Chapter 7: Structural Organisation in Animals Application Questions | biology Class 11 CBSE

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Chapter 7: Structural Organisation in Animals Application Questions | biology Class 11 CBSE | ByteNotes.in

Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 1

Applied Concept

A frog is placed in a container of clean, dry sand with no access to water. After some time, it is observed to become lethargic and dehydrated. With reference to the skin of the frog, explain why this happens and why frogs cannot survive in dry conditions.

The frog absorbs all the water it requires through its skin and never drinks water directly; without external moisture, the skin dries out rapidly.
The frog's skin must remain moist at all times because moist skin enables cutaneous respiration — diffusion of dissolved oxygen. On dry sand, this gas exchange becomes impossible, causing oxygen deprivation.
The mucous glands in the skin secrete mucus to maintain moisture, but these are insufficient in the complete absence of environmental water, leading to rapid desiccation.
Thus the frog becomes lethargic and dehydrated because it has lost its primary respiratory organ (moist skin) and its only source of water intake, highlighting how completely dependent the frog is on a moist environment.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 2

Applied Concept

During a biology practical, a student dissects a male frog and notices that the ureters are connected to both the kidneys and the cloaca, and appear to carry both urine and sperms. How would you explain this anatomical arrangement to the student?

In male frogs, the ureters function as urinogenital ducts — they serve the dual role of carrying both urine (from the kidneys) and sperms (from the reproductive system).
Sperms produced in the testes travel through vasa efferentia into Bidder's canal within the kidney, and then enter the urinogenital duct (ureter), which thus carries both types of products.
This shared ductal arrangement is a characteristic feature of the male frog's anatomy and reflects the anatomical integration between the excretory and reproductive systems.
This arrangement is different from female frogs, where the ureters (carrying urine) and oviducts (carrying ova) are completely separate structures that open independently into the cloaca.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 3

Applied Concept

A farmer notices that the frog population in his fields has drastically decreased. He is worried about increased crop damage from insects. With reference to the chapter, explain the farmer's concern and the role of frogs in agriculture.

Frogs are insectivores that feed on insects found in agricultural fields, thereby naturally controlling insect populations that can damage crops.
A decrease in frog population would mean fewer insects are consumed, leading to unchecked insect population growth and consequent increased crop damage.
Frogs also serve as key links in food chains and food webs in the ecosystem; their reduction disrupts ecological balance and affects organisms at other trophic levels.
Thus the farmer's concern is scientifically valid — frogs act as natural biological pest control agents, and their decline can significantly increase the cost and effort needed for crop protection.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 4

Applied Concept

A frog is observed to be completely inactive and buried in soil during the months of May–June in northern India. What is this phenomenon called and how does the frog's physiology support survival during this period?

This phenomenon is called aestivation or summer sleep, which frogs undergo during peak summer months to protect themselves from extreme heat.
During aestivation, frogs take shelter in deep burrows where temperatures are lower and moisture is retained, preventing lethal dehydration and overheating.
Since the lungs are not actively used during this dormant state, gaseous exchange takes place exclusively through the skin (cutaneous respiration), which remains the frog's only respiratory organ during aestivation.
Metabolic activities are greatly reduced during this dormant period, lowering the oxygen and energy demands of the frog, allowing it to survive on stored reserves without feeding.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 5

Applied Concept

A student reads that frogs have a three-chambered heart, while mammals have a four-chambered heart. With reference to the frog's circulatory system, explain the structure of the frog's heart and suggest why a four-chambered heart may provide an advantage.

The frog's heart has three chambers: two atria (right and left) and one ventricle. It is covered by the pericardium. The sinus venosus collects blood from the vena cava into the right atrium, and the conus arteriosus exits from the ventricle.
In the single ventricle, oxygenated blood (from lungs) and deoxygenated blood (from body) mix before being pumped out. This means the body receives partially oxygenated blood.
A four-chambered heart (two atria and two ventricles) completely separates oxygenated and deoxygenated blood, delivering fully oxygenated blood to the body. This is more efficient for high-metabolic-rate warm-blooded mammals.
Since frogs are poikilotherms with lower metabolic rates, a three-chambered heart is sufficient for their energy demands. The partial mixing in the single ventricle does not critically impair their survival but would be insufficient for the higher demands of endotherms.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 6

Applied Concept

With reference to the digestive system of a frog, explain why the duodenum is considered a critical site of digestion. What would happen if the common bile duct were blocked?

The duodenum is the first part of the small intestine and is a critical digestive site because it receives both bile from the gall bladder and pancreatic juice from the pancreas through the common bile duct.
Bile emulsifies fats (breaks large fat globules into smaller droplets), increasing the surface area for lipase action, while pancreatic juice contains enzymes that digest carbohydrates and proteins.
If the common bile duct were blocked, neither bile nor pancreatic juice would reach the duodenum, severely impairing fat emulsification and digestion of carbohydrates and proteins.
This would result in poor nutrient absorption, as final digestion in the intestine would be compromised, and undigested fats in particular would pass into the rectum and be excreted, causing nutritional deficiency.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 7

Applied Concept

A zoology student observes that frogs are not seen during December–January in a temperate region of India. Using concepts from Chapter 7, explain this observation.

The absence of frogs during December–January is explained by the phenomenon of hibernation (winter sleep), which frogs undergo during peak winter months.
Frogs are poikilotherms (cold-blooded), meaning their body temperature depends on the environmental temperature. In extreme cold, their metabolic processes slow down drastically, making normal activity impossible.
To protect themselves from extreme cold, frogs take shelter in deep burrows, remaining inactive until temperatures become favourable again in spring.
During hibernation, frogs rely exclusively on cutaneous respiration through their skin for gaseous exchange, as pulmonary respiration is effectively suspended during this dormant state.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 8

Applied Concept

You are given a dissected frog. How would you identify whether it is a male or a female, both externally and internally? Give at least four distinguishing features.

Externally, male frogs possess vocal sacs (for sound production) on either side of the throat that are absent in females; this is the most visible external distinction.
Male frogs also have a copulatory pad on the first digit of the forelimb to grip the female during mating, which is absent in female frogs. This feature demonstrates sexual dimorphism.
Internally, male frogs have a pair of yellowish ovoid testes attached to the kidneys by mesorchium, while female frogs have a pair of ovaries situated near (but not connected to) the kidneys.
In males, the ureters function as urinogenital ducts carrying both urine and sperms into the cloaca, whereas in females the ureters and oviducts are separate structures that open independently into the cloaca.

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Application Question

Hard difficulty • Concept in a practical situation

Hard

Question 9

Applied Concept

A biology teacher explains that the hepatic portal system in frogs is essential for the body's economy. With reference to the chapter, explain why blood from the intestine must pass through the liver before entering general circulation.

The hepatic portal system is a special venous connection in which blood from the intestine (rich in absorbed nutrients such as glucose, amino acids and other digested products) is carried directly to the liver before entering the general circulation.
By routing nutrient-rich blood through the liver first, the liver can process, store and regulate nutrient levels (such as storing excess glucose as glycogen) before the blood circulates to the rest of the body.
This arrangement also allows the liver to detoxify harmful substances absorbed from the intestine, preventing them from reaching vital organs directly.
Thus the hepatic portal system is critical for nutrient regulation and detoxification — without it, unregulated nutrient concentrations and toxins from digestion could reach the heart and brain, causing harm.

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Application Question

Medium difficulty • Concept in a practical situation

Medium

Question 10

Applied Concept

A student notices that a frog's eyes are much larger proportionally than those of most terrestrial animals and that they bulge outward. With reference to the chapter, explain what structure protects these eyes and the advantage of their large, bulging shape.

The bulging eyes of the frog are covered and protected by the nictitating membrane, a transparent protective covering that shields the eyes while the frog is submerged in water.
The large, bulging eyes are situated in orbits in the skull and are described as simple eyes (having only one unit). Their protruding position allows a wide field of vision in multiple directions simultaneously.
This wide field of vision is particularly advantageous for a frog because it can spot prey (insects) approaching from the sides and above without moving its head, and it can also detect predators from a wide angle.
The large eye size also improves light sensitivity, enabling frogs to hunt effectively in dim light conditions near water, making these eyes well-adapted for the frog's carnivorous and amphibious lifestyle.

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Chapter 7: Structural Organisation in Animals | Application Questions

A frog is placed in a container of clean, dry sand with no access to water. After some time, it is observed to become lethargic and dehydrated. With reference to the skin of the frog, explain why this happens and why frogs cannot survive in dry conditions.

During a biology practical, a student dissects a male frog and notices that the ureters are connected to both the kidneys and the cloaca, and appear to carry both urine and sperms. How would you explain this anatomical arrangement to the student?

A farmer notices that the frog population in his fields has drastically decreased. He is worried about increased crop damage from insects. With reference to the chapter, explain the farmer's concern and the role of frogs in agriculture.

A frog is observed to be completely inactive and buried in soil during the months of May–June in northern India. What is this phenomenon called and how does the frog's physiology support survival during this period?

A student reads that frogs have a three-chambered heart, while mammals have a four-chambered heart. With reference to the frog's circulatory system, explain the structure of the frog's heart and suggest why a four-chambered heart may provide an advantage.

With reference to the digestive system of a frog, explain why the duodenum is considered a critical site of digestion. What would happen if the common bile duct were blocked?

A zoology student observes that frogs are not seen during December–January in a temperate region of India. Using concepts from Chapter 7, explain this observation.

You are given a dissected frog. How would you identify whether it is a male or a female, both externally and internally? Give at least four distinguishing features.

A biology teacher explains that the hepatic portal system in frogs is essential for the body's economy. With reference to the chapter, explain why blood from the intestine must pass through the liver before entering general circulation.

A student notices that a frog's eyes are much larger proportionally than those of most terrestrial animals and that they bulge outward. With reference to the chapter, explain what structure protects these eyes and the advantage of their large, bulging shape.

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