ijmb model questions vol1 2018 biology | Essay

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Question 1 View Details
The labelled diagram shows a typical eukaryotic animal cell.
Question Parts
(a)
Identify and write the correct name of each structure that is labelled in the diagram.
(b)
State the principal function of each structure you identified in part (a).
(c)
Compare the presence or absence of the following organelles in plant cells versus animal cells: cell wall, chloroplast, large central vacuole, and centrioles.
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Question 2 View Details
The labelled diagram depicts the stages of mitosis in a typical animal cell.
Question Parts
(a)
List the stages of mitosis in the correct chronological order as shown in the diagram.
(b)
For each stage, describe one key morphological change that characterises that stage.
(c)
Explain why accurate segregation of chromosomes during mitosis is essential for organismal development.
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Question 3 View Details
The diagram shows a labelled plate model of a balanced daily diet illustrating the major food groups and typical portion sizes.
Question Parts
(a)
Identify three food groups shown in the diagram and give one example food item for each group.
(b)
Using the recommended daily energy intake of 2000 kcal, where carbohydrates should supply 55 %, proteins 15 % and fats 30 % of the total energy, calculate the amount in grams of each macronutrient required per day. (Carbohydrate = 4 kcal g⁻¹, Protein = 4 kcal g⁻¹, Fat = 9 kcal g⁻¹)
(c)
The diagram indicates that one standard serving of cooked rice (150 g) provides 130 kcal and that rice derives 80 % of its calories from carbohydrate. Estimate how many servings of rice would be needed to meet the daily carbohydrate energy requirement calculated in part (b). Show your reasoning.
(d)
Discuss two health consequences of a chronic deficiency of each macronutrient (carbohydrate, protein, and fat).
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Question 4 View Details
The diagram shows the human respiratory system with the structures labelled as follows: trachea (T), primary bronchi (B1), secondary bronchi (B2), bronchioles (Bo), alveolar sacs (A), diaphragm (D), intercostal muscles (IM), pleural cavity (PC) and lungs (L).
Question Parts
(a)
Describe the complete pathway that air follows from the external environment to the site of gas exchange, naming each structure it passes through.
(b)
Explain the mechanism of ventilation, describing the role of the diaphragm and intercostal muscles and how changes in thoracic volume affect intra‑thoracic pressure.
(c)
Given that the partial pressure of oxygen in alveolar air is 100 mmHg and in the pulmonary capillary blood is 40 mmHg, discuss how this gradient influences the rate of diffusion of O₂ according to Fick’s law, and state two pathological factors that could limit this diffusion.
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Question 5 View Details
Consider the processes of transport of water and minerals in a flowering plant and the transport of nutrients and gases in the human circulatory system.
Question Parts
(a)
Explain the cohesion‑tension mechanism that drives the upward movement of water in the xylem and list two environmental factors that can impede this movement.
(b)
Compare the structural differences between xylem vessels and phloem sieve tubes with respect to cell‑wall composition and the presence of a living protoplast.
(c)
Describe how oxygen is transported from the alveoli to peripheral tissues in the human circulatory system, emphasizing the role of haemoglobin and the partial pressure gradient.
(d)
Discuss two physiological adaptations of the circulatory system that occur during increased physical activity.
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Question 6 View Details
The human excretory system maintains homeostasis by removing metabolic wastes and regulating water and electrolyte balance.
Question Parts
(a)
Outline the pathway that blood follows from filtration in the renal corpuscle to its exit as urine, naming all major structures encountered.
(b)
Explain how the counter‑current multiplication mechanism in the loop of Henle concentrates urine, emphasizing the creation of an osmotic gradient.
(c)
A patient suffers from deficient secretion of antidiuretic hormone (ADH). Predict two physiological consequences and explain the renal changes that underlie each consequence.
(d)
Compare the excretory mechanisms of the kidney and the skin, highlighting the types of waste eliminated and the principal regulatory controls involved.
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Question 7 View Details
Homeostasis is essential for maintaining the internal environment of the human body.
Question Parts
(a)
Explain the role of negative feedback in the regulation of blood glucose concentration.
(b)
A diabetic patient has impaired insulin secretion. Discuss how this defect disrupts the homeostatic control of blood glucose and propose two management strategies.
(c)
Compare and contrast the regulation of body temperature with that of blood glucose, highlighting at least three similarities and three differences.
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Question 8 View Details
Coordination of movement in humans involves the integration of sensory input, central processing and motor output.
Question Parts
(a)
Describe the complete pathway of a stretch (myotatic) reflex, starting from the muscle‑spindle receptor to the effector muscle, and indicate the type of neuron involved at each synapse.
(b)
A patient suffers a lesion at the spinal cord segment that mediates the knee‑jerk reflex. Predict the effect on the reflex response and explain the underlying neurophysiological reason.
(c)
Explain how coordination between the cerebellum and the motor cortex contributes to the execution of a rapid, precise movement such as catching a ball. Include discussion of feed‑forward and feedback mechanisms.
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Question 9 View Details
Answer the following questions on human reproduction.
Question Parts
(a)
Describe the hormonal events that regulate the menstrual cycle, indicating the phase in which ovulation occurs.
(b)
Explain the process of fertilisation from sperm capacitation to the formation of the zygote, highlighting the role of the zona pellucida.
(c)
Compare and contrast the mechanisms of action of:
() Combined oral contraceptive pills (COCP).
() Intra‑uterine contraceptive devices (IUDs).
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Question 10 View Details
Answer the following questions on genetics.
Question Parts
(a)
A farmer crosses two true‑breeding pea plants, one with purple flowers (PP) and one with white flowers (pp). The F1 generation is self‑pollinated to produce an F2 generation. Calculate the expected phenotypic ratio and the probability that a randomly selected F2 plant will be heterozygous (Pp).
(b)
In a dihybrid cross involving genes A/a (seed shape) and B/b (seed colour), the parental genotypes are AaBb × AaBb. Assuming independent assortment, determine the genotypic ratio for the offspring that are homozygous recessive for both traits.
(c)
A pedigree shows a rare autosomal recessive disorder. Explain how you can determine whether the disorder is autosomal recessive or dominant from the pedigree, and describe the implications for recurrence risk in the offspring of two carrier parents.
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