Tissues
Unicellular Organisms:
In unicellular organisms (e.g., Amoeba), a single cell performs all essential functions such as movement, intake of food, gaseous exchange, and excretion.
Multicellular Organisms:
In multicellular organisms, there are millions of cells, most of which are specialized for specific functions.
Specialized cells perform a particular function very efficiently.
Examples in Human Beings:
Muscle Cells: Contract and relax to cause movement.
Nerve Cells: Carry messages throughout the body.
Blood: Transports oxygen, food, hormones, and waste materials.
Examples in Plants:
Vascular Tissues: Conduct food and water from one part of the plant to another.
Division of Labour:
Multi-cellular organisms show a division of labour where different groups of cells carry out different functions.
A particular function is carried out by a cluster of cells at a specific place in the body.
Tissues:
A tissue is a group of similar cells that work together to achieve a specific function.
Examples of Tissues:
Blood: A tissue that transports nutrients and waste.
Phloem: Tissue in plants responsible for transporting food.
Muscle Tissue: Responsible for movement in animals.
Differences Between Plant and Animal Tissues:
Plants vs. Animals:
Plants: Stationary and fixed; they do not move.
Animals: Move around in search of food, mates, and shelter.
Supportive Tissue:
Plants: Have a large amount of supportive tissue that helps them stay upright. This tissue is often made up of dead cells.
Animals: Have living tissues that support movement, and consume more energy than plants.
Growth Patterns:
Plants: Growth is limited to specific regions (e.g., tips of roots and stems). Some tissues divide throughout the plant's life and are localized in specific areas.
Meristematic Tissue: Tissues that grow and divide.
Permanent Tissue: Tissues that are non-dividing and mature.
Animals: Growth is more uniform across the body, and there is no clear demarcation between dividing and non-dividing tissues.
Organ and Organ System Specialization:
Plants: Organ systems are not as specialized as in animals. While complex, the organs and tissues in plants show a simpler structure compared to animals.
Animals: Organ systems are more specialized and localized, reflecting a higher degree of complexity.
Adaptation:
Plants: Adapted for a sedentary (non-moving) existence.
Animals: Adapted for active locomotion.
Feeding Methods:
Plants: Usually do not consume food actively; they use photosynthesis.
Animals: Actively consume food and are generally more energy-demanding.
Summary:
The structural and functional differences between plants and animals reflect their different life strategies—sedentary vs. active, with corresponding adaptations in tissues, organ systems, and growth patterns.
1. What is a Tissue?
A tissue is a group of similar cells that work together to perform a specific function. These cells have similar structure and are often specialized for a particular task. Tissues can be found in both plants and animals, and they are the building blocks that make up organs and organ systems.
2. What is the Utility of Tissues in Multi-cellular Organisms?
In multi-cellular organisms, tissues provide several benefits and essential functions:
Specialization of Functions: Tissues allow for the specialization of functions, as different groups of cells perform specific tasks more efficiently. For example, muscle tissue in animals helps in movement, while vascular tissue in plants helps in the transport of food and water.
Division of Labour: Tissues enable the division of labour within the organism. Each tissue type has a dedicated function, contributing to the overall survival and efficiency of the organism. For example, blood tissue transports oxygen and nutrients, while nerve tissue transmits signals.
Efficiency: Because tissues are made up of specialized cells, they can perform their tasks with high efficiency. The structure of a tissue is designed to maximize the performance of its function, ensuring the organism’s survival and proper functioning.
Meristematic Tissue and Growth Observations
Activity: Growth of Roots in Onion Bulbs
Procedure:
Fill two glass jars with water.
Place one onion bulb on each jar.
Observe the growth of roots for a few days, measuring the root length on days 1, 2, and 3.
On day 4, cut the root tips of the onion in jar 2 by about 1 cm.
Continue observing and measuring the root lengths for the next five days.
Questions and Answers:
Which onion has longer roots and why?
The onion in jar 1, which had its root tips intact, will likely have longer roots because the root tips contain meristematic tissue, which is responsible for growth.Do the roots continue growing after we cut their tips?
The roots in jar 2 will show reduced or halted growth after the tips are cut because the meristematic tissue responsible for growth is located in the root tips.Why do the tips stop growing in jar 2 after we cut them?
The root tips stop growing because the meristematic tissue at the tips, which is responsible for division and growth, was removed. Without this tissue, the root can no longer grow.
Meristematic Tissue in Plants:
Growth Regions:
Plant growth occurs only in specific regions where meristematic tissue is located.
Meristematic tissue is actively involved in cell division and growth.
Types of Meristematic Tissue:
Apical Meristem: Found at the growing tips of stems and roots. It increases the length of the plant.
Lateral Meristem (Cambium): Found along the sides of stems and roots. It increases the girth (width) of the plant.
Intercalary Meristem: Located near the nodes (regions where leaves attach to stems). It helps in growth at specific intervals.
Characteristics of Meristematic Tissue:
Active Cell Division: Cells in meristematic tissue divide actively.
Cell Structure: Cells have dense cytoplasm, thin cellulose walls, and prominent nuclei.
Lack of Vacuoles: Meristematic cells do not have vacuoles, which is likely because vacuoles are associated with storing water and waste products, while meristematic cells are focused on rapid division and growth rather than storage.
Function of Meristematic Tissue:
Meristematic tissues produce new cells that eventually mature into various specialized cells, forming different tissues in the plant.
Formation of Organs and Organ Systems: Tissues combine to form organs, which then work together in organ systems to carry out complex functions. For example, muscle tissues form the heart, which is an organ, and the heart works as part of the circulatory system.
Growth and Development: Tissues are essential for the growth and development of multicellular organisms. Certain tissues, like meristematic tissue in plants, continuously divide and enable the organism to grow.
Permanent Tissue and Cell Differentiation:
What Happens to Cells Formed by Meristematic Tissue?
Cells formed by meristematic tissue undergo differentiation, where they take up a specific role, lose the ability to divide, and become specialized.
These cells eventually form permanent tissue, which is involved in various functions in the plant.
What is Differentiation?
Differentiation is the process by which cells take up a permanent shape, size, and function.
It results in the development of various types of permanent tissues, each with a specific role in the plant's growth and survival.
Activity: Observation of Plant Stem Section
Procedure:
Cut a very thin section of a plant stem with the help of a teacher.
Stain the slices with safranin to make the cells visible.
Place a section on a slide, add a drop of glycerine, and cover with a cover-slip.
Observe under a microscope and compare with a reference figure (Fig. 6.3).
Observe the various types of cells and their arrangement.
Questions and Answers Based on Observation:
Are all cells similar in structure?
No, the cells are not all similar in structure. The permanent tissue will consist of different types of cells, each specialized for a particular function (e.g., parenchyma, xylem, phloem, etc.).
How many types of cells can be seen?
Several types of cells may be visible, depending on the plant and the type of tissue. These can include:
Parenchyma: Fundamental tissue involved in storage and photosynthesis.
Collenchyma: Provides support and flexibility to the plant.
Sclerenchyma: Provides strength and rigidity.
Xylem: Conducts water and minerals.
Phloem: Transports food (sugar) throughout the plant.
Why are there so many types of cells in plants?
Plants need a variety of specialized cells to perform different functions, such as transport (xylem and phloem), structural support (collenchyma and sclerenchyma), and storage (parenchyma). Each type of cell is adapted to its function to help the plant thrive in different environments.
Further Exploration:
Try cutting sections of plant roots and stems from different plants to compare the structure and arrangement of their permanent tissues.
Simple Permanent Tissue and Epidermal Tissue
Simple Permanent Tissues:
Parenchyma:
The most common simple permanent tissue.
Composed of unspecialized, living cells with thin walls.
Cells are loosely arranged with large intercellular spaces.
Functions:
Storage of food.
In some cases, performs photosynthesis (called chlorenchyma if chlorophyll is present).
In aquatic plants, contains air cavities for buoyancy (called aerenchyma).
Collenchyma:
Provides flexibility to plant parts such as tendrils and stems of climbers.
Allows bending without breaking and provides mechanical support.
Cells are living, elongated, and irregularly thickened at the corners.
Has very little intercellular space.
Sclerenchyma:
Provides rigidity and strength to the plant.
Cells are dead, long, and narrow with thickened walls made of lignin.
Walls are so thick that there is no internal space.
Found in stems, vascular bundles, veins of leaves, and in the hard coverings of seeds and nuts.
Epidermal Tissue:
Epidermis:
The outermost layer of cells covering all plant parts.
Generally consists of a single layer of cells. In some plants in dry habitats, it may be thicker for protection against water loss.
Protects against mechanical injury, water loss, and invasion by fungi.
In aerial parts of the plant, epidermal cells secrete a waxy layer (called cuticle) that is water-resistant.
Structure of Epidermal Cells:
Cells are relatively flat with thicker outer and side walls.
They form a continuous layer without intercellular spaces.
Small pores called stomata are present for gas exchange and transpiration (water loss).
Guard Cells and Stomata:
Guard cells: Kidney-shaped cells that surround each stoma (pore) in the epidermis.
Guard cells regulate the opening and closing of stomata for gas exchange and transpiration.
Root Epidermis:
Root epidermal cells often have root hairs that increase the surface area for water absorption.
Desert Plants:
Epidermis has a thick waxy coating of cutin (waterproof substance) to prevent water loss in dry conditions.
Cork and Aging Plants:
As plants age, their outer protective tissue undergoes changes:
A strip of secondary meristem in the cortex forms layers of dead cells called cork.
Cork cells are compactly arranged without intercellular spaces and contain suberin, which makes them impermeable to gases and water.
Activity:
Observing Epidermal Tissue:
Procedure:
Stretch and break a leaf (e.g., Rhoeo) gently to expose the epidermal peel.
Place the peel in water with safranin, wait, and transfer to a slide for observation.
Observe under a microscope and identify epidermal cells and stomata.
Purpose of Waxy Coating in Desert Plants:
The waxy cuticle helps prevent excessive water loss by evaporation in arid environments.
Complex Permanent Tissue
Definition of Complex Permanent Tissue:
Complex permanent tissues are made up of more than one type of cell that work together to perform a common function.
Unlike simple permanent tissues (which consist of a single type of cell), complex tissues involve different types of cells for specialized functions.
Examples of Complex Permanent Tissues:
Xylem:
Function: Conducts water and minerals from the roots to other parts of the plant.
Components:
Tracheids: Tubular, dead cells with thick walls. They help in water conduction.
Vessels: Also tubular, with thick walls, and dead at maturity. They are primarily responsible for transporting water and minerals.
Xylem Parenchyma: Living cells that store food.
Xylem Fibres: Provide structural support to the plant.
Phloem:
Function: Transports food (mainly sugars) from the leaves to other parts of the plant.
Components:
Sieve Cells: Tube-like cells with perforated walls that allow the flow of nutrients.
Sieve Tubes: Tubular structures connected end-to-end, with perforated walls for transporting food.
Companion Cells: Living cells that assist sieve tubes in their functions, particularly in maintaining pressure.
Phloem Fibres: Provide structural support to the phloem tissue.
Phloem Parenchyma: Stores food in the form of starch and other materials.
Vascular Bundle:
Both xylem and phloem are part of a vascular bundle, a system of conducting tissues that transport water, minerals, and food throughout the plant.
The vascular bundle is a distinguishing feature of complex plants, enabling them to survive in terrestrial environments by allowing efficient transport of essential substances.
Key Characteristics of Complex Tissues:
Coordination of Different Cell Types: The various cells in xylem and phloem coordinate to carry out their respective functions of transporting water, minerals, and food.
Specialized Functions: Xylem and phloem are specialized tissues crucial for plant survival, particularly for their transport functions in land plants.
These tissues, especially xylem and phloem, form the vascular system that allows plants to thrive in terrestrial habitats by ensuring that essential substances like water, nutrients, and food are effectively moved throughout the plant.
Questions
What are the types of simple tissue? Types of Simple Tissues:
Parenchyma: Unspecialized cells with thin walls, involved in storage, photosynthesis (chlorenchyma), and buoyancy (aerenchyma).
Collenchyma: Provides flexibility and mechanical support to plant parts.
Sclerenchyma: Provides strength and rigidity, made of dead cells with thickened lignified walls.
Where is Apical Meristem Found?:
The apical meristem is found at the growing tips of the plant’s roots and stems. It is responsible for increasing the length of the stem and root.
Which Tissue Makes Up the Husk of Coconut?:
The husk of coconut is made up of sclerenchyma tissue, which provides strength and stiffness.
What are the Constituents of Phloem?:
The constituents of phloem are:
Sieve Cells
Sieve Tubes
Companion Cells
Phloem Fibres
Phloem Parenchyma
Animal Tissues
Types of Animal Tissues:
Muscle Tissue:
Function: Responsible for movement through contraction and relaxation of muscle cells.
Example: Muscle cells in the chest enable the expansion and contraction during breathing.
Blood (Connective Tissue):
Function: Transports essential substances like oxygen, food, and hormones to different parts of the body. It also carries waste materials to organs like the liver and kidneys for disposal.
Blood is considered a connective tissue because it helps connect various parts of the body through the transport of nutrients and waste.
Other Types of Animal Tissues:
Epithelial Tissue: Covers body surfaces and lines cavities. It protects the body, absorbs nutrients, and excretes waste.
Connective Tissue: Supports, binds, and connects other tissues. It includes blood, bone, cartilage, and adipose tissue.
Muscular Tissue: Involved in movement. It is specialized for contraction and relaxation. Types include skeletal, smooth, and cardiac muscle.
Nervous Tissue: Transmits electrical signals throughout the body. It includes neurons and glial cells.
Functions of Tissues:
Muscle Tissue: Causes movement by contracting and relaxing.
Blood (Connective Tissue): Transports oxygen, food, and waste products.
Other Tissues: Each type of tissue plays a role in specific functions like protection, support, and signaling within the body.
These animal tissues work together to ensure the body functions efficiently, with each tissue specialized for a unique role in maintaining health and facilitating movement, transport, and communication.
Epithelial Tissue
Functions of Epithelial Tissue:
Protective Layer: Forms protective covering for most organs and cavities in the body.
Barrier Formation: Keeps different body systems separate.
Regulation of Material Exchange: Controls the exchange of materials between the body and the external environment (e.g., skin, lung alveoli, kidney tubules).
Tightly Packed Cells: Cells in epithelial tissue are tightly packed, forming a continuous sheet with minimal intercellular spaces, providing protection and barrier functions.
Separation by Basement Membrane: Epithelial tissue is separated from underlying tissue by an extracellular fibrous basement membrane.
Types of Epithelial Tissue:
Simple Squamous Epithelium:
Structure: Extremely thin, flat cells.
Function: Found in areas where transport of substances occurs, such as the lining of blood vessels and lung alveoli. It facilitates the exchange of gases and nutrients.
Example: Skin, oesophagus, and lining of the mouth.
Stratified Squamous Epithelium:
Structure: Multiple layers of squamous cells.
Function: Provides protection against mechanical stress and wear and tear.
Example: Skin (to prevent abrasion).
Columnar Epithelium:
Structure: Tall, pillar-like cells.
Function: Found in areas involved in absorption and secretion.
Example: Inner lining of the intestine.
Ciliated Columnar Epithelium:
Structure: Columnar cells with hair-like projections (cilia) on their surface.
Function: Cilia move to propel mucus and other substances along the respiratory tract.
Example: Respiratory tract.
Cuboidal Epithelium:
Structure: Cube-shaped cells.
Function: Provides mechanical support and is involved in secretion and absorption.
Example: Kidney tubules and ducts of salivary glands.
Glandular Epithelium:
Structure: Specialized epithelial cells that can secrete substances.
Function: Secretes substances like hormones, enzymes, and other fluids.
Example: Multicellular glands, such as salivary glands.
Key Points:
Epithelial cells are tightly packed with minimal intercellular spaces, providing a barrier for protection.
Different types of epithelial tissues are specialized for specific functions, such as absorption, secretion, protection, and material exchange.
The presence of cilia in certain epithelial cells helps in moving substances like mucus in the respiratory system.
These functions and structures of epithelial tissues are essential for maintaining the body's integrity and facilitating key physiological processes.
Connective Tissue
General Characteristics:
Loose Cell Arrangement: The cells in connective tissue are widely spaced and embedded in an intercellular matrix.
Matrix Variability: The matrix may be jelly-like, fluid, dense, or rigid, depending on the function of the connective tissue.
Function: Connective tissue connects, supports, and binds other tissues and organs in the body.
Types of Connective Tissue:
Blood:
Matrix: Fluid matrix called plasma, in which cells like red blood cells (RBCs), white blood cells (WBCs), and platelets are suspended.
Function: Transports gases (like oxygen), digested food, hormones, and waste materials throughout the body.
Components: Plasma contains proteins, salts, and hormones.
Bone:
Matrix: Hard matrix composed of calcium and phosphorus compounds.
Function: Provides structural support for the body, anchors muscles, and supports organs. It is strong and non-flexible, making it ideal for supporting and protecting the body.
Ligament:
Function: Connects bones to bones and provides flexibility with strength.
Characteristics: Elastic and strong, with very little matrix.
Tendon:
Function: Connects muscles to bones and provides strength.
Characteristics: Fibrous tissue with great strength but limited flexibility.
Cartilage:
Matrix: Solid matrix composed of proteins and sugars.
Function: Smoothens bone surfaces at joints and provides support in structures like the nose, ears, trachea, and larynx.
Characteristics: Widely spaced cells, pliable, can be bent (e.g., ear cartilage), but not as flexible as bone.
Areolar Connective Tissue:
Location: Found between skin and muscles, around blood vessels and nerves, and in bone marrow.
Function: Fills space inside organs, supports internal organs, and helps in tissue repair.
Adipose Tissue:
Location: Found below the skin and around internal organs.
Function: Stores fats, provides insulation, and serves as an energy reservoir.
Characteristics: Cells filled with fat globules.
Key Points:
Connective tissue plays a crucial role in binding and supporting organs and structures throughout the body.
The matrix type and properties vary to suit different functions, from fluid plasma in blood to rigid bone in bones.
Connective tissues like ligaments, tendons, and cartilage are specialized for flexibility, support, and movement.
Notes on Muscular Tissue:
General Characteristics:
Muscle Fibres: Muscular tissue consists of elongated cells known as muscle fibres, responsible for body movement.
Types of Muscular Tissue: There are three types of muscular tissues based on function and structure:
Voluntary (Skeletal) Muscles: Controlled consciously.
Involuntary Muscles: Not controlled by conscious thought, include smooth and cardiac muscles.
Types of Muscular Tissue:
Striated (Skeletal) Muscles:
Control: Voluntary (under conscious control).
Location: Mostly attached to bones, involved in body movement.
Appearance: Show alternate light and dark bands (striations) when stained.
Structure:
Long, cylindrical, unbranched cells.
Multinucleate (multiple nuclei per cell).
Function: Body movement, like walking, lifting, etc.
Smooth Muscles (Involuntary):
Control: Involuntary (not under conscious control).
Location: Found in the walls of internal organs like the alimentary canal, blood vessels, iris of the eye, ureters, and bronchi.
Appearance: Unstriated (no striations), smooth.
Structure:
Long, spindle-shaped cells with pointed ends.
Uninucleate (single nucleus per cell).
Function: Controls movements such as the movement of food in the digestive system and contraction of blood vessels.
Cardiac Muscles:
Control: Involuntary (not consciously controlled).
Location: Found only in the heart.
Appearance: Shows rhythmic contraction and relaxation.
Structure:
Cylindrical, branched cells.
Uninucleate (single nucleus per cell).
Function: Pumps blood throughout the body, ensuring circulation.
Comparison Table (for Activity 6.5):
Feature |
Striated (Skeletal) Muscles |
Smooth Muscles |
Cardiac Muscles |
|---|---|---|---|
Control |
Voluntary |
Involuntary |
Involuntary |
Location |
Attached to bones, throughout the body |
Walls of internal organs (e.g., alimentary canal, blood vessels) |
Heart |
Appearance |
Striated (light and dark bands) |
Unstriated (no striations) |
Rhythmic contractions |
Cell Shape |
Long, cylindrical, unbranched |
Long, spindle-shaped |
Cylindrical, branched |
Number of Nuclei |
Multinucleate (multiple nuclei) |
Uninucleate (single nucleus) |
Uninucleate (single nucleus) |
Function |
Body movement (e.g., walking, lifting) |
Movement of food, blood flow, etc. |
Pumps blood through the body |
Key Points:
Striated muscles allow voluntary control and help in body movement.
Smooth muscles control involuntary movements like digestion and blood flow.
Cardiac muscles are specialized for rhythmic contractions to pump blood in the heart.
Nervous Tissue
General Characteristics:
Nervous tissue is specialized for responding to stimuli and transmitting signals rapidly across the body.
It is found in the brain, spinal cord, and nerves.
The cells of nervous tissue are called neurons.
Structure of Neurons:
Cell Body: Contains the nucleus and cytoplasm.
Axon: A single long, hair-like extension that carries nerve impulses away from the cell body.
Dendrites: Short, branched extensions that receive signals from other neurons.
Length of Neuron: A neuron can be up to a meter long in some cases, like those extending from the spinal cord to the toes.
Function:
Nerve Impulses: The signal transmitted along the axon is called a nerve impulse, allowing rapid communication within the body.
Stimulus Transmission: Nerve impulses allow the body to respond quickly to stimuli, enabling movement and reactions to the environment.
Nervous System:
The nervous system combines nervous tissue with muscle tissue to enable rapid responses and movement.
This combination is essential for animals to move quickly and efficiently in response to external or internal stimuli.
Key Points:
Neurons are specialized cells that transmit electrical signals in the form of nerve impulses.
Nerve impulses allow quick reactions and movement by transmitting signals between the brain, spinal cord, and muscles.
Questions with Answers:
Name the tissue responsible for movement in our body.
Answer: Muscular tissue is responsible for movement in our body.
What does a neuron look like?
Answer: A neuron consists of a cell body with a nucleus and cytoplasm, and it has long thin extensions called axon and many short branched parts called dendrites.
Give three features of cardiac muscles.
Answer:
Cardiac muscles are involuntary.
The cells are cylindrical, branched, and uninucleate (having a single nucleus).
Cardiac muscles show rhythmic contraction and relaxation throughout life.
What are the functions of areolar tissue?
Answer: Areolar tissue is responsible for:
Supporting internal organs.
Filling spaces inside organs.
Helping in tissue repair.
Please don not use wrong word