করে?
Correct Answer: (A) Right Ventricle → Lungs → Left Atrium → Left Ventricle → Body
Explanation: In double circulation, deoxygenated blood is pumped from the right ventricle to the lungs (pulmonary circulation). Oxygenated blood returns to the left atrium, is pumped by the left ventricle to the rest of the body (systemic circulation), and then deoxygenated blood returns to the right atrium.
6. In C4 plants, the first stable product of carbon fixation is:
C4 উদ্ভিদে, কার্বন স্থিতিকরণের প্রথম স্থায়ী যৌগটি হল:
Correct Answer: (C) Oxaloacetic acid (OAA) (অক্সালোঅ্যাসেটিক অ্যাসিড)
Explanation: In C4 photosynthesis, atmospheric CO2 is first fixed into a 4-carbon compound, Oxaloacetic acid (OAA), in the mesophyll cells. This is different from C3 plants, where the first stable product is the 3-carbon compound 3-PGA.
7. The immunity acquired after an infection or through vaccination is an example of:
সংক্রমণের পরে বা টীকাকরণের মাধ্যমে অর্জিত অনাক্রম্যতা কিসের উদাহরণ?
Correct Answer: (B) Active Artificial Immunity (সক্রিয় কৃত্রিম অনাক্রম্যতা)
Explanation: This question has two parts. Immunity after an infection is ‘Active Natural’. Immunity from vaccination is ‘Active Artificial’. Since vaccination is a choice and mentioned, option B is the most specific for that part. Active immunity means the body produces its own antibodies. Artificial means it’s induced medically (vaccine) rather than by natural infection.
8. Which plant hormone is known as the “stress hormone” for its role in closing stomata during water scarcity?
জলের অভাবের সময় পত্ররন্ধ্র বন্ধ করার ভূমিকার জন্য কোন উদ্ভিদ হরমোনকে ‘স্ট্রেস হরমোন’ বলা হয়?
Correct Answer: (D) Abscisic Acid (ABA) (অ্যাবসিসিক অ্যাসিড)
Explanation: Abscisic Acid (ABA) plays a crucial role in mediating plant responses to environmental stresses like drought. It causes the guard cells to lose turgor, leading to the closure of stomata, which reduces water loss through transpiration.
9. According to the sliding filament theory of muscle contraction, what happens to the A-band?
পেশী সংকোচনের স্লাইডিং ফিলামেন্ট তত্ত্ব অনুসারে, A-ব্যান্ডের কী পরিবর্তন হয়?
Correct Answer: (D) It remains unchanged in length (এর দৈর্ঘ্যের কোনো পরিবর্তন হয় না)
Explanation: During muscle contraction, the thin actin filaments slide over the thick myosin filaments. This causes the H-zone and I-band to shorten, but the A-band, which represents the full length of the thick myosin filament, does not change its length.
10. The phenomenon where a single gene influences multiple phenotypic traits is known as:
যে ঘটনায় একটি একক জিন একাধিক ফিনোটাইপিক বৈশিষ্ট্যকে প্রভাবিত করে, তাকে কী বলে?
Correct Answer: (C) Pleiotropy (প্লিওট্রপি)
Explanation: Pleiotropy occurs when one gene affects multiple, seemingly unrelated characteristics. A classic example is the gene for phenylketonuria (PKU), which causes mental retardation and reduced hair/skin pigmentation. Polygenic inheritance is the opposite, where multiple genes affect a single trait.
11. What is the primary function of interferons in the body?
শরীরে ইন্টারফেরনের প্রধান কাজ কী?
Correct Answer: (B) To signal other cells about viral infection (অন্যান্য কোষকে ভাইরাল সংক্রমণ সম্পর্কে সংকেত দেওয়া)
Explanation: Interferons are signaling proteins released by host cells in response to the presence of viruses. They do not kill viruses directly but trigger the immune system and signal neighboring uninfected cells to produce antiviral proteins, thus inhibiting viral replication.
12. Double fertilization is a characteristic feature of:
দ্বি-নিষেক কোনটির একটি বৈশিষ্ট্যপূর্ণ ঘটনা?
Correct Answer: (C) Angiosperms (গুপ্তবীজী উদ্ভিদ)
Explanation: Double fertilization is a complex fertilization mechanism unique to flowering plants (angiosperms). It involves the joining of a female gametophyte with two male gametes. One fertilizes the egg cell to form the zygote (2n), while the other fuses with the two polar nuclei to form the endosperm (3n).
13. The role of restriction enzymes in genetic engineering is to:
জেনেটিক ইঞ্জিনিয়ারিং-এ রেস্ট্রিকশন এনজাইমের ভূমিকা হল:
Correct Answer: (C) Cut DNA at specific recognition sites (নির্দিষ্ট স্থানে DNA কে কাটা)
Explanation: Restriction enzymes, or restriction endonucleases, act like molecular scissors. They recognize specific nucleotide sequences in DNA and make a cut at or near those sites, which is a fundamental step in creating recombinant DNA.
14. What is the role of the Corpus Luteum in the menstrual cycle?
মাসিক চক্রে কর্পাস লুটিয়ামের ভূমিকা কী?
Correct Answer: (B) To secrete Progesterone to maintain the uterine lining (জরায়ুর আস্তরণ বজায় রাখতে প্রজেস্টেরন ক্ষরণ করা)
Explanation: After ovulation, the ruptured follicle develops into the corpus luteum, which is a temporary endocrine structure. Its primary role is to secrete high levels of progesterone, which thickens and maintains the endometrium (uterine lining) to prepare for a potential pregnancy.
15. The Hardy-Weinberg principle describes a population that is:
হার্ডি-উইনবার্গ নীতি এমন একটি পপুলেশনকে বর্ণনা করে যা:
Correct Answer: (B) Not evolving (বিবর্তিত হচ্ছে না)
Explanation: The Hardy-Weinberg equilibrium principle states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences. It provides a baseline model for a non-evolving population against which evolution can be measured.
16. Which of these is NOT a function of the human liver?
এর মধ্যে কোনটি মানুষের যকৃতের কাজ নয়?
Correct Answer: (D) Production of insulin (ইনসুলিন উৎপাদন)
Explanation: Insulin is a hormone produced by the beta cells of the islets of Langerhans in the pancreas. The liver has over 500 functions, including detoxification, bile production, and urea synthesis, but it does not produce insulin.
17. Crossing over, which leads to genetic recombination, occurs during which phase of meiosis?
জেনেটিক রিকম্বিনেশনের কারণ ক্রসিং ওভার, মিয়োসিসের কোন দশায় ঘটে?
Correct Answer: (C) Pachytene of Prophase I (প্রোফেজ I-এর প্যাকাইটিন উপদশা)
Explanation: Crossing over is the exchange of genetic material between non-sister chromatids of homologous chromosomes. This critical event, which creates genetic diversity, takes place during the Pachytene sub-stage of Prophase I in meiosis.
18. The biconcave shape of a Red Blood Cell (Erythrocyte) is advantageous because it:
লোহিত রক্তকণিকার দ্বি-অবতল আকৃতি সুবিধাজনক কারণ এটি:
Correct Answer: (B) Increases the surface area-to-volume ratio for gas exchange (গ্যাস বিনিময়ের জন্য পৃষ্ঠের ক্ষেত্রফল ও আয়তনের অনুপাত বাড়ায়)
Explanation: The biconcave shape provides a larger surface area for the diffusion of oxygen and carbon dioxide across the cell membrane. It also allows the RBCs to be flexible and squeeze through narrow capillaries.
19. In the context of evolution, the appendix in humans and the pelvic bones in whales are examples of:
বিবর্তনের পরিপ্রেক্ষিতে, মানুষের অ্যাপেন্ডিক্স এবং তিমির পেলভিক অস্থি কিসের উদাহরণ?
Correct Answer: (C) Vestigial structures (নিষ্ক্রিয় অঙ্গ)
Explanation: Vestigial structures are anatomical features or behaviors that have lost most or all of their ancestral function in a given species but have been retained through evolution. The human appendix and the remnants of hind limb bones in whales are classic examples.
20. The primary neurotransmitter released at the neuromuscular junction to cause muscle contraction is:
পেশী সংকোচনের জন্য নিউরোমাসকুলার সংযোগস্থলে নিঃসৃত প্রধান নিউরোট্রান্সমিটারটি হল:
Correct Answer: (C) Acetylcholine (অ্যাসিটাইলকোলিন)
Explanation: When a nerve impulse reaches the neuromuscular junction, the motor neuron releases acetylcholine. This neurotransmitter binds to receptors on the muscle fiber, leading to its depolarization and subsequent contraction.
21. What does PCR (Polymerase Chain Reaction) technology primarily do?
PCR (পলিমারেজ চেইন রিঅ্যাকশন) প্রযুক্তি প্রধানত কী করে?
Correct Answer: (B) Amplifies a specific segment of DNA (DNA-এর একটি নির্দিষ্ট অংশকে বহুগুণ বৃদ্ধি করে)
Explanation: PCR is a laboratory technique used to make millions of copies of a particular segment of DNA. This amplification allows scientists to study a small sample of DNA in greater detail, which is crucial for diagnostics, forensics, and research.
22. The endosymbiotic theory provides an explanation for the origin of which two organelles?
এন্ডোসিম্বায়োটিক তত্ত্ব কোন দুটি অঙ্গাণুর উৎপত্তির ব্যাখ্যা দেয়?
Correct Answer: (C) Mitochondria and Chloroplasts (মাইটোকনড্রিয়া ও ক্লোরোপ্লাস্ট)
Explanation: This theory proposes that mitochondria and chloroplasts were once free-living prokaryotic organisms that were engulfed by an ancestral eukaryotic cell. Evidence includes them having their own circular DNA, ribosomes, and a double membrane.
23. In human ABO blood groups, the inheritance of AB blood type is an example of:
মানুষের ABO রক্ত গ্রুপে, AB রক্ত গ্রুপের উত্তরাধিকার কিসের উদাহরণ?
Correct Answer: (D) Codominance (সহপ্রকটতা)
Explanation: Codominance occurs when both alleles for a gene are fully expressed in the phenotype of a heterozygote. In the AB blood type, both the A allele (for A antigen) and the B allele (for B antigen) are expressed simultaneously on the surface of red blood cells.
24. The Bohr effect describes the phenomenon where:
বোর প্রভাব (Bohr effect) কোন ঘটনাটি বর্ণনা করে?
Correct Answer: (A) Hemoglobin’s oxygen binding affinity is inversely related to acidity and CO2 concentration.
Explanation: The Bohr effect is a key physiological principle. In tissues with high CO2 levels (like exercising muscles), the blood becomes more acidic. This increased acidity decreases hemoglobin’s affinity for oxygen, causing it to release oxygen more readily to the tissues that need it most.
25. Primary ecological succession begins in an area that:
প্রাথমিক বাস্তুতান্ত্রিক পর্যায়ক্রম এমন একটি এলাকায় শুরু হয় যা:
Correct Answer: (C) Is a newly formed volcanic island (একটি নতুন সৃষ্ট আগ্নেয় দ্বীপ)
Explanation: Primary succession occurs in an environment devoid of vegetation and usually lacking topsoil. A new volcanic island or a bare rock exposed by a retreating glacier are prime examples. The other options describe areas where soil and some life already exist, leading to secondary succession.
26. Which of the following is an example of a connecting link between reptiles and birds?
নিম্নলিখিত কোনটি সরীসৃপ এবং পাখিদের মধ্যে একটি সংযোগকারী লিঙ্ক (connecting link)?
Correct Answer: (D) Archaeopteryx (আর্কিওপটেরিক্স)
Explanation: The fossil of Archaeopteryx is a classic connecting link. It had reptilian characteristics like teeth, a long bony tail, and claws on its wings, but also avian features like feathers, making it a transitional form between dinosaurs (reptiles) and modern birds.
27. Renin, an enzyme involved in blood pressure regulation, is secreted by the:
রেনিন, রক্তচাপ নিয়ন্ত্রণে জড়িত একটি উৎসেচক, কোথা থেকে ক্ষরিত হয়?
Correct Answer: (C) Juxtaglomerular cells of the kidney (বৃক্কের জাক্সটাগ্লোমেরুলার কোষ)
Explanation: The juxtaglomerular cells in the kidneys secrete renin in response to low blood pressure. Renin initiates the Renin-Angiotensin-Aldosterone System (RAAS), a hormone system that regulates blood pressure and fluid balance.
28. The conversion of atmospheric nitrogen into ammonia by certain bacteria is called:
কিছু ব্যাকটেরিয়া দ্বারা বায়ুমণ্ডলীয় নাইট্রোজেনকে অ্যামোনিয়াতে রূপান্তরিত করার প্রক্রিয়াকে বলা হয়:
Correct Answer: (C) Nitrogen Fixation (নাইট্রোজেন স্থিতিকরণ)
Explanation: Nitrogen fixation is the process by which inert atmospheric nitrogen (N2) is converted into ammonia (NH3) or other nitrogenous compounds. This is a crucial step in the nitrogen cycle as it makes nitrogen available for plants. Nitrification is the conversion of ammonia to nitrates, and denitrification is the conversion of nitrates back to N2.
29. The contraceptive pill primarily works by:
গর্ভনিরোধক বড়ি প্রধানত কীভাবে কাজ করে?
Correct Answer: (C) Inhibiting ovulation by hormonal feedback (হরমোনাল ফিডব্যাকের মাধ্যমে ডিম্বস্ফোটন বন্ধ করে)
Explanation: Most combination birth control pills contain estrogen and progestin. These hormones work by negative feedback on the pituitary gland, preventing the release of FSH and LH. The absence of the LH surge prevents ovulation (the release of an egg), thus preventing pregnancy.
30. Guttation, the exudation of water droplets from the tips of leaves, is caused by:
গাটেশন, পাতার ডগা থেকে জলের ফোঁটা নিঃসরণ, যার কারণে ঘটে তা হল:
Correct Answer: (B) Root pressure (মূলজ চাপ)
Explanation: Guttation occurs when transpiration is low (e.g., at night) and soil moisture is high. The roots continue to absorb water, creating a positive pressure (root pressure) in the xylem that forces water out of special pores called hydathodes at the leaf margins.