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Tissues – Complete Notes (Class 9 Science)
🔹 What is a Tissue?
A tissue is a group of similar cells that work together to perform a specific function. 👉 Example: Muscle tissue helps in movement.
🔹 Why do multicellular organisms need tissues?
Division of labour (different tasks done by different tissues) Efficiency increases Body functions smoothly
🔹 Plant Tissues
Plants have two main types of tissues :
1️ ⃣ Meristematic Tissue (Growing Tissue)
🔹 Definition:
Tissues made of actively dividing cells.
🔹 Characteristics:
Cells are small and thin-walled Dense cytoplasm Large nucleus Vacuole absent or very small No intercellular spaces
🔹 Types:
🔹 (a) Apical Meristem
Located at tips of roots and shoots
Helps in increase in length
🔹 (b) Intercalary Meristem
Located at base of leaves or internodes Helps in growth in length (especially in grasses)
🔹 (c) Lateral Meristem
Located on sides (cambium) Helps in increase in girth (thickness) 2️ ⃣ Permanent Tissue Cells lose the ability to divide and become specialized.
🔹 Types:
🔹 A. Simple Permanent Tissue Made of only one type of cells.
1️. Parenchyma
Living cells Thin cell walls Large vacuole 👉 Functions: Storage of food Photosynthesis (when chloroplast present → called chlorenchyma) Provides support
2️. Collenchyma
Living cells Uneven thickening at corners
👉 Function: Transport of food (sugars) Components: Sieve tubes Companion cells Phloem fibres Phloem parenchyma 👉 Movement: Both directions
🔹 Protective Tissues
1️. Epidermis
Outer layer of plant Protects from water loss and damage 👉 Has stomata for gas exchange
2️. Cork (Bark)
Dead cells Waterproof (contains suberin) 👉 Protects inner tissues
Animal Tissues
Animals have 4 main types of tissues :
1️ ⃣ Epithelial Tissue (Covering Tissue)
🔹 Function:
Protection Absorption Secretion
🔹 Types:
🔹 (a) Squamous Epithelium
Thin and flat 👉 Found in lungs (gas exchange)
🔹 (b) Cuboidal Epithelium
Cube-shaped 👉 Found in glands and kidney tubules
🔹 (c) Columnar Epithelium
Tall cells 👉 Found in stomach and intestine
🔹 (d) Ciliated Epithelium
Has hair-like cilia 👉 Moves substances (like mucus)
🔹 (e) Glandular Epithelium
Secretes substances (enzymes, hormones) 2️ ⃣ Connective Tissue
🔹 Function:
Flexible tissue 👉 Found in nose, ear 3 ⃣ Muscular Tissue
🔹 Function:
Movement of body
🔹 Types:
🔹 (a) Striated Muscle
Voluntary Found in limbs
🔹 (b) Smooth Muscle
Involuntary Found in stomach
🔹 (c) Cardiac Muscle
Found in heart Involuntary Works continuously 4 ⃣ Nervous Tissue
🔹 Function:
Controls and coordinates body activities
🔹 Structure:
Made of neurons 👉 Parts: Cell body Axon Dendrites
🔹 Difference Between Plant and Animal
Tissues
Feature Plant Tissue Animal Tissue Growth Continuous Limited Dead cells More Less Energy need Less More Movement No movement Movement present
🔹 Important Points to Remember
Tissue = group of similar cells Plants → meristematic & permanent Animals → epithelial, connective, muscular, nervous Xylem → water transport Phloem → food transport Muscles → movement Neurons → control
✍Top 5 Long Questions – Tissues
🔹 1️. Explain the structure and functions of different types of
plant tissues.
Answer: Plant tissues are of two main types:
(a) Meristematic Tissue
Helps in movement Types: o Striated (voluntary) o Smooth (involuntary) o Cardiac (heart)
4. Nervous Tissue
Made of neurons Controls and coordinates body functions 🔹 3. Differentiate between simple and complex permanent tissues. Answer: Feature Simple Tissue Complex Tissue Cells Same type Different types Function Storage & support Transport Types Parenchyma, collenchyma, sclerenchyma Xylem, phloem 👉 Simple tissues perform basic functions, while complex tissues help in transport. 🔹 4. Explain the structure and functions of xylem and phloem. Answer:
🔹 Xylem
Components: tracheids, vessels, fibres, parenchyma Function: transport water and minerals Movement: upward
🔹 Phloem
Components: sieve tubes, companion cells, fibres, parenchyma Function: transport food
Movement: both directions 👉 Xylem mainly consists of dead cells, while phloem has living cells.
🔹 5. Describe different types of muscular tissues and their
functions.
Answer:
(a) Striated Muscle
Voluntary Found in limbs Helps in body movement
(b) Smooth Muscle
Involuntary Found in stomach, intestine Helps in internal movements
(c) Cardiac Muscle
Found in heart Involuntary Works continuously without fatigue 👉 Muscles help in movement of body and internal organs.
🔹 Exam Tip
👉 Always include: Headings Diagrams (if possible) Examples
