Class 9 Science Chapter 6 Important Extra Questions

Sclerenchyma

Calcium and potassium

Tracheids

Suberin

Collenchyma

Cardiac muscular tissue.

Presence of cuticle on the surface of desert plants reduce the rate of loss of water.

Areolar tissue

A goblet cell is a unicellular mucus secreting gland.

Osteoblast cells

WBC (White blood cell)

Mucus cells

Nerve cells

Through blood

The girth of the stem or root increases due to lateral meristem.

Lignin is a chemical substance present in the cell wall of plants which acts as a chemical and hardens i.

Cutin is a chemical substance with waterproof quality covering the aerial parts of plants.

Epithelial tissue

Proteins and sugars

Contractile protein

Nerve impulse

Blood

Aerenchyma present in the swollen petiole provides buoyancy to the hyacinth, Thus it floats on water surface.

The epidermis has thick cuticles and waxy substance to prevent the invasion of parasites.

Any organism will have a wide range of cell types. This is because each cell type specialises in one particular function. And for the proper working of an organism many functions like food transport, immunity, strength etc., are needed to be performed properly.

This happen because of transpiration due to which water is released from the plant in the form of water vapour which appears on the glass jar.

Voluntary muscles are also called skeletal muscles because they are mostly attached to the bones and help in body movement.

The cells formed by meristematic tissue take up a specific role and lose their ability to divide. As a result, they form a permanent tissue. This process of taking up a permanent shape, size and function is called differentiation.

A thick waxy coating of cutin is present in desert plants to prevent excessive loss of water during transpiration. Due to this, plant can survive in scarcity of water in desert.

As plants grow older the outer protective tissue undergoes certain change. A layer of secondary meristem develops which is called as phellogen. It is also known as cork cambium. It replaces epidermis of stem and roots.

Bones form the framework that supports the body. It also anchors the muscles and serves as storage site of calcium and phosphate. It provides shape to the body and protects vital body organs such brain, lungs, tissue, etc.

Nervous tissue is made up of neurons that receives and conduct impulses. Neurons are highly specialized for being stimulated and then transmitting the stimulus very rapidly from one place to another within the body. Impulses are the passage of electrical activity along the axon of a nerve cell.

Stomata are small pores present in the epidermis of leaves and are enclosed by two kidney shaped cells called guard cell.
Function of stomata:
(a) Necessary for exchanging gases with the atmosphere during photosynthesis and respiration.
(b) Transpiration, i.e. loss of water take place through them.

Xylem is complex permanent tissue and is also known as conduction tissues. It consist of tracheids, vessels, xylem parenchyma and xylem fibres. The cells have thick walls and many of them are dead. Tracheids and vessels are tubular structures. This allow them to transport water and minerals vertically upwards. The parenchyma stores food and helps in the lateral conduction of water. Fibres are mainly supportive in function.

Blood is a type of connective tissue. It has a liquid matrix called plasma, in which the red blood cells (RBCs) white blood cells (WBCs) and platelets are suspended. The plasma contains proteins, salts and hormones. Blood flows and transport gases, digested food, hormones to tissue and waste materials from tissue to the liver and kidney.

The muscles which do not move on our will are called involuntary muscles. They movement of food in the alimentary canal or the contraction and relaxation of blood vessel are involuntary movements. These muscles are also called as smooth muscles. They are also found in the iris of the eye, in ureters and in bronchi of the lungs.

Voluntary muscles can be removed by the conscious will when we want them to move. For example muscles of limbs or skeletal muscles. Involuntary muscles function on their own. We cannot start or stop them from working by our desire. Example are cardiac muscles and smooth muscles.

Plants and animals are two different types of organisms. Plants are autotrophic organisms, so they prepare their own food by photosynthesis. Moreover, plants are stationary or field organisms. Since they do not consume or need much energy, so most of the tissues of plants are supportive. Most of these tissue such as xylem, phloem sclerenchyma and cork are dead tissue i.e. they do not contain living protoplasm.
Animal on the other hand are heterotrophic organisms. They have to move in search of food, mate and shelter; so they need more energy as compared to plants. Most of these tissue contain living protoplasm. There are some tissues in plants which divide throughout life. They divide for the growth and reproduction of the plants. In contrast to plants, growth in animals is uniform.

Nervous tissue contains highly specialised unit cells called nervous cells or neurons. Each neuron has the following three parts:
(i) The cyton or cell body: It contains a central nucleus and cytoplasm with characteristic deeply stained particles, called Nissl granules.
(ii) The dendrites: These are short processes arising from the cyton.
(iii) The axon: It is a single, long, cylindrical process of uniform diameter. It carries impulses away from the cell body.
Functions:
Neurons have the ability to receive stimuli from within or outside the body and conduct impulses to different parts of the body. The impulses travel from one neuron to another neuron and finally to brain or spinal cord.

The striated muscle fibres are long or elongated, non-tapering, cylindrical and unbranched. These cells have a number of nuclei called sarcolemma. These muscle fibres shows alternate dark and light stripes or striations and so they are called as striated muscles. These muscles occur in muscles of limbs, body wall, face, neck etc.
Functions of striated muscles:
(i) Striated muscles are powerful and undergo rapid contraction and expansion.
(ii) Striated muscles provide the force for locomotion and all other voluntary movements of the body.
The smooth muscles are also known as unstriated or involuntary muscles. Smooth muscles occur as bundles or sheets of elongated fusiform or spindle-shaped cells or fibres. They are held together by loose connective tissue. These muscle fibres are uninucleate and do not bear any bands, stripes or striation across them.
Functions of smooth muscles:
(i) Smooth muscles do not work according to our will so they are also called involuntary muscles. Movement of food in the alimentary canal or the contraction and relaxation of blood vessels are involuntary movements.
(ii) Smooth muscles contract slowly but can remain contracted for a long period of time. Due to this characteristic, the food passes to the next step of digestion in the alimentary canal.

Permanent tissue are derived from meristematic tissue but their cells have lost the power of division and have attained their definite forms.
Permanent tissue are classified into the following two types:
(i) Simple permanent tissue
(ii) Complex permanent tissue
Simple permanent tissues: These tissues are composed of cells which are structurally and functionally similar.
Simple permanent tissues are further classified into the following two types:
(a) Parenchyma: Parenchyma forms the bulk of the plant body. Parenchyma cells are living and posses the power of division.
(b) Collenchyma: Collenchyma tissue is also living. It is a characteristic by the deposition of extra cellulose at the corner or cells.
(c) Sclerenchyma: Sclerenchyma cells are dead cells and they are devoid of protoplasm. The cell walls of sclerenchyma are largely thickened with deposition of lignin.
(ii) Complex permanent tissues: The complex tissue consist of more than one type of cells having a common origin. All these cells coordinate to perform a common function.
Complex tissues are of the following two types:
(a) Xylem: Xylem is a vascular and mechanical tissue. It is a conducting tissue. Xylem is composed of four different types of cells: (i) Tracheids (ii) Vessels (iii) Xylem parenchyma (iv) Xylem sclerenchyma
Except xylem parenchyma all other xylem elements are dead and bounded by thick lignified walls.
(b) Phloem: Like xylem, phloem is also vascular but has no mechanical function. Phloem is composed of following four elements: (i) Sieve tubes (ii) Companion cells (iii) Phloem parenchyma (iv) Phloem fibres
Except phloem fibres all other phloem elements are living.
Xylem and phloem are both conducting tissue and are also known as vascular tissues. Together, Xylem and Phloem are both conducting tissues. Together, both of them constitute vascular bundle.

There are five type of connective tissues:
(i) Areolar connective tissue: It is a loose and cellular connective tissue. It joins skin to muscles, fills spaces inside organs, and is found around muscles, blood vessels and nerves.
Functions:
(a) It acts as a supporting and packing tissue between organs lying in the body cavity.
(b) It helps in repair of tissues after an injury.
(c) It also helps in combating foreign toxins.
(d) It fixes skin to underlying muscles.
(ii) Dense regular connective tissue: It is fibrous connective tissue, characterised by ordered and densely packed collection of fibres and cells. Dense regularly connective tissue is the principal component of tendons and ligaments.
Functions:
(a) Tendons: Tendons are cord like, strong, inelastic structures that join skeletal muscles to bones.
(b) Ligament: They: are an elastic structure which connects bones to bones.
(iii) Adipose tissue: Adipose tissue is basically an aggression of fat cells. The adipose tissue is abundant below the skin, between the internal organs and in the yellow bone marrow.
Function:
(a) It serves as a fat reservoir.
(b) It provides shape to the limbs and the body.
(c) It keeps visceral organs in position.
(d) It forms shock-absorbing cushion around kidneys and eyeballs.
(e) It acts as an insulator. Being a poor conductor of heat, it reduces heat loss from body i.e. regulates body temperature.
(iv) Skeletal tissue: The skeletal or supporting tissue includes bone and cartilage which forms the endoskeleton of vertebrate body.
(a) Cartilage: The cartilage is a specialised connective tissue which is compact and less vascular. Cartilage can be found in ear pinna, nose tip, epiglottis, intervertebral disc, end of long bones, lower ends of ribs and rings of trachea.
(b) Bone: Bone is a strong and not non-flexibility tissue. Like cartilage, bone is also a specialised connective tissue.
Functions:
(a) Cartilage provides support and flexibility to the body parts. It smoothens the surface at joints.
(b) Bone provide shape and skeletal support to the body.
(c) Bone protects vital body organs such as brain, lungs, etc.
(d) Bone anchor muscles.
(v) Fluid connective tissue: Fluid connective tissue links the different parts of the body and maintains continuity in the body. It includes blood and lymph.
(a) Blood: In this tissue, cells move in a fluid or liquid matrix or medium called blood plasma. Blood occurs in blood vessels called arteries, veins and capillaries which are connected together to form the circulatory system.
(b) Lymph: Lymph is a colourless fluid that has been filtered out of blood capillaries.
Functions:
(a) Blood transports nutrients, hormones and vitamins to the tissues and transports execratory product from the tissues to the liver and kidney.
(b) Lymph transports the nutrients (oxygen, glucose) that may have filtered out of the blood capillaries back into the heart to be recirculated in the body.
(c) Lymph brings CO2 and nitrogenous waste from tissue to the blood.

(a) Sclerenchyma:
(i) Cells are thick walled and lignified.
(ii) Tissues are made up of dead cell.
(iii) No intercellular spaces between the cell are found.
(iv) Provides strength to the plant part.
(v) The cells are long and narrow make the plant hard and stiff. The tissue is present in the stem around vascular bundles in the veins of leaves and the hard covering of seeds and nuts.
(b) Parenchyma:
(i) Cells are thin walled and unspecialised.
(ii) These are living cell.
(iii) Cells are usually loosely packed with large intercellular space.
(iv) Stores nutrient and water in stem and root.
(v) Some cells contain chlorophyll called chlorenchyma and perform photosynthesis. Other cells have large air cavities called aerenchyma which provide buoyancy to the hydrophytic plants.

Epithelial tissue are following types:
(a) Simple squamous epithelium
(b) Stratified squamous epithelium
(c) Columnar epithelium
(d) Cuboidal epithelium.
(a) Simple squamous epithelium: They are present in cells lining blood vessels or lung alveoli where transportation of substances occurs through a selectively permeable surface, there is a simple flat kind of epithelium.
(b) Stratified squamous epithelium: Skin epithelial cells are arranged in many layers to prevent wear and tear. Since they are arranged in a pattern of layers, the epithelium is called stratified squamous epithelium.
(c) Columnar epithelium: Where absorption and secretion occur, as in the inner lining of the intestine these tall epithelial cells are present. This columnar epithelial facilities movement across the epithelial barrier. In the respiratory tract, the columnar epithelial tissue also have move and their movement pushes the mucus forward to clear it. This type of epithelium is thus ciliated columnar epithelium.
(d) Cuboidal epithelium: These form the lining of the kidney tubules and ducts of salivary glands where these provide mechanical support. Sometimes, a portion of the epithelial tissue folds inward and multicellular gland is formed. This is glandular epithelium.

(a) Meristematic cells are continuously dividing cell so they have a prominent nucleus and dense cytoplasm. But since these cells do not store food material or wastes materials they lack vacuole.
(b) Sclerenchyma cells have lignified cell walls which make them compact and leave no intercellular spaces.
(c) Pear has sclerenchymatous stone cells which are granular in texture. Hence we get the crunchy and granular feeling while chewing a pear.
(d) The branches of a tree have collenchyma cells which provide tensile strength to plant parts. So it move and bend freely when wind blows.
(e) The husk of a coconut tree is made up of sclerenchyma cells which have lignified cell walls. Lignin makes the cells compact and leaves no intercellular spaces.

The characteristic of cork are as follows:
(a) Cells of cork are dead at maturity.
(b) These cells are compactly arranged.
(c) Cells do not posses intercellular spaces.
(d) Cells posses a chemical substance suberin in their walls.
(e) There are several thick layers.
As plants grow older a strip of secondary meristem replace the epidermis of the stem. Cells on the outside are cut off from this layer. This forms the several layer thick cork or the bark of the tree.

The covering or protective tissue in the animal body are epithelial tissues. Epithelial tissue cells are tightly packed and form a continuous sheet. They have only a small amount of cementing material between them and almost no intercellular spaces. Epithelium covers most organs and cavities within the body. It forms a barrier to keep different body systems separate. The skin, the lining of the mouth, the lining of blood vessels, lungs alveoli and kidney tubules are all made of epithelial tissue.
Functions of epithelial tissue:
(i) Epithelial cells protects the underlying cells from drying, injury and chemical effects. They also protect the body from viral or bacterial infections.
(ii) It helps in the absorption of water and nutrients.
(iii) It performs secretary functions by secreting useful chemical like sweat, saliva, enzymes from the food, etc., in the body.

The plants will die within few days of replanting it. This is because since the root tips are cut, the roots won’t grow because of absence of meristematic tissue. And if the roots will not grow, proper absorption of water and minerals will not occur.