1. Explain the respiratory system of fish with reference to gills.
Answer:
Introduction:
Fish primarily rely on gills for respiration, an adaptation to aquatic life. Gills extract dissolved oxygen from water and expel carbon dioxide.
Structure of Gills:
- Gills are composed of gill arches, gill filaments, and lamellae.
- The lamellae are thin, vascularized structures that maximize the surface area for gas exchange.
Mechanism of Respiration:
- Water enters through the mouth and passes over the gills.
- Oxygen diffuses from water into blood within the gill lamellae, while carbon dioxide diffuses out.
- The countercurrent exchange mechanism ensures efficient oxygen uptake.
2. Describe the tracheal respiratory system in insects.
Answer:
Introduction:
Insects possess a tracheal system for direct gas exchange with tissues, bypassing the circulatory system.
Structure:
- The tracheal system comprises spiracles, tracheae, and tracheoles.
- Spiracles are external openings; tracheae are larger tubes, and tracheoles are fine branches reaching cells.
Mechanism of Respiration:
- Air enters through spiracles and travels through tracheae to tracheoles.
- Gas exchange occurs directly at the cellular level.
- Rhythmic body movements assist in ventilation.
3. Compare the respiratory systems of amphibians and reptiles.
Answer:
Amphibians:
- Use multiple modes: cutaneous, buccopharyngeal, and pulmonary respiration.
- Skin is moist and vascularized for cutaneous respiration.
- Lungs are simple and sac-like.
Reptiles:
- Solely rely on pulmonary respiration.
- Lungs are more developed with internal folds to increase surface area.
- Ventilation is achieved by rib cage movement.
4. How do birds achieve efficient respiration at high altitudes?
Answer:
Birds have a highly efficient respiratory system with air sacs and parabronchi.
Mechanism:
- Air sacs store and direct airflow.
- Parabronchi allow unidirectional airflow, maintaining a continuous oxygen supply.
- Crosscurrent exchange maximizes oxygen absorption.
5. Explain the role of alveoli in mammalian respiration.
Answer:
Alveoli are microscopic air sacs in the lungs where gas exchange occurs.
Structure:
- Thin walls surrounded by capillaries.
- Large surface area and moist lining facilitate diffusion.
Function:
- Oxygen diffuses from alveoli into blood; carbon dioxide diffuses out.
- Surfactants reduce surface tension, preventing alveolar collapse.
6. Discuss the countercurrent exchange system in fish respiration.
Answer:
The countercurrent exchange system enhances oxygen uptake in fish.
Mechanism:
- Blood flows in the opposite direction to water across the gill lamellae.
- This maintains a gradient where oxygen-rich water meets oxygen-poor blood, optimizing diffusion.
Significance:
- Ensures maximum oxygen extraction from water.
7. What are book lungs, and in which animals are they found?
Answer:
Book lungs are respiratory organs found in arachnids like spiders.
Structure:
- Consist of stacked lamellae resembling pages of a book.
- Lamellae are enclosed in a chamber with a slit-like opening for air entry.
Function:
- Oxygen diffuses into hemolymph; carbon dioxide diffuses out.
8. Explain cutaneous respiration with examples.
Answer:
Definition:
Cutaneous respiration involves gas exchange through the skin.
Examples:
- Amphibians like frogs and earthworms.
- Skin must be moist and vascularized for effective diffusion.
Significance:
- Supports oxygen intake when lungs or gills are less functional.
9. Describe the respiratory adaptations in aquatic mammals.
Answer:
Aquatic mammals like whales and seals have adapted to hold their breath underwater.
Adaptations:
- Large myoglobin stores in muscles for oxygen storage.
- Reduced heart rate during dives (bradycardia).
- Efficient oxygen utilization and carbon dioxide tolerance.
10. How do reptiles ventilate their lungs?
Answer:
Reptiles use negative pressure breathing.
Mechanism:
- Rib cage expansion increases thoracic volume, reducing pressure.
- Air is drawn into the lungs.
- Expiration occurs as muscles contract, compressing the lungs.
11. Discuss the evolutionary significance of lungs in vertebrates.
Answer:
Lungs mark a major evolutionary step, enabling life on land.
Development:
- First appeared in early amphibians.
- Allowed gas exchange in terrestrial environments.
Adaptations:
- Complex alveolar structures in mammals for efficient gas exchange.
12. What is buccopharyngeal respiration in amphibians?
Answer:
Buccopharyngeal respiration occurs in the mouth and pharynx lining of amphibians.
Mechanism:
- Oxygen diffuses through the moist lining of the buccal cavity into blood.
- Carbon dioxide diffuses out.
13. How do air sacs function in bird respiration?
Answer:
Air sacs in birds store air and maintain unidirectional flow through lungs.
Function:
- Fresh air enters lungs even during exhalation.
- Enhances oxygen absorption and supports flight.
14. Explain the tracheal system in terrestrial arthropods.
Answer:
Terrestrial arthropods, like insects, use a tracheal system.
Features:
- Spiracles regulate air entry.
- Tracheae and tracheoles deliver oxygen directly to tissues.
Advantages:
- No reliance on circulatory system for gas transport.
15. How does the respiratory system of annelids work?
Answer:
Annelids, like earthworms, use cutaneous respiration.
Mechanism:
- Oxygen diffuses through the moist, vascularized skin.
- Capillaries transport gases to and from tissues.
16. Compare respiration in aquatic and terrestrial environments.
Answer:
Aquatic Respiration:
- Gills extract dissolved oxygen from water.
- Efficient countercurrent exchange in fish.
Terrestrial Respiration:
- Lungs evolved to extract oxygen from air.
- Structures like alveoli enhance gas exchange efficiency.
17. What is the role of hemoglobin in respiration?
Answer:
Hemoglobin is a respiratory pigment in blood.
Function:
- Binds oxygen in the lungs and releases it in tissues.
- Transports carbon dioxide back to the lungs.
18. Describe the respiratory system in amphibians during metamorphosis.
Answer:
- Larvae (e.g., tadpoles) use gills.
- Adults develop lungs and use cutaneous respiration.
- Transition supports life both in water and on land.
19. What is the significance of respiratory pigments in animals?
Answer:
Respiratory pigments enhance oxygen transport.
Examples:
- Hemoglobin in vertebrates.
- Hemocyanin in arthropods and mollusks.
20. Explain the role of surfactants in mammalian lungs.
Answer:
Surfactants reduce surface tension in alveoli.
Function:
- Prevents alveolar collapse during exhalation.
- Ensures efficient gas exchange.
