A complete visual guide — levels of organisation, plant tissues (meristematic, parenchyma, collenchyma, sclerenchyma, xylem & phloem, epidermis & cork) and animal tissues (epithelial, connective, muscular and nervous), plus joints, movement and muscular injuries.
📌 Chapter 2
Plant Tissues
Animal Tissues
Xylem & Phloem
Muscles & Neurons
Joints
150 Practice Qs
Section 2.1 – 2.3
Levels of Organisation & What a Tissue Is
A unicellular organism like Amoeba does every job with one cell. In multicellular bodies there is a division of labour — groups of similar cells specialise and work together. Such a group of similar cells doing a specific job is a tissue.
Cell → Tissue → Organ → Organ system → Organism — increasing levels of organisation
❖ Tissue
A group of similar cells that are structurally organised to carry out a specific function. The term was coined by Xavier Bichat (the "father of histology"); the study of tissues is histology.
Section 2.4
Plant Tissues vs Animal Tissues
Plants are fixed and keep growing at certain spots; animals move and grow all over. Their tissues reflect this.
Feature
Plant tissues
Animal tissues
Growth
At specific regions (meristems)
Uniform, all over
Cells
Many dead cells for support (sclerenchyma, xylem)
Mostly living cells
Support tissue
Plenty (collenchyma, sclerenchyma)
Less (bone, cartilage)
Movement
Stationary — no movement tissue
Muscle tissue for movement
Main types
Meristematic & permanent
Epithelial, connective, muscular, nervous
🌱 Classification of plant tissues
By their ability to divide, plant tissues are meristematic (actively dividing) or permanent (non-dividing). Permanent tissues are simple (one cell type: parenchyma, collenchyma, sclerenchyma) or complex (many cell types: xylem and phloem).
Section 2.5
Meristematic Tissue
Undifferentiated, actively dividing cells in the growing regions (meristems). They are small, thin-walled, with dense cytoplasm, a prominent nucleus and no vacuole, packed tightly with no intercellular space.
Where meristems sit: apical (root & shoot tips, length), lateral (sides, girth) and intercalary (base of internodes in grasses)
Meristem
Location
Adds
Apical
Tips of roots and shoots
Length (height)
Intercalary
Base of internodes (grasses, bamboo)
Length of internode
Lateral
Sides of root, stem & branches
Girth (width)
💡 Did You Know?
In the onion-root experiment, cutting the root tip stops the root growing — proving the dividing apical meristem sits right at the tip.
Section 2.5 (Permanent tissues)
Simple Permanent Tissues
Formed when meristematic cells stop dividing and take up a fixed shape, size and job (differentiation). Made of one cell type: parenchyma, collenchyma and sclerenchyma.
The three simple tissues: parenchyma (thin walls + air spaces), collenchyma (thickened corners), sclerenchyma (thick lignin walls, dead)
🌿 Parenchyma
Living, thin cellulose walls, isodiametric cells with intercellular spaces. Stores food (potato tuber) and gives temporary support. With chlorophyll it is chlorenchyma (photosynthesis); with big air cavities in water plants it is aerenchyma (buoyancy).
Collenchyma
Living cells with extra thickening of cellulose & pectin at the corners, no intercellular space. Gives flexible mechanical support to growing stems and leaves so they bend without breaking. Found in dicot stems/leaf edges.
Sclerenchyma
Dead cells with hard, thick lignified walls and a narrow lumen, no intercellular space. Gives strength & protection. Shapes: long fibres (jute, flax, coir) or stone cells/sclereids (the grit in a pear).
💡 Did You Know?
Lignin is the natural "cement" that hardens cell walls and makes them waterproof. Coconut coir and the grit in pears are both sclerenchyma.
Section 2.5 (Complex tissues)
Complex Tissues: Xylem & Phloem
Made of more than one cell type, these vascular (conducting) tissues carry water and food through the plant.
Xylem (tracheids & vessels) carries water upward; phloem (sieve tubes with sieve plates + companion cells) carries food both ways
Xylem — water & minerals
Four elements: tracheids (tapering, pitted), vessels (open tubes), xylem parenchyma (living, storage) and xylem fibres (support). All dead and lignified except the parenchyma. Flow is one-way (roots → leaves).
Phloem — food
Four elements: sieve tubes (with perforated sieve plates), companion cells (help the sieve tube), phloem parenchyma (storage) and phloem fibres (support). All living except the fibres. Flow is two-way.
Section 2.5 (Protective tissues)
Protective Tissues: Epidermis, Cork & Bark
The outer layers that protect the plant and control water loss and gas exchange.
Stomata in the leaf epidermis, opened and closed by a pair of kidney-shaped guard cells
Epidermis
A single, outermost living layer with no intercellular space, covering the whole plant. Cells lack chloroplasts (except guard cells). It may secrete a waxy cutin in dry plants to cut water loss; root epidermal cells form root hairs for absorption; leaf epidermis has stomata for gas exchange.
Cork & Bark
In older plants the cork cambium (phellogen) forms cork — dead, compact cells with suberin that makes them waterproof. Bark is the outer protective covering (mostly cork): prevents water loss, resists microbes and insulates.
💡 Did You Know?
Suberin waterproofs cork — it is why an onion bulb is water-resistant, and why cork is used for insulation, shuttlecocks and cricket-ball cores. Bark also gives us quinine (anti-malaria) and taxol (anti-cancer).
Section 2.6 (Animal tissues)
Epithelial Tissue
The covering and lining tissue. Cells are tightly packed in a sheet with almost no intercellular space, resting on a basement membrane. It protects, absorbs, secretes and regulates exchange.
Epithelial types by cell shape: squamous (flat), cuboidal (cube), columnar (pillar) and ciliated (with cilia) — all on a basement membrane
Lining of stomach & intestine; absorption & secretion.
Glandular
Modified columnar
Oil, salivary, sweat glands; secretion.
Ciliated
With cilia
Trachea, bronchi, oviduct; moves particles in one direction.
Section 2.6 (contd.)
Connective Tissue
Connects, supports and packs around organs. Living cells are spread in a non-living matrix that may be jelly-like, solid (bone, cartilage) or fluid (blood, lymph).
Class
Type
Role
Proper
Areolar
Fills spaces, supports organs, repairs tissue
Adipose
Stores fat; insulates and cushions
Fibrous (tendon/ligament)
Tendon: muscle→bone; ligament: bone→bone
Supportive
Cartilage
Flexible, smooth surface at joints, nose, ear
Bone
Hard, rigid framework; protects organs
Fluid
Blood
Transports O₂, food, wastes, hormones
Lymph
Defence; returns fluid & fats to blood
Tendon vs Ligament
Tendon — tough, non-elastic white fibres joining muscle to bone. Ligament — strong, elastic (yellow + white) fibres joining bone to bone; over-stretching causes a sprain.
Cartilage vs Bone
Cartilage — soft, flexible, non-porous, no blood vessels; cells = chondrocytes. Bone — hard, rigid, porous with blood vessels; cells = osteocytes in rings (lamellae), connected by canaliculi; matrix rich in calcium & magnesium salts.
Blood = plasma (55%) + cells: biconcave RBCs (haemoglobin, no nucleus), nucleated WBCs (defence) and platelets (clotting)
💡 Did You Know?
An adult has about 5 litres of blood. RBCs live ~120 days and carry oxygen; WBCs live a few days and fight infection; platelets help clotting. Plasma minus fibrinogen is serum.
Section 2.6 (contd.)
Muscular Tissue
Elongated contractile cells (muscle fibres) with special proteins that contract and relax to cause movement.
The three muscle types: striated/skeletal (voluntary), smooth (involuntary) and cardiac (branched, with intercalated discs)
Striated
Smooth
Cardiac
Shape
Long, cylindrical, unbranched
Spindle, tapering
Branched
Nuclei
Many (at edges)
One (central)
One (central)
Bands
Present
Absent
Present
Control
Voluntary
Involuntary
Involuntary
Where
Limbs (attached to bones)
Stomach, blood vessels
Heart
Section 2.6 (contd.)
Nervous Tissue
Specialised to receive stimuli and transmit messages quickly. Found in brain, spinal cord and nerves; made of nerve cells (neurons).
A neuron: dendrites receive signals → cell body (cyton) with nucleus → long axon (with myelin sheath) → terminal branches pass the signal on
Dendrites — short branched processes that receive signals.
Cyton (cell body) — contains the nucleus and Nissl granules.
Axon — a single long process that carries the impulse away; ends in synaptic knobs.
The junction between two neurons is a synapse; the neurotransmitter is acetylcholine. A neuron can be up to a metre long.
Section 2.7 – 2.10
Joints, Movement & Muscular Injuries
A joint is where two or more bones meet, held by ligaments. Joints make movement possible.
Movable (synovial) joints: ball-and-socket (all directions), hinge (one plane), pivot (rotation); gliding joints let bones slide (wrist, ankle)
Joint
Movement
Example
Immovable
None
Skull sutures, tooth sockets
Slightly movable
Limited (cartilage pad)
Between vertebrae
Ball & socket
All directions
Shoulder, hip
Hinge
One plane (bend/straighten)
Elbow, knee
Pivot
Rotation
Neck (head turning)
Gliding
Sliding
Wrist, ankle
🧼 Movement & muscular injuries
Bones (levers), muscles (force, working in pairs), cartilage (smooth, shock-absorbing surface), tendons (muscle→bone) and ligaments (bone→bone) work together for movement. Injuries: strain (muscle fibres torn), sprain (ligaments torn), tear (severe). First aid is R.I.C.E. — Rest, Ice, Compression, Elevation.
Glossary
Key Terms
Quick definitions for fast revision.
Tissue
A group of similar cells working together for a specific function.
Histology
The microscopic study of tissues.
Meristematic tissue
Actively dividing plant tissue at growing regions (apical, lateral, intercalary).
Permanent tissue
Non-dividing differentiated tissue: simple or complex.
Parenchyma / Collenchyma / Sclerenchyma
Storage (living) / flexible support (thick corners) / rigid support (dead, lignified).
Xylem / Phloem
Conducts water & minerals (one-way) / conducts food (two-way).