شعبة نصف الحبليات تنوع الحيوانات الجزء الأول الصف الحادي عشر علم الحيوان تيلانجانا أك

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شعبة نصف الحبليات تنوع الحيوانات الجزء الأول الصف الحادي عشر علم الحيوان تيلانجانا أك

Khan Academy India - English · ⏱ 1:58 · 417 مشاهدة · 2 months ago

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النص الكامل للفيديو

Finally we have reached the end of the films constituting the invertebrates. In this video we are going to discuss the most advanced invertebbrate which is phylm hemicordata. This fila consists of wormlike marine animals. They are also called as econorms. They have bilateral symmetry. They are triplastic organisms and celamates. They have cylindrical body. These are some of the different marine worms. Examples of these are balanoglosses and sacoglosses which are also called as tongue worms because look at this organism. It looks like tongue is projecting out from the body. The body of these organisms are divided into three segments. The anterior most segment is the probosus. Next comes collar and the longest part is the trunk. If you look within the organism, there is specialized structure called as the stomach cord or the buckle diverticulum. It is seen to extend into the probosus. This structure was once thought to be no cord and originally hemicordates were considered to be part of cordates. But on further studies they realized that this tissue is nothing like notocord and it was put back into the invertebrates. In spite of having dorsal heart these organisms have an open circulation. Respiration occurs through paired gill slits that are present on the fairings. It looks something like this over here. For excretion the organisms use the probosus gland which is the anteriormost part. The sexes are separate in this organism and fertilization occurs externally in the water. They show indirect development through laral forms like the torieria larva.