Comparative characteristics of freshwater hydra andwhite planaria gives a clear idea of the features of the organization and development of two types of multicellular animals - coelenterates and flatworms. In this article we will consider this issue in the context of the complication of the features of their structure.
On this issue, a comparative characteristicfreshwater hydra and white planaria is similar. The first animal got its name from its habitat. Although many of its related species live in the seas. Planaria also prefers small fresh water reservoirs, where it hides under driftwood and stones.
The type of freshwater hydra is a single polyp. To the underwater objects it is fastened by the base of its stalk - the sole, which acts as a sucker. At the opposite end of the body of the hydra are the tentacles. With their help, the animal captures, holds the prey and directs it into the mouth opening. Due to the presence of specialized skin-muscle cells, the hydra can contract and tilt. In contrast to the freshwater polyp, the planaria leads a mobile way of life.
Many representatives of coelenterates and flatworms lead a completely different way of life. For example, the liver flukes and the wide ribbon, which are parasitic worms, attach themselves to the ducts of the internal organs of the hosts.
Comparative characteristics of freshwater hydra andwhite planaria is impossible without considering the question of the type of food. In this issue, these organisms have much in common. Planaria and hydra are heterotrophic organisms. And both of these species are predators. Hydra hunts with the help of stinging cells, which paralyze prey.
The planaria also attacks small aquatic animals. The epithelial cells that swell in the water help her to capture and fix the victim. The organs of the digestive system of the planaria are the oral opening and the intestine. The latter has a front and middle divisions that end blindly.
Hydra has a ray symmetry. Its body is formed by two layers - ecto- and endoderm. They include various types of specialized cells: digestive, sexual, epithelial-muscular, stinging, glandular, digestive, nervous. They are scattered over the body of the polyp and do not form tissues.
The White Planaria, which is the representativetype flat worms, has a characteristic body shape. It flattened in the dorsal-ventral direction and resembles a small leaf. This animal has a two-sided symmetry. Planaria has real tissues, organs and their systems. It is musculoskeletal, digestive, excretory, nervous, sexual. A common feature of these animals is a high level of regeneration. So, the hydra can recover from the mushy state, and the planaria is capable of vegetative reproduction.
Comparative characteristics of freshwater hydra andwhite planaria indicates a significant increase in the level of organization of flatworms. The intestinal, along with sponges, are the first multicellular creatures of the animal world. However, they do not have real tissues. This structure appears only in flat worms. Therefore, their structure and life activity is characterized by a higher level. The primitive features of their structure are the absence of respiratory and circulatory system. Therefore, gas exchange in flat worms is carried out through the surface of the body.
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