Tissues
Detailed NCERT Solutions & Analysis
In-Text Questions (Page 69)
Q1. What is a tissue?
A group of cells that are similar in structure and/or work together to achieve a particular function forms a tissue. Examples: Blood, Phloem, Muscle.
Q2. What is the utility of tissues in multicellular organisms?
In multicellular organisms, tissues provide specific structural and mechanical strength and allow division of labour. Specialized cells are grouped together to perform specific functions efficiently (e.g., nerve cells carry messages, muscle cells cause movement).
In-Text Questions (Page 74)
Q1. Name types of simple tissues.
The three main types of simple permanent tissues in plants are:
- Parenchyma
- Collenchyma
- Sclerenchyma
Q2. Where is apical meristem found?
Apical meristem is found at the growing tips of stems and roots. It increases the length of the stem and the root.
Q3. Which tissue makes up the husk of coconut?
The husk of a coconut is made up of sclerenchymatous tissue. These cells are dead, long, and narrow with thick lignified walls.
Q4. What are the constituents of phloem?
Phloem is made up of four types of elements:
- Sieve tubes
- Companion cells
- Phloem parenchyma
- Phloem fibres (only dead element)
In-Text Questions (Page 78)
Q1. Name the tissue responsible for movement in our body.
Muscular tissue is responsible for movement in our body.
Q2. What does a neuron look like?
A neuron consists of a cell body (cyton) with a nucleus and cytoplasm, from which long thin hair-like parts arise. It has a single long part called the axon, and many short, branched parts called dendrites. It looks like a small tree with branches.
Q3. Give three features of cardiac muscles.
- They are involuntary muscles (found only in the heart).
- They are cylindrical, branched, and uninucleate.
- They show rhythmic contraction and relaxation throughout life.
Main Textbook Exercises
Q1. Definitions
Tissue: A group of cells similar in structure and function.
Meristematic Tissue: Dividing tissue present in growing regions of plants.
Q2. Features of Phloem vs Xylem.
| Xylem | Phloem |
|---|---|
| Transports water and minerals. | Transports food. |
| Movement is unidirectional (upwards). | Movement is bidirectional. |
| Mainly dead elements (tracheids, vessels, fibres). | Mainly living elements (except fibres). |
Q3. Name the following.
- (a) Tissue that forms inner lining of mouth: Squamous Epithelium
- (b) Tissue that connects muscle to bone: Tendon
- (c) Tissue that transports food in plants: Phloem
- (d) Tissue that stores fat in our body: Adipose tissue
- (e) Connective tissue with a fluid matrix: Blood
- (f) Tissue present in the brain: Nervous tissue
Q4. What is the function of areolar tissue?
It fills the space inside the organs, supports internal organs, and helps in the repair of tissues. It is found between skin and muscles, around blood vessels and nerves.
Tissues
Detailed Analysis: Plant vs Animal Tissues
1. Plant Tissues
Plant tissues are broadly classified into two main groups based on their ability to divide.
A. Meristematic Tissue (Dividing Tissue)
- Apical Meristem: Present at growing tips of stems and roots (increases length).
- Lateral Meristem (Cambium): Increases the girth of the stem or root.
- Intercalary Meristem: Present at the base of leaves or internodes (growth of twigs).
B. Permanent Tissue (Non-dividing)
Formed from meristematic tissue that has lost the ability to divide (Process called Differentiation).
- Parenchyma: Basic packing tissue. Living cells with thin cell walls. Stores food. (Chlorenchyma: with chlorophyll; Aerenchyma: with air cavities).
- Collenchyma: Provides flexibility. Living cells, thickened at corners.
- Sclerenchyma: Makes plant hard and stiff (e.g., coconut husk). Dead cells with thick lignin walls.
- Xylem: Transports water/minerals. (Tracheids, Vessels, Xylem Parenchyma, Xylem Fibres).
- Phloem: Transports food. (Sieve tubes, Companion cells, Phloem Parenchyma, Phloem Fibres).
2. Animal Tissues
A. Epithelial Tissue (Protective)
Squamous: Flat cells (lining of mouth, blood vessels). Diffusion/filtration.
Cuboidal: Cube-like (kidney tubules). Mechanical support.
Columnar: Tall, pillar-like (intestine). Absorption/secretion.
B. Connective Tissue (Binding/Support)
Fluid matrix (plasma) with RBC, WBC, Platelets.
Hard matrix (calcium/phosphorus).
Connects Bone to Bone. Elastic.
Connects Muscle to Bone. Fibrous.
Also: Cartilage (flexible bone), Areolar (repair), Adipose (fat storage).
C. Muscular Tissue (Movement)
- Striated (Skeletal): Voluntary, cylindrical, multinucleate (limbs).
- Smooth (Unstriated): Involuntary, spindle-shaped, uninucleate (stomach, iris).
- Cardiac: Involuntary, cylindrical, branched, uninucleate (heart).
D. Nervous Tissue (Control)
Neurons transmitted signals. Brain, spinal cord, and nerves are composed of nervous tissue.
3. Quick Comparison: Meristematic vs Permanent
| Meristematic | Permanent |
|---|---|
| Cells divide repeatedly. | Cells do not divide. |
| Undifferentiated. | Fully differentiated. |
| Dense cytoplasm, prominent nucleus. | Large vacuole, cytoplasm pushes to periphery. |
Key Facts & Definitions
50+ Important Points to Remember
Group of cells similar in structure performing a specific function.
Study of tissues.
Dividing tissue in plants; responsible for growth.
Found at tips of root and stem; increases length.
At base of leaves or internodes; increases length of organs.
Cambium; increases girth (thickness) of stem and root.
Process where meristematic tissue takes up a permanent shape, size, and function.
Simple permanent tissue; thin walls; stores food.
Parenchyma containing chlorophyll; performs photosynthesis.
Parenchyma with large air cavities (in aquatic plants); provides buoyancy.
Provides flexibility and mechanical support; thickened at corners.
Dead tissue; thick lignified walls; provides hardness (e.g., coconut husk).
Chemical substance acting as cement in sclerenchyma walls.
Outermost layer of cells in plant body; protective function.
Small pores in epidermis of leaf; gas exchange and transpiration.
Kidney-shaped cells enclosing stomata; regulate opening/closing.
Dead protective tissue in older roots/stems; has suberin.
Chemical in cork walls making them impervious to gases and water.
Complex tissue; transports water and minerals vertically.
Complex tissue; transports food (translocation) in both directions.
Tube-like dead cells; main water conducting elements in angiosperms.
Tubular cells with perforated walls (sieve plates) in Phloem.
Covering or protective tissue in animals.
Flat, thin cells; forming lining of mouth, oesophagus.
Cube-shaped cells; kidney tubules, salivary ducts.
Pillar-like cells; intestinal lining (absorption).
Columnar cells with cilia (hair-like); respiratory tract.
Connects, supports, binds other tissues. Cells loosely spaced in matrix.
Fluid connective tissue. Plasma matrix.
Hard, non-flexible connective tissue. Calcium/Phosphorus matrix.
Connects bone to bone. Very elastic.
Connects muscle to bone. Fibrous, limited flexibility.
Solid but flexible matrix (sugar/protein). Nose, ear, trachea.
Found between skin and muscles; fills space, supports organs.
Fat-storing tissue below skin. Acts as insulator.
Consists of muscle fibers; responsible for movement.
Actin and Myosin; cause contraction and relaxation.
Voluntary, skeletal muscles. Multinucleate, unbranched.
Involuntary, unstriated. Spindle shaped, uninucleate.
Involuntary, heart muscles. Cylindrical, branched, rhythmic.
Specialized for receiving and transmitting impulses.
Structural unit of nervous system (Nerve cell).
Cell body of a neuron containing nucleus.
Long single part of neuron (transmits impulse away).
Short branched parts of neuron (receive impulse).
Signal that passes along the nerve fibre.
Can be moved by our will (e.g., limbs).
Cannot be moved by our will (e.g., iris, bronchi).
Tubular dead cells in Xylem with tapering ends.
Living cells associated with sieve tubes in Phloem.