Which ones are ammonotelic animals?
(a) Amphibian and reptiles
(b) Bony fishes and amphibian tadpoles
(c) Cartilaginous and bony fishes
(d) Amphibians and mammals

Options

A. Amphibian and reptiles
B. Bony fishes and amphibian tadpoles
C. Cartilaginous and bony fishes
D. Amphibians and mammals

Answer

To determine which animals are ammonotelic, we need to understand what ammonotelism means and analyze each option provided in the question.

**Step 1: Understand Ammonotelism**
- Ammonotelic animals are those that excrete ammonia as their primary nitrogenous waste. Ammonia is highly toxic and requires a large amount of water for its excretion. Therefore, ammonotelic animals are typically aquatic, as they have access to sufficient water to dilute and excrete ammonia.

**Step 2: Analyze Each Option**
- **Option (a): Amphibians and reptiles**
- Amphibians can be ammonotelic during their larval stage (like tadpoles), but as adults, they often switch to ureotelism (excreting urea). Reptiles primarily excrete uric acid and are not ammonotelic. Therefore, this option is incorrect.

- **Option (b): Bony fishes and amphibian tadpoles**
- Bony fishes are known to be ammonotelic, as they excrete ammonia directly into the water. Amphibian tadpoles, being aquatic, also excrete ammonia. Thus, this option is correct.

- **Option (c): Cartilaginous and bony fishes**
- While bony fishes are ammonotelic, cartilaginous fishes (like sharks) are ureotelic, excreting urea instead of ammonia. Therefore, this option is incorrect.

- **Option (d): Amphibians and mammals**
- Most amphibians are not strictly ammonotelic as adults, and mammals are ureotelic, excreting urea. Thus, this option is incorrect.

**Conclusion:**
The correct answer is **(b) Bony fishes and amphibian tadpoles**, as both groups are ammonotelic.

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