CBSE Class 11 Biology Structural Organisation In Animals Notes

Download CBSE Class 11 Biology Structural Organisation In Animals Notes in PDF format. All Revision notes for Class 11 Biology have been designed as per the latest syllabus and updated chapters given in your textbook for Biology in Standard 11. Our teachers have designed these concept notes for the benefit of Grade 11 students. You should use these chapter wise notes for revision on daily basis. These study notes can also be used for learning each chapter and its important and difficult topics or revision just before your exams to help you get better scores in upcoming examinations, You can also use Printable notes for Class 11 Biology for faster revision of difficult topics and get higher rank. After reading these notes also refer to MCQ questions for Class 11 Biology given our website

Revision Notes for Class 11 Biology Structural Organisation In Animals

Class 11 Biology students should refer to the following concepts and notes for Structural Organisation In Animals in standard 11. These exam notes for Grade 11 Biology will be very useful for upcoming class tests and examinations and help you to score good marks

Structural Organisation In Animals Notes Class 11 Biology

CBSE Class 11 Biology Structural Organisation in Animals Notes. Learning the important concepts is very important for every student to get better marks in examinations. The concepts should be clear which will help in faster learning. The attached concepts made as per NCERT and CBSE pattern will help the student to understand the chapter and score better marks in the examinations.

7. Structural Organisation in Animals


Tissue : A group of similar cells along with intercellular substances which perform a specific function.

ANIMAL TISSUES : Animal tissues are classified into four types:

• Epithelial tissues.

• Connective tissues.

• Muscular tissues.

• Neural tissues.

Epithelial tissues :

• These tissues commonly called epithelium.

• Has free surface, which faces either a body fluid or the outside environment.

• Cells are compactly packed with little intercellular matrix.

• There are two types of epithelial tissues:

o Simple epithelium.

o Compound or stratified epithelium.

• Simple epithelium is composed of a single layer of cells and functions as a lining for body cavities, ducts and tubes.

• The compound epithelium consists of two or more cell layers and has protective function as it does in our skin.

Simple epithelium, on the basis of modification, divided into three types:

• Squamous

• Cuboidal

• Columnar.

Squamous epithelium :

• Made of single thin layer of flattened cells with irregular boundaries.

• Found in the wall of blood vessels and air sacs of lungs.

• Functions as diffusion boundary.

Cuboidal epithelium :

• Composed of a single layer cube – like cells.

• Found in ducts of glands and tubular part of nephrons in kidneys.

• Main function is secretion and absorption.

Columnar epithelium :

• Composed of a single layer of tall and slender cells.

• Their nuclei located at the base.

• Free surface may have microvilli.

• Found in the lining of stomach and intestine

• Helps in absorption and secretion.

Ciliated epithelium :

• It is a modified Cuboidal or columnar epithelium.

• Cell bears cilia on their free surfaces.

• Found in the inner surface of hollow organs like bronchioles and fallopian tubes.

• Their function is to move particles or mucus in a specific direction over the epithelium.

Glandular epithelium :

• It is a modified Cuboidal or columnar epithelium.

• Get specialized for secretion.

• Simple glands having unicellular and isolated cells of alimentary canal.

• Multicellular glands: consisting of cluster of cells, as in salivary gland.

• Exocrine gland: the secretory product transported to a point by means of a duct. These glands secrete mucus, saliva, ear wax, milk, digestive enzymes etc

• Endocrine gland: commonly called as ductless gland, because the secretory products directly poured into blood. The glands secretes hormone.

Compound epithelium :

• Made of more than one layer of cells.

• Limited role in absorption and secretion.

• Main function is to provide protection against chemical and mechanical stresses.

• They cover the dry surface of skin, moist surface of buccal cavity, pharynx, inner lining of duct of salivary gland and pancreatic duct.

Cell junction :

• Cells of the epithelium are held together with little intercellular matrix.

• Cell junction provide structural and functional link between the cells

• Tight junction: help to stop substances from leaking across a tissue.

• Adhering junctions: perform cementing to keep neighboring cells together.

• Gap junctions: facilitate the cells to communicating the cytoplasm of adjoining cells, for rapid transfer of ions, small molecules.

Connective tissues :

• Most abundant and widely distributed tissues.

• Special function of linking and supporting other tissues/organs of the body.

• Connective tissues include cartilage, bone, adipose, and blood.

• In all connective tissue except blood, the cells secrete fibres of proteins called collagen and elastin.

• The fibre provides strength, elasticity and flexibility to the tissue.

• Presence of ground substance or matrix in between the cells, modified polysaccharides.

Loose connective tissue :

• Has cells and fibres loosely arranged in a semisolid ground substance.

Areolar tissue :

• Areolar tissue is one example of loose connective tissue.

• Present beneath the skin.

• It supports the framework for epithelium.

• It contains cell like fibroblasts (secretes fibres), macrophages and mast cells.

Adipose tissue:

• Another type of loose connective tissues.

• Located mostly beneath the skin.

• Cells of this tissue specialized to store fats called adipocytes.

Dense connective tissue :

• Fibres and fibroblasts are compactly packed.

Dense regular tissues :

• Orientation of fibres shows a regular pattern.

• The collagen fibres are present in rows between many parallel bundles of fibres.

• Tendons: joints muscles to bone.

• Ligaments: joins bone to bone are the examples.

Dense irregular tissues:

• Fibroblasts and many fibres are oriented differently.

• This tissue present in skin.

Specialized connective tissues :

• Cartilage bone and blood are the special connective tissues.


• Intercellular material of cartilage is solid.

• Chondrocytes are the cells of cartilage.

• Pliable and resists compression.

• Cells are enclosed in small cavities within the matrix.

• Most of the cartilage of the embryo replaced by bones in adult.

• Cartilage present in nose tips, ear pinna, between adjacent vertebrae.


• Have hard and non pliable matrix or ground substance.

• The matrix is rich in calcium salts and collagen fibers which give the bone its strength.

• Provides the structural frame of human body.

• Support and protect the soft tissues and organs.

• The bone cells called Osteocytes are present in fluid filled cavity called lacunae.

• Sustain body weight.

Important Questions for NCERT Class 11 Biology Structural Organisation in Animals


46. Pheretima and its close relatives derive nourishment from
(a) sugarcane roots
(b) decaying fallen leaves and soil organic matter
(c) soil insects
(d) small pieces of fresh fallen leaves of maize, etc.

Answer: B


47. One very special feature in the earthworm (Pheretima) is that
(a) fertilization of eggs occurs inside the body
(b) the typhlosole greatly increases the effective absorption area of the digested food in the intestine
(c) the S-shaped setae embedded in the integument are the defensive weapons used against the enemies
(d) it has a long dorsal tubular heart. 

Answer: B


48. Which one of the following structures in Pheretima is correctly matched with its function?
(a) Clitellum - Secretes cocoon
(b) Gizzard - Absorbs digested food
(c) Setae - Defence against predators
(d) Typhlosole - Storage of extra nutrients

Answer: B


50. Which one of the following correctly describes the location of some body parts in the earthworm Pheretima?
(a) Four pairs of spermathecae in 4th-7th segments
(b) One pair of ovaries attached at intersegmental septum of 14th and 15th segments
(c) Two pairs of testes in 10th and 11th segments
(d) Two pairs of accessory glands in 16th-18th segments 

Answer: C


51. If a live earthworm is pricked with a needle on its outer surface without damaging its gut, the fluid that comes out is
(a) coelomic fluid    (b) haemolymph
(c) slimy mucus      (d) excretory fluid.

Answer: A


52. Earthworms have no skeleton but during burrowing, the anterior end becomes turgid and acts as a hydraulic skeleton. It is due to
(a) gut peristalsis    (b) setae
(c) coelomic fluid    (d) blood. 

Answer: C


53. Earthworms are
(a) ammonotelic when plenty of water is available
(b) ureotelic when plenty of water is available
(c) uricotelic when plenty of water is available
(d) uricotelic under conditions of water scarcity.

Answer: A


54. Primary function of enteronephric nephridia of Pheretima is
(a) osmoregulation
(b) excretion of nitrogenous wastes
(c) respiration (d) locomotion.

Answer: A


55. Earthworm possesses hearts
(a) 6 pairs     (b) 4 pairs
(c) 2 pairs     (d) 1. 

Answer: B


56. Blood of Pheretima is
(a) blue with haemocyanin in corpuscles
(b) blue with haemocyanin in plasma
(c) red with haemoglobin in corpuscles
(d) red with haemoglobin in plasma. 

Answer: D


57. Pheretima posthuma is highly useful as
(a) their burrows make the soil loose
(b) they make the soil porous, leave their castings and take organic debris in the soil
(c) they are used as fish meal
(d) they kill the birds due to biomagnification of chlorinated hydrocarbons. 

Answer: B


58. Earthworms are
(a) useful                                 (b) harmful
(c) more useful than harmful     (d) more harmful. 

Answer: A


59. Photoreceptors of earthworm occur on
(a) clitellum              (b) many eyes
(c) dorsal surface      (d) lateral sides. 

Answer: C

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