1. Four Basic Animal Tissues
| Tissue | Core feature | Main functions / examples |
|---|---|---|
| Epithelial | Sheet of closely packed cells with little intercellular material | Covers body surface and lines cavities; protection, absorption, secretion |
| Connective | Cells separated by abundant intercellular matrix | Binding, support, storage and transport; blood, bone, cartilage, areolar tissue |
| Muscular | Elongated cells with contractile proteins | Movement of body and internal organs |
| Neural | Neurons specialised for stimulus reception and impulse conduction | Control, coordination and communication |
2. Types of Epithelial Tissue
| Type | Structure | Location / function |
|---|---|---|
| Simple squamous | Single layer of flat cells | Alveoli and blood vessels; diffusion and exchange |
| Cuboidal | Single layer of cube-shaped cells | Kidney tubules and ducts; secretion and absorption |
| Columnar | Tall cells with nuclei near base | Stomach and intestine; secretion and absorption |
| Ciliated | Columnar/cuboidal cells with cilia | Bronchioles and oviducts; movement of particles or ovum |
| Glandular | Secretory epithelial cells | Glands; secretion of hormones, enzymes and mucus |
| Compound | Many cell layers | Skin and buccal cavity; protection against wear and tear |
3. Connective Tissues Compared
| Tissue | Matrix / cells | Function / location |
|---|---|---|
| Areolar | Fibroblasts, macrophages and mast cells in loose matrix | Fills spaces between tissues, supports internal organs and repairs tissue |
| Adipose | Adipocytes filled with fat | Stores fat; insulation and cushioning below skin and around organs |
| Cartilage | Chondrocytes in lacunae; solid, pliable matrix | Support and flexibility; nose tip, external ear, joints |
| Bone | Osteocytes in lacunae; calcified matrix | Rigid support, protection and muscle attachment |
| Blood | Fluid plasma with RBCs, WBCs and platelets | Transport of gases, nutrients and wastes |
| Lymph | Colourless fluid with lymphocytes | Returns fluid to blood and transports absorbed fats |
4. Striated vs Smooth vs Cardiac Muscle
| Feature | Striated / skeletal | Smooth / visceral | Cardiac |
|---|---|---|---|
| Shape / appearance | Long, cylindrical, unbranched; striations present | Spindle-shaped; striations absent | Short, cylindrical and branched; striated |
| Nuclei | Multinucleate; peripheral nuclei | Single, central nucleus | Usually one, central nucleus |
| Control | Voluntary | Involuntary | Involuntary and rhythmic |
| Location | Attached to skeleton | Walls of visceral organs and blood vessels | Heart wall |
| Special feature | Rapid, forceful contraction | Slow, sustained contraction | Intercalated discs join cells |
5. Frog: External Features and Organ Systems
| System / feature | NCERT facts |
|---|---|
| Habitat and limbs | Amphibian; lives on land and fresh water. Hindlimbs larger with five webbed digits; forelimbs have four digits. |
| Sexual dimorphism | Male has vocal sacs and copulatory pad on first digit of forelimb. |
| Respiration | Cutaneous in water; on land uses skin, buccal cavity and lungs. Lungs are pink sac-like structures. |
| Circulation | Three-chambered heart: two atria and one ventricle; incomplete double circulation. |
| Excretion | Kidneys, ureters, urinary bladder and cloaca; frog is ureotelic. |
| Nervous system | CNS, PNS and autonomic system; ten pairs of cranial nerves. |
6. Male vs Female Frog Reproductive System
| Feature | Male frog | Female frog |
|---|---|---|
| Gonads | Pair of testes attached to kidneys | Pair of ovaries near kidneys, without functional kidney connection |
| Ducts | Vasa efferentia → kidneys → urinogenital ducts → cloaca | Paired oviducts open separately into cloaca |
| Gametes | Sperms | Can lay 2500-3000 ova at a time |
| Fertilisation and development | External fertilisation in water; tadpole larva undergoes metamorphosis to adult. | |
Ecological value Frogs control insects, protect crops and form an important link in food chains and food webs.