Structural Organisation In Animals Class 11 Notes Biology Chapter 7 - CBSE

Chapter : 7

What Are Structural Organisation In Animals?


It is the study of the size, shape, and structure of animals, plants, and microorganisms and of the relationships of their constituent parts. The term refers to the general aspects of biological form and arrangement of the parts of a plant or an animal.

Digestive System

Alimentary canal is divided into foregut, midgut and hindgut.

Mouth → Pharynx → Oesophagus → Crop (stores food) → Gizzard (grind ing of food) → Hepatic caeca (at junction of fore and midgut; secretes digestive juice) → Hindgut (ileum, colon, rectum) → Anus.

Blood Vascular System

Open type, visceral organs bathed in haemolymph (colourless plasma and haemocytes). Heart consists of elongated muscular tube and differentiated into funnel shaped chambers with ostia on either side. Blood from sinuses enters heart through ostia and is pumped anteriorly to sinuses again. Blood colourless (haemolymph).

Respiratory System

Network of trachea which open through 10 spiracles. Spiracles regulated by sphincters. Oxygen delivered directly to cells. Excretion and osmoregulation by Malpighian tubules; uricotelic (Uric acid as excretory product).

Nervous System

Consists of series of fused segmentally arranged ganglia joined by paired longitudinally connectives on the ventral side. Three ganglia in thorax, six in abdomen. Brain represented by supra-oesophageal ganglion.

Reproductive System

  • Male Reproductive System: Pair of testes (4th-6th segments) →vas deferens → ejaculatory duct →male gonophore. Glands − Seminal vesicle (stores sperms), mushroom shaped gland (6th- 7th segment).
  • Female Reproductive System: A pair of ovaries (with 8 ovarian tubules) → Oviduct → Genital chamber Sperms transferred through spermatophores. Fertilised eggs encased in capsules called oothecae; development of P. americana paurometabolous (incomplete metamorphosis).

Morphology Of Frogs

  • Though larvae have tails, adult frogs are tailless. An adult frog has a stout body which is differentiated into head and trunk.
  • Other external features are a pair of nostrils, protruding eyes, a membranous tympanum (ear), slippery or warty moist skin and webbed limbs.
  • Frogs generally have a slippery moist and highly permeable skin through which they absorb water and respire. Thus, the moist skin acts as a respiratory organ in frogs.
  • Also, the skin is glandular in nature, which produces mucus and toxic substances to warn them of their
  • The colour of the skin can vary from brown and green to vivid colours as per secretions.
  • The locomotion of frogs takes place with the help of their forelimbs and hind limbs.
  • Frogs are unisexual i.e.; they show sexual dimorphism. A male frog is distinguished from a female frog by the presence of vocal sacs and a copulatory pad on forelimbs. A female frog lacks these body features.