CBSE Class 9 Science Tissues Sure Shot Questions Set 03

CBSE Class 9 Science Tissues Sure Shot Questions C. There are many more useful educational material which the students can download in pdf format and use them for studies. Study material like concept maps, important and sure shot question banks, quick to learn flash cards, flow charts, mind maps, teacher notes, important formulas, past examinations question bank, important concepts taught by teachers. Students can download these useful educational material free and use them to get better marks in examinations.  Also refer to other worksheets for the same chapter and other subjects too. Use them for better understanding of the subjects.

ASSIGNMENT QUESTIONS SET - 3
CLASS 9 SCIENCE : CHAPTER - 6 TISSUES

1. Which of the following tissues has dead cells?
(a) Parenchyma
(b) Sclerenchyma
(c) Collenchyma
(d) Epithelial tissue

Answer: (b) Sclerenchyma

1. Sclerenchyma cells have thick, lignified secondary walls, and they are dead at maturity.
2. Parenchyma, collenchyma and epithelial tissue are made of living cells.

Teacher's Note:
a) Sclerenchyma gives mechanical strength, and its cells lose their protoplasm.
b) Living plant tissues such as parenchyma and collenchyma are a common confusion here.

2. Find out incorrect sentence
(a) Parenchymatous tissues have intercellular spaces
(b) Collenchymatous tissues are irregularly thickened at corners
(c) Apical and intercalary meristems are permanent tissues
(d) Meristematic tissues, in its early stage, lack vacuoles

Answer: (c) Apical and intercalary meristems are permanent tissues

1. Apical and intercalary meristems are meristematic, that is, dividing tissues.
2. Permanent tissues are formed when meristematic cells stop dividing, so statement (c) is wrong.

Teacher's Note:
a) Parenchyma has intercellular spaces, and collenchyma is thickened at the corners, so (a) and (b) are correct.
b) Meristematic cells in the early stage have small or no vacuoles, so (d) is correct.

3. Girth of stem increases due to
(a) apical meristem
(b) lateral meristem
(c) intercalary meristem
(d) vertical meristem

Answer: (b) lateral meristem

1. Lateral meristem, or cambium, adds cells to the sides of the stem.
2. This increases the girth (thickness) of the stem.

Teacher's Note:
a) Apical and intercalary meristems increase length, not girth.

4. Which cell does not have perforated cell wall?
(a) Tracheids
(b) Companion cells
(c) Sieve tubes
(d) Vessels

Answer: (a) Tracheids

1. Vessels have perforated end walls, forming a perforation plate.
2. Sieve tubes have perforated sieve plates, which are also perforated walls.
3. Tracheids have pits, not perforations, so they do not have perforated walls.

Teacher's Note:
a) Companion cells also lack a sieve plate, but they are not a xylem element and are not the usual answer for this question.
b) Look for the word perforation: sieve tubes and vessels have it, tracheids do not.

5. Intestine absorb the digested food materials. What type of epithelial cells are responsible for that?
(a) Stratified squamous epithelium
(b) Columnar epithelium
(c) Spindle fibres
(d) Cuboidal epithelium

Answer: (b) Columnar epithelium

1. The lining of the small intestine is made of tall, column-like cells with microvilli.
2. These tall cells give a large surface area for absorbing digested food.

Teacher's Note:
a) Spindle fibres are part of cell division, not epithelial tissue.
b) Stratified squamous epithelium is protective, not absorptive.

6. A person met with an accident in which two long bones of hand were dislocated. Which among the following may be the possible reason?
(a) Tendon break
(b) Break of skeletal muscle
(c) Ligament break
(d) Areolar tissue break

Answer: (c) Ligament break

1. Ligaments join bone to bone at a joint and hold the bones in place.
2. When ligaments break, the bones can move out of position, which is a dislocation.

Teacher's Note:
a) Tendons join muscle to bone, so a tendon break does not dislocate bones.
b) Areolar tissue fills spaces and does not hold bones together.

7. While doing work and running, you move your organs like hands, legs etc. Which among the following is correct?
(a) Smooth muscles contract and pull the ligament to move the bones
(b) Smooth muscles contract and pull the tendons to move the bones
(c) Skeletal muscles contract and pull the ligament to move the bones
(d) Skeletal muscles contract and pull the tendon to move the bones

Answer: (d) Skeletal muscles contract and pull the tendon to move the bones

1. Limb movement is voluntary, so it is produced by skeletal muscles.
2. Skeletal muscles are attached to bones by tendons, and their contraction pulls the tendon to move the bone.

Teacher's Note:
a) Smooth muscles are not attached to bones and work involuntarily.
b) Ligaments join bones to bones, not muscles to bones.

8. Which muscles act involuntarily?
(i) Striated muscles
(ii) Smooth muscles
(iii) Cardiac muscles
(iv) Skeletal muslces

Answer: (b) (ii) and (iii)

1. Smooth muscles work involuntarily, for example in the stomach and intestine.
2. Cardiac muscles work involuntarily, for example in the heart.

Teacher's Note:
a) Striated and skeletal muscles are the same type, and they work voluntarily.
b) The word skeletal is misspelt as "muslces" in the printed question.

9. Meristematic tissues in plants are
(a) localised and permanent
(b) not limited to certain regions
(c) localised and dividing cells
(d) growing in volume

Answer: (c) localised and dividing cells

1. Meristematic tissues are found at specific regions of the plant, such as root tips and shoot tips.
2. Their cells keep dividing, which is why they are called dividing tissues.

Teacher's Note:
a) Permanent tissues are not meristematic, so option (a) is wrong.

10. Which is not a function of epidermis?
(a) Protection from adverse condition
(b) Gaseous exchange
(c) Conduction of water
(d) Transpiration

Answer: (c) Conduction of water

1. The epidermis protects the plant body and allows gaseous exchange through stomata.
2. It also takes part in transpiration through stomata, but conduction of water is done by xylem.

Teacher's Note:
a) Water is conducted through xylem vessels and tracheids, not through the epidermis.

11. Select the incorrect sentence
(a) Blood has matrix containing proteins, salts and hormones
(b) Two bones are connected with ligament
(c) Tendons are non-fibrous tissue and fragile
(d) Cartilage is a form of connective tissue

Answer: (c) Tendons are non-fibrous tissue and fragile

1. Tendons are made of dense, strong fibrous connective tissue, so they are not non-fibrous or fragile.
2. The other statements are correct: blood plasma contains proteins, salts and hormones, bones are joined by ligaments, and cartilage is a connective tissue.

Teacher's Note:
a) Tendons are strong, which is needed to transmit the force of muscle contraction.
b) Look for the word "fibrous" when comparing tendons and ligaments.

12. Cartilage is not found in
(a) nose
(b) ear
(c) kidney
(d) larynx

Answer: (c) kidney

1. Cartilage is found in the nose, the external ear and the larynx.
2. The kidney is made of kidney tissues and does not contain cartilage.

Teacher's Note:
a) Cartilage is flexible and supports structures such as the nose and the windpipe.
b) Cartilage is not found in the kidney or in the bones of a grown person, except at the joints.

13. Fats are stored in human body as
(a) cuboidal epithelium
(b) adipose tissue
(c) bones
(d) cartilage

Answer: (b) adipose tissue

1. Adipose tissue is a connective tissue whose cells store fat.
2. It is found under the skin and between internal organs.

Teacher's Note:
a) Cuboidal epithelium covers and lines surfaces, not stores fat.
b) Adipose tissue also acts as an insulator and a cushion.

14. Bone matrix is rich in
(a) fluoride and calcium
(b) calcium and phosphorus
(c) calcium and potassium
(d) phosphorus and potassium

Answer: (b) calcium and phosphorus

1. Bone matrix contains calcium phosphate, which makes bone hard.
2. Calcium and phosphorus are the main minerals in bone.

Teacher's Note:
a) Potassium is not a major mineral of bone matrix.
b) The hardness of bone comes from these minerals, while collagen fibres give it flexibility.

15. Contractile proteins are found in
(a) bones
(b) blood
(c) muscles
(d) cartilage

Answer: (c) muscles

1. Contractile proteins, actin and myosin, are present in muscle fibres.
2. Their interaction makes the muscle contract.

Teacher's Note:
a) Contractile proteins are the reason muscles can shorten and pull on bones.

16. Voluntary muscles are found in
(a) alimentary canal
(b) limbs
(c) iris of the eye
(d) bronchi of lungs

Answer: (b) limbs

1. Voluntary muscles are skeletal muscles, which move the limbs.
2. The alimentary canal, iris and bronchi have involuntary smooth muscles.

Teacher's Note:
a) Voluntary muscles are under conscious control.
b) The iris controls the size of the pupil without conscious effort.

17. Nervous tissue is not found in
(a) brain
(b) spinal cord
(c) tendons
(d) nerves

Answer: (c) tendons

1. Nervous tissue is found in the brain, the spinal cord and the nerves.
2. Tendons are made of fibrous connective tissue and contain no nervous tissue.

Teacher's Note:
a) Nervous tissue carries electrical impulses.
b) Tendons attach muscles to bones and are not part of the nervous system.

18. Nerve cell does not contain
(a) axon
(b) nerve endings
(c) tendons
(d) dendrites

Answer: (c) tendons

1. A nerve cell (neuron) has dendrites, which receive signals, and an axon, which carries signals away.
2. Its axon ends in nerve endings, while tendons are a connective tissue outside the nerve cell.

Teacher's Note:
a) Dendrites receive impulses and axons send them on.
b) Tendons are connective tissue, not a part of the nerve cell.

19. Which of the following helps in repair of tissue and fills up the space inside the organ?
(a) Tendon
(b) Adipose tissue
(c) Areolar
(d) Cartilage

Answer: (c) Areolar

1. Areolar tissue is a loose connective tissue that fills the spaces inside organs.
2. It also helps in repairing damaged tissues.

Teacher's Note:
a) Adipose tissue stores fat, but it does not mainly repair tissues.
b) Areolar tissue is found under the skin and around blood vessels and nerves.

20. The muscular tissue which function throughout the life continuously without fatigue is
(a) skeletal muscle
(b) cardiac muscle
(c) smooth muscle
(d) voluntary muscle

Answer: (b) cardiac muscle

1. Cardiac muscle works continuously throughout life without tiring.
2. It is found only in the heart and works involuntarily.

Teacher's Note:
a) Skeletal muscles tire with prolonged use.
b) Smooth muscles work involuntarily but are not found in the heart.

21. Which of the following cells is found in the cartilaginous tissue of the body?
(a) Mast cells
(b) Basophils
(c) Osteocytes
(d) Chondrocytes

Answer: (d) Chondrocytes

1. Chondrocytes are the cells found in cartilage.
2. Osteocytes are found in bone, and mast cells and basophils are blood or connective tissue cells.

Teacher's Note:
a) Chondro- refers to cartilage, and osteo- refers to bone.

22. The dead element present in the phloem is
(a) companion cells
(b) phloem fibres
(c) phloem parenchyma
(d) sieve tubes

Answer: (b) phloem fibres

1. Phloem fibres are sclerenchymatous cells with thick walls, and they are dead at maturity.
2. Companion cells, phloem parenchyma and sieve tubes are living cells.

Teacher's Note:
a) Sieve tube cells lose their nucleus but remain living, so they are not the dead element here.
b) Phloem fibres give strength to the phloem tissue.

23. Which of the following does not lose their nucleus at maturity?
(a) Companion cells
(b) Red blood cells
(c) Vessel
(d) Sieve tube cells

Answer: (a) Companion cells

1. Companion cells keep their nucleus at maturity and help the sieve tube cells.
2. Mature red blood cells, vessels and sieve tube cells all lose their nucleus.

Teacher's Note:
a) Companion cells control the metabolism of the sieve tube cells that lack a nucleus.

24. In desert plants, rate of water loss gets reduced due to the presence of
(a) cuticle
(b) stomata
(c) lignin
(d) suberin

Answer: (a) cuticle

1. The cuticle is a thick waterproof layer on the epidermis.
2. It reduces transpiration, which reduces the loss of water in desert plants.

Teacher's Note:
a) Stomata open to the air and increase water loss, so option (b) is wrong.
b) Lignin and suberin are not the main barriers to water loss in leaves.

25. A long tree has several branches. The tissue that helps in the side ways conduction of water in the branches is
(a) collenchyma
(b) xylem parenchyma
(c) parenchyma
(d) xylem vessels

Answer: (b) xylem parenchyma

1. Xylem parenchyma cells are living cells that store food and help in the sideways (lateral) movement of water.
2. Xylem vessels carry water mainly upwards, along their length.

Teacher's Note:
a) Collenchyma gives flexibility and does not conduct water.
b) Lateral conduction of water is one of the special roles of xylem parenchyma.

26. If the tip of sugarcane plant is removed from the field, even then it keeps on growing in length. It is due to the presence of
(a) cambium
(b) apical meristem
(c) lateral meristem
(d) intercalary meristem

Answer: (d) intercalary meristem

1. Sugarcane grows in length from intercalary meristem located at the nodes, at the base of each internode.
2. Because the growing region is not at the tip, the plant keeps growing even when the tip is removed.

Teacher's Note:
a) Apical meristem is at the tip, so removing the tip would remove it.
b) Cambium and lateral meristem increase girth, not length.

27. A nail is inserted in the trunk of a tree at a height of 1 metre from the ground level. After 3 years the nail will
(a) move downwards
(b) move upwards
(c) remain at the same position
(d) move sideways

Answer: (c) remain at the same position

1. A tree grows in length only at its tips, through apical meristem.
2. Its trunk grows in girth by adding new layers at the cambium, which does not lift the nail above the ground.

Teacher's Note:
a) The nail stays at the same height because the part of the trunk at that height does not stretch upwards.
b) The nail gets pushed outward as the trunk thickens, but its height does not change.

28. Parenchyma cells are
(a) relatively unspecified and thin walled
(b) thick walled and specialised
(c) lignified
(c) none of these

Answer: (a) relatively unspecified and thin walled

1. Parenchyma cells are living, relatively unspecialised and have thin cellulose walls.
2. Thick-walled, specialised and lignified cells are typical of sclerenchyma.

Teacher's Note:
a) The printed options repeat the letter (c) twice; the lignified option is the second (c) and the last option is none of these.
b) Parenchyma is the most common ground tissue in the plant body.

29. Flexibility in plants is due to
(a) collenchyma
(b) sclerenchyma
(c) parenchyma
(d) chlorenchyma

Answer: (a) collenchyma

1. Collenchyma has living cells with unevenly thickened cellulose walls, which allow bending.
2. Sclerenchyma gives rigidity and strength, not flexibility.

Teacher's Note:
a) Young stems and leaf stalks are flexible because of collenchyma.
b) Chlorenchyma is parenchyma with chloroplasts, used for photosynthesis.

30. Cork cells are made impervious to water and gases by the presence of
(a) cellulose
(b) lipids
(c) suberin
(d) lignin

Answer: (c) suberin

1. Cork cell walls are impregnated with suberin, a waterproof fatty substance.
2. Suberin makes the cork impervious to water and gases.

Teacher's Note:
a) Lignin strengthens cell walls but is not the substance that makes cork impervious.
b) Cellulose is the normal wall material and does not block water or gases.

31. Survival of plants in terrestrial environment has been made possible by the presence of
(a) intercalary meristem
(b) conducting tissue
(c) apical meristem
(d) parenchymatous tissue

Answer: (b) conducting tissue

1. On land, plants must transport water and minerals from the soil to all parts of the body.
2. Xylem and phloem, the conducting tissues, make this transport possible.

Teacher's Note:
a) Aquatic plants can take in water directly from their surroundings, so they need less conducting tissue.
b) Meristems grow the plant, but they do not carry materials.

32. Choose the wrong statement
(a) The nature of matrix differs according to the function of the tissue
(b) Fats are stored below the skin and in between the internal organs
(c) Epithelial tissues have intercellular spaces between them
(d) Cells of striated muscles are multinucleate and unbranched

Answer: (c) Epithelial tissues have intercellular spaces between them

1. Epithelial cells are closely packed with very little intercellular space.
2. Statements (a), (b) and (d) are correct.

Teacher's Note:
a) Parenchymatous tissue, not epithelium, is the tissue that has intercellular spaces in plants.
b) Striated muscle fibres are long, unbranched and contain many nuclei.

33. Animals of colder regions and fishes of cold water have thicker layer of subcutaneous fat. Describe why?

Answer:
1. Subcutaneous fat lies under the skin and is a poor conductor of heat.
2. A thicker layer of this fat reduces the loss of body heat to the cold surroundings.
3. The fat also acts as an energy store, which is useful when food is scarce in winter.

Teacher's Note:
a) Fat acts as an insulating layer, similar to a blanket, for animals in cold regions.
b) Stored fat also provides energy during long periods without food.

34. The water conducting tissue generally present in gymnosperm is
(a) vessels
(b) sieve tube
(c) tracheids
(d) xylem fibres

Answer: (c) tracheids

1. Gymnosperms mainly have tracheids as their water-conducting elements.
2. Vessels are found in most angiosperms, while sieve tubes conduct food.

Teacher's Note:
a) Xylem fibres give support, and they do not conduct water.

35. Match the column (A) with the column (B)

Answer:
1. (a) - (v) Blood
2. (b) - (iv) Areolar tissue
3. (c) - (iii) Skeletal muscle
4. (d) - (i) Subcutaneous layer
5. (e) - (ii) Cartilage
6. (f) - (vi) Skin

Teacher's Note:
a) Blood is a fluid connective tissue, with plasma as its matrix.
b) Adipose tissue lies in the subcutaneous layer, so the two are matched in that way.
c) Cartilage covers the surfaces of joints, which reduces friction.

36. Match the column (A) with the column (B)

Answer:
1. (a) - (i) Thin walled, packing cells
2. (b) - (ii) Carbon fixation
3. (c) - (iv) Buoyancy
4. (d) - (iii) Localized thickenings
5. (e) - (v) Sclerenchyma

Teacher's Note:
a) Photosynthesis and carbon fixation both take place in chloroplasts of green parenchyma.
b) Aerenchyma has large air spaces, which keep aquatic plants afloat.
c) Sclerenchyma is a permanent tissue, so it matches item (e).

37. If a potted plant is covered with a glass jar, water vapours appear on the wall of glass jar. Explain why?

Answer:
1. The plant loses water as vapour from its leaves through transpiration.
2. The water vapour rises inside the jar and condenses on its cooler glass wall.
3. Therefore water droplets appear on the inner wall of the glass jar.

Teacher's Note:
a) Transpiration is the loss of water vapour from aerial parts of the plant, mainly the leaves.
b) The glass is cooler than the air inside the jar, which makes the vapour condense.

38. Name the different components of xylem and draw a living component?

Answer:
1. The components of xylem are tracheids, xylem vessels, xylem parenchyma and xylem fibres.
2. The living component is xylem parenchyma.
3. Diagram: [Figure: diagram to be added] of xylem parenchyma, showing thin cellulose walls, a nucleus and a large central vacuole.

Teacher's Note:
a) Tracheids, vessels and xylem fibres are dead at maturity.
b) Xylem parenchyma stores food and helps in sideways conduction of water.

39. Draw and identify different elements of phloem.

Answer:
1. The elements of phloem are sieve tubes, companion cells, phloem parenchyma and phloem fibres.
2. Diagram: [Figure: diagram to be added] showing a sieve tube with its sieve plates, a companion cell beside it, phloem parenchyma and phloem fibres, each labelled.

Teacher's Note:
a) Sieve tubes have perforated sieve plates and lack a nucleus at maturity.
b) Companion cells keep their nucleus and help the sieve tubes.

40. Write true (T) or false (F)
(a) Epithelial tissue is protective tissue in animal body.
(b) The lining of blood vessels, lung alveoli and kidney tubules are all made up of epithelial tissue.
(c) Epithelial cells have a lot of intercellular spaces.
(d) Epithelial layer is permeable layer.
(e) Epithelial layer does not allow regulation of materials between body and external environment.

Answer:
1. (a) T
2. (b) T
3. (c) F
4. (d) T
5. (e) F

Teacher's Note:
a) Epithelial cells are tightly packed, so they have very little intercellular space.
b) An epithelial layer selectively allows materials to pass, such as absorption in the intestine, and regulates exchange with the environment.

41. Differentiate between voluntary and involuntary muscles. Give one example of each type.

Answer:

Teacher's Note:
a) Voluntary muscles tire quickly with long use, while involuntary muscles keep working.
b) The heart is an involuntary muscle, but it is cardiac muscle, not smooth muscle.

42. Water hyacinth float on water surface. Explain.

Answer:
1. The leaves and stalks of water hyacinth contain large air-filled spaces called aerenchyma.
2. These air spaces make the plant light, so it floats on the water surface.

Teacher's Note:
a) Aerenchyma is a permanent tissue with large intercellular air spaces.
b) The buoyancy also helps the plant to receive sunlight on the water surface.

43. Which structure protects the plant body against the invasion of parasites?

Answer: The epidermis, with its waxy cuticle, protects the plant body against the invasion of parasites and other harmful organisms.

Teacher's Note:
a) The cuticle is a waxy waterproof layer on the outer surface of the epidermis.
b) Epidermis also protects against water loss and mechanical damage.

44. Differentiate the following activities on the basis of voluntary (V) or involuntary (IV) muscles.
(a) Jumping of frog
(b) Pumping of the heart
(c) Writing with hand
(d) Movement of chocolate in your intestine

Answer:
1. (a) Jumping of frog: V
2. (b) Pumping of the heart: IV
3. (c) Writing with hand: V
4. (d) Movement of chocolate in your intestine: IV

Teacher's Note:
a) Jumping and writing are controlled by skeletal muscles, which are voluntary.
b) Movement of food through the intestine is peristalsis, which is done by smooth muscles.

45. Fill in the blanks
(a) Lining of blood vessels is made up of ______.
(b) Lining of small intestine is made up of ______.
(c) Lining of kidney tubules is made up of ______.
(d) Epithelial cells with cilia are found in ______ of our body.

Answer:
1. (a) simple squamous epithelium
2. (b) simple columnar epithelium
3. (c) cuboidal epithelium
4. (d) the respiratory tract (for example, the trachea)

Teacher's Note:
a) Flat, thin squamous cells allow quick diffusion across the blood vessel wall.
b) Columnar cells with microvilli give a large surface for absorption in the small intestine.
c) The cilia beat to move mucus and trapped dust out of the airway.

46. Fill in the blanks
(a) Cork cells possesses ______ on their walls that makes it impervious to gases and water.
(b) ______ have tubular cells with perforated walls and are living in nature.
(c) Bone possesses a hard matrix composed of ______ and ______.

Answer:
1. (a) suberin
2. (b) sieve tubes
3. (c) calcium and phosphorus

Teacher's Note:
a) Suberin is a waxy, waterproof substance deposited in cork cell walls.
b) Sieve tubes are living at maturity, even though they have no nucleus.

47. Why is epidermis important for the plants?

Answer:
1. It protects the inner tissues from mechanical injury and from attack by pathogens.
2. Its cuticle reduces water loss by transpiration.
3. Stomata in the epidermis allow gaseous exchange.

Teacher's Note:
a) The epidermis is a single layer of cells on the outer surface of the plant.
b) Guard cells control the opening and closing of stomata.

48. Fill in the blanks
(a) ______ are forms of complex tissue.
(b) ______ have guard cells.
(c) Cells of cork contain a chemical called ______.
(d) Husk of coconut is made of ______ tissue.
(e) ______ gives flexibility in plants.
(f) ______ and ______ are both conducting tissues.
(g) Xylem transports ______ and ______ from soil.
(h) Phloem transport ______ from ______ to other parts of the plant.

Answer:
1. (a) Xylem and phloem
2. (b) Stomata (the epidermis with its guard cells)
3. (c) suberin
4. (d) sclerenchyma
5. (e) collenchyma
6. (f) Xylem and phloem
7. (g) water and minerals
8. (h) food (prepared sugars) from the leaves

Teacher's Note:
a) Complex tissues are made of more than one type of cell.
b) Sclerenchyma gives strength to the husk of coconut, which is why it is hard to pull out.

49. Differentiate between sclerenchyma and parenchyma tissues. Draw well labelled diagram.

Answer:

Diagram: [Figure: diagram to be added] showing a sclerenchyma cell with thick walls and a parenchyma cell with a thin wall, a large vacuole and a nucleus, each labelled.

Teacher's Note:
a) Sclerenchyma cells have thick walls and a small lumen.
b) Parenchyma cells are the least specialised plant cells.

50. Describe the structure and function of different types of epithelial tissues. Draw diagram of each type of epithelial tissue.

Answer:
1. Squamous epithelium: a single layer of thin, flat cells, which allows diffusion and filtration. It lines blood vessels and alveoli.
2. Cuboidal epithelium: cube-shaped cells that secrete and absorb substances. It lines kidney tubules.
3. Columnar epithelium: tall, column-like cells that absorb and secrete. It lines the small intestine.
4. Ciliated epithelium: cells with hair-like cilia that beat to move mucus or fluid. It lines the trachea.
5. Glandular epithelium: cells that form glands and secrete substances such as enzymes and hormones.
Diagrams: [Figure: diagram to be added] of each type, labelled with the shape of the cells, the nucleus and the cilia where present.

Teacher's Note:
a) Epithelial tissue covers and lines the surfaces and cavities of the body.
b) Cell shape gives the best clue to the function of each epithelial type.

51. Draw well labelled diagrams of various types of muscles found in human body.

Answer:
1. Skeletal (striated) muscle: long, cylindrical, unbranched fibres with many nuclei and visible light and dark striations.
2. Smooth muscle: spindle-shaped cells with a single central nucleus and no striations.
3. Cardiac muscle: branched, striated fibres with a single central nucleus and intercalated discs between cells.
Diagrams: [Figure: diagram to be added] of each type, with the nuclei and striations labelled.

Teacher's Note:
a) Striations show the regular arrangement of contractile proteins.
b) Intercalated discs let cardiac cells contract together.

52. Give reasons for
(a) Meristematic cells have a prominent nucleus and dense cytoplasm but they lack vacuole.
(b) Intercellular spaces are absent in sclerenchymatous tissues.
(c) We get a crunchy and granular feeling, when we chew pear fruit.
(d) Branches of a tree move and bend freely in high wind velocity.
(e) It is difficult to pull out the husk of a coconut tree.

Answer:
1. (a) Meristematic cells are dividing cells, so they need a large nucleus and dense cytoplasm. Vacuoles are small or absent because the cells are still young and growing.
2. (b) Sclerenchyma cells have thick, lignified walls that fill the space completely, so no intercellular spaces are left.
3. (c) The flesh of pear contains groups of sclereids, which are stone cells with thick walls, and these cause the gritty feeling.
4. (d) Branches contain flexible collenchyma tissue, which allows them to bend without breaking.
5. (e) The husk is made of strong, thick-walled sclerenchyma fibres, which are very difficult to pull apart.

Teacher's Note:
a) Young meristematic cells prepare to divide, so they keep the cytoplasm and nucleus active.
b) Collenchyma gives flexibility, and sclerenchyma gives strength.
c) Stone cells in pear are a kind of sclerenchyma.

53. List the characteristics of cork. How are they formed? Mention their role.

Answer:
1. Characteristics: the cells are dead, compact and without intercellular spaces, the walls contain suberin, which makes them impervious to water and gases, and the tissue is light and elastic.
2. Formation: cork is formed by the cork cambium (phellogen), which cuts off layers of cells towards the outside of the stem or root.
3. Role: cork protects the plant from water loss, mechanical injury, infection and extreme temperature.

Teacher's Note:
a) Cork forms the outer bark of trees, and it is used for stoppers and insulation.
b) Suberin is the key chemical responsible for its waterproof nature.

54. Why are xylem and phloem called complex tissues? How are they different from one other?

Answer:
1. Xylem and phloem are called complex tissues because each is made of more than one type of cell.
2. Xylem is made of tracheids, vessels, xylem parenchyma and xylem fibres. It conducts water and minerals from roots to other parts, and its cells are mostly dead.
3. Phloem is made of sieve tubes, companion cells, phloem parenchyma and phloem fibres. It conducts food from leaves to other parts in both directions, and its sieve tubes are living.

Teacher's Note:
a) Xylem conducts materials mostly upwards, while phloem can carry food up and down.
b) Water in xylem moves in a continuous column, driven by transpiration.

55. (a) Differentiate between meristematic and permanent tissues in plants
(b) Define the process of differentiation
(c) Name any two simple and two complex permanent tissues in plants.

Answer:

(a)

(b) Differentiation is the process by which cells lose their ability to divide and acquire a definite shape, size and function to form permanent tissues.

(c) Simple permanent tissues: parenchyma and collenchyma (any two). Complex permanent tissues: xylem and phloem (any two).

Teacher's Note:
a) Meristematic tissues are the source of all permanent tissues.
b) Sclerenchyma is also a simple permanent tissue, and it is not listed here as one of the two examples.

56. Label the parts of the neuron below:

[Figure: Drawing of a neuron. Left side shows branched dendrites around the cell body with its nucleus. A long axon runs to the right with myelin sheath segments and a small node between them. The branched axon terminals (nerve endings) are at the right end. Labels: A and B point to dendrites, C points to the nucleus of a Schwann cell inside a sheath segment, D points to the branched end of the axon, E points to the nerve endings at the axon terminal, and F points to a node of Ranvier between two sheath segments.]

Answer:
1. A: Dendrite
2. B: Dendrite
3. C: Nucleus of a Schwann cell
4. D: Axon terminal (branched end of the axon)
5. E: Nerve endings
6. F: Node of Ranvier

Teacher's Note:
a) Dendrites receive signals and carry them towards the cell body.
b) The myelin sheath speeds up the signal along the axon, and the gaps between sheath segments are called nodes of Ranvier.

57. (a) Observe the diagram given below carefully and label the regions marked A, B and C in the diagram.
(b) Which meristematic tissue is responsible for increase in length of root and for the transformation of the stem of a plant into trunk when it grows into a tree.

[Figure: Growing shoot tip drawn as a stem. The top is a green cap at the growing tip, labelled A. Below it, a green band marks a node, labelled B. A lower section of the stem between two nodes is labelled C.]

Answer:
1. (a) A: Apical meristem (growing tip)
2. (a) B: Node
3. (a) C: Internode
4. (b) The apical meristem increases the length of the root, and the lateral meristem (cambium) increases the girth that turns the stem into a trunk.

Teacher's Note:
a) Apical meristem is at the tip of roots and stems, and it causes elongation.
b) Lateral meristem adds layers of wood and bark, which makes the stem thick like a trunk.