9 Class Chapter: Tissues Revision Notes

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🌿 Class 9 – Chapter: Tissues


1️⃣ Introduction to Tissues

🔹 Tissue Definition

  • A group of cells similar in structure and function.

  • Shows division of labour in multicellular organisms.

🔹 Why Tissues?

  • Increase efficiency

  • Specialisation of functions

  • Example:

    • Muscle → Movement

    • Blood → Transport

    • Phloem → Food transport

2️⃣ Difference Between Plants and Animals (Tissue Basis)

PlantsAnimals
Stationary    Move from place to place
More supportive tissue    More living tissue
Growth at specific regions            Growth occurs throughout body
Dead cells common    Mostly living cells

🌱 3️⃣ Plant Tissues

A) Meristematic Tissue (Growing Tissue)

🔹 Features

  • Actively dividing cells

  • Dense cytoplasm

  • Prominent nucleus

  • No vacuoles

  • Thin cell walls

🔹 Types

1. Apical Meristem

  • Present at tips of roots & stems

  • Increases length

2. Lateral Meristem (Cambium)

  • Increases girth

  • Helps in secondary growth

3. Intercalary Meristem

  • Present at nodes

  • Helps in regrowth (grass)

B) Permanent Tissue

🔹 Definition

  • Derived from meristematic tissue

  • Lose ability to divide

  • Process called Differentiation

🌿 4️⃣ Simple Permanent Tissue

1. Parenchyma

  • Living cells

  • Thin cell walls

  • Large intercellular spaces

  • Function: Storage

Special types:

  • Chlorenchyma → Photosynthesis

  • Aerenchyma → Air spaces (aquatic plants)

2. Collenchyma

  • Living cells

  • Uneven thickening at corners

  • Provides flexibility

3. Sclerenchyma

  • Dead cells

  • Thick lignified walls

  • Provides strength

  • Example: Coconut husk

🌳 5️⃣ Complex Permanent Tissue

1. Xylem

Components:

  • Tracheids

  • Vessels

  • Xylem parenchyma

  • Xylem fibres

Function:

  • Water & mineral transport

  • Mostly dead cells

2. Phloem

Components:

  • Sieve tubes

  • Companion cells

  • Phloem parenchyma

  • Phloem fibres

Function:

  • Food transport

  • Mostly living cells

🌿 6️⃣ Protective Tissues

Epidermis

  • Outer protective layer

  • No intercellular spaces

  • Stomata present

  • Reduces water loss

Cork

  • Formed by secondary meristem

  • Dead cells

  • Suberin present

  • Waterproof & protective

🐾 7️⃣ Animal Tissues

A) Epithelial Tissue

Types:

  • Squamous

  • Cuboidal

  • Columnar

  • Ciliated

  • Glandular

Function:

  • Protection

  • Absorption

  • Secretion

B) Connective Tissue

Examples:

  • Blood

  • Bone

  • Cartilage

  • Ligament

  • Tendon

  • Areolar

  • Adipose

Blood Components

  • Plasma

  • RBC

  • WBC

  • Platelets

C) Muscular Tissue

TypeControlNucleiExample
StriatedVoluntaryManyLimbs
SmoothInvoluntaryOneStomach
CardiacInvoluntaryOneHeart

D) Nervous Tissue


Neuron Structure:

  • Cell body

  • Dendrites

  • Axon

Function:

  • Transmits nerve impulses

  • Controls body activities