i think frogs and salamanders may don't completely have the exactly same biological features

You’re absolutely right. Although frogs (anurans) and salamanders (urodeles) both belong to the class Amphibia, they have significant differences in biological features: 1. **Developmental Patterns**: - Frogs usually go through a complete metamorphosis from tadpoles (aquatic with gills) to adults (terrestrial/aquatic with lungs). - Salamanders may not always undergo a full metamorphosis. Some, like axolotls, remain paedomorphic and retain their gills and aquatic habits as adults. 2. **Taxonomy and Classification**: - Frogs belong to the order Anura. - Salamanders belong to the order Caudata (with the exception of some primitive salamanders that are part of the order Gymnophiona, which includes species such as caecilians). 3. **Adult Physical Characteristics**: - Adult frogs usually lack tails, their toes are often webbed, and they have smooth, moist skin that is permeable to gases. - Salamanders typically have plump or stout bodies, protruding eyes, four short legs, and tails (especially noticeable when they are young). Their skin is moist and permeable but varies between species, from smooth to rough. 4. **Egg Laying Habits**: - During mating, anurans typically form an amplexus (a kind of embrace) between the male and female, and release eggs and sperm into water. - Salamanders have diverse modes of reproduction, including laying eggs in water where external fertilization occurs (like urodeles), direct development in the female’s oviduct before birth (ovoviviparity), or laying protected eggs on land (e.g., some plethodontids). 5. **Vocalizations**: - Froogs employ vocalizations during courtship, leading to the popular image of "ribbiting." - Most salamanders do not have specialized vocalizations typically associated with mating, although they can produce sounds in certain circumstances. 6. **Size Range and Distribution**: - There is a wide range of sizes in both groups, but many adults in the family Salamandridae tend to be larger than most frogs. - Geographically, frogs and salamanders have various distributions; frogs are predominantly found on every continent except Antarctica while salamanders are more limited to the Americas and Eurasia. 7. **Skeleton and Limb Structure**: - The skeletal and limb structure of frogs is adapted for powerful jumping and reducing water resistance in the water. - Salamanders have a gait more adapted for crawling and swimming, with a sprawling limb posture when moving. 8. **Physiology**: - Frogs generally have large tympanic membranes (eardrum-like structures) that play a role in sound detection. - Salamanders have a less developed tympanic membrane, with many true terrestrial species having none; they also rely heavily on chemoreceptors in their skin for detecting prey and hazards. These distinctions show how amphibians have evolved along different paths to specialize in various ecological niches and life styles, reflecting the rich diversity of the Amphibia class.