25 Q 4

Compare the general life history patterns of salamanders with those of frogs. Which group shows a greater variety of evolutionary changes of the ancestral biphasic amphibian life cycle?

Salamanders reproduce by internal fertilization: the male drops the spermatophore and the female picks it up in her vent. Eggs are laid in plants on the bottom of the water. Then, some species have aquatic larva with external gills and a finlike tail. They then morph into terrestrial adults (unless they are aquatic forms). The terrestrial species do not have a larval form. Frogs undergo a process called amplexus when they mate; although it appears to be internal fertilization, it is really external. Eggs are laid in water, each surrounded by a jelly material. They hatch into tadpoles with gills and a tail. The tail and gills gradually disappear, and the frog moves on to its adult terrestrial life (unless it is aquatic!)

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