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These are complete NCERT Solutions for CBSE Class 11 Biology Chapter 7 — Structural Organisation in Animals. Attempt each question before checking. Use precise tissue and organ names — marks are given for terms like 'mesentery', 'septa', 'hepatic caeca', 'malpighian tubules', etc.
Key Concepts (Quick Recap)
- Epithelial tissue: Simple (squamous, cuboidal, columnar) and stratified; covers body surfaces, lines cavities.
- Connective tissue: Areolar, adipose, dense, cartilage (hyaline, fibrous, elastic), bone, blood.
- Muscular tissue: Skeletal/striated (voluntary), smooth (involuntary), cardiac (involuntary, branched, intercalated discs).
- Neural tissue: Neurons (dendrites, cell body, axon) + neuroglia.
- *Earthworm (Pheretima):* Segmented (metameres), clitellum (14-16 segments), 4 pairs of hearts (7-12), nephridia for excretion, closed blood vascular system.
- *Cockroach (Periplaneta):* Brown body, chitinous exoskeleton, 3 tagmata (head, thorax, abdomen), malpighian tubules for excretion, 10th segment with anal cerci.
- *Frog (Rana tigrina):* Amphibian, streamlined body, webbed feet, moist skin, hibernation and aestivation, closed blood vascular system, ureotelic.
Intext Questions
Page 95
Q1. Answer in one word or one line: (i) Give the common name of Periplanata americana. (ii) How many spermathecae are found in earthworm? (iii) What is the position of ovaries in cockroach? (iv) How many segments are present in the abdomen of cockroach? (v) Where do you find malpighian tubules?
Answer
(i) Cockroach (ii) 4 pairs (8 spermathecae — one pair each in segments 6, 7, 8, and 9) (iii) 2nd and 6th abdominal segments (ovaries are paired, each consisting of 8 ovarian tubules) (iv) 10 segments in both male and female (v) At the junction of midgut and hindgut in cockroaches (they are excretory structures)
Q2. What are the following and where do you find them in animal body: (a) Chondriocytes (b) Axons (c) Ciliated epithelium
Answer
(a) Chondriocytes: Cells of cartilage (chondrocytes embedded in lacunae within the cartilage matrix). Found in cartilage tissue — in nose tip, external ear (pinna), intervertebral discs, tracheal rings, and at the ends of long bones.
(b) Axons: Long, cylindrical processes arising from the cell body of a neuron. They conduct nerve impulses away from the cell body. Found in neural tissue — throughout the nervous system (brain, spinal cord, and nerves).
(c) Ciliated epithelium: Epithelial tissue bearing cilia on its free surface. The cilia beat rhythmically to move particles or mucus in a specific direction. Found in the lining of the respiratory tract (moves mucus and dust) and fallopian tubes (moves the ovum towards the uterus).
Page 99
Q1. Mark the odd one out in each series: (i) Areolar tissue, blood, neuron, tendon (ii) RBC, WBC, platelets, cartilage (iii) Exocrine, endocrine, salivary gland, liver (iv) Mast cell, macrophage, fibroblast, platelet
Answer
(i) Neuron — it is a cell of neural tissue; the others (areolar tissue, blood, tendon) are types of connective tissue.
(ii) Cartilage — it is a connective tissue; the others (RBC, WBC, platelets) are cellular components of blood.
(iii) Endocrine — it is a type of gland (ductless); the others (exocrine, salivary gland, liver) are glands with ducts.
(iv) Platelet — it is a cell fragment of blood; the others (mast cell, macrophage, fibroblast) are cells of areolar connective tissue.
Q2. Match the epithelium with its location:
Answer
| Epithelium | Location |
|---|
| (a) Simple squamous | (iii) Walls of blood vessels |
| (b) Stratified squamous | (i) Skin |
| (c) Ciliated columnar | (iv) Respiratory tract |
| (d) Simple cuboidal | (ii) Lining of kidney tubules |
Chapter-End Exercise
Q1. Answer in one word or one line: (i) Give the common name of Periplanata americana. (ii) How many spermathecae are found in earthworm? (iii) What is the position of ovaries in cockroach? (iv) How many segments are present in the abdomen of cockroach? (v) Where do you find malpighian tubules?
Answer
(See Intext Page 95 Q1 — answered above.)
Q2. What are the following and where do you find them in animal body: (a) Chondriocytes (b) Axons (c) Ciliated epithelium
Answer
(See Intext Page 95 Q2 — answered above.)
Q3. Draw a neat diagram of digestive system of frog.
Answer
The digestive system of a frog consists of:
Alimentary canal: Mouth → Buccal cavity → Pharynx → Oesophagus → Stomach → Small intestine (duodenum + ileum) → Large intestine (rectum) → Cloaca → Cloacal aperture.
Associated glands: Liver (largest gland, 3 lobes, secretes bile stored in gall bladder) and Pancreas (irregular gland between stomach and duodenum, secretes pancreatic juice with digestive enzymes).
The buccal cavity contains a bifid (forked) tongue attached at the front (not the back) — it can be flicked out to catch insects. The stomach is J-shaped. The small intestine is the longest part where digestion and absorption occur. The cloaca is a common chamber for digestive, excretory, and reproductive products.
(Draw as per NCERT Fig 7.20 — showing the complete alimentary canal with liver, gall bladder, and pancreas.)
Q4. Distinguish between: (a) Prostomium and Peristomium (b) Septal nephridium and Pharyngeal nephridium
Answer
(a) Prostomium vs Peristomium:
| Feature | Prostomium | Peristomium |
|---|
| Position | Small lobe above the mouth | First body segment (segment 1) |
| Function | Sensory — helps in probing the soil | Contains the mouth |
| Relation | Covers the mouth from above | Bears the mouth ventrally |
(b) Septal Nephridium vs Pharyngeal Nephridium:
| Feature | Septal Nephridium | Pharyngeal Nephridium |
|---|
| Location | On each side of the septa (behind 15th segment) | In 4th, 5th, and 6th segments |
| Number | 40-50 per septum | Paired tufts |
| Duct | Short, opens into intestine | Ducts open into buccal cavity |
| Function | Excretion — removes nitrogenous waste from coelomic fluid | Excretion — removes waste from blood |
| Type | Closed (funnel with nephrostome) | Closed |
Q5. What are the cellular components of blood?
Answer
The cellular components of blood are: 1. Erythrocytes (Red Blood Cells): Biconcave, enucleated (in mammals), contain haemoglobin, transport oxygen and CO₂. 2. Leucocytes (White Blood Cells): Nucleated, colourless, involved in immune defence. Types: Granulocytes (neutrophils, eosinophils, basophils) and Agranulocytes (lymphocytes, monocytes). 3. Platelets (Thrombocytes): Cell fragments involved in blood clotting.
Q6. What are the main functions of: (a) Areolar tissue (b) Adipose tissue
Answer
(a) Areolar tissue: It is the most widely distributed connective tissue. Functions: 1. Acts as a packing material between organs. 2. Supports and binds other tissues. 3. Provides defence — contains macrophages, mast cells, and fibroblasts that help fight infection. 4. Helps in tissue repair and wound healing.
(b) Adipose tissue: It is a specialised connective tissue with fat-storing cells (adipocytes). Functions: 1. Insulation: The fat layer beneath the skin reduces heat loss and keeps the body warm. 2. Cushioning: Protects internal organs from shock and injury. 3. Energy reserve: Fat is a concentrated energy source. 4. Filler: Fills spaces between organs.
Q7. Distinguish between: (a) Simple epithelium and Compound epithelium (b) Cardiac muscle and Striated muscle (c) Dense regular and Dense irregular connective tissues
Answer
(a) Simple vs Compound Epithelium:
| Feature | Simple Epithelium | Compound (Stratified) Epithelium |
|---|
| Cell layers | Single layer | Multiple layers |
| Function | Absorption, secretion, filtration | Protection against wear and tear |
| Location | Lining of blood vessels, alveoli, kidney tubules | Skin, oesophagus, mouth, vagina |
(b) Cardiac vs Striated Muscle:
| Feature | Cardiac Muscle | Striated (Skeletal) Muscle |
|---|
| Location | Walls of the heart | Attached to bones |
| Control | Involuntary | Voluntary |
| Cell shape | Branched, cylindrical, uninucleate | Unbranched, cylindrical, multinucleate |
| Striations | Present (but faint) | Clearly present |
| Intercalated discs | Present | Absent |
| Fatigue | Never fatigues | Fatigues easily |
(c) Dense Regular vs Dense Irregular Connective Tissue:
| Feature | Dense Regular | Dense Irregular |
|---|
| Fibre arrangement | Parallel, regular orientation | Random, irregular orientation |
| Strength | Great tensile strength in one direction | Strength in all directions |
| Examples | Tendons (muscle to bone), ligaments (bone to bone) | Skin dermis, capsule of kidney, spleen |
Internal Links
- [Chapter 7 Guide — Structural Organisation in Animals](/school/cbse/class/11/biology/cbse-structural-organisation-animals)
- [All Class 11 Biology Solutions](/school/cbse/class/11/biology/solutions)
- [Class 11 Biology Subject Guide](/school/cbse/class/11/biology)
