There is an evolution of paired limbs, their gradual change from swimming organs to crawling, walking, running, jumping, and climbing organs. The spine of terrestrial animals is located not in the center of the body, but in its upper part, it serves as a beam supported by limbs, to which the body and internal organs are suspended. The fish that collected food from the bottom of the reservoir, with a medium density close to unity, easily moved the entire body from a horizontal to a vertical position. For a terrestrial animal, this would require a lot of energy. A cow grazes the grass with only her head down, and a giraffe collects tree leaves with her head up. The mobility of the animal's head is determined by the neck. So: a spine with a body suspended from it, supported by 4 paired limbs, and a movable head — this is the structural scheme of a terrestrial animal.
Characteristics and systematics of amphibians
Amphibians are animals that evolved from water to land, but are still associated with water during reproduction. This duality of habitat is emphasized by the Russian and Latin names Amphibia — bi-life. Larvae breathe through their gills and live in water, while adults breathe through their lungs. The skin of modern amphibians is bare, without integumentary formations, and moist. The number of species is over 2,000, especially amphibians in the humid tropics. There are 33 species in Russia. The amphibian class is divided into three groups: I. The legless group (not considered). 2. The order of the tailed. 3. The tailless squad.
The appearance and internal structure of amphibians
The body shape corresponds to the conditions of life on land, but the strongly developed hind limbs with webbed fingers allow frogs to swim well. The skin performs several functions.
The amphibian class. Part Three
The skin plays an important role in breathing. The frog absorbs water with its skin. Moisture evaporates through the skin. The bactericidal properties of the skin are also necessary, since microorganisms develop in a humid environment, but skin poisons not only kill them, but also dissolve them, and the skin absorbs them along with water. Toads have particularly well-developed skin glands that secrete burning, strong-smelling substances that make amphibians inedible for predators.
Skeleton
The frog's skull is wide and flat, with a small number of bones. The upper jaw is attached to the axial (cerebral) skull and forms one whole with it. When considering the spine, the first thing to pay attention to in amphibians is the appearance of a movable joint between the spine and the skull. It is performed using the first and so far only cervical vertebra. The head is not very mobile yet. Hoy en día, la mayoría de las apuestas se hacen desde el celular. Una buena app de apuestas estable debe funcionar sin caídas, incluso en partidos con mucho tráfico. Antes de registrarte, prueba la versión móvil del sitio web. Abre un mercado en vivo, crea un cupón combinado y simula una apuesta. Si la pantalla se traba o los botones desaparecen, esa casa no es confiable. Las mejores apps permiten depositar, retirar, ver el historial y activar bonos en menos de tres clics. Apostar en vivo requiere velocidad y estabilidad.
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