Each of us, even if only in the pictures, saw frogs and lizards, crocodiles and toads - these animals belong to the classes Amphibians and Reptiles. The example we cited is far from the only one. There are really a lot of such creatures. But how to distinguish who is who? What is the difference between amphibians and reptiles and how significant are these differences?
Crocodile and toad can coexist perfectly in one pond. Therefore, it is likely that it may seem that they are relatives and have common ancestors. But this is a huge mistake. These animals belong to different systematic classes. There are many fundamental differences between them. And they are not only in appearance and size. A crocodile and a lizard are reptiles, and a frog and a toad are amphibians.
But, of course, amphibians and reptiles have some similarities. They prefer areas with a warm climate. True, amphibians choose humid places, preferably near ponds. But this is dictated by the fact that they reproduce only in water. Reptiles are not connected with water bodies. On the contrary, they prefer drier and hotter regions.
Let's look at the structure and physiological characteristics of reptiles and amphibians, and compare how they differ from each other.
Class Reptiles (reptiles)
The Reptiles, or Reptiles, are terrestrial animals. They got their name thanks to the method of movement. Reptiles do not walk on the ground, they crawl. It was the reptiles for the first time that completely switched from aquatic to land lifestyles. The ancestors of these animals spread widely on the earth. An important feature of reptiles is internal fertilization and the ability to lay eggs rich in nutrients. They are protected by a dense shell, which includes calcium. It was the ability to lay eggs that contributed to the development of reptiles outside the reservoir on land.
Reptile structure
The body of reptiles has strong formations - scales. They tightly cover the skin of reptiles. This protects them from moisture loss. Reptile skin is always dry. Evaporation through it does not occur. Therefore, snakes and lizards are able to live in deserts, without experiencing discomfort.
Reptiles breathe with the help of fairly well-developed lungs. It is also important that intensive breathing in reptiles became possible due to the appearance of a fundamentally new skeleton department. The chest occurs for the first time in reptiles. It is formed by ribs extending from the vertebrae. From the ventral side they are already connected to the sternum. Thanks to the special muscles, the ribs are mobile. This contributes to the expansion of the chest at the time of inspiration.
The Reptile class has undergone changes from the circulatory system. This is due to the complication of the structure of the lungs. The vast majority of reptiles have a three-chambered heart; they, like amphibians, have two circles of blood circulation. However, there are some differences. For example, there is a septum in the ventricle. With a contraction of the heart, it practically divides it into two halves (right - venous, left - arterial). The location of the main blood vessels more clearly distinguishes between arterial and venous flows. As a result, the body of reptiles is supplied with oxygen-enriched blood much better. Moreover, they have more established processes of intercellular metabolism and the removal of metabolic products and carbon dioxide from the body. There is an exception in the Reptiles class, an example is a crocodile. His heart is four-chamber.
The main large arteries of the small and large circles of blood circulation are fundamentally the same for all groups of terrestrial vertebrates. Of course, there were some minor differences. In reptiles in the pulmonary circulation , skin veins and arteries disappeared. Only the pulmonary vessels remained.
Currently, about 8 thousand species of reptiles are known. They live on all continents, except, of course, Antarctica. Four groups of reptiles are divided: crocodiles, scaly, turtles and first-movers.
Breeding reptiles
Unlike fish and amphibians, reproduction in reptiles is internal. They are dioecious. The male has a special organ with the help of which he introduces sperm into the cloaca of the female. They penetrate the eggs, after which fertilization occurs. Eggs develop in the body of a female. Then she lays them in a prepared place, as a rule, this is a dug hole. Outside, reptile eggs are covered with a dense calcium shell. They contain the embryo and the supply of nutrients. Not a larva emerges from an egg, as in fish or amphibians, but individuals capable of independent life. Thus, the reproduction of reptiles fundamentally goes to a new level. The embryo undergoes all stages of development in the egg. After hatching, it does not depend on the reservoir and may well survive on its own. As a rule, adults do not care about their offspring.
Class Amphibians
Amphibians, or amphibians, are frogs, toads and newts. With rare exceptions, they always live near a reservoir. But there are species that live in the desert, such as the toad-aquifer. During rain, she draws fluid into the subcutaneous sacs. Her body is swelling. Then it burrows in the sand and, secreting a large amount of mucus, experiences a long drought. Currently, about 3400 species of amphibians are known. They are divided into two orders - tailed and tailless. The former include salamanders and newts, while the latter include frogs and toads.
Amphibians are very different from the Reptiles class, for example, the structure of the body and organ systems, as well as the method of reproduction. Like their distant ancestors of fish, they spawn in the water. For this, amphibians often look for puddles separated from the main body of water. Here, fertilization and the development of larvae occur. This means that during the breeding season, amphibians have to return to water. This greatly interferes with their resettlement and limits their mobility. Only a few species were able to adapt to life away from water bodies. They give birth to mature offspring. That is why these animals are called semi-aquatic.
Amphibians are the first of the chordates to develop limbs. Thanks to this, in the distant past, they were able to land. Naturally, this caused a number of changes in these animals not only anatomical, but also physiological. Compared to species remaining in the aquatic environment, amphibians have wider breasts. This contributed to the development and complication of the lungs. Amphibians improved their hearing and vision.
Amphibian habitats
Like reptiles, amphibians prefer to live in warm regions. Usually frogs are found in humid places near water bodies. But you can see them in the meadows and in the forests, especially after heavy rain. Some species feel great even in deserts. For example, the Australian toad. She is very well adapted to survive a long drought. In such circumstances, other species of toads would certainly die quickly. But she learned how to store vital moisture in her hypodermic pockets during the rainy season. In addition, during this period, it multiplies, laying eggs in puddles. For tadpoles, one month is enough for a complete transformation. Australian toad, in extreme conditions for its appearance, not only found a way to reproduce offspring, but also successfully search for myself writing.
Differences between reptiles and amphibians
Although at first glance it seems that amphibians are not much different from reptiles, this is far from the case. In reality, there are not so many similarities. Amphibians have less perfect and developed organs than the Reptile class, for example, amphibian larvae have gills, while the offspring of reptiles are already born with formed lungs. In fairness, it should be noted that newts, and frogs, and turtles, and even snakes may well coexist on the territory of one reservoir. Therefore, some do not see significant differences in these units, often confused about who is who. But the fundamental differences do not allow combining these species into one class. Amphibians always depend on their habitat, that is, a reservoir, in most cases they cannot leave it. With reptiles, things are different. In the event of drought, they may well make a short trip and find a more favorable place.
This is largely due to the fact that the skin of reptiles is covered with horny scales that do not allow moisture to evaporate. Reptile skin is devoid of glands that secrete mucus, so it is always dry. Their body is protected from drying out, which gives them distinct advantages in a dry climate. Moults are characteristic of reptiles. For example, the body of a snake grows all its life. Her skin is wearing out. They inhibit growth, so once a year she "dumps" them. Amphibians have bare skin. It is rich in glands that secrete mucus. But in extreme heat, amphibian can get heat stroke.
Ancestors of reptiles and amphibians
The ancestors of amphibians were cysterae fishes. Five-fingered limbs subsequently formed from their paired fins. The external structure of the reptiles indicates that their distant ancestors were amphibians. This is evidenced by both anatomical and physiological similarities. Among the vertebral orders, they were the first to leave the aquatic environment and land. For many thousands of years, they have dominated other species. The end to this was the accession of mammals. Why this happened is not known for certain. There are many assumptions, most of which are supported by undeniable evidence. This is a global catastrophe caused by a meteorite fall, and the appearance of flowering plants, and a change in climate. Subsequently, many reptiles returned to the aquatic environment. But their internal organs remained quite suitable for life on land. Currently, a representative of such species is a sea turtle.
Differences in the structure of organs
Amphibians and reptiles breathe atmospheric air through their lungs. But amphibian larvae retain gills. Reptiles do not have them. In addition, reptiles have a more complex nervous system. They have the rudiments of the cerebral cortex, the cerebellum and sense organs are more developed. Crocodiles, lizards and chameleons are better adapted to life on land. They have better hearing, vision, and the organs of taste, smell, and touch are quite well developed. Amphibians have almost no taste buds . Although they have a well-developed, acute sense of smell.
In reptiles, the circulatory and excretory systems are complicated. Their blood in large vessels is better divided into arterial and venous. In addition, skin vessels, which are very developed in amphibians, disappeared in reptiles. This is due to the fact that about half of the oxygen of a frog and newts are obtained through skin respiration. Being under water, they do not use the lungs. Reptiles cannot absorb oxygen in this way. Therefore, they do not need skin arteries and veins. They breathe exceptionally well developed lungs.
Amphibians and reptiles have a different number of parts of the spine. Reptiles have five, and amphibians have four. Tailless species have no ribs.
The difference in breeding methods
Fish, amphibians, reptiles vary significantly in the method of reproduction. Reptiles have internal fertilization. Eggs are formed inside the female. Then, as a rule, she lays them in the dug hole and digs them on top. Both crocodiles and turtles do the same. Cubs hatch fully developed, from adults they differ only in size. Viviparous reptiles also exist. They "give birth" to the light of the formed cub in the leathery shell. This method of reproduction is inherent in some species of snakes. A born baby breaks the shell and crawls away. He leads an independent life. It was the ability to lay eggs in a hard shell that gave an evolutionary advantage to reptiles over amphibians. This made possible their resettlement in various corners of the earth. They exist in forests, deserts, mountains and plains. The structural features of reptiles allow them to live in water.
In amphibians, reproduction occurs in a pond. Females spawn in the water. The males let in the sperm, which fertilize the eggs. First, larvae hatch. Only after two or three months will they finally turn into cubs.
The way of life of reptiles and amphibians
Many amphibians are only born in water, and they spend their entire adult life on land. But there are species of amphibians, for example, newts, which do not leave the aquatic environment. In adverse conditions, such land species as frogs, toads can again return to the reservoir. Amphibians feed on plant foods and invertebrates. They do not live long. Some species of toads can live up to 8 years, and newts - only 3 years.
The peculiarities of reptiles are that they are not dependent on water. They are able to reproduce in its absence. Reptiles eat a variety of foods. Insects are included in the diet of small lizards. Snakes prey on rodents. They can eat bird eggs. Crocodiles and monitor lizards prefer herbivorous mammals - roe deer, antelopes and even large buffalo. Turtles eat plant foods. Reptiles are real centenarians. Ground turtles were discovered, whose age is more than 200 years. Crocodiles can live 80 years, and snakes and monitor lizards - up to 50.
conclusions
Reptiles differ from amphibians in the following ways:
1. Habitats. Amphibians prefer damp and moist places near ponds. Reptiles are not related to water.
2. The skin of reptiles is devoid of glands. It is dry and covered in scales. In amphibians, on the contrary, it is dotted with glands that secrete a large amount of mucus.
3. Moults are inherent in reptiles.
4. The ancestors of reptiles are amphibians.
5. In reptiles, the nervous and circulatory systems are more developed and improved.
6. In crocodiles, lizards, snakes and other species, internal fertilization.
7. Amphibians have four sections of the spine, and reptiles have five. There are similarities between mammals and reptiles.
Interesting Facts
The largest reptiles that ever existed on earth are dinosaurs. They disappeared about 65 million years ago. They inhabited both the sea and the land. Some species were able to fly. Currently, the oldest reptiles are turtles. They are over 300 million years old. They existed in the era of dinosaurs. Crocodiles and the first lizard appeared a little later (see their photo in this article). Snakes are “only” 20 million years old. This is a relatively young species. Although their origin is currently one of the great mysteries of biology.