Answer: In amphibians, metamorphosis is generally associated with the changes that prepare an aquatic organism for a primarily terrestrial existence In (frogs and toads), the metamorphic changes are more dramatic, and almost every organ is subject to modification Regressive changes include the loss of the tadpole's teeth and internal gills, as well as the destruction of the tail. At the same time, constructive processes such as limb development are also evident. The means of locomotion changes as the paddle tail recedes while the hind limbs and forelimbs develop. The tadpole's cartilaginous skull is replaced by the predominantly bony skull of the frog. The teeth used for tearing pond plants disappear as the mouth and jaw take a new shape, and the tongue muscle develops. Meanwhile, the large intestine characteristic of herbivores shortens to suit the more carnivorous diet of the adult frog. The gills regress, and the gill arches degenerate. The lungs enlarge, and muscles and cartilage develop for pumping air in and out of the lungs. The sensory apparatus changes, too, as the lateral line system of the tadpole degenerates, and the eye and ear undergo further differentiation The middle ear develops, as does the tympanic membrane characteristic of frog and toad outer ears. In the eye, both ingratiating membranes and eyelids emerge.
jagged line of protein discs which attach thin filaments from
end to end, trace the boundary where
sarcomeres connect, thick type of
smallest muscle unit: composed of staggered arrays of many myosin molecules
which interact with actin when calcium is present.
