Science Que-Ans (Each of 5 Mark )

Meristematic	Permanent
Cells of this tissue divide throgh out their life.	They lose the ability to divide to take up specific function.
They are located at specific regions of the plant viz apical lateral, intercalary.	They are distributed throught the plant body.
Cells of this tissue are very active, have dense cytoplasm, thin walls and prominent. They lack vacuoles.	They are vacuolated vary in shape and size. their cell wall may be thick.
Cell wall is cellulosic.	Cell wall is made up of cellulose.

The different tissues in animals are:

1. Epithelial Tissues: These are the protective tissues of the animal body. Depending upon the shape and function of the cells, the epithelial tissues are classified as follows:

1. Squamous epithelium.
2. Cuboidal epithelium.
3. Columnar epithelium.
4. Glandular epithelium.
5. Ciliated epithelium.

2. Muscular Tissues: The muscular tissues form the contractile tissues and are made up of muscle cells. On the basis of their location, structure and function, there are three types of muscular tissues:

1. Striated muscles.
2. Smooth muscles.
3. Cardiac muscles.

3. Connective Tissues: The connective tissues are specialised to connect and anchor various body organs. They are of five types:

1. Aerolar connective tissue.
2. Dense regular connective tissue.
3. Adipose tissues.
4. Skeletal tissues.
5. Fluid connective tissues.

4. Nervous Tissues: These tissues are specialised to transmit messages within our body. Brain, spinal cord and nerves are all composed of nervous tissues.

Meristematic tissues are the tissues in which the cells divide continuously and help in increasing the length and girth of the plant. According to their position in the plant, meristems are of three types:

1. Apical Meristems: These are situated at the growing tip of the stems and roots and increase the height of the plant.
2. Lateral Meristems: These are found beneath the bark and in vascular bundles of dicot roots and stems. These are responsible for the growth of cambium and hence increases the girth of the plant.
3. Intercalary Meristems: They are located at the base of leaves or internodes or below the nodes. It increases the length of the plant​​​​​​​

Muscular tissues form the muscles in the body and are responsible for movement and locomotion. Muscle cells are elongated and are called muscle fibres. They are capable of contraction and relaxation.
There are three types of muscular tissues:

1. Striated Muscles or Skeletal muscles: These are called skeletal muscles as they are found attached to the bones and help in the body movements. The cells are cylindrical, unbranched, striated and multi nucleated. They are involuntary in nature.
2. Non-Striated muscles or smooth muscles: The cells are spindle shaped, uni-nucleated, elongated and have no striations. They are found within the walls of elementary canal, bladder and blood vessels. They are involuntary in nature.
3. Cardiac Muscles: These are found exclusively in heart. They are cylindrical, non-tapering, branched with faint striations. They have one or two nuclei in each cell. They are involuntary. Their function is rhythmic contraction and relaxation throughout life.

A: Striated muscle.
B: Smooth muscle.
C: Cardiac muscle.

A neuron consists of a cell body witha nucleus and cytoplasm. It has two important extensions known as the axon and dendrites. An axon is a long thread-like extension of nerve cells that transmits impulses away from the cell body. Dendrites, on the other hand, are thread-like extensions of cell body that receive nerve impulses. Thus, the axon transmits impulses away from the cell body, whereas the dendrite receives nerve impulses. This coordinated function helps in transmitting impulses very quickly.

Xylem is a complex vescular tissue which is composed of several types of cells. Xylem consists of tracheids, vessels, xylem parenchyma and xylem fibres. The cells of this tissue have thick walls and many of them are non-living.

1. Tracheids: These are long elongated tubular cells. Tracheids cells are dead. Its main function is conduction of water and minerals from root to stem.
2. Vessels: These are pipe-like structure. Vessels are dead and have lignified cell wall. They also participate conduction of water and minerals.
3. Xylem parenchyma: These are living cells which store food material.
4. Xylem fibres: These are dead cells provide mechanical support to the plant.

Simple tissue	Complex tissue
These tissues consist of only one type of cells.	These tissues are made up of more than one type of cells.
The cells are more or less similar in structure and perform similar functions.	Different types of cells perform different functions. For example, in the xylem tissue, tracheids help in water transport, whereas parenchyma stores food.
Three types of simple tissues in plants are parenchyma, collenchyma, and sclerenchyma.	Two types of complex permanent tissues in plants are xylem and phloem.

Dense connective tissue is of two types- tenonds and ligaments.

Tendon	Ligament
It connects bone to muscle.	It connects bone to bone at joints.
It is strong and non-flexible.	It is elastic and flexible.

Lymph is a colorless or slightly yellowish fluid. It is a medium of circulation in human body which flows only in one direction from body tissues to the heart.
The functions of lymph are:

1. Lymph helps in removing the waste products.
2. Lymph carries digested fat from the small intestine to the entire body.
3. Lymph nodes contain lymphocytes which kill the germs or foreign bodies.

Both xylem and phloem consist of more than one type of cells, which coordinate to perform a common function.

Xylem	Phloem
Consists of tracheids, vessels, xylem, parenchyma and xylem fibers.	Consist of sieve tubes, comanion cell, phloem parenchyma and phloem fibers.
They transport water and minerals vertically from soli to parts of plant.	They transport parensport food from leaves tp other parts of the plant.
Most of the cells except xylem parenchyma are dead cells.	Most of the cells except phloem fiberes are living cells.

Differences between striated and smooth muscle tissues:

Striated muscle tissues	smooth muscle tissues
Striated muscles are voluntary	smooth muscles are involuntary in function.
Striated muscles show stripes	smooth muscles do not show stripes.
Skeletal muscle fibres are cylindrical	smooth muscle fibres are spindle shaped.

Diagram of the muscle tissue:

The neuron consists of three parts:

1. The Cyton or Cell body: It contains a central nucleus and cytoplasm with deeply stained particles called Nissl's granules.
2. Dendrites: The dendrons are short processes arising from the cyton and branches into dendrites.
3. Axon: It is a single, long cylindrical process which forms fine branches terminally. It has a swollen structure at its end called synaptic knob or bouton. It is also termed as the nerve fibre.

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Phloem is made up of four types of elements: Sieve tubes, companion cells, phloem fibres and the phloem parenchyma.

1. Sieve tubes: These are tubular cells with perforated walls. These cells are responsible for transportation of food and nutrients.
   
2. Companion cells: These cells are found associated with sieve tubes and connected with it by simple pits. These cells are long, narrow and thin walled. These cells are living.
   
3. Phloem fibres: They have thick cell wall and they provide mechanical support to plant.
   
4. Pholem parenchyma: These cells are living and often cylindrical in shape.
   

The transport of food from leaves to other parts of the plant is called translocation

Simple tissues: These tissues are composed of cells which are structurally and functionally similar.
There are three types of simple tissues:

1. Parenchyma: Parenchyma cells are living and posses the power of division. The cell wall is thin and encloses a dense cytoplasm which contains a small nucleus and surrounds a large central vacuole.
2. Collenchyma: It tissues also consists of living cells. It is characterized by the deposition of extra cellulose at the corners of the cells. In collenchymas, intercellular spaces are generally absent. Collenchyma cells are elongated in shape. They often contain a few chloroplasts.
3. Sclerenchyma: Sclerenchyma cells are dead cells and they are devoid of protoplasm. The cells walls of Sclerenchyma are greatly thickened by the deposition of lignin. The cells of sclerenchyma are closely packed without intercellular spaces.

1. Apical meristems are the growing parts of the roots and stems and are present at the tips of roots, branches, leaves and shoots. If the apical meristems are damanged or cut, the growth of that part of the plant will stop.
2. If cork is not formed in older stems or roots, the outer tissues will rupture due to increase in girth which expose the interior to dessication and infection.
3. Lymph is transported through lymph vessels of the lymphatic system. If lymph is not returned to blood, the blood volume will decrease during passage of materials from tissues to blood and vice versa.

1. Figure A: squamous epithelium.

Figure B: columnar epithelium.

2. Squamous epithelium is also known as tesselated epithelium or pavement epithelium.
3. Simple columnar epithelium lines the gastrointestinal tract and epiglottis.
4. Simple squamous epithelial cells are extremely thin and flat which allows diffusion of substances through it.

Cartilage is compact with widely spaced cells. Its solid matrix is composed of proteins and sugars. The cells of cartilage are called chondrocytes. They don’t have blood vessels. Cartilage is present in the tip of nose, outer ear joints, between adjacent bones of the vertebral column, limbs and hands in adults. Cartilage smoothens bone surfaces at joints. It provides support and flexibility to the body parts.

Simple tissues: These tissues are composed of cells which are structurally and functionally similar.
There are three types of simple tissues:

1. Parenchyma: Parenchyma cells are living and posses the power of division. The cell wall is thin and encloses a dense cytoplasm which contains a small nucleus and surrounds a large central vacuole.

2. Collenchyma: It tissues also consists of living cells. It is characterized by the deposition of extra cellulose at the corners of the cells. In collenchymas, intercellular spaces are generally absent. Collenchyma cells are elongated in shape. They often contain a few chloroplasts.

3. Sclerenchyma: Sclerenchyma cells are dead cells and they are devoid of protoplasm. The cells walls of sclerenchyma are greatly thickened by the deposition of lignin. The cells of sclerenchyma are closely packed without intercellular spaces.

Parenchyma	Collenchyma	Sclerenchyma
Cell walls are relatively thin, and the cells in parenchyma tissues are loosely packed.	The cell wall is irregularly thickened at the corners, and there is very little space between the cells.	The cell walls are uniformly thickened, and there are no intercellular spaces.
The cell wall in this tissue is made up of cellulose.	Pectin and hemicellulose are the major constituents of the cell wall.	An additional layer of the cell wall composed mainly of lignin is found.

Bone is a strong and non-flexible tissue. The cells of bones are called osteocytes. Bone cells are embedded in a hard matrix that is composed of calcium and phosphorus compounds. Each cell is enclosed in a small cavity called the lacuna. Functions:

1. It provides shape to the body.
2. It forms the framework that supports the body.
3. It anchors the muscles.
4. It protects the vital body organs like brain, lungs, etc.

Cells derived from the division of meristematic tissues take up specific roles and gradually lose their ability to divide. Thus, they form permanent tissue. The process by which the cells divide meristematically to take a permanent shape, size and function is called differentiation.

The cells of the nervous tissue are called nerve cells or neurons. A neuron or nerve cell is structural and functional unit of the nervous tissue. It consists of:

• Cell body or cyton.
• Axon.
• Dendrons or dentrites.

Cell body or cyton has a prominent nucleus and cytoplasm. Cell organelles like golgi bodies, mitochondria, etc are also present in the cytoplasm. From the cell body extend out two kinds of cytoplasmic extensions called dentrites and axons. The axon is covered by a fatty myelin sheath. Myelin sheath is discontinuous and broken at intervals by nodes of Ranvier. Axons usually a long, unbranched, cylindrical process that ends in many terminal end fibres. The axon ending of one nerve cell is lossely placed on the cell body of another nerve cell. The other small branch given out by the cyton are called dendrons which branch further into numerous thin hair-like dentrites.

1. A: Transverse section of collenchyma.

B: T.S. parenchyma.
C: T.S. sclerenchyma fibres.

2. Sclerenchym tissue has heavy deposition of lignin.
3. Collenchyma tissue provides both mechanical strength and flexibility.
4. In aquatic plants, large air cavities are present in parenchyma tissue to given buoyancy to the plants to help them float. Such a modified parenchyma is called aerenchyma.
5. Fibres of Hemp and Jute are obtained from the sclerenchyma fibres.

	Parenchyma		Sclerenchyma
1.	Cells are thin walled and unspecialized.	1.	Cells are thick walled and lignifieg.
2.	These are living cells.	2.	Tissues are made up of dead cells.
3.	Cells are usually loosely packed with large intercellular space.	3.	No intercellular apaces between the calls are found.
4.	Stores nutrient and water in stem and roots.	4.	Provides strength to the plant parts.
5.	Some cells contain chlorophyll called chlorenchyma and photosynthesis. other cells have large air which provid buoyancy to the hydrophytic plants.	5.	The cells are long and narrow. make the plant hard and stiff. The tissue is present in the stem around of leaves and seeds and nuts.

Epithelial cells of following types:

1. Squamous Epithelium: These are thin, flat cells that are closely packed. The squamous epithelial cells line the cavities of the mouth, oesophagus, alveoli, and blood vessels. This tissue gives protection against mechanical injury and also blocks the entry of germs. If the squamous epithelium is arranged in many layers, it is a compound squamous tissue called the stratified squamous epithelium. We find these kinds of tissues in the skin and also the lining of the oesophagus.

2. Cuboidal Epithelium: These cells are cuboidal in shape. They are found in the salivary glands, kidney tubules, sweat glands etc. Their main function includes absorption, secretion, and excretion. If the cuboidal epithelium is arranged in many layers it forms the stratified cuboidal epithelium. It is found on the inner side of the pancreatic ducts and salivary glands. They mainly help in protection.

3. Columnar Epithelium: The columnar epithelium has cells that are pillar-like and column-like. We can find them in the lining of the stomach and intestine. Its functions include absorption and secretion.

4. Ciliated Epithelium: When the columnar epithelial tissues have cilia, then they are ciliated epithelium. They are present in the lining of the trachea, kidney tubules etc. The rhythmic movement of the cilia helps in the movement of material in one direction.

5. Glandular Epithelium: These are modified columnar epithelial tissues. They are large cells that present in the tear glands, sweat glands etc. Their main function is secretion.

The complex tissue consists of more than one type of cells having a common origin. They are of two types:

1. Xylem: Xylem is a vascular and mechanical tissue which conducts water. Xylem is composed of cells of four different types:

1. Tracheids.
2. Vessels or tracheae.
3. Xylem parenchyma.
4. Xylem Sclerenchyma.

Except xylem parenchyma, all other xylem elements are dead and bounded by thick lignified walls. Vessels are shorter and wider than tracheids. Vessels are very long tube-like structures formed by a row of cells placed end to end. Tracheids are elongated cells with tapering ends. They also conduct water.

2. Phloem: Phloem is also a vascular tissue which transports food from the leaves to the various parts of the plant. It is composed of:

1. Sieve tubes: Sieve tubes are slender, tube-like structures composed of elongated thin-walled cells, placed end to end. Their end walls are perforated by numerous pores and are called sieve plates.
2. Companion Cells: It is a small thin-walled cell containing dense and very active cytoplasm and large elongated nucleus.
3. Phloem parenchyma: These are thin-walled, living cells of parenchyma of phloem. They have two functions, storage and slow lateral conduction of food.
4. Phloem Fibres: These are thick-walled, elongated spindled shaped dead cells which posses narrow lumen. They provide mechanical strength to the tissue.

Meristematic cells are the continously dividing cells of the plant body i.e., they remain metabolically active and as we know that vacuoles serve the purpose of storage in plant cells. Therefore meristematic cells do not require vacuole.

Epithelial tissue is the thin protective layer of cells which covers the surface of the body and lines the internal organs. The cells of this tissue are generally packed close together. The shape of the cells depends on the location and function of the tissue. Epithelial tissue originates from the ectoderm. But, epithelial tissue lining the intestine originates from the endoderm.
Epithelial tissue may be simple, i.e., composed of single layer of cells or stratified, i.e., made up of several layers of cells. Depending upon the shape and function of cells epithelial tissues are classified as:

1. Squamous epithelial tissue: This tissue is composed of a single layer of thin and flat, plate like ceils. The cells fit closely, like the bricks in a wall, to form a smooth membrane. It is also known as tesselated and pavement epithelium. It is found in the outer layer of the skin, and covers internal cavities and ducts. Tongue, oesophagus and the lining of the mouth are made up of squamous epithelium.It is also found in blood vessels and alveoli. It protects the underlying parts of body from mechanical injury, entry of germs, chemicals and drying. It also forms a selectively permeable surface through which filtration occurs.

2. Cuboidal epithelial tissue: This tissue is composed of cube like cells that fit closely. The cells look like squares in section, but the free surface appears hexagonal. This tissue lines the inside of the kidney tubules (the tubes leading from the cups of nephrons) thyroid vesicles and in glands like sweat glands, exocrine pancreas and the salivary glands. It forms germinal epithelium of gonads (testes and ovaries). It helps in absorption, excretion and secretion. It also provides mechanical support.

3. Columnar ciliated epithelial tissue: This tissue is generally composed of a single layer of column like cells. The presence of a conspicuous striated border of microvilli at the free surface end of each cell increases the surface area of the cell for absorption and secretion. It is generally found in the inner lining of the alimentary canal. It also forms the lining of gall bladder and oviducts. The major functions of this tissue includes secretion (e.g., mucus of goblet cells) and absorption (e.g., stomach and intestine).

In some parts of the body, columnar epithelium develops protoplasmic outgrowths called cilia. The constant lashing movements of the cilia help to move substances. It is found in the sperm ducts. It also lines the trachea (wind-pipe), bronchi (lungs), kidney tubules and oviducts (Fallopian tubes). Ciliated epithelium helps the movement of ova in the fallopian tubes and the movement of mucus in the respiratory tract.

4. Stratified squamous epithelial tissue: This tissue is found in skin and covers the external dry surface of the skin. Cells of this tissue are arranged in many layers, but the cells forming different layers of this epithelium are not similar. Deeper layers of the tissue have cuboidal cells which become polygonal and finally flattened (squamous) towards the free surface. The flattened cells of superficial layer may contain a fibrous protein, the keratin and become, dead cells and are called keratinised stratified squamous epithelium. This epithelium is water proof and highly resistant to mechanical injury.

5. Glandular epithelial tissue: Epithelial tissue often acquire additional specialisation as gland cells, which can secrete substances at the epithelial surface. Sometimes, a portion of epithelial tissue folds in wards and a multicellular gland is formed. This is called glandular epithelium.​​​​​​​

Connective tissues are most abundant and widely distributed in the body of complex animals. The cells of connective tissue are loosely spaced and embedded in an inercellular matrix. The matrix may be jelly like, fluid, dense or rigid.Functions of connective tissue:

1. It binds different structure with another like skin with muscles and muscles with bones, etc.
2. It forms a supporting framework of cartilage and bones in the body.
3. Blood flows and transports gases, digested food, hormones and waste materials to different parts of the body.
4. Adipose tissue helps in the storage of fats.

Epithelium is the simplest tissue. It is the protective tissue of the animal body in which the cells are tightly packed having no intercellular matrix. Epithelial cells lie on a delicate non-cellular basement membrane which contains a special form of matrix protein, called collagen. These tissues perform the function of excretion, secretion and absorption. Depending upon the shape and functions of the cells. The epithelial tissue is of various types:

1. Squamous: The cells are flat and polygonal and are arranged as tiles. These tissues occur in skin, lining of alveoli of lungs, blood vessels etc. Its function includes protection, diffusion and osmosis.
2. Cuboidal: The cells are cube like. These occur in glands, germinal layer of ovary, kidney tubules etc. Its function is secretion and absorption.
3. Columnar: The cells are pillar or column like resting on a thin membrane. Such tissues occur in the lining of stomach, intestine etc. Its function includes protection, absorption and secretion.
4. Ciliated: It has cuboidal, columnar cells with fine hair like structures called cilia. It is present in the lining of respiratory tract, fallopian tube, nephron etc. Its function is protection, spreading of mucus and motion of gases and liquids by cilia.
5. Glandular: The cells are cubical. These can be branched or unbranched. Such tissues are present in glands. Its main function is secretion.

The connective tissue is specialized to connect and anchor various body organs. There are five types of connective tissues:

1. Areolar: This tissue is a loose and cellular connective tissue. Its matrix consists of white collagen fibre and yellow elastic fibre. It joins skin to muscles, fills spaces inside organs and is found around muscles, blood vessels and nerves.
2. Dense Regular Connective tissue: It is fibrous connective tissue having densely packed fibres and cells. It is the principal component of tendons, ligaments and aponeuroses.
3. Adipose tissue: It is an aggregation of fat cells or adipocytes. The fat cells are arranged into lobules separated by partitions of collagen and elastin fibres. These are found abundant below the skin, between the internal organs and in yellow bone marrow.
4. Skeletal tissue: It is a supporting tissue which includes cartilage and bone. Both these tissues form the endoskeleton of a vertebrate body. Cartilage is located in ear pinna, nose tip, epiglottis etc. Bone forms the endoskeleton in human beings and provides shape to the body.
5. Fluid tissue: It links the different parts of the body and maintains continuity in the body. It includes blood and lymph.

Types of tissues:

1. Epithelial tissue: Functions of epithelial tissue:

• The cells of the body's surface form the outer layer of skin.
• Inside the body, epithelial cells form the lining of the mouth and alimentary canal and protect these organs.
• Epithelial tissues help in absorption of water and nutrients.

2. Connective tissue: Connective tissues are fibrous tissues made up of cells separated by non-living material, which is called an extracellular matrix. This matrix can be liquid or rigid. For example, blood contains plasma as its matrix and bone's matrix is rigid. Connective tissue gives shape to organs and holds them in place. Blood, bone, tendon, ligament, adipose, and areolar tissues are examples of connective tissues. One method of classifying connective tissues is to divide them into three types: fibrous connective tissue, skeletal connective tissue, and fluid connective tissue.
3. Muscular tissue: Muscle cells form the active contractile tissue of the body known as muscle tissue or muscular tissue. Muscle tissue functions to produce force and cause motion, either locomotion or movement within internal organs. Muscle tissue is separated into three distinct categories: visceral or smooth muscle, found in the inner linings of organs; skeletal muscle, typically attached to bones, which generate gross movement; and cardiac muscle, found in the heart, where it contracts to pump blood throughout an organism.
4. Nervous tissue: Cells comprising the central nervous system and peripheral nervous system are classified as nervous (or neural) tissue. In the central nervous system, neural tissues form the brain and spinal cord. In the peripheral nervous system, neural tissues form the cranial nerves and spinal nerves, inclusive of the motor neurons.
5. Plant tissues: In plant anatomy, tissues are categorized broadly into three tissue systems: the epidermis, the ground tissue, and the vascular tissue.

• Epidermis: Cells forming the outer surface of the leaves and of the young plant body.
• Vascular tissue: The primary components of vascular tissue are the xylem and phloem. These transport fluids and nutrients internally.
• Ground tissue: Ground tissue is less differentiated than other tissues. Ground tissue manufactures nutrients by photosynthesis and stores reserve nutrients.

6. Meristematic tissues: Meristematic tissue consists of actively dividing cells, and leads to increase in length and thickness of the plant. The primary growth of a plant occurs only in certain, specific regions, such as in the tips of stems or roots. It is in these regions that meristematic tissues are present. Cells in these tissues are roughly spherical or polyhedral, to rectangular in shape, and have thin cell walls. New cells produced by meristem are initially those of meristem itself, but as the new cells grow and mature, their characteristics slowly change and they become differentiated as components of the region of occurrence of meristematic tissues.
7. Permanent tissues: Permanent tissues may be defined as a group of living or dead cells formed by meristematic tissue and have lost their ability to divide and have permanently placed at fixed positions in the plant body. Meristematic tissues that take up a specific role lose the ability to divide. This process of taking up a permanent shape, size and a function is called cellular differentiation. Cells of meristematic tissue differentiate to form different types of permanent tissues.

There are three types of permanent tissues:

• Simple permanent tissues.
• Complex permanent tissues.
• Special or secretory tissues (glandular).

Epithelial tissue is the simplest animal tissue which composed of one or more layer of cells covering external and internal body organs.
Characteristics of epithelial tissue:

1. The cells of epithelial tissue are tightly packed and form continuous sheets.
2. Epithelial cells have small amount of cementing material between them and almost no intercellular space.
3. The surface of cells may be smooth, columnar or cuboidal.
4. The cells of the lowermost layer rest on non-cellular basement membrane which separates it from the underlying connective tissue.

Functions:
Epithelial tissue performs following functions:

1. It protects the organs which it covers.
2. It absorbs water and other nutrients inside the body.
3. Some epithelial cells secrete ear wax, mucus and digestive juices.
4. It keeps different organs separate.