Excretory Products and their Elimination
The excretory system in humans is responsible for removing waste products from the body to maintain homeostasis. Here are the key excretory products and how they are eliminated:

1. Ammonia:
- Ammonia is a toxic waste product produced by the breakdown of proteins.
- Aquatic animals like fish excrete ammonia directly into the water through their gills.
- Terrestrial animals convert ammonia into less toxic urea or uric acid for excretion.

2. Urea:
- Urea is the primary nitrogenous waste product in humans, formed in the liver from ammonia.
- It is eliminated from the body through the kidneys in the form of urine.

3. Uric Acid:
- Uric acid is another nitrogenous waste product that is less toxic than ammonia and urea.
- It is excreted by birds and reptiles as a paste or solid waste.

4. Carbon Dioxide:
- Carbon dioxide is a waste product of cellular respiration.
- It is eliminated from the body through the lungs during exhalation.

5. Water and Electrolytes:
- Excess water and electrolytes like sodium, potassium, and chloride are excreted by the kidneys to maintain proper balance in the body.
The excretory system plays a crucial role in maintaining the internal environment of the body by eliminating waste products and regulating the balance of fluids and electrolytes. Understanding the excretory system is essential for students studying biology in Class 11, as it provides insights into how the body rids itself of waste to ensure optimal functioning.