A tissue is a group of cells, similar in structure, working together to do one job.
Different cells doing different jobs is more efficient than one cell trying to do everything.
Cells → tissues → organs → organ systems → one organism.
Plant cells have a rigid cell wall for support; animal cells don't — which is exactly why animals can move and plants (mostly) can't.
Plants grow in three different ways — longer, thicker, or bushier. Three tissues, three jobs.
At root and shoot tips — makes the plant grow taller and roots grow deeper.
A ring inside the stem — adds girth. This is what makes tree trunks thicker every year.
At the base of internodes, just above a node — lets grass and hedges regrow after being cut or grazed.
Nothing slowing down rapid division.
Packed with the machinery cell division needs.
Vacuoles are for storage — meristem cells aren't storing, they're dividing.
Cells that stop dividing change shape and function — they differentiate into permanent tissue.
Two onion bulbs grow roots in water. On day 3, Jar B's root tips are cut by 1 cm. Both jars are watched for 4 more days.
Which jar's roots keep growing, and which one stops?
Jar A keeps growing — its root tips (with the apical meristem intact) keep dividing. Jar B stops, because cutting the tip removes the only actively dividing cells.
"Meristematic cells are located only at the root and shoot tips."
That's only the apical meristem. Lateral meristem runs along the stem (girth), and intercalary meristem sits at the base of internodes (regrowth) — three locations, not one.
Once a cell stops dividing, it specialises. These three differ mainly in how thick — and how alive — their walls are.
Thin walls, loosely packed, living. Stores food; photosynthesises in green parts.
Unevenly thickened corners (pectin), living. Flexible support — lets stems bend without breaking.
Thick, lignified walls, mostly dead. Hard and strong — husks, shells, leaf veins.
Coconut husk fibres are tough, hard and fibrous — used for mats and ropes.
And why couldn't living parenchyma do the same job?
Sclerenchyma — thick, lignified, mostly-dead walls make it hard and strong. Parenchyma's thin walls simply can't provide that kind of rigid strength.
"All permanent tissue is dead, because it can't divide anymore."
Only sclerenchyma is mostly dead. Parenchyma and collenchyma are very much alive — "permanent" means it stopped dividing, not that it stopped living.
Two transport pipelines, running through the same plant.
Carries water & minerals, roots → rest of plant. Tracheids, vessels, fibres — mostly dead, thick-walled tubes.
Carries food, leaves → rest of plant. Sieve tubes + companion cells — living cells.
The epidermis — outer covering, protection, reduces water loss.
Parenchyma, collenchyma, sclerenchyma — the main body of the plant.
Xylem + phloem, arranged in bundles — the transport network.
A plant's stem is damaged in a way that stops food (not water) from moving from leaves to roots.
Think about what each tissue actually carries.
Phloem — it's the tissue that transports food. Xylem would still be moving water and minerals just fine.
"Xylem is 'dead' tissue, so it can't be doing anything useful."
Xylem cells die on purpose — losing their contents turns them into hollow, thick-walled pipes. Being dead is exactly what makes them efficient at carrying water under pressure.
Epithelial tissue forms the skin outside and lines organs inside — always closely packed, almost no gaps.
Many stacked layers of flat cells — skin, mouth, oesophagus.
A single layer of thin, flat cells — fast diffusion. Lines blood vessels and lungs.
A single layer of tall, column-like cells. Lines the small intestine.
"The lungs use many layers of tall cells to protect against gas loss."
Backwards. Gas exchange needs speed, not protection — so the lungs use a single layer of thin, flat cells, the shortest possible diffusion path. Multiple thick layers would slow gas exchange down, not speed it up.
Connective tissue connects and supports other tissues. Every type is built around a matrix — the material between the cells — and the matrix decides its properties.
Watery, fluid matrix (plasma). Carries cells and dissolved substances around the body.
Hard, rigid matrix (calcium + phosphorus). Gives strength and structure.
Soft, jelly-like matrix. Flexible cushioning — nose, ears, joint ends.
Connects muscle to bone. Transmits the pull of a contracting muscle so a joint moves.
Connects bone to bone. Limits movement at a joint and prevents dislocation.
Touch your elbow gently (hard, rigid) · press your nose (soft, springs back) · wiggle your fingers while feeling your forearm move.
Elbow = bone. Nose = cartilage. Forearm-to-finger movement = tendon.
"Tendons connect bone to bone and allow joint movement."
That's ligament's job. Tendons connect muscle to bone — mixing the two up is one of the most common slips in this chapter.
All muscle tissue contracts — but three different structures produce three different kinds of movement.
Long, cylindrical, striated, many nuclei. Voluntary — attached to bones.
Spindle-shaped, unstriated, one nucleus. Involuntary — stomach, intestines.
Branched, striated, one nucleus. Involuntary — only in the heart, never tires.
"Involuntary muscle is always smooth, unstriated muscle."
Cardiac muscle breaks that rule — involuntary AND striated. Voluntary/involuntary describes control; striated/unstriated describes structure. They don't always pair the way you'd expect.
Nervous tissue senses, decides, and sends messages. Its cells — neurons — are built to carry signals across long distances.
Branches that receive signals from other neurons.
Contains the nucleus; controls the cell's activities.
A long fibre that carries the message away, ending in axon terminals that pass it on.
You touch something hot and pull your hand away instantly. Which tissue made that possible, and which of its parts first picked up the signal?
Nervous tissue — the dendrites of a neuron first receive the signal, which the axon then carries onward.
Muscles can only pull, never push. Tendons transmit that pull to bones. A joint decides how far and which way a bone can move.
Muscle contracts → tendon pulls → bone moves at a joint.
Roughly the share of an adult's body weight that comes from bone.
Shoulder — moves in every direction.
Elbow, knee — bends in one plane only.
Neck — turns side to side.
Skull — no movement at all.
Which joint lets you: (a) turn your head to say "no", (b) swing your arm in a full circle, (c) bend your knee one way only?
Match each motion to the junction that allows exactly that kind of movement — no more, no less.
(a) Pivot joint. (b) Ball-and-socket joint. (c) Hinge joint.
"In a hinge joint, the bone ends are shaped to allow sliding in all directions."
A hinge joint moves in one plane only, like a door — that's the entire point of its shape. "All directions" describes a ball-and-socket joint, not a hinge.
A tissue — a group of similar cells, working together to do one job.
Plant tissues — meristematic (dividing) and permanent (parenchyma, collenchyma, sclerenchyma, xylem, phloem).
Animal tissues — epithelial (cover/line), connective (connect/support), muscular (movement), nervous (signals).
Musculoskeletal system — muscles pull, tendons transmit, joints allow movement in different ways.
A group of cells, similar in structure, that work together to perform a specific function.
The process by which a meristematic cell stops dividing and becomes specialised — for support, transport or storage.
Meristematic tissues divide repeatedly. What property of their cells allows this? (i) Thick walls (ii) Large vacuoles (iii) Thin walls, dense cytoplasm, large nucleus (iv) Functionally differentiated cells.
If a plant can't transport food from its leaves to its roots, which tissue is malfunctioning? (i) Xylem (ii) Phloem (iii) Epidermis (iv) Sclerenchyma.
Why are the epithelial tissues lining internal organs usually only one or a few cells thick? (i) To store food (ii) Maximum strength (iii) Quick exchange of materials (iv) To reduce friction.