Editing Content :: Admin Scraper

Chapter

Content type

Position

Value

84 BIOLOGY canal. Finally it communicates with the urinogenital duct that comes out of the kidneys and opens into the cloaca. The cloaca is a small, median chamberthatisusedtopassfaecalmatter,urineandspermstotheexterior. The female reproductive organs include a pair of ovaries (Figure 7.4). Theovariesaresituatednearkidneysandthereisnofunctionalconnection with kidneys. A pair of oviduct arising from the ovaries opens into the cloaca separately. A mature female can lay 2500 to 3000 ova at a time. Fertilisation is external and takes place in water. Development involves a larval stage called tadpole. Tadpole undergoes metamorphosis to form the adult. Frogs are beneficial for mankind because they eat insects and protect the crop. Frogs maintain ecological balance because these serve as an important link of food chain and food web in the ecosystem. In some countries the muscular legs of frog are used as food by man. S UMMARY Cells, tissues, organs and organ systems split up the work in a way that ensures the survival of the body as a whole and exhibit division of labour. A tissue is defined as group of cells along with intercellular substances performing one or more functions in the body. Epithelia are sheet like tissuesliningthebody’ssurfaceanditscavities,ductsandtubes.Epithelia have one free surface facing a body fluid or the outside environment. Their cells are structurally and functionally connected at junctions. The Indian bullfrog, Rana tigrina, is the common frog found in India. Body is covered by skin. Mucous glands are present in the skin which is highly vascularised and helps in respiration in water and on land. Body is divisibleintoheadandtrunk.Amusculartongueispresent,whichisbilobed at the tip and is used in capturing the prey. The alimentary canal consists ofoesophagous,stomach,intestineandrectum,whichopenintothecloaca. The main digestive glands are liver and pancreas. It can respire in water through skin and through lungs on land. Circulatory system is closed with single circulation. RBCs are nucleated. Nervous system is organised into central, peripheral and autonomic. The organs of urinogenital system are kidneys and urinogenital ducts, which open into the cloaca. The male reproductive organ is a pair of testes. The female reproductive organ is a pair of ovaries. A female lays 2500-3000 ova at a time. The fertilisation and development are external. The eggs hatch into tadpoles, which metamorphose into frogs. E XERCISES 1. Draw a neat diagram of digestive system of frog. 2. Mention the function of the Ureters in frog. Reprint 2026-27