Chapter 3: Tissues in Action — Notes
1. Tissue: Meaning and Importance
- A tissue is a group of similar cells working together to perform a specific function.
-
In multicellular organisms:
- Cells → Tissues → Organs → Organ Systems → Organism
- Tissues help in division of labour, making body functions more efficient.
Examples
- Muscle tissue → movement
- Nervous tissue → control and coordination
- Xylem → transports water
- Phloem → transports food
2. Difference Between Plant and Animal Tissues
3. Meristematic Tissues (Growth Tissues)
- Meristematic tissues contain actively dividing cells.
- Responsible for plant growth.
Characteristics
- Small cells
- Thin cell walls
- Dense cytoplasm
- Large nucleus
- No vacuoles
- Cells tightly packed
Types of Meristematic Tissue
(a) Apical Meristem
- Present at root and shoot tips.
- Increases length of plant.
(b) Lateral Meristem
- Present along sides of stem.
- Increases girth (thickness).
(c) Intercalary Meristem
- Present at nodes/internodes.
- Helps in regrowth after cutting or grazing.
4. Differentiation
- Process by which meristematic cells become specialised permanent tissues.
5. Permanent Tissues
Permanent tissues lose the ability to divide.
Types
- Simple Permanent Tissue
- Complex Permanent Tissue
6. Simple Permanent Tissues
(a) Parenchyma
Features
- Living cells
- Thin cell walls
- Intercellular spaces present
Functions
- Storage of food
- Photosynthesis
- Floating in aquatic plants
(b) Collenchyma
Features
- Living cells
- Unevenly thickened corners
Functions
- Flexibility
- Support
(c) Sclerenchyma
Features
- Dead cells
- Thick lignified walls
Functions
- Strength and rigidity
Examples
- Coconut husk
- Walnut shell
7. Complex Permanent Tissues
(a) Xylem
Function
- Transports water and minerals upward.
Components
- Tracheids
- Vessels
- Xylem parenchyma
- Xylem fibres
Important Point
- Mostly dead cells.
(b) Phloem
Function
- Transports food from leaves to other parts.
Components
- Sieve tubes
- Companion cells
- Phloem parenchyma
- Phloem fibres
Important Point
- Mostly living cells.
8. Tissue Systems in Plants
(a) Dermal Tissue System
- Outer protective covering.
- Includes epidermis.
(b) Ground Tissue System
- Main body tissue.
- Includes parenchyma, collenchyma, sclerenchyma.
(c) Vascular Tissue System
- Conducting tissues.
- Includes xylem and phloem.
9. Epidermis
- Outermost protective layer.
- Covered by waxy cuticle.
Functions
- Protection
- Prevents water loss
- Gas exchange through stomata
- Root hairs absorb water
10. Animal Tissues
Four Main Types
- Epithelial tissue
- Connective tissue
- Muscular tissue
- Nervous tissue
11. Epithelial Tissue
- Forms outer covering and lining of organs.
- Cells are tightly packed.
Functions
- Protection
- Absorption
- Secretion
- Exchange of gases
- Sensory functions
12. Connective Tissue
- Connects and supports body parts.
Types and Functions
13. Muscular Tissue
(a) Skeletal Muscle
- Voluntary movement
- Striated
- Multinucleate
(b) Smooth Muscle
- Involuntary movement
- No striations
- Single nucleus
(c) Cardiac Muscle
- Found in heart
- Branched
- Rhythmic contraction
14. Nervous Tissue
- Made of neurons (nerve cells).
- Controls and coordinates body activities.
Parts of Neuron
- Cell body
- Dendrites
- Axon
- Axon terminals
Functions
- Receive messages
- Process signals
- Transmit impulses
15. Musculoskeletal System
Includes:
- Bones
- Muscles
- Tendons
- Ligaments
- Cartilage
- Joints
Functions
- Movement
- Support
- Posture
- Protection
16. Types of Joints
17. Skeletal System
Functions
- Gives shape and support
- Protects organs
- Helps movement
Important Parts
- Skull
- Vertebral column
- Rib cage
Rib Cage
- 12 pairs of ribs
- Protects heart and lungs
- Helps in breathing
18. Totipotency
- Ability of a plant cell to develop into a complete plant.
- Demonstrated by F. C. Steward using carrot phloem cells.
Importance
- Plant tissue culture
- Crop improvement
- Genetic engineering
19. Crown Gall Disease
- Caused by Agrobacterium tumefaciens
- Causes tumour-like growths in plants.
- Used in modern genetic engineering.
20. Key Points to Remember
- Tissues perform specialised functions.
- Plant tissues are mainly for growth, support and transport.
- Animal tissues help in movement, protection and coordination.
- Xylem transports water; phloem transports food.
- Muscles and bones work together for movement.
- Nervous tissue controls body activities.
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