What gland is found in Human Skin but not Frog Skin?

The answer is a structure specific to mammals and it's sweat glands

Answers:

1. Adaptations to survive in specific island conditions:

Morphological adaptations for eating food resources from a specific island. For example, a mandibular structure adapted to eat the food that they obtain.

Behavioral adaptations to avoid depredators. For example, diurnal habits because predators have nocturnal habits.

Physiological adaptations to survive in specific conditions. For example, a lower metabolic rate if food resources are limited.  

Stress-induced adaptations to survive in specific stressful conditions. For example, reduction in transpiration is a stress-induced adaptation that enables to rat survive if water resources are limited.

2. Example: Introduction of the rat with diurnal habits in the island with predators that has the same habits is a challenge to survive in this new environment. In this case, the rat can develop different strategies to avoid predators: specific sounds to alert other members of the population on the presence of predators, an immobile pose to simulate death, etc.