Crocodile, fish and frog on one hand and squirrel and crows on the other differ in the following.

Options

A. The former have four appendages, the latter have only two.
B. The body temperature of the former changes with environmental temperature , the temperature of the latter remains more or less constant.
C. The former undergo metamorphosis, the latter do not.
D. The former are oviparous, the latter are viviparous.

Answer

To analyze the differences between crocodiles, fish, and frogs on one hand and squirrels and crows on the other, we can break it down into several key points:

### Step-by-Step Solution:

1. **Classification of Animals**:
- Crocodiles belong to the class Reptilia.
- Fish belong to the class Pisces.
- Frogs belong to the class Amphibia.
- Squirrels belong to the class Mammalia.
- Crows belong to the class Aves (birds).

2. **Number of Appendages**:
- Crocodiles, fish, and frogs have four appendages (two pairs of limbs).
- Squirrels and crows have two pairs of appendages (two forelimbs and two hind limbs).

3. **Body Temperature Regulation**:
- Crocodiles, fish, and frogs are ectothermic (cold-blooded), meaning their body temperature changes with the environment.
- Squirrels and crows are endothermic (warm-blooded), meaning they can regulate their body temperature internally, keeping it constant regardless of the environment.

4. **Metamorphosis**:
- Crocodiles and frogs undergo metamorphosis (frogs transition from tadpoles to adult frogs).
- Squirrels and crows do not undergo metamorphosis; they develop directly into their adult forms.

5. **Reproductive Strategies**:
- Crocodiles and most fish are oviparous, meaning they lay eggs.
- Squirrels are viviparous, meaning they give birth to live young.

### Conclusion:
The primary differences between the two groups of animals can be summarized as follows:
- The former group (crocodiles, fish, frogs) has four appendages, is ectothermic, undergoes metamorphosis, and is primarily oviparous.
- The latter group (squirrels and crows) has two pairs of appendages, is endothermic, does not undergo metamorphosis, and is viviparous.