Common forms of nitrogenous waste of organisms are

Answer

### Step-by-Step Solution:

1. **Identify the Common Forms of Nitrogenous Waste**:
The common forms of nitrogenous waste produced by organisms are ammonia, urea, and uric acid.

2. **Define Each Form**:
- **Ammonia**: This is the most toxic form of nitrogenous waste. It is highly soluble in water and is primarily excreted by aquatic organisms.
- **Urea**: This is less toxic than ammonia and is soluble in water. It is excreted by many terrestrial animals, particularly mammals.
- **Uric Acid**: This is the least toxic and is excreted in a semi-solid form. It is primarily produced by organisms that need to conserve water, such as reptiles and birds.

3. **Classify Organisms Based on Nitrogenous Waste**:
- **Ammonotelic Organisms**: These organisms excrete ammonia. Examples include protozoans and the tadpoles of amphibians.
- **Ureotelic Organisms**: These organisms excrete urea. Examples include mammals.
- **Uricotelic Organisms**: These organisms excrete uric acid. Examples include reptiles and birds.

4. **Summarize the Information**:
The three common forms of nitrogenous waste are:
- Ammonia (excreted by ammonotelic organisms like protozoans and tadpoles)
- Urea (excreted by ureotelic organisms like mammals)
- Uric Acid (excreted by uricotelic organisms like reptiles)