Structural Organisation in Animals Notes

The "Structural Organisation in Animals" chapter, typically found in Class 11 biology, explores how cells, tissues, organs, and organ systems are organized to form a complex animal body, focusing on the four main tissue types: epithelial, connective, muscular, and nervous. 

ORGAN AND ORGAN SYSTEM 

The basic tissues as you have learnt in earlier classes, organise to form organs 

which in turn associato form organ systems in the multicellular organisms. 

Such an organisation is essential for more efficient and better coordinated activities 

of millions of cells constituting an organism.

 FROGS

Frogs can live both on land and in freshwater and belong to class 

Amphibia of phylum Chordata. 

The most common species of frog found in India is Rana tigrina.

Morphology

Have you ever touched the skin of frogThe skin is smooth and slippery due to the presence of mucus. 

The skin is always maintained in a moist condition. 

The colour of dorsal side of body is generally olive green with dark irregular spots. 

On the ventral side the skin is uniformly pale yellow. 

The frog never drinks water but absorb it through the skin.

Anatomy

The body cavity of frogs accommodate different organ systems such as digestive, circulatory, respiratory, nervous, excretory and reproductive systems with well developed structures and functions

The digestive system consists of alimentary canal and digestive glands. The alimentary canal is short because frogs are carnivores and hence the length of intestine is reduced. The mouth opens into the buccal cavity that leads to the oesophagus through pharynx. Oesophagus is a short tube that opens into the stomach which in turn continues as the intestine, rectum and finally opens outside by the cloaca. Liver secretes bile that is stored in the gall bladder. Pancreas, a digestive gland produces pancreatic juice

SUMMARY 

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 tissues lining the body’s surface and its cavities, ducts and tubes. 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 divisible into head and trunk. A muscular tongue is present, which is bilobed at the tip and is used in capturing the prey. The alimentary canal consists of oesophagous, stomach, intestine and rectum, which open into the cloaca. 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.