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Amphibians


In the vicinity of streams, ponds, dams, wetlands and other wetlands, you can hear the sounds of amphibians - frogs, frogs, tree frogs.

What are amphibians anyway? The word amphibian, of Greek origin, means "double life", because these animals are able to live in the terrestrial environment in adulthood, but depend on water for reproduction.

In the evolution of life on our planet, amphibians were the first vertebrates to occupy the terrestrial environment, although not effectively. In addition to having a very thin skin that does not protect from dehydration, they lay eggs without shell, which become dry if they remain out of water or humid environments. So this group of animals, not independent of watersince at least one phase of life for most amphibians happens in the water and they need it for reproduction.

Coverage and body temperature

They have no hair or external scales. They are unable to keep their body temperature constant, so they are called cold-blooded animals (pecyrothermic).

Thin skin, rich in blood vessels and glands, through breathing allows them to absorb water, which acts as an organic defense. When they are "thirsty", amphibians touch the ventral region of their body in water and absorb it through their skin.

At glands on your skin are of two types: mucous membranes, which produce mucus, and serous, which produce poison. All amphibians produce toxic substances. There are more and less toxic species and accidents with humans will only happen if these substances come into contact with mucous membranes or blood.


Salamander

Breath

At the stage of aquatic life, when they are larvae, amphibians breathe through gills like fish. As adults, they live in a terrestrial environment and perform pulmonary respiration. Because their lungs are simple and have little contact surface for gas exchange, lung breathing is inefficient, and skin breathing is important - a process of exchanging gases with the environment through the skin.

The skin must necessarily be moist, as gases do not diffuse on dry surfaces. The thin walls of superficial skin cells allow oxygen to pass into the blood. Amphibian skin is well vascularized, that is, with many blood vessels.

Nutrition, Digestion and Excretion

In adulthood, which occurs in the terrestrial environment, amphibians are carnivores. They feed on earthworms, insects, spiders, and other vertebrates.

THE language, in some amphibian species is one of their most important adaptive characteristics. Frogs hunt insects in mid-flight using the tongue that is attached to the front of the mouth rather than the innermost part. When stretched out of the mouth, the tongue of these animals reaches a great distance, besides being sticky, another facilitating factor in catching prey.

They have well-developed stomach, intestine ending in a cloaca, glands such as liver and pancreas. Your digestive system produces substances that can digest the "shell" of insects.

Amphibians excrete through the kidneys, and their urine is abundant and well diluted, that is, there is plenty of water in the urine relative to the other substances that form it.

Circulation

Amphibians have closed circulation (blood circulates inside the vessels). As venous blood (rich in carbon dioxide) and arterial blood (rich in oxygen) mix, circulation in this group of animals is incomplete. The heart of the amphibians is divided into three cavities: two atria or atria and one ventricle.

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Reproduction

The place for amphibian breeding varies among species. It can be a transient puddle formed after a rain, a river, a lake or a weir. There are also those who breed in the land, provided it is very wet.

The mating of most amphibians happens in water. The male toad's croaking is part of the "prenuptial" ritual. The female in her fertile period is attracted to her sexual partner through her singing and croaking.

This chant varies by species. Most species have two or three different corner types. In addition to bridal singing (which attracts mates), there are warning corners with which the male defends his territory from approaching other males.

The female with an egg-filled body is grabbed by the male with a strong "hug". This "hug" may take days, until the female throws her gametes (ie her eggs) into the water. Then the male also releases his sperm, which fertilize the eggs, whose development occurs in water.

The frog, frog and tree frog perform external fertilization. The salamander and the blind snake perform internal fertilization.

In the numerous eggs protected by a thick layer of gelatinous substances, which usually attach themselves to aquatic plants, cells divide and form embryos. Fertilized eggs hatch and larvae called tadpoles, live and grow in water until they metamorphose into adulthood.

Metamorphosis

Metamorphosis involves a series of transformations and is a rather slow process that transforms the young amphibian (tadpole) into an adult. During this process the gills disappear and the lungs develop. And also paws appear on the body of the animal.

In this phase, tadpoles feed primarily on the gelatin that surrounds them and then on algae and microscopic aquatic plants.

They reproduce through soft, shelled eggs placed in water or soaked places, giving rise to a larva and then an adult through the process of metamorphosis. There are exceptions to this rule, some of them are viviparous.

In general, there is no care for offspring among amphibians.

They are divided into three groups: frogs, frogs, Anura tree frogs, Caudata salamanders and Apoda cecilias.