Please refer to Tissue Class 9 Science Notes and important questions below. The Class 9 Science Chapter wise notes have been prepared based on the latest syllabus issued for the current academic year by CBSE. Students should revise these notes and go through important Class 9 Science examination questions given below to obtain better marks in exams
Tissue Class 9 Science Notes and Questions
The below Class 9 Tissue notes have been designed by expert Science teachers. These will help you a lot to understand all the important topics given in your NCERT Class 9 Science textbook.
Refer to Chapter 6 Tissue Notes below which have been designed as per the latest syllabus issued by CBSE and will be very useful for upcoming examinations to help clear your concepts and get better marks in examinations.
1. Tissue is a group of cells having similar origin, structure & function. Study of tissues is called Histology
2. In unicellular organism (Amoeba), single cell performs all basic functions, whereas in multi-cellular organisms (Plants and Animals) shows division of labour as Plant tissue & Animal tissues.
3. Plant tissues are two types: Meristems & Permanent tissues.
4. Meristems: The Meristems are the tissues having the power of cell division. It is found on those region of the plant which grows.
Types of Meristems;
1. The Apical meristems – It is present at the growing tip of the stem and roots and increases the length.
2. The lateral meristems – present at the lateral side of stem anf root (cambium) and increases the girth.
3. The intercalary meristems – present at internodes or base of the leaves and increases the length between the nodes.
Permanent tissues: Two types such as Simple permanent tissues & Complex permanent tissues.
a) Simple permanent tissues: subdivided as
(i): Parenchyma: Tissues provide the support to plants.They are loosly packed and has large intracellular space.
- Parenchyma with chlorophyll which performs photosynthesis is called as chlorenchyma.
- The parenchyma with large air spaces to give buoyancy is called as aerenchyma.
- Parenchyma also stores food and water.
(ii) Collenchyma: Tissue provides mechanical support, thickened at the corners, have very little intercellular space. It allows easy bending of various parts of a plants without breaking
(iii) Sclerenchyma: Tissue makes the plant hard and stiff, thickened due to lignin and no intercellular space. Cells of this tissue are dead and commonly seen in the husk of coconut.
(iv) Guard cells& Epidermal tissue: the tissue aids in protection and exchange of gases.
Guard cells are kidney shaped in dicots, dumb bell shaped in monocots to guard the stomata. The epidermal tissues of roots aid in absorption of water and minerals. The epidermal tissues in desert plants have a thick waxy coating of Cutin with waterproof quality. The epidermal tissues form the several layer thick Cork or the Bark of the tree.
b) Complex permanent tissues: The complex tissues are made of more than one type of cells. All these cells coordinate to perform a common function. They are subdivided as;
Xylem: It consists of tracheids, vessels, xylem parenchyma and xylem fibers. The cells have thick walls,
Function – help in conduction of water and minerals.
Phloem: It consists of sieve tubes, companion cells, phloem parenchyma, and phloem fibers.
Function:- Phloem transports food material to other parts of the plants.
6. Animal tissues: Sub divided as epithelial tissue, connective tissue, muscular tissue and nervous tissue.
- Epithelial tissue: It is a protective covering forming a continuous sheet. Simple epithelium is the one which is extremely thin in one layer, whereas stratified epithelium are arranged in pattern of layers.
Depending on shape and function they are classified as:
a) Squamous epithelium in the lining of mouth and esophagus.
b) Cuboidal epithelium in the lining of kidney tubules and salivary glands.
c) Columnar epithelium in the intestine &Columnar epithelium with cilia in the lining of respiratory tract.
d) Glandular epithelium in the Glands aids in a special function as gland cells, which can secrete at the epithelial surface.
ii) Connective Tissue:
a) Blood: The Blood is a fluid connective tissue. Blood plasma has RBCs (Red Blood Cells) WBCs (White Blood Cells) and platelets. Blood plasma contains proteins, salts and hormones. Blood flows and transports gases, digested food, hormones and waste materials.
b) Bone: The bone is a connective tissue with hard matrix, composed of calcium and phosphorus. A bone is connected by another bone with another connective tissue called ligaments. A bone is connected by muscle with another connective tissue called tendon.
c) Cartilage: The cartilage is a connective tissue with solid matrix composed of proteins and sugars. It is commonly seen in nose, ear, trachea, and larynx.
d) Areolar Connective Tissue: It is found between the skin and muscles, around the blood vessels. It supports internal organs and aids in repair of tissues.
e) Adipose Connective Tissue: It is filled with fat globules for the storage of fat. It acts as insulator.
Muscular tissues: They have special contractile proteins responsible for movements. Three types, such as;
Striated muscles/skeletal muscles/voluntary muscles : They are cylindrical, un-branched and multinucleated. They have dark bands and light bands.
Unstriated muscles /smooth muscles/involuntary muscles: They are commonly called as Smooth muscles, having no striations (dark bands/ light bands are absent). Commonly found alimentary canal, uterus, Iris of an Eye. They are spindle shaped. Involuntary in nature.
Cardiac Muscles: They are commonly called as Heart muscles, cylindrical, branched and uni-nucleate. Involuntary in nature .
Nervous Tissue: The tissue responds to stimuli. The brain, spinal cord and nerves are composed of nervous tissue or neurons. A neuron consists of Cell Body, cytoplasm, Nucleus, Dendrite, Axon, nerve ending. The neuron impulse allow us to move our muscles when we want to respond to stimuli.
Questions for Class 9 Science Chapter 6 Tissue
Question. What are the two main components of blood? Why is blood considered a type of connective tissue?
Ans : (i) Blood has two main components :
(a) Fluid (liquid) matrix called plasma.
(b) Suspended red blood cells (RBCs), white blood cells (WBCs) and platelets.
(ii) Blood is considered as connective tissue because :
(a) It has the same origin as the other connective tissues.
(b) It flows to different parts of the body and thus connects different parts of the body with one another to exchange materials and gases.
Question. Why does epidermal tissue not have intercellular space?
What is the function of epidermis in plants?
Ans : Epidermal tissue forms a protective layer for plants and helps to protect the internal parts of plants which prevent the plant from loss of water, attack by parasitic fungi and outer injury.
Question. Mention the different types of blood cells.
Ans : (i) WBCs (ii) RBCs (iii) Platelets
Question. Name the tissue which is responsible for the movement of our body?
Ans : A combination of following two tissues is responsible for the movement of our body : (i) Muscular tissue (ii) Nervous tissue
Question. Mention the functions of cartilage.
Ans : (i) Support to the body (ii) Flexibility (iii) At joints, smoothens surface
Question. What are the four important types of tissues found in animal?
Ans : The four animal tissues are :
(i) Epithelial tissues,
(ii) Connective tissues,
(iii) Muscular tissues, and
(iv) Nervous tissue.
Question. What are the three types of muscle fibres (muscle cells)?
Ans : These are three types of muscle fibres :
1. Striated muscle (skeletal muscle or voluntary muscle),
2. Unstriated muscle (smooth muscle or involuntary muscle),
3. Cardiac muscle.
Question. Name the connective tissue that is found between skin and muscles.
Ans : Areolar connective tissue fills the space between skin and muscles.
Question. What will happen if ligaments are over stretched?
Ans : Sprain will occur.
Question. Explain how the bark of a tree is formed. How does it act as a protective tissue?
Ans : As trees grow old, a strip of secondary meristem replaces the epidermis of the stem. Cell on the outside are cut off this layer. This forms the several layer thick cork or the bark of the tree. Bark is a mass of dead tissue lying in the peripheral region of the plant body as a hard dry covering. Its function is protection. It protects the inner tissues against the attack of fungi and insects, against loss of water by evaporation, etc.
Question. Complete the sentences.
(i) _____ conducts minerals and water.
(ii) _____ conducts food in higher plants.
(iii) Blood is a _____ type of tissue.
(iv) Bone has _____ cells. (v) Cartilage has _____ cells.
(vi) The connective tissue where fibres are not present is _____.
Ans : (i) Xylem (ii) Phloem (iii) connective (iv) osteocyte (v) chondrocyte (vi) blood
Question. What are the four main functions of epithelial tissue?
Ans : The main functions of epithelial tissue are :
1. It forms the outer layer of skin and hence it protects the underlying cells from drying, injury, bacterial and chemical effects.
2. It forms lining of mouth, alimentary canal and other internal organs and thus protects these organs.
3. It helps in absorption of water and other nutrients in alimentary canal. Some of them are greatly specialized and perform secretory function.
Question. Explain the structure of parenchyma. What are its major modifications?
Ans : Parenchyma : It is the basic or fundamental tissue found in plants. Cells of this tissue are thin walled, circular or polygonal. They are living with a nucleus and a vacuole. Intercellular spaces are present between the cells of this tissue. Two modifications of parenchyma are chlorenchyma and aerenchyma.
(a) Chlorenchyma : Sometimes cells of the parenchyma contain chlorophyll and perform photosynthesis. This kind of parenchyma is known as chlorenchyma.
(b) Aerenchyma : In aquatic plants, parenchyma contains big air spaces in between them. Such a parenchyma tissue is known as aerenchyma.
Question. Explain connective tissue along with its types.
Ans : Connective tissue consists various types of cells which perform the same function. These are of three types :
(i) Proper connective tissue
(ii) Fluid tissue
(iii) Skeletal tissue
Proper connective tissue : These are of four types–
Areolar and ligament connective tissue : It is present between muscles and skin and in the bone marrow. It is also present around nerves and blood vessels. They fill the space inside the organ. They also provide strength to internal organs and helps in repair of tissues.
Adipose tissue : It is found below the skin and also between internal organs. It stores fat and due to this fat storage, it behaves as an insulator.
Tendon : It is fibrous, strong and flexible and joins muscles with bone.
Ligament : It is elastic and strong and joins bone with bone.
Fluid tissue consists of :
Blood : It is a liquid tissue called plasma which has RBCs, WBCs, plasma and blood platelets. It helps to transport substances like gases, hormones, digested food and waste material. Lymph : It transports digested fat and white blood cells in plasma.
Skeletal tissue is made up of :
Bone : It is a hard tissue which helps in the movement and support of our body.
Cartilage : It softens the bone surface at joints. It is found in our ear, nose, trachea and larynx.
Question. What is the use of tissues in multicellular organisms?
Ans : Tissue provides structural and mechanical strength as well as to allow division of labour in multicellular organisms.
Question. Where is chlorenchyma tissue present?
Ans : It is present in the centre of stems and roots. If it has chlorophyll then it is called chlorenchyma. It is present in green leaves.
Question. What are three main categories of connective tissue?
Ans : Categories of connective tissue are : Connective tissue proper : There is a matrix in which generally two types of (white and yellow) fibres are present. In between these fibres some connective tissue cells are present. Example of this kind of connective tissues are aerolar tissue and adipose tissue. Skeletal tissue : This type of tissues form the skeleton of an organism. It is of two types : Cartilage and bone. a. Cartilage has solid matrix called chondrin, in which fibres and cells known as chondrocytes are present. Usually cells are present in clusters of 2-3 cells in small spaces called lacunae. Cartilage is found in the regions of pinna, nose, trachea and larynx. b. In bones, matrix is formed of a protein called ossein impregnated with phosphate and carbonates of calcium and magnesium. Fluid tissue : Blood and lymph are examples of fluid connective tissues. These are specialized connective tissues. It consists of liquid matrix with no fibres. In liquid matrix called plasma corpuscles remain suspended. Blood transports food material, gases and other substances to the various parts of the body.
Question. Describe the structure of cartilage and bone.
Ans : Cartilage : It is a solid but semi-rigid and flexible connective tissue. It has large bluntly angular cartilage cells called chondrocytes. They occur in clusters of 2 and 3 in small spaces (lacunae) scattered in the matrix. Cartilage smoothens bone surfaces at joints and is also present in the nose, ear, trachea and larynx. Bone : Bone is a solid, rigid and strong connective tissue. Its matrix become hard due to the deposition of salts of calcium and phosphorous. Osteocytes or bone cells are present in irregular spaces lacunae in the matrix, interconnected by fine canals called canaliculi. In this tissue, matrix deposits in concentric rings around narrow longitudinal cavities called haversian canals. These canals carries blood vessels and nerves.
Question. Write the main functions of collenchyma?
Ans : The main functions of collenchyma are to provide mechanical support, tensile strength, elasticity and flexibility to stem, leaf stalks and leaves.
Question. Write the various functions of all types of epithelial tissues?
Ans : Epithelial tissues help in protection, absorption, excretion, exchange of respiratory gases and secretion.
Question. What is basement membrane?
Ans : It is very thin non-cellular membrane on which cells of epithelial tissue rest. It also separates the epithelial tissue from the underlying tissues.
Question. Describe the structure of phloem.
Ans : Structure of phloem : The main conducting part of the phloem is sieve tube which is formed of elongated cylindrical cells arranged in vertical rows. The walls between the cells have many minute pores through which food material can pass from one cell to the next. The porous walls between the cells is termed as sieve plate. Each sieve tube member is supported by a long parenchymatous cell called companion cell which helps the sieve tubes in the conduction of food material. Phloem also contains phloem fibres, which provide support. Another component of phloem is parenchyma cells which stores food.
Question. What is xylem? Explain its structure. Which one of its component is very important and why?
Ans : Xylem is a complex plant tissue which transports water and dissolved minerals from roots to all other plant parts. Structure : Xylem consists of four kinds of cells (also known as elements). Tracheids : A tracheid is an elongated, hollow cell with its both ends tapering. The walls of these cells are thick by the deposition of lignin. At certain spots lignin is not present. These spots are termed as pits. The tracheids are dead cells. Vessels : These are tube-like structures formed by a number of cells placed end to end with their transverse walls dissolved. The side walls of these tubes also have deposition of lignin. The thickening of the walls show various kinds of patterns. They are also dead cells. Xylem Parenchyma : They are prenchymatous, thin walled, living cells. They help in lateral conduction of water and sap. They also store food. Xylem Fibres : They are lignified dead fibres which provide mechanical support to plant. The most important element of xylem is vessel because most of the water and minerals are carried upward through this component of xylem.
Question. Explain the structure of three types of muscle fibres. Also write the locations where they are found in the body.
Ans : The followings are the three types of muscle cells :
1. Unstriated muscles (also known as smooth, involuntary muscles) : This type of muscular tissue consists of spindle-shaped, long uninucleated cells. This type of muscles are present in alimentary canal, blood vessels, iris of eye, in ureters and bronchi of lungs, etc.
2. Striated muscles (also known as voluntary muscles because oftheir function being in our control or will) : This type ofmuscular cells are long multinucleated and enclosed in a membrane called sarcolemma. Each fibre has several longitudinal filaments embedded in cytoplasm. These filaments give these muscles striated appearance. These muscles are attached to the skeleton; so they are called skeletal muscles.
3. Cardiac muscles : These muscles are found in heart. They are not under the control of the will. They contract rhythmically and involuntarily throughout life without the sign of fatigue. Structurally they show the characters of both unstriated and striated muscles. They are made up of branched fibres. These fibres are uninucleated and show alternate light and dark bands (striation).
Question. Explain plant tissue in detail.
Ans : Plant tissue is mainly divided into two categories :
• Meristematic tissue
• Permanent tissue
Meristematic tissue : The cells divide very fast. It helps in the growth of the plants. The shape of the cell is oval, round and polygonal. There is no intercellular space. There are three types of meristematic tissues :
(i) Apical meristem : Growth in length
(ii) Lateral meristem : Growth in breadth or thickness
(iii) Intercalary meristem : Growth in inter-nodes Permanent tissue : When meristematic tissue stops dividing and gets mature, then it forms permanent tissue. There are two types of permanent tissues : (i) Simple tissue (ii) Complex tissue (i) Simple
Tissue : Simple tissues are same in structure and perform the same functions. There are three types of simple
tissues : (a) Parenchyma : It is present in soft parts.
(b) Collenchyma : It provides mechanical strength to plants and is found in stalks.
(c) Sclerenchyma : It provides support as well as flexibility to plants.
(ii) Complex Tissue : They are different in structure but perform the same function in group. There are two
types of complex tissues :
(a) Xylem : It transports water from roots to shoot in plants.
(b) Phloem : Transports foods to all parts of the plant.
Question. Name two types of plant tissues.
Ans : (i) Permanent tissue
(ii) Meristematic tissue
Question. Explain epidermis in plants.
Ans : It forms the outermost layer of the plant. It is comprised of a single cell layer. This tissue forms a protective layer for plants and that helps to protect the internal parts of plants. It helps in protection against loss of water, attack by parasitic fungi and mechanical injury. Epidermis has small pores known as stomata. They are small holes or pores on the surface of leaves which help in exchange of gases and also in transpiration. Epidermis has long parts like hair that provide greater surface area for water absorption in roots. In plants found in deserts, epidermis consists of a thick waxy coating called cutin which makes the outer layer water resistant.
Question. How many types of meristems are present in plants, on the basis of position?
Ans : On the basis of location of meristem, it is classified into three types :
1. Apical meristem is present at the tip of stem, roots and their branches.
2. Intercalary meristem is found at the leaf base, above the nodes (i.e. at the base of internodes as in grasses) or below the nodes (i.e. at the uppermost region of internode as in mint).
3. Lateral meristem
4. Vascular cambium and cork cambium are the examples of lateral meristem.
5. Vascular cambium is found in vascular bundles while cork cambium is found underneath the bark of trees. Both of these cause increase in girth of plants.
Question. What are permanent tissues?
Ans :The cells of meristematic tissue lose the ability to divide and get differentiated into specialised cells. These differentiated cells form different types of tissues which are known as permanent tissues. Some examples of permanent tissues are : parenchyma, sclerenchyma, etc.
Question. What are areolar tissues’ junctions?
Ans : Areolar tissues are connective tissue found in animals. We can find them between skin and muscles, around blood vessels and nerves, in bone marrow. These tissues fill the space inside the organs. They support internal organs and help to repair tissues.
Question. Name the two types of tissues.
Ans : (i) Animal tissues
(ii) Plant tissues
Question. What are characteristic structural features of meristematic cells?
Ans : Meristematic cells have :
1. Thin cell walls.
2. Abundant or dense cytoplasm and single large nucleus.
3. Spherical, oval, polygonal or rectangular shape.
4. No intercellular spaces between them.
5. Either no vacuoles at all or few vacuoles.
Question. Name the following tissues.
(i) Which tissue covers the external surface in animals?
(ii) Which tissue stores fat in animals?
(iii) Which tissue joins bone to bone?
(iv) Which tissue divides and re-divides and responsible for growth in plants?
Ans : (i) Epithelial tissue
(ii) Adipose tissue
(iv) Meristematic tissue
Question. Write the characteristics of collenchyma.
Ans : The cells in this type of tissue are living, elongated and thickened with cellulose at the corners. There is very little intercellular space. This tissue provides flexibility and mechanical support to plants. This tissue is found in hypodermis of stems and leaf stalks.
Question. What are blood platelets?
Ans : Blood platelets are minute (about 2 to 4 μm in diameter), anucleated, disc like bodies. The main function of platelets is to help in clotting of blood.
Question. Where is parenchyma tissue present?
Ans : Parenchyma tissue is present below the epidermis.
Question. What is the function of connective tissue?
Ans : Connective tissue connects different tissues and organs. It provides support to different parts of the body by forming packing around different organs of the body.
Question. Describe the structure of sclerenchyma. Write its major functions.
Ans : Sclerenchyma is the chief mechanical tissue of plants. The cells of this tissue are usually long, narrow and pointed at both ends. Due to deposition of lignin their walls are often very highly thickened hence the lumen or cell cavity is nearly obliterated. They are usually provided with simple pits which may be oblique or straight. It provides strength to the plant parts.
Question. Define differentiation.
Ans : The process of taking up permanent size, shape and function of cell is called differentiation.
Question. Why do meristematic cells lack vacuoles?
Ans : Meristematic cells divide frequently to give rise to new cells. So, they need dense cytoplasm and soft cell wall. Vacuoles cause hindrance in cell division as they are full to cell sap and provide turgidity and rigidity to the cell.
Question. There was a paralytic patient, who cannot walk.
(i) Which tissues are responsible for the movement of the body?
(ii) Which tissues are present in spine and brain?
Ans : (i) Muscular and nervous tissues are responsible for the movement of the body.
Question. What is epithelial tissue?
Ans : Epithelial tissue : Epithelial tissue forms covering of entire surface of the body and lines the internal organs, because of this epithelial tissue is called protective tissue. It also forms a barrier to keep different body system separate. In this tissue, cells are closely associated and arranged on a very thin extracellular fibrous basement membrane. Epithelial tissue may be composed of one (simple epithelium) or more layers of cells (compound epithelium).
Question. What are muscular tissue? What is their function?
Ans : This is a specialised tissue which is composed of contractile, fibre-like cell. This tissue is responsible for movement in our body. Function : The movement of the body or limbs is brought about by contraction and relaxation of contractile proteins present in muscle cells.
Question. What is the location of stratified squamous epithelium? Also, mention its functions.
Ans : Stratified squamous epitheliums are found in the skin. They are present in layers to prevent wear and tear.
Question. Which tissue is present in the husk of a coconut?
Ans : Sclerenchyma.
Question. Mention the types of simple and complex tissues.
Ans : Simple : (i) Sclerenchyma, (ii) Parenchyma, (iii) Collenchyma Complex : (i) Phloem (ii) Xylem
Question. Explain complex tissue in plants.
Ans : Generally, complex tissues consist of more than one type of cell. They are different in structure but together perform the same function. There are two types of complex tissues : 1. Xylem : It transports water from roots to shoot in plants. The movement is only in one direction that is, from roots to shoot. It provides mechanical support to the plant. It has mostly dead elements. Its elements are tracheids, xylem sclerenchyma, xylem parenchyma, vessel elements.
2. Phloem : Conduct foods to all parts of the plant. The movement of phloem is bidirectional that is, movement in both the directions is possible. Its elements are mostly living. Its elements are sieve tubes, phloem parenchyma, companion cells and intermediary cells. Above given both complex tissues are conductive tissues and form the vascular bundle.
Question. Which tissue gives flexibility in plants?
Ans : Collenchyma.
Question. Define tracheids.
Ans : Tracheids have tapering ends and are basically elongated cells.
Question. Give one function of each of the following : (a) Stomata, (b) Root nodules, (c) Cardiac muscle fibres.
Ans : (a) Exchange of gases in plants.
(b) Root nodules are found in leguminous plants. They harbour bacteria which can fix free atmospheric nitrogen into nitrates and nitrites which plants like pulses can use for protein synthesis.
(c) Cardiac muscles show rhythmic contraction and relaxation throughout life. Because of this heart can pump the blood.
Question. What do you mean by aerenchyma?
Ans : Aerenchyma is the cell with large air-filled cavities of parenchyma. It helps aquatic plants to float.
Question. Name the tissues which are present in the plants at the nodes.
Ans : Intercalary tissues.
Question. What is the main function of vascular tissue in plants?
Ans : Vascular tissue transport :
(i) Water and dissolved minerals from roots to various parts of the plant (xylem).
(ii) Prepare food material from leaves to different plant parts (phloem).
Question. Give the types of meristematic tissues.
Ans : (i) Intercalary tissue — nodes (ii) Apical tissue — tips of shoot and roots (iii) Lateral tissue — stem sides
Question. What is a cardiac muscle? Mention its features too.
Ans : Cardiac muscle is an extremely specialized tissue developed to pump blood throughout the body. Features :
(i) Cylindrical in shape
(ii) Branched and single celled
(iii) Striated muscle fibres
(iv) Involuntary in nature
Question. List any four salient features of meristematic tissue?
Ans : (i) This tissue consists of actively dividing cells.
(ii) This tissue is present in growing regions of plants.
(iii) In this tissue, cells are packed closely without intercellular spaces.
(iv) Cells of this tissue have thin cell walls, dense cytoplasm and prominent nuclei.
Question. Mention the functions of cuboidal epithelium.
Ans : (i) Absorption (ii) Excretion (iii) Secretion (iv) Mechanical support
Question. What are protective tissues?
Ans : All parts of plants, e.g. leaves, flowers, stem, and root are covered by a single outermost protective layer called epidermis. It consists of rectangular, closely fitted relatively flat cells which lack intercellular spaces. Usually it is one cell thick and is covered with cutin. Epidermis protects internal tissues of the plant. In old dicot plants, epidermis is replaced by secondary meristem which cuts cells toward outerside. Cork cells do not have intercellular spaces and are dead cells. The walls of cork cells are heavily thickened due to the position of suberin. Presence of suberin makes the cells impervious to gases and water and thus prevents evaporation of water.
Question. Where can we find apical meristem?
Ans : It is found in the growing tips of roots and stem. The length of roots and stem is increased due to the presence of apical meristem.
Question. What is the structure of a neuron?
Ans : Building block of a nervous tissue is a neuron. It has a thread-like structure with axon and cell body.
Question. Explain the structure of a fluid connective tissue.
Ans : Blood is a fluid connective tissue. Blood consists of :
1. Blood plasma,
2. Blood cells.
1. Blood plasma : It is the fluid matrix which contains 85 to 95% water, 7% different types of proteins, 0.9% of salts, about 0.1% glucose and a very small amount of hormones, wastes, etc. In the plasma, blood corpuscles (cells) are suspended.
2. Blood cells : Three kinds of blood cells are found suspended in the blood plasma. These are :
(i) Red blood corpuscles (Erythrocytes) or RBCs (ii) White blood corpuscles (leucocytes) or WBCs and
(iii) Blood platelets. (i) Red blood corpuscles (Erythrocytes) or RBCs : The red blood corpuscles are biconcave, disc-like cells which are devoid of nucleus. They contain a substance called haemoglobin because of this they appear red in colour. The most important function of the RBCs is the transport of oxygen and carbon dioxide. (ii) White blood corpuscles (Leucocytes) or WBCs : These cells are comparatively large in size, colourless and irregular in appearance. They are devoid of haemoglobin. They protect our body from diseases by destroying germs. (iii) Blood platelets : These are small, 2-4 m in diameter. They are without nucleus. Their main function is to liberate some substances which helps in blood clotting.
Question. What will happen if apical meristem is damaged?
Ans : Growth of plant in length will stop.
Question. Mention the functions of bone.
Ans : (i) Provides support to skeletal (ii) Provides shape to body (iii) Protects the internal organs (iv) Support muscles
Question. How is ligament different from tendons?
Ans : Ligaments are elastic connective tissue which attach bone to bone to keep them in their place. Tendons are less elastic connective tissues which attach muscles to a bone.
Question. _____ tissues make the coconut husk.
Ans : Sclerenchymatous tissue
Question. Define guard cells.
Ans : Guard cells are kidney-shaped epidermal cells and a pair of these cells bound each stomata.