Class 9 Science Chapter 6 Question Answers - Tissues

Q1: Explain the structure of a nervous tissue with details about its location and function.
Ans: 

Structure: Nervous tissue is composed of specialized cells called neurons, which consist of a cell body containing the nucleus and cytoplasm. Neurons have long, slender extensions known as axons, which transmit electrical signals, and shorter, branching extensions called dendrites, which receive signals from other neurons. These neurons are interconnected in complex networks.

Location: Nervous tissue is primarily found in the brain, spinal cord, and nerves throughout the body.

Function: Nervous tissue plays a crucial role in transmitting and processing information within the body. It facilitates communication between different parts of the body, coordinates responses to stimuli, and regulates various bodily functions, including movement, sensation, and cognition.

Q2: 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.

• Chlorenchyma : Sometimes cells of the parenchyma contain chlorophyll and perform photosynthesis. This kind of parenchyma is known as chlorenchyma.
• Aerenchyma : In aquatic plants, parenchyma contains big air spaces in between them. Such a parenchyma tissue is known as aerenchyma.

Q3: 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 t issue
(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) X ylem : It transports water from roots to shoot in plants.
(b) P hloem : Transports foods to all parts of the plant.

Q4: 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.

Q5: 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.

Q6: Give the difference between the types of muscle fibres diagrammatically
Ans:

Q7: 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 : 

• X ylem : 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. 
• P hloem : 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.

Q8: 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 : 

• 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. 
• 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. 
• 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).

Q9: Draw a labelled diagram of section of a phloem.
Ans:

Q10: What is the difference between meristematic cells and permanent cells?
Ans:
Difference between meristematic cells and permanent cells :
Meristematic cells:

• They have dense cytoplasm and a large centrally placed nucleus.
• These cells are capable of dividing to _produce new cells.

Permanent cells:

• They have a large central vacuole and normal nucleus.
• They attain permanent shape and are not capable of producing new cells.

Q11: 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 : 

• A pical meristem is present at the tip of stem, roots and their branches. 
• In tercalary 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). 
• La teral meristem 
• V ascular cambium and cork cambium are the examples of lateral meristem. 
•  V ascular 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.

Q12: Differentiate between parenchyma and collenchyma.
Ans: Difference between parenchyma and collenchyma :

Q13: Differentiate between collenchyma and sclerenchyma.
Ans: Difference between collenchyma and sclerenchyma :


Q14: Describe the structure of phloem.
Ans: Phloem is a complex tissue responsible for transporting organic nutrients, primarily sugars, throughout the plant. It consists of several cell types, including:

• Sieve tube elements: Elongated cells with perforated end walls called sieve plates, through which nutrients flow. These cells lack nuclei and are supported by companion cells.
• Companion cells: Adjacent to sieve tube elements, companion cells are metabolically active and provide support and assistance in nutrient transport.
• Phloem fibers: Long, slender cells that provide structural support to the phloem tissue.
• Phloem parenchyma: Thin-walled cells that store reserves of organic compounds and provide structural support.

The interconnectedness of these cell types facilitates the efficient transport of nutrients, such as sugars produced during photosynthesis, from sources (such as leaves) to sinks (such as roots, fruits, and developing tissues) throughout the plant.

Q15: Differentiate between chlorenchyma and arenchyma.
Ans: Difference between chlorenchyma and arenchyma:


Q16: 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.

Q17: Differentiate between :
(i) Xylem and phloem
(ii) Vessel and sieve tube
(iii) Tracheid and vessel 
Ans: 
(i) Xylem and phloem

(ii) Vessel and sieve tube

(iii) Tracheids and vessel

Q18: 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. 

• C artilage 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.
• 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.

Q19: Explain the structure of a fluid connective tissue.
Ans: Blood is a fluid connective tissue. Blood consists of:
(i) Blood plasma,
(ii) Blood cells.

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. 

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.
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.
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.
 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.

Q20:Differentiate between bone and cartilage.
Ans:
Q21: 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.

Q22: Describe the structure of cartilage and bone.
Ans: Cartilage: Cartilage is a flexible and resilient connective tissue found in various parts of the body, including the nose, ears, trachea, and joints. It consists of chondrocytes (cartilage cells) embedded in a matrix of collagen and elastic fibers. Chondrocytes reside within small spaces called lacunae and maintain the integrity of the cartilage matrix. Cartilage provides support and cushioning to joints and other structures, allowing for smooth movement and shock absorption.

Bone: Bone is a rigid connective tissue that forms the skeletal framework of the body. It consists of osteocytes (bone cells) embedded in a matrix of collagen fibers and mineral salts, primarily calcium phosphate. Osteocytes are housed within small cavities called lacunae and are interconnected by tiny channels called canaliculi. Bone tissue is highly vascularized, allowing for the exchange of nutrients and waste products. It provides structural support, protection of internal organs, and serves as a reservoir for minerals such as calcium and phosphorus.

Q23: What are the two main components of blood? Why is blood considered a type of connective tissue?
Ans:

• Blood has two main components :
  (a) Fluid (liquid) matrix called plasma.
  (b) Suspended red blood cells (RBCs), white blood cells (WBCs) and platelets. 
• 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.