ijmb model questions vol1 2023 biology | Essay

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Question 1 View Details
The diagram shows a typical animal cell with its major organelles labelled.
Question Parts
(a)
Identify any three organelles shown in the diagram and state the principal function of each.
(b)
Explain how the plasma membrane contributes to the cell’s selective permeability.
(c)
Using the diagram, compare the presence of a cell wall in plant cells with the animal cell shown, and discuss one functional implication of this difference.
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Question 2 View Details
The labelled diagram depicts the sequential stages of mitosis in a eukaryotic cell.
Question Parts
(a)
List the stages of mitosis in their correct order and state one key event that characterises each stage.
(b)
During which stage does crossing‑over occur, and why is this stage not part of mitosis?
(c)
If a cell is observed to have chromosomes lined up at the equatorial plate, which stage of mitosis is it in? Provide a brief justification.
(d)
Explain the significance of cytokinesis following telophase in animal cells.
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Question 3 View Details
The diagram shows a transverse cross‑section of the adult human small intestine. The labelled parts include the duodenum (D), jejunum (J), ileum (I), villi (V), microvilli (M) lining the villi, and lacteals (L). The total length of the small intestine is approximately 6 m and its average internal diameter is 2.5 cm.
Question Parts
(a)
Identify the three regions of the small intestine shown in the diagram.
(b)
Explain how the structure of villi and microvilli enhances nutrient absorption in the small intestine.
(c)
Using the data provided, estimate the total effective absorptive surface area of the small intestine. Show all steps of your calculation.
(d)
Discuss two nutritional disorders that can result from impaired absorption in the small intestine, describing the underlying pathology for each.
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Question 4 View Details
The diagram depicts the major structures of the human respiratory system.
Question Parts
(a)
Write the correct anatomical name for each labelled part (1‑8) shown in the diagram.
(b)
Describe, in sequential order, the pathway that air follows from the external environment to the site of gas exchange, indicating the specific function of each structure encountered.
(c)
Explain the mechanism of external respiration at the alveolar‑capillary membrane, including the role of partial pressure gradients and diffusion.
(d)
A patient has chronic obstructive pulmonary disease (COPD) that reduces the elasticity of the alveolar walls. Using the diagram, discuss how this pathology alters ventilation and gas exchange, and state two likely physiological consequences.
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Question 5 View Details
A tropical shrub was studied under two contrasting atmospheric conditions. The leaf temperature, relative humidity and stomatal conductance (gₛ) measured for each condition are given below. Condition A: leaf temperature = 25 °C, relative humidity = 40 %, gₛ = 0.30 mol m⁻² s⁻¹. Condition B: leaf temperature = 30 °C, relative humidity = 70 %, gₛ = 0.15 mol m⁻² s⁻¹. The saturation vapour pressure (eₛ) at 25 °C is 3.17 kPa and at 30 °C is 4.24 kPa. Transpiration rate (E) can be approximated by the equation E = gₛ × VPD, where VPD (kPa) = eₛ – eₐ and eₐ is the actual vapour pressure (eₐ = RH × eₛ, with RH expressed as a decimal). Answer the following:
Question Parts
(a)
Calculate the vapour pressure deficit (VPD) for each condition and the corresponding transpiration rate (E) in mmol m⁻² s⁻¹.
(b)
State which condition yields the higher transpiration rate and give a concise physiological explanation for the difference.
(c)
Discuss how stomatal regulation helps the plant to control water loss when ambient humidity changes.
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Question 6 View Details
A 45‑year‑old male patient undergoes a renal function assessment. The following data are obtained from a 24‑hour urine collection: - Urine flow rate (V) = 1.5 mL min⁻¹ - Urine creatinine concentration (U) = 120 mg dL⁻¹ - Plasma creatinine concentration (P) = 0.9 mg dL⁻¹ Creatinine clearance (C) is calculated using C = (U × V) / P, where V must be expressed in mL min⁻¹ and concentrations in the same units. Answer the following:
Question Parts
(a)
Calculate the creatinine clearance in mL min⁻¹.
(b)
Interpret the calculated clearance in relation to the normal glomerular filtration rate (GFR) for an adult male.
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Question 7 View Details
The maintenance of internal stability (homeostasis) is essential for the proper functioning of the human body.
Question Parts
(a)
Define homeostasis and outline the general features of a negative‑feedback control system.
(b)
The regulation of blood glucose concentration involves the pancreas.
() Name the two principal hormones released by the pancreas that are directly involved in blood‑glucose control.
() For each hormone, describe its site of secretion, the direction of its effect on blood glucose, and the principal target tissues.
(c)
A 45‑year‑old man with type‑2 diabetes mellitus presents with a fasting plasma glucose concentration of 180 mg dL⁻¹. Explain why this value indicates a failure of homeostatic control and list two clinical manifestations that are likely to result from sustained hyperglycaemia.
(d)
Propose two non‑pharmacological strategies that could assist the patient in re‑establishing glucose homeostasis, and justify how each strategy influences the feedback loop.
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Question 8 View Details
Coordination of movement in humans depends on the integrated activity of the nervous and muscular systems.
Question Parts
(a)
Describe the sequence of events that constitute a monosynaptic stretch reflex, beginning with the sensory stimulus and ending with the motor response. Include the types of neurons involved and the synaptic connections.
(b)
A 28‑year‑old athlete suffers a complete transection of the spinal cord at the level of the T12 vertebra.
() Identify which major spinal tracts are interrupted at this level and the primary functions of those tracts.
() Predict the loss of voluntary motor and sensory functions below the level of injury, specifying the dermatomes and myotomes affected.
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Question 9 View Details
A tropical plant species, *Lythrum tropicalis*, exhibits both sexual reproduction via flowers and asexual reproduction through stoloniferous runners. In a region experiencing prolonged drought, the plant population declines sharply.
Question Parts
(a)
Describe the anatomical structures involved in sexual reproduction of angiosperms and explain how they function to ensure successful fertilisation.
(b)
Explain the physiological and ecological advantages of asexual reproduction by stolons in *L. tropicalis* under drought conditions.
(c)
Considering the drought scenario, predict which mode of reproduction will dominate the next generation and justify your prediction with reference to resource allocation and survival probability.
(d)
The menstrual cycle in humans is regulated by feedback loops involving estrogen, progesterone, LH and FSH.
() Outline the hormonal changes that occur during the follicular phase.
() Describe how a disruption in the LH surge could affect ovulation and subsequent fertility.
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Question 10 View Details
A pedigree analysis is carried out for a rare autosomal recessive disorder, hereditary neuropathy, in a large extended family. The disorder manifests only when an individual is homozygous recessive (nn). In the pedigree, affected individuals are observed in two successive generations, and a consanguineous marriage is recorded.
Question Parts
(a)
Calculate the probability that a child of the marriage between two heterozygous carriers will be affected.
(b)
The disease gene is located on chromosome 12 and shows complete linkage with a marker locus M (alleles M1 and M2) with a recombination frequency of 5 %. A test cross is performed between an individual heterozygous for both the disease allele and the marker (nM1 / NM2) and a homozygous recessive individual (nnM2M2). Predict the phenotypic ratio of the offspring.
() List the possible gametes produced by the heterozygous parent, taking recombination into account.
() From the gamete list, derive the expected phenotypic ratio among the progeny.
(c)
Discuss two molecular mechanisms that could lead to the observed autosomal recessive inheritance pattern, and explain how each mechanism would be detected in a laboratory setting.
(d)
Propose a genetic counselling strategy for the family, highlighting the role of carrier testing and prenatal diagnosis.
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