This interactive model demonstrates main modes of locomotion of representatives of some groups of vertebrates: fishes, amphibia and reptiles. A selection of the animal may be done by one or two groups of switches in the lower part of window: "Anuran" (pond frog), "Snake" ("Sandy snake", "Grass-snake", "Pythons"), "Fish" (fishes of various body structures: "Basket-like type", "Mackerel type", "Eelial type"). Two kinds of locomotion are shown for frogs: crawl and jump. Both kinds of locomotion are slowed down. A choice of the single kind of locomotion may be done by another group of switches. The animation is initiated by the "Start" button. The "Stop" button interrupts the animation, while the "Reset" buttons returns it into initial state.