Science Chapter 3 - Tissues
Page No 169:Short Answer Questions
Question 1:
What is the importance of tissues?
Answer:
Tissues are important because of the following reasons:
(i) They divide the work labour in multicellular organisms.
(ii) They get organised to form different organs and organ systems.
(iii) They provide a higher efficiency to multicellular organisms by improving their organisation.
Question 2:
Why do plants and animals possess different types of tissues?
Answer:
Plants and animals are different kinds of organisms; hence, they require different types of tissues to carry out their bodily functions.
Plants are autotrophic and stationary, whereas animals have to move from one place to another in search of food, mate, and shelter. Plant tissues are suited for the stationary habit of plants, whereas tissue organisation in animals is targeted at providing higher mobility.
Question 3:
Tabulate differences between plants and animal tissues.
Answer:
| Plant Tissues | Animal Tissues |
| Dead supportive tissues are more abundant than living tissues in plants. | Living tissues are more than dead tissues. |
| Less energy maintenance is required. | More energy maintenance is required. |
| Plants grow throughout their life due to meristematic tissues. | Animals do not grow after reaching maturity. There is only reparative growth. |
| Tissue organisation is meant for stationary habits. | Tissue organisation is meant for high mobility. |
Question 4:
Write a short note on intercalary meristem.
Answer:
Intercalary meristems are located at the base of leaves or internode and below the nodes. These type of meristems are involved in increasing the length of an plant organs such as leaves and internodes.
Examples: Stems of grasses (meristems are located at the base of leaves) and mint (meristems are located below the nodes).
Question 5:
Write one main function of
(a) Apical meristem(b) Lateral meristem
Answer:
(a) Apical meristems: They are responsible for root and stem elongation, resulting in an increase in the height of the plant (primary growth).
(b) Lateral meristems: They cause an increase in the diameter and girth of stems or roots (secondary growth).
Question 6:
What are simple tissues? Explain their three different types.
Answer:
Simple tissues consist of cells that are structurally and functionally similar. They are made up of only one type of cells.
The three types of simple tissues are as follows:
(a) Parenchyma: It forms the bulk of the plant body. The main function of parenchyma is to store and assimilate food.
(b) Collenchyma: It is located below the epidermis of dicotyledonous stem and petiole. It provides mechanical support to the plant body.
(c) Sclerenchyma: It consists of dead cells. It provides mechanical support and protection to the plant.
Page No 170:
Question 7:
Draw a well labelled diagram of parenchyma and collenchyma.
Answer:
Diagram of Parenchyma
Diagram of Collenchyma
Question 8:
Draw a well labelled diagram of phloem.
Answer:
Phloem
Question 9:
Draw a well labelled diagram of xylem.
Answer:
Xylem
Question 10:
Give two functions of collenchyma.
Answer:
Functions of collenchyma:
(i) It provides mechanical support and elasticity in young dicotyledonous stems.
(ii) They manufacture sugar and starch if their cells possess chloroplast.
Question 11:
Write a short note on sclerenchyma.
Answer:
Sclerenchyma cells are dead cells devoid of protoplasm. Its cell walls are thick and lignified. There are no intercellular spaces between the cells. Middle lamella exists between two sclerenchymatous cells. They are found in stems, roots, veins of leaves, hard covering of seeds, and nuts. Cells of collenchyma are of two types:
(a) fibres and
(b) sclereids (grit cells or stone cells).
The main function of sclerenchyma is to provide mechanical support and protection to the plant.
Question 12:
Distinguish between xylem and phloem.
Answer:
| Xylem | Phloem |
| It conducts water and minerals. | It conducts organic solutes or food materials. |
| Conduction is unidirectional (from roots to apical parts). | Conduction is bidirectional. |
| Conducting cells of xylem are tracheids and vessels. | Conducting cells of phloem are sieve tubes. |
| It provides mechanical strength to the plants. | It has no mechanical function in the plants. |
| Except xylem parenchyma, it is composed of dead cells. | Except phloem fibres, it is composed of living cells. |
Question 13:
Distinguish between tracheids and vessels.
Answer:
| Tracheids | Vessels |
| They are single celled. | They are made up of row of cells. |
| The end walls remain intact. | The end walls get dissolved and become perforated. |
| Its walls are very thick with a narrow lumen. | Its walls are less thick with a wider lumen. |
Page No 170:Short Answer Questions
Question 1:
Explain different types of elements present in phloem.
Answer:
Phloem consists of following four elements:
(i) Sieve tubes: These are slender, tube-like structures composed of elongated thin walls placed end to end. Their end walls, sieve plate, are perforated by large number of pores. Sieve tube elements lack nuclei, but they remain alive via adjacent companion cells.
(ii) Companion cells: They are connected with the sieve tubes via plasmodesmata. They are thin-walled cells consisting of dense and active cytoplasm and large, elongated nucleus.
(iii) Phloem parenchyma: As the name suggest, they consist of living parenchyma cells. They are involved in storage and lateral conduction of food.
(iv) Phloem fibres or bast fibres: These are dead cells of phloem possessing a narrow lumen. They are meant for providing mechanical support to the phloem.
Question 2:
What are tracheary elements? Describe their functions.
Answer:
Tracheary elements are the elongated cells of xylem tissue. They are of two types:
(i) Vessels: These are long tube-like structures that are formed by a row of cells placed end to end. The transverse walls between the vessel elements are completely dissolved forming water pipes.
(ii) Tracheids: These are elongated cells with tapering ends. Since their end walls have closed ends, water has to pass from cell to cell via pits.
Both these elements are involved in the conduction of water.
Question 3:
Write the functions of parenchyma, collencyma and sclerenchyma.
Answer:
Functions of parenchyma:
(i) The main function of parenchyma is to store and assimilate food. Hence, they are referred to as food storage tissues.
(ii) It serves as a packing tissue to fill the spaces between other tissues and maintain the shape and firmness of the plant.
(iii) It stores waste products of plants.
Functions of collenchyma:
(i) It is a mechanical tissue and provides mechanical support and elasticity to the stems of dicot plants.
(ii) If its cells possess chloroplast, then it is involved in manufacturing sugar and starch.
(iii) It provides tensile strength and flexibility to the plant body.
Function of sclerenchyma:
(i) It provides mechanical strength to the plant.
(ii) It is involved in providing protection and strength to the plant body.
(iii) It makes the plant body rigid, flexible, and elastic.
Question 4:
What is the difference between parenchyma and collenchyma?
Answer:
| Parenchyma | Collenchyma |
| It consists of thin-walled living cells. | In collenchyma, cells are thickened at a localised regions. |
| It is distributed in almost all the parts of the plant. | It is mostly present in the aerial parts of the plant. |
| They are involved in food storage. | They are the chief mechanical tissue in young plants, particularly dicot stems. |
Question 5:
What is the differences between collenchyma and sclerenchyma?
Answer:
| Collenchyma | Sclerenchyma |
| It consists of living cells. | It consists of dead cells. |
| Cell wall thickenings are not uniform. | Cell wall thickenings are uniform. |
| Its cell walls are cellulosic. | Its cell walls are lignified. |
| Its cells possess cytoplasm. | Its cells lacks cytoplasm. |
| It provides mechanical support and elasticity to the plant body. | It is mainly a mechanical tissue. |
Question 6:
Name the different types of elements found in the xylem.
Answer:
Different types of elements found in xylem are:
(i) tracheids,
(ii) vessels,
(iii) xylem parenchyma, and
(iv) xylem fibre.
Question 7:
What are the functions of xylem?
Answer:
Following are the functions of xylem:
(i) To carry water and mineral salts upwards from the root to different parts of shoots.
(ii) To provide mechanical support to the plant as the walls of tracheids, vessels, and fibres of xylem are lignified.
Question 8:
What are the functions of phloem?
Answer:
Following are the functions of phloem:
(i) It is the chief tissue that conducts photosynthetically prepared food materials from the leaves to the storage organs and later from storage organs to the growing regions of the plant body.
(ii) Phloem fibres or bast fibres of some plants such as jute, hemp, and flax have commercial or economic value.
Question 9:
Write down names of different types of plant tissues.
Answer:
Plant tissues are divided into two broad categories:
(i) Meristematic tissue:
It is further subdivided into apical, lateral, and intercalary meristems.
(ii) Permanent tissue: They are of two types.
(a) Simple permanent tissues include parenchyma, collenchyma, and sclerenchyma.
(b) Complex permanent tissues include xylem and phloem.
Question 10:
Explain how sieve tubes manage to be living?
Answer:
Sieve tube elements of phloem tissue lack nucleus but still they manage to live. This is because they are connected to the companion cells of phloem tissue via numerous plasmodesmata. Both sieve tube elements and companion cells develop from the same meristematic cell and form a functional unit. Companion cells provide proteins, ATP, and other signalling molecules to the sieve tube member as it contains extra number of mitochondria and chromosomes.
Question 11:
Give four important functions of epithelial tissue. Name one specific place in the body where each function is carried out.
Answer:
Functions of epithelial tissue:
(i) It protects the underlying parts of body from mechanical injury, entry of germs and chemicals, and drying by lining cavities of mouth, oesophagus, nose, and blood vessels.
(ii) It helps in excretion (in kidney tubules).
(iii) It helps in absorption (in stomach and intestine).
(iv) It helps in different body secretion (mucus by goblet cells in various parts of the body).
Question 12:
Enlist three types of muscles with their locations.
Answer:
Following are the three types of muscles:
(i) Striated muscles: They are located in the limbs, body wall, face, neck, etc. They also form in tongue, pharynx, diaphragm, and upper part of oesophagus as visceral striated muscles.
(ii) Smooth muscles: They are found in the walls of the hollow visceral organs except in heart and are called as visceral muscles. They form in alimentary canal, ducts of glands, urogenital ducts, blood vessels, bronchi, iris of eye, etc.
(iii) Cardiac muscles: They are located in the walls of the heart.
Question 13:
In which tissue is found anyone of the following structures : neuron, dendrite, cilia, collagen fibres, elastin fibre.
Answer:
Neuron and dendrite are found in nervous tissue.
Cilia is found in ciliated epithelial tissue.
Collagen fibres and elastin fibres are found in loose, connective tissue.
Question 14:
List one function for each of following : osteoblast, chondroblast, goblet cell, neuron, muscle cell.
Answer:
(a) Osteoblast or bone cells are involved in the process of bone formation.
(b) Chondroblast produces and maintains the matrix of cartilage.
(c) Goblet cells perform the function of secreting mucus in the body.
(d) Neuron conducts impulses to different parts of the body.
(e) Muscle cells are responsible for bringing about the movement of body or limbs by contraction and relaxation of contractile proteins that are present in them.
Question 15:
State two characteristics of nerve cells.
Answer:
Characteristics of nerve cells:
(i) It consists of three parts—that is, cyton or cell body, dendron, and axon. All the three parts are further composed of many subparts.
(ii) Nerve cell is involved in transmitting or conducting the impulses (signals) to different parts of the body.
Question 16:
What is the function of bone, cartilage and ligament?
Answer:
Function of bone:
Bone provides shape and skeletal support to the body. It also protects the vital body organs and serves as a storage site of calcium and phosphate.
Function of cartilage:
Cartilage provides support and flexibility to the body parts and smoothens the surface at joints.
Function of ligament:
Ligament strengthens the joint and permits normal movement and prevents over-flexing and over-extension.
Question 17:
Name the following :
(a) Tissue which stores fat ;(b) Epithelium which lines lung alveoli.
Answer:
(a) Adipose tissue stores fat.
(b) Squamous epithelium lines lung alveoli.
Question 18:
Give three functions of blood.
Answer:
Functions of blood:
(i) It transports nutrients, hormones, and vitamins to the tissues and excretory products from tissues to the liver and kidney.
(ii) RBCs carry oxygen to the tissues for oxidation of food.
(iii) WBCs destroy the pathogens that enter our body.
(iv) Blood platelets disintegrate at the site of injury and help in blood clotting.
Question 19:
What are the different tissues in animals.
Answer:
There four types of tissues that are found in animals are as follows:
1. Epithelial tissue: It is further subdivided into squamous, cuboidal, columnar, and ciliated epithelial tissue.
2. Muscular tissue: It has three subtypes—that is, striated, smooth, and cardiac muscles.
3. Connective tissue: It has four subdivisions—that is, areolar, adipose, skeletal, and fluid connective tissue.
4. Nervous tissue: It is composed of nerve cells.
Question 20:
Draw and label a neuron.
Answer:
Diagram showing a neuron
Question 21:
Diagrammatically show the difference in three types of muscle fibres.
Answer:
| Striated Muscle | Smooth Muscle | Cardiac Muscle |
|
|
|
Page No 170:Long Answer Questions
Question 1:
What are different types of tissues in plants? Describe simple tissues.
Answer:
Plant tissues are divided into two broad categories:
(i) Meristematic tissue: It is further subdivided into apical, lateral, and intercalary meristems.
(ii) Permanent tissue: They are of two types.
(a) Simple permanent tissues include parenchyma, collenchyma, and sclerenchyma.
(b) Complex tissues include xylem and phloem.
Simple tissue:
These tissues are composed structurally and functionally of similar cells.
They are of three types.
(i) Parenchyma:
It is widely distributed in plant bodies such as stems, roots, leaves, flowers, and fruits. Its cells are isodiametric and contains live protoplasm. It serves as a food storage and packing tissue. It also stores waste products of plants.
(ii) Collenchyma:
It is located below the epidermis of dicot stem and petiole. It consists of living cells and is characterised by an extra deposition of cellulose at the corners. It is a mechanical tissue in young plants. It also provide elasticity to the plant, particularly stem of dicots.
(iii) Sclerenchyma:
It consists of dead lignified cells. It occurs in abundance or in patches in definite layers in stems, roots, veins of leaves, hard covering of seeds, and nuts. It provides mechanical support to the plant.
Question 2:
What are meristematic tissues? Explain with the help of suitable diagram. Give their classification on the basis of their position in the plant body.
Answer:
Meristematic tissue consists of cells that are capable of division and possesses totipotency—that is, capability to give rise to all cell types of the body. Its cells divide and help in increasing the length and girth of the plant.
The meristematic cells are compactly arranged and have thin cellulosic cell walls. They occur in growing regions of the plant. They are responsible for the formation of new cells of the plants and also heal the injured parts of the plants.
Meristematic tissues are classified into following three types depending upon their position in the plant body:
(i) Apical meristems: They are present at the tip of stems (shoot apex) and roots (root apex) and also in apices of leaves. They bring about elongation of root and stems; hence, they cause an increase in the length of the plant.
(ii) Lateral meristems: They are found beneath the bark and in vascular bundles of dicot stems and roots. They increase the diameter of stems and roots and the girth of the plant.
(iii) Intercalary meristems: They are located at the base of leaves or internodes. They increase the length of leaves and internodes.
Question 3:
What is simple tissue? Classify and explain its different types with suitable diagram.
Answer:
Simple tissue:
These tissues are composed of structurally and functionally similar cells.
They are of three types.
(i) Parenchyma:
It is widely distributed in plant bodies such as stems, roots, leaves, flowers, and fruits. Its cells are isodiametric and contains live protoplasm. It serves as a food storage and packing tissue. It also stores waste products of plants.
(ii) Collenchyma:
It is located below the epidermis of dicot stem and petiole. It consists of living cells and is characterised by an extra deposition of cellulose at the corners. It is a mechanical tissue in young plants. It also provides elasticity to the plant, particularly stem of dicots.
(iii) Sclerenchyma:
It consist of dead lignified cells. It has two types of cells—that is, fibres and sclereids. It occurs in abundance or in patches in definite layers in stems, roots, veins of leaves, hard covering of seeds, and nuts. It provides mechanical support to the plant.
Question 4:
What do you know about complex tissue? Classify and explain its different types in plants with suitable diagrams.
Answer:
Complex tissues:
The complex tissues consist of more than one type of cells having a common origin. These tissues are involved in transporting water, mineral salts (nutrients), and food materials to various parts of plant.
The complex tissues are of following two types:
1. Xylem:
It is a conducting tissue composed of cells of four different types—that is, tracheids, vessels, xylem parenchyma, and xylem fibre. Except xylem parenchyma, all other xylem components are dead and lignified. Tracheids and vessels are involved in the conduction of water. Xylem parenchyma stores food and helps in lateral conduction of water.
2. Phloem:
It is also a conducting tissue and consists of four elements—that is, sieve tubes, companion cells, phloem parenchyma, and phloem fibres. Except phloem fibres, all phloem elements are living. Sieve tubes and companion cells work as a single unit.
Phloem transports photosynthetically prepared food materials from the leaves to the storage organs and later from storage organs to the growing regions of the plant body.
Question 5:
Distinguish between the following pairs in one or two sentences for each
(a) RBCs and WBCs;(b) bone and cartilage;
(c) blood and lymph;(d) striated and unstriated muscles;
(e) tendon and ligament;(f) axon and dedrite.
Answer:
(a)
| RBCs | WBCs |
| They are red in colour. | They are colourless. |
| Their number is 4–6 million/mm3. | Their number is 6,000–9,000 million/mm3. |
| The cells contain haemoglobin. | The cells lack haemoglobin. |
(b)
| Bone | Cartilage |
| They are hard and flexible. | They are flexible. |
| They are porous. | They are non-porous. |
| They contain blood vessels. | They lack blood vessels. |
(c)
| Blood | Lymph |
| It is red in colour. | It is colourless. |
| RBCs are present. | RBCs are absent. |
| It transports nutrients, hormones, and vitamins to the tissues. | It transports nutrients (oxygen and glucose) that may have been filtered out of blood capillaries back into the bloodstream. |
(d)
| Striated Muscles | Unstriated Muscles |
| They are cylindrical. | They are spindle-shaped. |
| They help in locomotion. | They help in rhythmic contraction of the internal organs. |
(e)
| Tendon | Ligament |
| It is inelastic. | It is elastic. |
| It connects muscles to bones. | It connects two bones. |
| It is made up of white fibres. | It is made up of white and yellow fibres. |
(f)
| Axon | Dendrite |
| It is long and uniformly thickened. | It is a short tapering process of a neuron. |
| A sheath is present. | Sheath is absent. |
| It lacks Nissl's granules. | It contains Nissl's granules. |
Question 6:
Describe the structure and functions of epithelium.
Answer:
Epithelium is the simplest animal tissue that functions as a protective tissue in the animal body. Epithelial cells are tightly packed and contain very little or no matrix. It covers most of the organs and cavities within the body. It also forms a barrier to keep different body systems separate. The skin and lining of buccal cavity, blood vessels, alveoli, and kidney tubules are made of epithelial tissue. Epithelial cells lie on a delicate non-cellular basement membrane that contains a special form of matrix protein known as collagen.
Epithelium may be simple (composed of a single layer of cells) or stratified (made up of several layers of cells).
Epithelial tissue is classified into following four types depending upon the shape and function of its cells:
(a) Squamous epithelium.
(b) Cuboidal epithelium.
(c) Columnar/glandular epithelium.
(d) Ciliated epithelium.
The main functions of epithelial tissue are as follows:
(i) It forms the outer layer of skin and protects the underlying cells from drying, injury, and chemical effects.
(ii) It forms the lining of mouth and alimentary canal and protects these organs.
(iii) It helps in elimination of waste products.
(iv) It helps in absorption of water and nutrients.
Question 7:
Classify connective tissue and give one example of each type.
Answer:
Connective tissues are specialised to connect and anchor various body organs. Connective tissues are classified into following five types:
(i) Aerolar or loose connective tissue:
Its matrix consists of white collagen fibres and yellow elastin fibres. It joins skin to muscles, fills spaces inside organs, and is found around muscles, blood vessels, and nerves. It acts as a supporting tissue between organs lying in the body cavity and also helps in the repair of tissues after injury.
(ii) Dense regular connective tissue:
It is a fibrous connective tissue characterised by ordered and densely packed collection of fibres and cells. It consist of:
(a) Tendons: They join skeletal muscles to bones.
(b) Ligaments: They connect two bones.
(c) Aponeuroses: They cover and form terminations and attachments of various muscles.
(iii) Adipose connective tissue:
It is an aggregation of fat cells or adipocytes. It is located below the skin and between the internal organs and in yellow bone marrow. Its main function is to store fat.
(iv) Skeletal connective tissue:
It includes cartilage and bone.
Cartilage is located in ear pinna, nose tip, epiglottis, intervertebral discs, end of long bones, lower ends of ribs, and rings of trachea. It provides support and flexibility to the body parts.
Bone forms the endoskeleton in vertebrates except shark. Its main function is to provide shape and skeletal support to the body.
(v) Fluid connective tissue:
It includes blood and lymph.
Blood transports nutrients, hormones, and vitamins to the tissues and transports excretory products from the tissues to liver and kidney.
Lymph is a colourless fluid that transports nutrients (oxygen and glucose) that may have been filtered out of the blood capillaries back into the bloodstream to be recirculated in the body.
Question 8:
Describe the composition and functions of blood.
Answer:
Blood is a fluid connective tissue. In blood, cells move in a medium called blood plasma. It is composed of following three types of blood cells:
(a) RBCs (red blood corpuscles) or erythrocytes.
(b) WBCs (white blood cells) or leucocytes.
(c) Platelets.
RBCs and WBCs are living cells, while plasma and platelets are non-living cells.
Blood plasma is a complex fluid consisting of inorganic salts and organic compounds. Albumins, globulins, fibrinogen, glucose, amino acids, lipids, enzymes, hormones, and waste materials are the organic substance of plasma.
WBCs consist of phagocytes (granulocytes and agranular leucocytes) and immunocytes.
Draw figure 3.34 from page no. 141 P.S.Verma and V.K.Aggarwal -grade 9 (biology)
Functions of blood:
(i) It transports nutrients, hormones, and vitamins to the tissues.
(ii) It transports excretory products from the tissues to the liver and kidney.
(iii) The RBCs carry oxygen to the tissues for the oxidation of food.
(iv) WBCs fight against diseases either by engulfing foreign bodies or by producing antioxidants and antibodies.
(v) Blood platelets help in clotting the blood at the site of injury.
Question 9:
Define muscular tissue. Classify and explain different types of muscles with the help of suitable diagrams.
Answer:
Contractile tissue is made up of muscle cells or muscle fibres. The muscle cells bring about the movements of body or limbs by contraction and relaxation of contractile proteins located in the muscle cells.
On the basis of location, structure, and function of muscle cells, muscle tissue is classified into following three types:
1. Striated muscles:
These are also referred to as voluntary muscles, because they work according to our will. The striated muscle fibres are elongated, non-tapering, cylindrical, and unbranched, and each fibre is enclosed in a thin plasma membrane called sarcolemma. These are located in the muscle of the limbs, body wall, face, neck, etc. Striated muscles provide the force for locomotion and all other voluntary movements of the body.
2. Smooth muscles:
They are also referred to as involuntary muscles, as they do not work according to our will. The smooth muscle cells are spindle-shaped and held together via loose connective tissue. Myofibrils are contractile threads that run longitudinally throughout the cell. They are located in the walls of hollow visceral organs (except heart) such as walls of alimentary canal, ducts of glands, urogenital ducts, and blood vessels. The peristaltic movements of gastrointestinal tract are brought about by smooth muscle cells.
3. Cardiac muscles:
They consist of branched fibres that join to form a network. Each cells consist of myofibrils and sarcolemma. They are located in the walls of the heart. The contraction and relaxation of these muscles help the heart to pump blood and distribute it to different parts of the body.
Question 10:
Explain the structure of neuron with the help of a labelled diagram.
Answer:
Structure of neuron:
A neuron is the building material of the nervous tissue. Neurons are involved in conducting impulses to different parts of the body on receiving an external or internal stimuli. It consists of the following three parts:
(i) Cyton:
It refers to the cell body of neuron and is composed of nucleus and cytoplasm. Clumps of ribosomes called Nissl's granules are distributed in its cytoplasm.
(ii) Dendron:
They are short processes that arise from the cell body. They get further branched into dendrites.
(iii) Axon (nerve fibre):
It is the long and cylindrical part of the cell that forms fine branches terminally. Each branch of axon is swollen at an end, forming a synaptic knob (bouton) that contains acetylcholine (neurotransmitter) filled vesicles.