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UPSC MainsZOOLOGY-PAPER-I201915 Marks
Q14.

Describe urinogenital system in both the sexes of Amniotes with the help of diagrams only (No description is required).

How to Approach

This question requires a purely diagrammatic answer focusing on the urinogenital systems of male and female amniotes. The approach should involve creating clear, labelled diagrams showcasing the key components of each system. Emphasis should be on anatomical accuracy and proper labelling of structures like kidneys, ureters, urinary bladder, urethra, gonads (testes/ovaries), and associated ducts. Since no description is asked for, the diagrams must be self-explanatory. A comparative approach, highlighting similarities and differences between the sexes, is beneficial.

Model Answer

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Introduction

Amniotes, a clade of tetrapod vertebrates comprising reptiles (including birds) and mammals, exhibit a sophisticated urinogenital system adapted for efficient waste removal and reproduction in terrestrial environments. The system is intricately linked, sharing common ducts for excretory and reproductive functions. Understanding the anatomical organization of these systems is crucial for comprehending physiological processes like osmoregulation, nitrogenous waste elimination, and gamete transport. This answer will present detailed, labelled diagrams illustrating the urinogenital systems in both male and female amniotes, adhering to the question's specific instructions.

Urinogenital System in Male Amniotes

The male amniote urinogenital system consists of kidneys, ureters, a urinary bladder, the urethra, and the reproductive organs – testes, epididymis, vas deferens, seminal vesicles, and penis. The kidneys filter blood, producing urine which travels through the ureters to the urinary bladder for storage. The urethra serves as a common pathway for both urine and semen.

Male Amniote Urinogenital System

Key Labels: 1. Kidney, 2. Ureter, 3. Urinary Bladder, 4. Urethra, 5. Testis, 6. Epididymis, 7. Vas Deferens, 8. Seminal Vesicle, 9. Penis.

Urinogenital System in Female Amniotes

The female amniote urinogenital system shares similarities with the male system, including kidneys, ureters, and a urinary bladder. However, the reproductive components differ significantly. The system includes ovaries, oviducts (fallopian tubes), uterus, cervix, and vagina. The urethra is shorter in females and opens separately from the vagina.

Female Amniote Urinogenital System

Key Labels: 1. Kidney, 2. Ureter, 3. Urinary Bladder, 4. Urethra, 5. Ovary, 6. Oviduct, 7. Uterus, 8. Cervix, 9. Vagina.

Comparative Table: Male vs. Female Amniote Urinogenital Systems

Feature Male Amniote Female Amniote
Gonads Testes Ovaries
Ducts Vas Deferens, Seminal Vesicles Oviducts
Accessory Glands Seminal Vesicles, Prostate Gland None
Urethra Length Longer Shorter
Common Opening Urethra serves both urinary and reproductive functions Separate openings for urethra and vagina

Detailed View of Kidney Structure (Common to both sexes)

Kidney Structure

Key Labels: 1. Renal Cortex, 2. Renal Medulla, 3. Renal Pelvis, 4. Ureter, 5. Nephron.

Conclusion

The urinogenital systems of male and female amniotes, while sharing fundamental components like the kidneys and ureters, exhibit distinct anatomical adaptations reflecting their respective reproductive roles. The diagrams presented illustrate the key structures and their arrangement, highlighting the functional integration of excretory and reproductive systems in these vertebrates. Understanding these anatomical differences is crucial for comprehending the physiological processes governing osmoregulation, waste elimination, and reproduction in amniotes.

Answer Length

This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.

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Additional Resources

Key Definitions

Amniotes
Amniotes are a clade of tetrapod vertebrates characterized by the presence of an amnion, a membrane surrounding the embryo, allowing for reproduction on land. This group includes reptiles, birds, and mammals.
Nephron
The nephron is the functional unit of the kidney, responsible for filtering blood, reabsorbing essential substances, and excreting waste products in the form of urine.

Key Statistics

Approximately 95% of vertebrate species are amniotes, demonstrating their evolutionary success and dominance in terrestrial ecosystems.

Source: Pough, F.H., Janis, C.M., & Cadle, J.S. (2015). Vertebrate Life (9th ed.). Pearson Education.

Mammalian kidneys receive approximately 20-25% of the cardiac output, demonstrating their high metabolic demand and crucial role in maintaining homeostasis.

Source: Silverthorn, D. U. (2016). Human Physiology: An Integrated Approach (7th ed.). Pearson Education.

Examples

Bird Excretory System

Birds lack a urinary bladder, excreting uric acid as a semi-solid paste to conserve water, an adaptation to their flight and terrestrial lifestyle. This is a specific adaptation within the amniote urinogenital system.

Frequently Asked Questions

▶What is the significance of the cloaca in some amniotes?

The cloaca is a common chamber and outlet for the digestive, urinary, and reproductive systems found in many reptiles, birds, and some mammals. It serves as a single opening for waste elimination and reproduction.

Topics Covered

ZoologyAnatomyAmniotes, Urinogenital System, Anatomy, Reptiles, Birds, Mammals
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