HOTS Questions: Tissues

Q1: What will happen if

(i) Apical meristem is damaged or cut ?

(ii) Cork is not formed in older stems and roots ?

(iii) Cells of epithelial tissue are not compactly packed.

Ans:

(i) Apical Meristem Removed: Growth in length of roots and stems will stop because apical meristems contain actively dividing cells that add new cells at the tips. Without them, the plant cannot extend upward or downward.
(ii) Cork is Not Formed: If cork does not form in older stems and roots, the expanding girth will cause the outer tissues to rupture. This exposes the inner living tissues to drying out and to infections by microbes and pests, reducing the plant's protection and survival.
(iii) Epithelial Cells Not Compactly Packed: Epithelial tissue will fail to act as an effective protective and impermeable layer. Gaps between cells would allow pathogens, dust and excess water loss, and would reduce selective absorption or secretion where needed.

Q2:

(i) Identify the figure. What is its function ?

(ii) Label X, Y and Z .

(iii) X loses its nucleus in mature state. Still it remains alive. How ?

Ans:

(i) Identification: Phloem tissue. Function: Conduction of organic food (mainly sugars) from leaves to other parts of the plant.

(ii) Labels: X - Sieve tube cell, Y - Sieve plate, Z - Companion cell.

(iii) How Sieve Tube Cells Remain Alive: Mature sieve tube cells lack a nucleus, but they stay functionally alive because companion cells, which have a nucleus, control their metabolic activities. Companion cells are connected to sieve tube cells by plasmodesmata, allowing transfer of nuclei-controlled substances and maintaining sieve tube function.

Q3: 

(i) Identify the figure.

(ii) Label X, Y and Z.

(iii) What is the chemical composition of material of the figure ?

(iv) What is the function of Y

Ans:

(i) Identification: Section of bone.

(ii) Labels: X - Periosteum, Y - Haversian canal, Z - Canaliculus (plural: canaliculi).

(iii)Composition: The bone cells are embedded in a hard matrix. This matrix is composed of calcium and phosphorus compounds.
(iv) Function of Haversian Canal (Y): Haversian canals contain blood vessels and nerve fibres and help to carry nutrients and remove wastes from the inner regions of compact bone, thus keeping bone cells alive.

Q4: What will happen if

(i) Ligament gets overstretched ?

(ii) Striated muscles contract rapidly for longer duration ?

Ans:

(i) Overstretching of Ligament: A ligament that is overstretched may tear or get sprained. This causes pain, swelling and instability of the joint because ligaments normally hold bones together and stabilise joints.

(ii) Prolonged Rapid Contraction of Striated Muscles: If striated (skeletal) muscles contract rapidly for a long time, they will become fatigued. Lactic acid builds up and energy stores are used up, causing pain, reduced efficiency and the need for rest to recover.

Q5:

(i) Identify figures : A,B and C.

(ii) Which one of them provides both mechanical strength as well as flexibility ?(iii) Which one of them is commercially exploited to obtain Hemp and Jute ?

(iv) Which one of them can be modified to form air cavities in aquatic plants ?

(v) Which one of them has heavy deposition of lignin ?

Ans:

(i) Identification:
A - T.S. sclerenchyma fibres.
B - T.S. parenchyma cells.
C - T.S. collenchyma.

(ii) Provides Strength and Flexibility: Collenchyma (C) provides both mechanical strength and flexibility because its walls are thickened at the corners, allowing support while permitting growth.

(iii) Hemp and Jute: Sclerenchyma fibres (A) are commercially exploited to obtain fibres like hemp and jute; these fibres are strong and used for ropes and textiles.

(iv) Modified to Form Air Cavities (Aerenchyma): Parenchyma (B) can be modified to form large air-filled spaces (aerenchyma) in aquatic plants to help buoyancy and gas exchange.

(v) Heavy Deposition of Lignin: Sclerenchyma (A) shows heavy lignin deposition in cell walls, making the cells hard and woody.

Q6:  

(i) Identify figures A and B.

(ii) Which is called tesselated and pavement epithelium ?

(iii) Which one lines gastro-intestinal tract and epiglottis ?

(iv) Which one allows diffusion of substances ?

Ans: 

(i) Identification:
A - Squamous epithelium.
B - Ciliated columnar epithelium.

(ii) Pavement (Tesselated) Epithelium: Squamous epithelium (A) is also called pavement or tesselated epithelium because its flat, tile-like cells fit closely together.

(iii) Lining of Gastro-intestinal Tract and Epiglottis: The gastro-intestinal tract is mainly lined by simple columnar epithelium which helps in absorption and secretion. The epiglottis is lined by stratified squamous columnar epithelium in areas that require extra protection.

(iv) Allows Diffusion of Substances: Simple squamous epithelium (a type of simple epithelium) allows rapid diffusion of gases and small molecules because of its thin, flat cell shape.

Q7: What will happen if

(i) Bone is dipped in HCl

(ii) Bone is dried ?

Ans:

(i) Bone Dipped in HCl: The mineral matter (calcium and other salts) dissolves in acid, leaving behind mainly the organic part (ossein). The bone becomes soft and flexible after mineral removal.

(ii) Dried Bone: Drying destroys much of the organic material, leaving mainly the mineral component. The bone becomes brittle and hard when organic matter is lost.

Q8:

(i) Identify figures A and B.

(ii) Label X, Y and Z.
(iii) Which one acts as impulse booster ?
(iv) Which one is under control of our will ?

Ans: 

(i) Identification: A - Cardiac muscle fibres.
B - Striated (skeletal) muscle fibre.

(ii) Labels: X - Intercalated disc.
Y - Dark band (A band).
Z - Light band (I band).

(iii) Impulse Booster: Intercalated discs help in rapid transmission and coordination of electrical impulses between cardiac muscle cells. They act as junctions that synchronise impulses rather than boosting them in power.

(iv) Under Control of Our Will: Striated (skeletal) muscles (B) are under voluntary control and contract when we decide to move them.

Q9: A person met with an accident in which two long bones of the hand were dislocated. What could be the reason?
Ans: Dislocation of the bones of the hand was caused due to the breakage of the ligament which connects the two bones and keeps them in place. Ligaments are strong bands of fibrous tissue that stabilise joints; when they tear, bones can move out of their normal position.

Q10: A nail is inserted in the trunk of a tree at a height of 1 metre from the ground level. After 3 years, where will the nail be present?
Ans: The nail will remain at the same height from the ground even after 3 years. Trees grow in length from the tips (apical meristems), so vertical growth happens at the top and root tips, not by moving existing parts up. Radial growth (increase in girth) occurs by lateral meristems, which expand the trunk outward but do not change the nail's vertical position.

Q11: Tissue A and tissue B constitute tissue C. A carries water while B carries food for the plants. Identify A, B, C.
Ans: A. Xylem
B. Phloem
C. Vascular bundles

Q12: If the tip of a sugarcane plant is removed from the field, even then it keeps on growing in length. Why?
Ans: Removing the tip of sugarcane does not remove the intercalary meristem which is present at the base of the internodes. This meristematic region can still divide and add cells, allowing the stem to continue increasing in length despite the tip being removed.

Q13: The root tips of a plant were cut and the plant was replanted. What will happen to the plant and why?
Ans: The plant's growth will stop, and it will gradually wither due to inability to absorb water and minerals. Cutting off the root tips removes the root apical meristems, so roots cannot grow or repair themselves. Without active roots the plant cannot absorb sufficient water and mineral salts, leading to wilting and death.