Ans: Stomata are pores in leaves that allow exchange of gases (CO₂ and O₂) and transpiration of water vapour.

Ans: Squamous epithelial tissue forms the inner lining of the mouth and cheeks.

Ans: Ligament (dense fibrous connective tissue) connects bone to bone.

Ans: Sclerenchyma tissue (a type of simple permanent plant tissue) is present in the husk of coconut.

Ans: Plants need mechanical support to maintain their shape against gravity but do not move. Dead cells like sclerenchyma and xylem vessels provide structural rigidity and support without the metabolic cost of maintaining living cells. They also serve as permanent conducting and supportive structures throughout the plant life.

Ans: Tendon: dense fibrous connective tissue that connects skeletal muscle to bone; inelastic but strong. Ligament: dense fibrous connective tissue that connects bone to bone at a joint; slightly elastic and very strong to provide stability to joints.

Ans: Blood is a connective tissue because it has cells (RBCs, WBCs, platelets) scattered in a fluid matrix called plasma. It connects and serves all body parts by transporting oxygen, nutrients, hormones and waste products, fulfilling the main function of connective tissue — linking different body parts.

Ans: A neuron is the structural and functional unit of nervous tissue. Structure: it has a cell body (cyton) containing the nucleus and cytoplasm. From the cyton arise short, branched projections called dendrites that receive nerve impulses, and one long fibre called axon that carries impulses away from the cell body. The axon ends in small bulb-like structures called synaptic knobs. Function: Neurons transmit electrical nerve impulses rapidly from one part of the body to another, allowing coordination and response to stimuli.

Ans: Meristematic tissue consists of actively dividing cells that give rise to all other tissues. Types: (1) Apical meristem – found at the tips of roots and shoots; causes the plant to grow in length (primary growth). (2) Lateral meristem (cambium) – found along the sides of roots and stems; causes increase in girth or thickness (secondary growth); responsible for the formation of wood. (3) Intercalary meristem – located at the base of leaves or internodes; found in grasses and helps the plant regrow after being grazed.

Ans: Plant tissues are of two main types: (A) Meristematic – actively dividing cells located at growing regions (apical, lateral, intercalary); responsible for growth. (B) Permanent tissues – derived from meristematic tissue, have stopped dividing. Further divided into: Simple permanent – Parenchyma (storage, photosynthesis), Collenchyma (flexibility), Sclerenchyma (rigidity). Complex permanent – Xylem (conducts water and minerals upward; made of tracheids, vessels — both dead, and xylem parenchyma, fibres) and Phloem (conducts food downward; made of sieve tubes — living but no nucleus, companion cells, phloem parenchyma, phloem fibres). [Diagram: Draw a chart showing the classification of plant tissues with labels.]

Ans: Xylem is the water-conducting tissue in plants. It transports water and dissolved minerals from roots to the leaves.

Ans: Cardiac muscle causes rhythmic contraction and relaxation of the heart throughout life (involuntarily and without fatigue), pumping blood to all parts of the body.

Ans: Parenchyma: (1) Living cells with thin cell walls. (2) Large intercellular spaces present. (3) Functions: storage, photosynthesis, secretion. (4) Found throughout plant body. Sclerenchyma: (1) Dead cells with very thick, lignified cell walls. (2) No intercellular spaces. (3) Function: provides rigidity and mechanical support. (4) Found in seed coats, around vascular bundles, nut shells.

Ans: Meristematic tissue: (1) Cells capable of active division. (2) Small cells with dense cytoplasm, large nucleus, thin walls and no vacuoles. (3) No intercellular spaces. (4) Located at growing regions (root tips, shoot tips, cambium). Permanent tissue: (1) Cells have lost the ability to divide. (2) Cells may be living or dead, often with thick walls. (3) Intercellular spaces may be present. (4) Found throughout the mature plant body.

Ans: Epithelial tissue types: (1) Squamous epithelium — flat, tile-like cells; forms the skin surface and inner lining of mouth and blood vessels; protection against mechanical damage. (2) Cuboidal epithelium — cube-shaped cells; found in kidney tubules and salivary glands; functions in absorption and secretion. (3) Columnar epithelium — tall cells; lines the intestine; functions in absorption and secretion of mucus. (4) Ciliated epithelium — columnar cells bearing cilia on their free surface; found in respiratory tract (trachea, bronchi); cilia move mucus and trapped particles. (5) Glandular epithelium — cells specialized for secretion; forms glands like sweat glands, mucus glands.

Ans: In unicellular organisms (like Amoeba), one cell performs all functions — nutrition, respiration, excretion, reproduction. But in multicellular organisms, the body is much larger and complex, so a single cell cannot efficiently perform all functions. Therefore, groups of similar cells become specialized to perform specific functions — this is called division of labour. Different tissues form as cells differentiate during development. For example: epithelial tissue protects; muscular tissue enables movement; nervous tissue coordinates responses; connective tissue supports and connects. This specialization makes each function more efficient and allows the organism to carry out all life processes simultaneously. The more complex the organism, the more specialized and diverse its tissues.

Ans: Diagram of a neuron labels: cell body (with nucleus), dendrites, axon, myelin sheath, Schwann cells, nodes of Ranvier, axon terminals/synaptic knobs. Nerve impulse transmission: (1) Dendrites receive chemical signals (neurotransmitters) from adjacent neurons at synapses. (2) These signals generate an electrical impulse (action potential) in the cell body. (3) The impulse travels along the axon as an electrical signal. (4) Myelin sheath (fatty covering) insulates the axon and speeds conduction — impulse jumps from one node of Ranvier to the next (saltatory conduction). (5) When the impulse reaches the synaptic knobs at the axon terminal, neurotransmitters are released into the synaptic cleft. (6) These chemicals bind to receptors on the dendrites of the next neuron, generating a new impulse. The process repeats until the signal reaches the effector (muscle or gland).