In this article we will look at the stages of frog development. But first, let's talk a little about what kind of creatures. The frog belongs to the class of amphibians, the order of tailless.
Many people noticed that her neck was not pronounced - she seemed to have grown together with her body. Most amphibians have a tail, which the frog is missing, which, by the way, is reflected in the name of the squad.
The frog's development takes place in several stages, we will return to them immediately after we analyze some features of these creatures.
For a start, a head.Everyone knows that a frog has rather large and expressive eyes, located on both sides of its flat skull. The frogs have eyelids, this feature is inherent in all terrestrial vertebrate creatures. The mouth of this creature has small teeth, and a little above it there are two nostrils with small valves.
The forelimbs of frogs are less developed than the hind ones. The first have four fingers, the second - five. The space between the fingers is connected by a membrane, the claws are missing.
The development of a frog takes place in several stages:
Оплодотворение у них внешнее - самцы fertilize eggs already laid by the female. By the way, there are such species that lay more than 20 thousand eggs for one throwing. If everything goes well, then in ten days tadpoles are born. And after 4 months of them are obtained full frogs. Three years later, a mature individual grows, which is fully prepared for reproduction.
Now a little more about each stage.
Now we will examine all the stages of the frog's development.separately. Let's start from the very first - eggs. Although these creatures live on land, while spawning, they set off into the water. This usually occurs in the spring. The masonry takes place in quiet places, at a shallow depth, so that the sun can warm it. All the eggs are interconnected, and this mass resembles jelly. From one individual it is barely one teaspoonful. All this jelly mass is necessarily attached to the algae in the pond. Small species lay about 2-3 thousand eggs, large individuals - 6-8 thousand.
Икринка выглядит как маленький шарик, диаметром about 1.5 millimeters. It is very light, has a black shell and with time greatly increases in size. Gradually, the roe proceeds to the next stage of development of the frog - the appearance of tadpoles.
After the birth of the tadpoles begin to eat the yolk, which is still left in a small amount in their intestines. This is a very fragile and helpless creature. This individual has:
Tadpoles, in addition, are equipped with smallVelcro, with which they are attached to different water objects. These velcro are located between the mouth and abdomen. In the attached state, the babies are about 10 days, after which they begin to swim and eat algae. Their gills gradually overgrown after 30 days of life and, as a result, they are completely tightened by the skin and disappear.
Важно знать и то, что даже у головастиков уже there are small teeth needed to consume algae, and their intestines, arranged in the form of a spiral, allows you to maximize the nutrients from the eaten. In addition, they have a chord, two-chamber heart and blood circulation in the form of one circle.
Even at this stage of the frog's development, tadpoles can be considered quite social creatures. Many of them interact with each other, like fish.
Так как мы рассматриваем развитие лягушки по stages, then the next stage select the tadpoles with legs. Their hind limbs appear much earlier than the front, after about 8 weeks of development - they are still very tiny. In the same period, you can see that the head of the kids becomes more distinct. Now they can eat larger prey, such as dead insects.
Fore limbs are just starting.form, and here we can distinguish such a feature - the elbow appears first. Only after 9-10 weeks a full-fledged frog will form, however, it is much smaller than its mature congeners, and even has a long tail. After 12 weeks, it disappears completely. Now small frogs can go on land. And in 3 years a mature individual will be formed and will be able to continue its genus. This is discussed in the next section.
After three long years have passed, the frog can reproduce offspring into the light. This cycle in nature is endless.
To fix once again we will list the stages of development of the frog, the scheme will be our assistant in this:
fertilized egg presentedeggs, - a tadpole with external gills - a tadpole with internal gills and skin breathing - a formed tadpole with lungs, limbs and a gradually disappearing tail - a frog - an adult individual.
