The VIDYANKER team has thoughtfully prepared the NCERT Solutions for Class 11 Biology Chapter 7, "Structural Organisation in Animals" These solutions are designed to help you tackle the NCERT textbook questions with ease. We recommend going through the chapter's theory before diving into the solutions for a deeper understanding. Feel free to share these NCERT Solutions for Class 11 Biology with others—learning is always better when shared!
NCERT TEXTBOOK QUESTIONS SOLVED
1. Answer in one word or one line.
(i) Give the common name of Periplaneta americana.
Ans. American cockroach.
(ii) How many spermathecae are found in earthworm?
Ans. Four pairs
(iii) What is the position of ovaries in cockroach?
Ans. Between 12th and 13th abdominal segments
(iv) How many segments are present in the abdomen of cockroach?
Ans. Ten segments
(v) Where do you find Malpighian tubules?
Ans. Malpighian tubules are present at the junction of midgut and hindgut in cockroach.
2. What are the following and where do you find them in animal body?
(a) Chondrocytes
(b) Axons.
(c) Ciliated epithelium
Ans. (a) Chondrocytes – Chondrocytes are the only cells found in cartilage. They reside in spaces known as lacunae and produce and maintain the matrix of cartilage. Chondrocytes are responsible for the bending ability of cartilage. Cartilage is found at the tip of nose, pinna of ear, epiglottis etc.
(b) Axon-axon is one of the processes of neuron which is the structural and functional unit of nervous system. The part of cyton-where axon arises n'here is called axon hillock, axon ends in group of branches called terminal arborizations. It conducts impulses away from the cyton. Neurons (nerve cells)
are found in the brain and spinal cord.
(c) Ciliated epithelium – If the columnar or cuboidal cells bear cilia on their free surface they are called ciliated epithelium. Their function is to move particles or mucus in a specific direction over the epithelium. They are mainly present in the inner surface of hollow organs like bronchioles and Fallopian tube.
3. Draw a labelled diagram of the reproductive organs of an earthworm.
Ans. 
4. Answer the following.
(i) What is the function of nephridia?
(ii) How many types of nephridia are found in earthworm based on their location?
Ans. (i) Nephridia are the excretory organs of earthworms, that accomplish the process of excretion as well as osmoregulation. The volume and concentration of body fluids get regulated due to nephridia. A nephridium is an elongated spiral tubular microstructure beginning like a funnel; it is drawn fluid excess in the coelomic chamber. The pore opening leads this to a tubular waste connecting this funnel and passing through pores for excretion both in body walls or inside digestive tube.
(ii) In earthworm, nephridia are present in all segments except the first two. There are three types of nephridia on the basis of their location:
(a) Septal nephridia, occurring on both sides of intersegmental septa from segment 15 to the last that open into intestine.
(b) Integumentary nephridia, attached to lining of the body wall of segment 3 to the last that open on the body surface and
(c) Pharyngeal nephridia, consisting of three paired tufts in the 4th, 5th, and 6th segments.
5. Draw a labelled diagram of alimentary canal of a cockroach.
Ans. 
6. What are the cellular components of blood?
Ans. Components of blood include erythrocytes (RBCs), leucocytes (WBCs), and thrombocytes (platelets). These components constitute 45% of blood. They are suspended in the remaining fluid portion, known as plasma. Mammalian erythrocytes are biconcave, colored cells without a nucleus. They assist in transporting respiratory gases. Leucocytes or white blood cells are nucleated cells. They can be classified into two types, granulocytes (neutrophils, eosinophils, and basophils) and agranulocytes (lymphocytes and monocytes). They help combat several disease-causing agents entering the body. Thrombocytes are fragments of cells that are produced from megarkaryocytes of the bone. They are very important in the process of blood coagulation.
7. Distinguish between the following:
(a) Prostomium and peristomium
(b) Septal nephridium and pharyngeal
Ans. (a) Differences between prostomium and peristomium are
| Prostomium | Peristomium |
|---|---|
| Prostomium is a small fleshy lobe, which overhangs the mouth of an earthworm. It helps the organism push into the soil and is sensory in function. | The first body segment in the earthworm is called the peristomium. It surrounds the mouth opening. |
(b) Differences between septal and pharyngeal nephridia are:
| Septal nephridium | Pharyngeal nephridium |
|---|---|
| They are present on both sides of inter-segmental septa behind the 15thsegment and they open into the intestine. | They are present as three paired tufts in the fourth, fifth, and sixth segments. |
8. Mark the odd one in each series.
(a) Areolar tissue; blood; neuron; tendon
(b) RBC; WBC; platelets; cartilage
(c) Exocrine; endocrine; salivary gland; ligament
(d) Maxilla; mandible; labrum; antennae
(e) Protonema; mesothorax; metathorax; coxa.
Ans. (a) Neuron: Areolar tissue, blood and tendon are connective tissues while neuron is a part a nervous tissue.
(b) Cartilage: RBC, WBC and platelets are components of vascular connective tissue whereas cartilage is skeletal connective tissue.
Ligament: Ligament is a type of connective tissue.
(d) Antennae: Maxilla, mandible and labrum are mouth parts of cockroach while antennae are sense organs.
(e) Protonema: Protonema is a filamentous juvenile stage in life cycle of Bryophytes, while mesothorax, metathorax and coxa are appendages of cockroach.
9. Match the terms in column I with those in column II.
| Column I | Column II |
|---|---|
| (a) Compound epithelium | (i) Alimentry canal |
| (b) Compound eye | (ii) Cockroach |
| (c) Septal nephridia | (iii) Skin |
| (d) Open circulatory system | (iv) Mosaic vision |
| (e) Typhlosole | (v) Earthworm |
| (f) Osteocytes | (vi) Phallomere |
| (g) Genitalia | (vii) Bone |
Ans. (a) – (iii), (b) – (iv), (c) – (v), (d) – (ii), (e) – (i), (f) – (vii), (g) – (vi)
10. Mention briefly about the circulatory system of earthworm.
Ans. Earthworm has a closed type of blood vascular system, as the blood flows through closed blood vessels. Blood is red in color due to respiratory pigment haemoglobin. Prominent blood vessels in earthworm includes dorsal, ventral, sub- neural, lateral oesophageal and supra- oesophageal blood vessels. There are four pairs of tubular hearts, provided with valves. The anterior two pairs of hearts are called lateral hearts, which lie in the 7th and 9th segments. These connect the dorsal blood vessel with the ventral blood vessel. They take blood from the dorsal blood vessel and convey it to the ventral blood vessel. The posterior two pairs of hearts are called latero-oesophageal hearts, which lie in the 12th and 13th segments. Apart from joining the dorsal and ventral blood vessels, latero-oesophageal hearts are also joined with the supra oesophageal blood vessel. Latero-oesophageal hearts carry blood from the dorsal vessel and the supra oesophageal vessel to the ventral blood vessel. Contractions keep blood circulating in one direction. Blood glands are present in the 4th, 5th and 6lh segments which produce blood cells and haemoglobin which is dissolved in blood plasma. Blood cells are phagocytic in nature.
11. Describe various types of epithelial tissues with the help of labelled diagrams.
Ans. Epithelial tissue A tissue consisting of one or more layers of compactly placed cells which forms the cover on the external and internal free surfaces of body organs and which has a basement membrane underlying it. The following shows the different kinds of epithelial tissue along with the diagram
(i) Simple epithelium : It is made up of single layer of cells resting on basement membrane. Simple epithelium primarily occurs over the secretory and absorptive surfaces and forms a lining of the body cavities, ducts, and tubes. Simple epithelium consists of several kinds.
(a) Squamous epithelium: It is made up of a single layer of flat cells, tightly held together and have centrally located oval or spherical nucleus. It is also known as pavement epithelium. It is present in walls of blood vessels, air sacs of lungs, and lining of eye lens.
(b) Cuboidal epithelium: Cells of cuboidal epithelium are as tall as wide, with centrally placed nucleus. Its main functions are secretion and absorption. It lines sweat gland, thyroid follicles, salivary glands. Brush bordered cuboidal epithelium, i.e., cells having microvilli on their free surface lines proximal part of uriniferous tubule, pancreatic duct, testis and ovary.
(c) Columnar epithelium: Cells are with basally located nucleus. It helps in secretion and absorption. It occurs in lining of intestine, stomach, gall bladder.
(d) Ciliated epithelium: Free surface of columnar and cuboidal cells are covered with cilia. Cilia help in moving fluids, particles, mucus, etc. in a specific direction. It occurs in the inner surface of Fallopian tubules, nasal passage, bronchioles.
(ii) Compound epithelium /stratified epithelium: It is multilayered epithelium where cells of only the lowermost or basal layer are in contact with basement membrane. It provides protection against mechanical and chemical stresses and has limited role in secretion and absorption. It covers dry surface of skin, moist surface of buccal cavity, pharynx, etc. Different types of compound epithelium are:
(a) Stratified squamous epithelium: The cells of outer layer are flattened and squamous while the inner layers are cuboidal cells. There are two kinds: Non-keratinised lining oesophagus, pharynx, buccal cavity, cornea, vagina and anal canal and keratinised (comified): forming epidermis of skin, hair, horn and nail.
(b) Stratified cuboidal epithelium: The outer layer of cuboidal cells and basal layer of columnar cells. It lines ducts of sweat glands, large salivary and pancreatic ducts.
(c) Stratified columnar epithelium: The upper and basal layers are of columnar cells, e.g., epiglottis covering, part of urethra.
(d) Stratified ciliated columnar epithelium: Outer lamina contains the ciliated columnar cells along with the baso-laminal layer consists of columnar cells, for instance larynx.
(iii) Transitional Epithelium: This is stratified epithelium having cuboidal or columnar-shaped cells, that are thin and stretchable. No basement membrane is present since it would restrain stretchability. It lines the inner surface of renal calyces, urinary bladder, ureter. Owing to t distribution, it is also referred to as urothelium.
(iv) Glandular epithelium: It contains specialized epithelial cells, which synthesize intracellular macromolecules. It synthesizes protein in the case of pancreas, lipids in adrenal glands, glycoprotein in salivary glands, and all the three in mammary glands and pour them out in the form of a useful fluid secretion different from blood or any other extracellular fluid. Glands can be unicellular or multicellular on the basis of number of cells.
(a) Unicellular glands: Single celled, eg, goblet (mucous) cells of respiratory tract and alimentary canal.
(b) Multicellular glands: A cluster of cells, e.g., Salivary glands.
On the basis of presence or absence of duct glands may be classified as:
(a) Exocrine glands : Such glands pour their secretion through a duct. The milk, saliva, mucus, earwax are secreted by them. eg goblet cells, salivary glands, tear glands, gastric glands, intestinal glands.
(b) Endocrine glands: They are ductless glands, which pour their secretions into blood or lymph for reaching the target region. Their secretion is called hormone e.g., pituitary gland, thyroid gland, parathyroid glands, adrenal glands.
(c) Heterocrine glands: Both exocrine and endocrine, e.g., pancreas.
On basis of mode of secretion glands can be:
(a) Merocrine: Secretion is discharged
through diffusion, e g., goblet cells, sweat glands.
(b) Apocrine glands : Glandular secretion collects at the distal end of the cell which pinched off, for example mammary glands.
(c) Holocrine glands: In this, entire cell packed with secretory material disintegrates in time of its product release, e.g., sebaceous gland.
(v) Modified epithelium: These are of the following types:
(a) Germinal epithelium (usually cuboidal, gives rise to gametes), (b) Glandular epithelium (columnar or cuboidal secretes chemical and mucus), (c) Sensory epithelium or neuroepithelium. Epithelial cells bearing sensory hair on free surface and associated with nerve fibres on other surface (usually columnar, receives and transmits stimuli), e.g., nasal epithelium, taste buds, retina, sensory spots of internal ear. (d) Pigmented epithelium – The cells contain melanin granules, e.g., retinal layer in contact with choroid of eye.
12. Distinguish between
(a) Simple epithelium and compound epithelium.
(b) Cardiac muscle and striated muscle.
(c) Dense regular and dense irregular connective tissues.
(d) Adipose and blood tissue.
(e) Simple gland and compound gland.
Ans. (a) Differences between simple and compound epithelium are as follows:
(d) Differences between adipose tissue and blood tissue are as follows:
13. Draw a neat diagram of digestive system of frog.
Ans. 
14. Mention the function of the following:
(a) Ureters in frog
(b) Malpighian tubules
(c) Body wall in earthworm.
Ans. (a) Ureters in frogs: A ureter acts as a urinogenital duct which carries sperms along with urine in male frogs.
(b) Malphigian tubules: The malphigian tubules in cockroaches are the excretory organs.
(c) Body wall in earthworms: In earthworms, the body wall is made up of muscle layers. It aids in movement and burrowing.
