In this article, we will consider the stages of development of a frog. But first, let's talk a little about what kind of creatures these are. The frog belongs to the class of amphibians, the order of tailless.
Many noticed that her neck was not expressed - she seemed to have grown together with the body. Most amphibians have a tail, which the frog does not have, which, incidentally, is reflected in the name of the order.
The development of the frog takes place in several stages, we will return to them immediately after we analyze some features of these creatures.
What does a frog look like?
To begin with - the head. Everyone knows that the frog has rather large and expressive eyes located on both sides of its flat skull. Frogs also have eyelids, this feature is inherent in all terrestrial vertebrate creatures. The mouth of this creature has small teeth, and slightly above it are two nostrils having small valves.
The front legs of the frogs are less developed than the hind legs. The first have four fingers, the second - five. The space between the fingers is connected by a membrane, there are no claws.
Frog development takes place in several stages:
- Throwing caviar.
- Tadpoles of the early stage.
- Tadpoles late stage.
- Adults.
Their fertilization is external - the males fertilize the eggs already laid by the female. Incidentally, there are species that lay more than 20 thousand eggs in one throw. If everything goes well, then in ten days tadpoles are born. And after 4 months, full frogs are obtained from them. Three years later, a mature individual grows, which is completely ready for reproduction.
Now a little more about each step.
Caviar
Now we will analyze all stages of the development of the frog separately. Let's start with the very first - eggs. Although these creatures live on land, while throwing eggs, they are sent to the water. This usually occurs in the spring. Masonry takes place in quiet places, at a shallow depth, so that the sun can warm it. All eggs are interconnected, and this mass resembles jelly. One teaspoon is barely recovered from one individual. 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.
Caviar looks like a small ball with a diameter of about 1.5 millimeters. It is very light, has a black shell and increases greatly in size over time. Gradually, the caviar proceeds to the next stage of development of the frog - the appearance of tadpoles.
Tadpoles
After the birth of the light, the tadpoles begin to feed on the yolk, which still remains in small quantities in their intestines. This is a very fragile and helpless creature. This individual has:
- poorly developed gills;
- mouth;
- tail.
The tadpoles, in addition, are equipped with small Velcro, with which they are attached to various water objects. These Velcro bands 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 heal after 30 days of life and, as a result, are completely tightened by the skin and disappear.
It is important to know that even tadpoles already have small teeth necessary to consume algae in their food, and their intestines, arranged in the form of a spiral, allow maximum extraction of nutrients from what they eat. In addition, they have a chord, a two-chamber heart and blood circulation in the form of one circle.
Even at this stage of the development of the frog, the tadpoles can be considered completely social creatures. Many of them interact with each other, like fish.
The appearance of the legs
Since we consider the development of a frog in stages, the next step is to select tadpoles with legs. Their hind limbs appear much earlier than their front ones, after about 8 weeks of development - they are still very tiny. In the same period, you can see that the head in babies becomes more distinct. Now they can eat larger prey, such as dead insects.
The forelimbs are just beginning to form, and here we can highlight such a feature - the first elbow appears. Only after 9-10 weeks will a full-fledged frog form, although it is much smaller than its mature relatives, and even has a long tail. After 12 weeks, it completely disappears. Now small frogs can go to land. And after 3 years, a mature individual will form and will be able to continue its genus. We will talk about this in the next section.
Adult
After three long years, the frog can reproduce offspring into the light. This cycle in nature is endless.
To consolidate, we once again list the stages of development of the frog, the scheme will be our assistant in this:
the fertilized egg, represented by eggs, - a tadpole with external gills - a tadpole with internal gills and skin respiration - a formed tadpole with lungs, limbs and a gradually disappearing tail - a frog - an adult .