Chapter 29, Problem 15STP

Summary Introduction

To write:

The changes a tadpole goes through before becoming a frog.

Introduction:

Amphibians include toads, frogs, salamanders, newts, and legless caecilians. Most amphibians are distinguished by moist skin without scales, four legs, exchange of gases through skin, a circulatory system with double loop, lungs, and aquatic larvae.

Explanation of Solution

The female frog laid eggs to be fertilized by males in the water. The eggs do not have shells or protective coverings to keep them from drying out. The eggs are surrounded by a jelly-like sticky substance that helps them remain attached to vegetation in the water. After fertilization, the developing embryo uses the yolk in the egg for nourishment until it hatches into a tadpole. The tadpole moves from a gill-breathing, legless herbivore with fins and a two-chambered heart. The periods of metamorphosis are mainly under the influence of chemicals released into the body of the tadpole.When the tadpole hatches it looks like a fish than a frog. It has gills that helped them to breathe under the water. The tadpole can swims, eats algae and plants from the water, and develops for a few weeks.During this time, the tadpole begins to build the lungs so that it can breathe out of the water when it becomes a frog. The tadpole, also, begins to develop two hind legs. Now, instead of just floating, it can hop around. Although the tadpole is starting to look a little bit more like a frog, it still has a very long tail.The tadpole develops two front legs, and its long tail develops shorter and shorter. The tadpole uses the nutrients contained in its tail as food, so it doesn't need much else to eat until its tail is absolutely gone. But there is just a little stub of his tail left, and the tadpole is a small frog. It jumps out of the water and onto the dry land for the first time.

Conclusion

Thus, the tadpole progresses through the growth of the front legs, changes in the structure of the face, replacement of the cartilage with the hard bone in the head, loss of gills and enlargement of the lungs.