Greeting the Outside World
Imagine a world, a very large world, much bigger than you and I will ever experience. Imagine you are trapped inside a hard casing, with no way to get out. And even if you could get out, you would still be nothing but a soupy mixture, not fully formed.
You retain this form for a couple of weeks, your body slowly taking shape. During this time, you unhurriedly float past many wondrous beings. You spy a large fish devouring dozens of tiny organisms, floating through the water. They’re just as helpless as you are. You also spy dozens of your brethren, all trapped inside the same hard casing as you, submerged in the deep. Many of them are swallowed up by numerous predators, each one more diverse and terrifying than the last.
Becoming a Tadpole
You soon begin to grow too large for the casing. You are ready to hatch. Many others of your species are nearing this point as well. You begin to emerge, piercing the soft inner layer of your egg. This is the easy part, for once you puncture your way through the inner layer, you must force your way out of the extremely hard outer layer.
You wriggle through the tiny opening you have made in the egg. You swim to safety as quickly as possible, as you don’t want any bodily harm from a predator. You use your long, sinuous tail to quickly glide through the water to a small alcove in a rock wall. You check the interior before making yourself at home, for you never know what may lay hidden in the deep places of the world.
Once you grow a little bigger, you leave the cave to go and find some food. Quickly, carefully, you speed through the water in search of your first meal. This goes on for about two weeks. During this time, you begin to experience several changes in your body. You begin to form small back legs and lungs.
The latter change allows you to breathe in air, while your original gills allow you to breathe in water as well. This is what makes you an amphibian, able to survive on land as well as in water. Your body grows much larger and you continue to develop into your adult form. As your body grows, your tail becomes much shorter, as you don’t need it much for swimming anymore.
Soon, you are ready to walk on land with your tail now nothing more than a stub. Your back legs are large and strong, enabling you to jump great distances. Your front legs are smaller and used for balance for when you are jumping.
You have also developed the ability to breathe right through your skin, which is a very useful talent. And finally, you have formed a great tongue that can stretch great distances to catch prey. Your tongue is also sticky so that when the tongue touches your prey, it will stick to it and be taken into your mouth as your meal.
You catch a bug, and when your tongue arrives back at your mouth with the prey; you crush it and are satisfied. You continue to hunt and feed for a few weeks, all while preparing for the mating season. By the time the mating season comes near, you’ve grown quite a bit, almost doubling in size from the time when you could crawl out of the water.
The process which you have just gone through is known as metamorphosis. It’s a fascinating transformation, with a tadpole being very different from a fully-grown frog. Though frogs might be of different species, they usually all start off the same way; as a mass of black eggs in a sort of jelly, which is called frogspawn. The number of eggs in any such mass depends on what species of frog laid it.
Metamorphosis itself is triggered by the thyroid gland in each tadpole. This happens a few weeks after hatching. Until this activation occurs, the tadpoles have to live underwater all the time.
When you’re an adult frog on land, each of your organs has almost completely changed from the time when you were a tadpole. This is why you first gradually developed hind legs, then front legs, then lost your tail and began to grow rapidly. When your tail starts to disappear, you may already have developed a frog-like face instead of that tadpole head. As a tadpole, your skull was of cartilage, which is little more than a hard tissue. During metamorphosis, however, that cartilage will slowly transform into bone.
Finally, you have obviously developed the ability to croak! This will come in very handy for communicating with others of your species, especially during mating season. You won’t be able to find a mate unless you croak for her!
The Invisible Changes
The change from a soft skull to a fully formed bony structure and from gills to lungs might be apparent in the way you look and act. For instance, when you crawl onto the shore, you now have fully formed lungs to help you breathe. There are also some changes that may not be immediately apparent to the outside eye, such as your teeth.
As your tongue grows, your tadpole teeth start to disappear. You once had horn-like teeth that could tear up plants, but now your tongue provides you with the insects and bugs you need to survive. Your tadpole form also had a large intestine, which was essential for digesting your diet of plants and algae. Now, that intestine has shrunk in order to accommodate your meaty diet. Again, one can’t notice the change unless they slice open a tadpole and then a frog, then scrutinizing their innards using the correct equipment.
Encountering a Crocodile
The day before the mating season begins, you taste the scent of danger in the air. You tense up as you prepare for flight. It’s a crocodile, one of the most feared predators of all! This amphibian is a literal killing machine, armed with teeth as sharp as a woodpecker’s beak and talons that can slice through flesh like butter. And if that was not enough, the crocodile has a heavily armored body and can swim faster than sleek silverfish itself. The crocodile nears. You hunker down in a dark corner, hoping that it doesn’t see or smell you.
This hope is in vain, for the crocodile has an incredible sense of smell and can detect the scent of prey amid a host of different odors. It snarls and draws near. For a time, it seems like there is nothing you can do but accept your fate.
But then, something very unexpected happens. A deafening crack shoots through the air, and the crocodile roars in pain and agony. It slumps down to the ground and begins to feebly crawl away. A large creature that walks on two legs emerges from the trees. Whoever, whatever it is, it has somehow saved your life. Apparently, Mother Nature has decided to take pity on you today. You can now move on to the mating season, find a suitable mate, and carry your species forward.
Keeping the Species Alive
The mating season begins on the next day. Frog mating is a strange affair. You, as a male frog, must attract a female by making long, croaking noises with your throat. If the female approves, then you will undergo the mating ceremony, and the female will go and lay her eggs. Once this is completed, you and your mate will most likely never see each other again, but you will have accomplished your goal. This goal is the evolutionary one of keeping alive your species of shape-shifting wonders, the frogs.