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Punjab Biology 2023 Paper 2 — Solved Past Paper with Answers
All 17 MCQs from Punjab Biology 2023 Paper 2, solved with the correct answer highlighted and a full explanation for every question. This is a free MDCAT Punjab / UHS past paper — no signup, no ads. Practise it interactively in timed mode, drill more with free MDCAT MCQs, or browse all Punjab / UHS papers.
Attempt this paper interactively →Q1. Freshwater flatworms excrete very dilute_.
- A. Plasma
- B. Tissue fluid
- C. Urine✓
- D. Uric acid
Explanation: Freshwater flatworms excrete very dilute urine. The parasitic flatworms, which are isotonic to the host environment mainly function in disposing of nitrogenous wastes.
Why the other options are wrong
- A. Freshwater flatworms excrete very dilute urine. The parasitic flatworms, which are isotonic to the host environment mainly function in disposing of nitrogenous wastes.
- B. Freshwater flatworms excrete very dilute urine. The parasitic flatworms, which are isotonic to the host environment mainly function in disposing of nitrogenous wastes.
- D. Freshwater flatworms excrete very dilute urine. The parasitic flatworms, which are isotonic to the host environment mainly function in disposing of nitrogenous wastes.
Q2. Mature bone cells are called:
- A. Osteoblast
- B. Osteoclast
- C. Chondrocytes
- D. Osteocytes✓
Explanation: Osteoblasts are bone-forming cell, osteoclasts resorb or break down bone, and osteocytes are mature bone cells.
Why the other options are wrong
- A. Osteoblasts are bone-forming cell, osteoclasts resorb or break down bone, and osteocytes are mature bone cells.
- B. Osteoblasts are bone-forming cell, osteoclasts resorb or break down bone, and osteocytes are mature bone cells.
- C. Chondrocytes maintain the extracellular matrix (ECM) and produce the cartilage matrix. Surrounded by collagenous fibers, chondrocytes release substances to make cartilage strong yet flexible. In general, chondrocytes are found within intervertebral discs and in any form of articular cartilage (AC).
Q3. Each myosin filament is surrounded by _actin filaments on each end.
- A. 03
- B. 06✓
- C. 09
- D. 12
Explanation: There are Six actin filaments surround each myosin filament, and each actin filament is surrounded by three myosin filaments. This arrangement gives the muscles a striated appearance under magnification.
Why the other options are wrong
- A. There are Six actin filaments surround each myosin filament, and each actin filament is surrounded by three myosin filaments. This arrangement gives the muscles a striated appearance under magnification.
- C. There are Six actin filaments surround each myosin filament, and each actin filament is surrounded by three myosin filaments. This arrangement gives the muscles a striated appearance under magnification.
- D. There are Six actin filaments surround each myosin filament, and each actin filament is surrounded by three myosin filaments. This arrangement gives the muscles a striated appearance under magnification.
Q4. The number of spinal nerves in Man is:
- A. 31 pairs✓
- B. 13 pairs
- C. 24 pairs
- D. 62 pairs
Explanation: Spinal nerve, in vertebrates, any one of many paired peripheral nerves that arise from the spinal cord. In humans there are 31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.
Why the other options are wrong
- B. Spinal nerve, in vertebrates, any one of many paired peripheral nerves that arise from the spinal cord. In humans there are 31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.
- C. Spinal nerve, in vertebrates, any one of many paired peripheral nerves that arise from the spinal cord. In humans there are 31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.
- D. Spinal nerve, in vertebrates, any one of many paired peripheral nerves that arise from the spinal cord. In humans there are 31 pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.
Q5. The selective weed killer is:
- A. NAA
- B. IPA
- C. 2,3,D
- D. Ethene✓
Explanation: 2,4 D (2,4 Dichloro phenoxy acetic acid), Selective weed killer Kills broad leaved species.
Why the other options are wrong
- A. NAA (a synthetic auxin) is used in many commercial rooting products. It is used to promote rooting from stem and leaf cuttings. NAA is also used in plant tissue culture work.
- B. Intensive Plant Agriculture (IPA) is a form of agriculture that uses higher inputs, labour and resources, and higher crop yields per size of land area.
- C. 2,4 D (2,4 Dichloro phenoxy acetic acid), Selective weed killer Kills broad leaved species.
Q6. Menstruation usually lasts for:
- A. 3-7 days✓
- B. 3-9 days
- C. 1-3 days
- D. 4-8 days
Explanation: Menstrual bleeding might happen every 21 to 35 days and last 3 to 7 days. For the first few years after menstruation begins, long cycles are common. However, menstrual cycles tend to shorten and become more regular as people age.
Why the other options are wrong
- B. Menstrual bleeding might happen every 21 to 35 days and last 3 to 7 days. For the first few years after menstruation begins, long cycles are common. However, menstrual cycles tend to shorten and become more regular as people age.
- C. Menstrual bleeding might happen every 21 to 35 days and last 3 to 7 days. For the first few years after menstruation begins, long cycles are common. However, menstrual cycles tend to shorten and become more regular as people age.
- D. Menstrual bleeding might happen every 21 to 35 days and last 3 to 7 days. For the first few years after menstruation begins, long cycles are common. However, menstrual cycles tend to shorten and become more regular as people age.
Q7. Meristems are growing tissues or group of cells that retain the potential to
- A. Regeneration
- B. Penetration
- C. Survive
- D. Divide✓
Explanation: Meristem: A plant tissue consisting of actively dividing, undifferentiated cells that can divide, multiply, and differentiate to form different tissues and organs of a plant.
Why the other options are wrong
- A. Meristem: A plant tissue consisting of actively dividing, undifferentiated cells that can divide, multiply, and differentiate to form different tissues and organs of a plant.
- B. Meristem: A plant tissue consisting of actively dividing, undifferentiated cells that can divide, multiply, and differentiate to form different tissues and organs of a plant.
- C. Meristem: A plant tissue consisting of actively dividing, undifferentiated cells that can divide, multiply, and differentiate to form different tissues and organs of a plant.
Q8. In E. Coli, the true replicating enzyme is:
- A. DNA polymerase I
- B. DNA polymerase II
- C. DNA polymerase III✓
- D. RNA polymerase III
Explanation: In E. coli the replicase is DNA polymerase III holoenzyme (HE), a dimeric enzyme that contains two copies of DNA polymerase III, one for each strand. A schematic depiction of HE containing its various associated subunits at a replication fork (replisome)
Why the other options are wrong
- A. In E. coli the replicase is DNA polymerase III holoenzyme (HE), a dimeric enzyme that contains two copies of DNA polymerase III, one for each strand. A schematic depiction of HE containing its various associated subunits at a replication fork (replisome)
- B. In E. coli the replicase is DNA polymerase III holoenzyme (HE), a dimeric enzyme that contains two copies of DNA polymerase III, one for each strand. A schematic depiction of HE containing its various associated subunits at a replication fork (replisome)
- D. In E. coli the replicase is DNA polymerase III holoenzyme (HE), a dimeric enzyme that contains two copies of DNA polymerase III, one for each strand. A schematic depiction of HE containing its various associated subunits at a replication fork (replisome)
Q9. Which does one has higher molecular mass among bases of nucleic acid?
- A. Guanine✓
- B. Cytosine
- C. Thymine
- D. Uracil
Explanation: Since guanine is double ringed structure so it has higher molecular mass than the other.
Why the other options are wrong
- B. It is single ringed structure so this is not correct.
- C. It is single ringed structure so this is not correct.
- D. It is single ringed structure so this is not correct.
Q10. The plan of new cell wall for.... a dividing cell is determined by:
- A. Endoplasmic reticulum
- B. Ribosomes
- C. Golgi bodies
- D. Microtubules✓
Explanation: Plane of cell wall formation in a dividing cell is determined by microtubules.
Why the other options are wrong
- A. The endoplasmic reticulum (ER) is a large, dynamic structure that serves many roles in the cell including calcium storage, protein synthesis and lipid metabolism. The diverse functions of the ER are performed by distinct domains; consisting of tubules, sheets and the nuclear envelope.
- B. A ribosome is an intercellular structure made of both RNA and protein, and it is the site of protein synthesis in the cell. The ribosome reads the messenger RNA (mRNA) sequence and translates that genetic code into a specified string of amino acids, which grow into long chains that fold to form proteins.
- C. A Golgi body, also known as a Golgi apparatus, is a cell organelle that helps process and package proteins and lipid molecules, especially proteins destined to be exported from the cell. Named after its discoverer, Camillo Golgi, the Golgi body appears as a series of stacked membranes.
Q11. Which one of the ....... genotypic ratio is observed for cross between heterozygous round and homozygous wrinkled .........
- A. 3:1
- B. 1:1✓
- C. 2:1
- D. 1:3
Explanation: This can be taken as a test cross and when gametes of both parents combine 2 of the offspring will be heterozygous round and two will be homozygous wrinkled so the ratio will be 1:1.
Why the other options are wrong
- A. This can be taken as a test cross and when gametes of both parents combine 2 of the offspring will be heterozygous round and two will be homozygous wrinkled so the ratio will be 1:1.
- C. This can be taken as a test cross and when gametes of both parents combine 2 of the offspring will be heterozygous round and two will be homozygous wrinkled so the ratio will be 1:1.
- D. This can be taken as a test cross and when gametes of both parents combine 2 of the offspring will be heterozygous round and two will be homozygous wrinkled so the ratio will be 1:1.
Q12. Which one is used to make the ........ eggs transgenic?
- A. By agro bacterium
- B. Particle gun
- C. Micro propagation
- D. Vortex mixing✓
Explanation: It is possible to micro eggs by hand, but another method uses vortex mixing. The eggs and silicon - carbide needles, and the needles make DNA can enter. When these eggs are fertilized, the resulting offspring are transgenic animals.
Why the other options are wrong
- A. It is possible to micro eggs by hand, but another method uses vortex mixing. The eggs and silicon - carbide needles, and the needles make DNA can enter. When these eggs are fertilized, the resulting offspring are transgenic animals.
- B. It is possible to micro eggs by hand, but another method uses vortex mixing. The eggs and silicon - carbide needles, and the needles make DNA can enter. When these eggs are fertilized, the resulting offspring are transgenic animals.
- C. It is possible to micro eggs by hand, but another method uses vortex mixing. The eggs and silicon - carbide needles, and the needles make DNA can enter. When these eggs are fertilized, the resulting offspring are transgenic animals.
Q13. Which of the following organisms are used to prevent airborne chemical pollutants?
- A. Transgenic bacteria✓
- B. Transgenic Plants
- C. Transgenic Animals
- D. Transgenic Fungi
Explanation: Industry has found that bacteria can be used as biofilters to prevent airborne chemical pollutants from being vented into the air.
Why the other options are wrong
- B. Industry has found that bacteria can be used as biofilters to prevent airborne chemical pollutants from being vented into the air.
- C. Industry has found that bacteria can be used as biofilters to prevent airborne chemical pollutants from being vented into the air.
- D. Industry has found that bacteria can be used as biofilters to prevent airborne chemical pollutants from being vented into the air.
Q14. The prokaryotes may have arisen more than_ billion years ago.
- A. 6.5
- B. 5.5
- C. 4.5
- D. 3.5✓
Explanation: The prokaryotes may have arisen more than 3.5 billion years ago.
Why the other options are wrong
- A. The prokaryotes may have arisen more than 3.5 billion years ago.
- B. The prokaryotes may have arisen more than 3.5 billion years ago.
- C. The prokaryotes may have arisen more than 3.5 billion years ago.
Q15. Succession is initiated by a few hardy invaders called:
- A. Predators
- B. Pioneers✓
- C. Parasites
- D. Gravers
Explanation: In each case succession is initiated by a few hardy invaders called pioneers and it ends with a diverse and relatively stable climax community.
Why the other options are wrong
- A. An animal that lives by killing and eating other animals
- C. A parasite is an organism that lives on or in a host organism and gets its food from or at the expense of its host. There are three main classes of parasites that can cause disease in humans: protozoa, helminths, and ectoparasites. Protozoa.
- D. A graver tool is a small, handheld tool, often similar to a chisel, that is used to engrave metal. Gravers are small and are often differentiated by the point shapes on the blade, and the different grades of steel from which the tool is manufactured.
Q16. The desert ecosystem of Southern Punjab is:
- A. Thal
- B. Thar✓
- C. Cholistan
- D. Sahara
Explanation: In southern Punjab, areas like Fort Abbass, Bahawal Nagar, Yazman, Bahawal Pur (Cholistan), Khan pur and Rahim yar khan also have deserts. In Sindh, this desert ecosystem is called “Thar”
Why the other options are wrong
- A. In southern Punjab, areas like Fort Abbass, Bahawal Nagar, Yazman, Bahawal Pur (Cholistan), Khan pur and Rahim yar khan also have deserts. In Sindh, this desert ecosystem is called “Thar”
- C. In southern Punjab, areas like Fort Abbass, Bahawal Nagar, Yazman, Bahawal Pur (Cholistan), Khan pur and Rahim yar khan also have deserts. In Sindh, this desert ecosystem is called “Thar”
- D. In southern Punjab, areas like Fort Abbass, Bahawal Nagar, Yazman, Bahawal Pur (Cholistan), Khan pur and Rahim yar khan also have deserts. In Sindh, this desert ecosystem is called “Thar”
Q17. A good example of environmental buffer is:
- A. Forest✓
- B. River
- C. Lake
- D. Desert
Explanation: Forest buffers act as natural filters and are often the last line of defense, protecting streams and ultimately the Chesapeake Bay from polluted runoff. Forest buffers protect streams and local drinking water supplies by helping to intercept and process excess nutrients, sediments, and pathogens from entering them.
Why the other options are wrong
- B. Forest buffers act as natural filters and are often the last line of defense, protecting streams and ultimately the Chesapeake Bay from polluted runoff. Forest buffers protect streams and local drinking water supplies by helping to intercept and process excess nutrients, sediments, and pathogens from entering them.
- C. Forest buffers act as natural filters and are often the last line of defense, protecting streams and ultimately the Chesapeake Bay from polluted runoff. Forest buffers protect streams and local drinking water supplies by helping to intercept and process excess nutrients, sediments, and pathogens from entering them.
- D. Forest buffers act as natural filters and are often the last line of defense, protecting streams and ultimately the Chesapeake Bay from polluted runoff. Forest buffers protect streams and local drinking water supplies by helping to intercept and process excess nutrients, sediments, and pathogens from entering them.
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