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(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.

 


a) Meristematic tissues and Permanent tissues differ in the following ways-

Meristematic tissue

Permanent tissue

It consists of only living cells which are spherical or polygonal and undifferentiated.

It consists of both dead and living cells which are large and differentiated with different shapes.

The cell wall is thin and elastic.

The cell wall can be thin or thick.

Its cells contain a large and prominent nucleus with dense cytoplasm and no vacuoles.

Its cells contain a small nucleus and a large central vacuole.

The intercellular spaces are absent.

The intercellular spaces are often present.

Its cells keep on dividing and growing regularly.

The cells do not divide after differentiation.

The cell organelles are simple.

Its cell organelles are fully developed.

It helps in the growth of the plant.

It helps in the protection, support, conduction, photosynthesis, etc

 

(b) The process by which the cells divide meristematically and take a permanent shape, size, and function is called differentiation. The differentiated cells take up specific roles and lose their ability to divide and form permanent tissue.

(c) Simple permanent tissue- parenchyma and collenchyma. Complex permanent tissue- xylem and phloem. 

 

 

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Why are the xylem and phloem called complex tissues? How are they different from each other?

 

Tissues are of different types- simple and complex. A complex tissue consists of more than one type of cells having a common origin which coordinate to perform a common function. The xylem and phloem are called complex tissues because they are made up of different types of cells.
Xylem consists of four different types of elements-

  1. Tracheids                                                                       
  2. Vessels
  3. Xylem parenchyma                                               
  4. Xylem fibres
    Phloem also consists of four different types of elements-
  5. Sieve tubes                                                               
  6. Companion cells
  7. Phloem parenchyma                                              
  8. Phloem fibres
    The basic difference between xylem and phloem is-

Xylem

Phloem

It helps in the conduction of water and minerals.

It helps in the conduction of food materials.

The process of conduction is unidirectional, i.e., from roots to apical parts of the plant.

The process of conduction is bidirectional, i.e., from leaves to storage organs or growing parts or storage organs to growing parts of plants.

The conducting channels are tracheids and vessels.

The conducting channels are sieve tubes.

Most of the elements of the xylem i.e., tracheids, vessels and fibres are dead. Only xylem parenchyma consists of the living elements.

Most of the elements of phloem are living in nature i.e., sieve tubes, companion cells, and phloem parenchyma. Only phloem fibres are dead elements.

Xylem also provides mechanical strength to the plant.

Phloem performs no such function for the plants.

 

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

The characteristics of cork cells are-

  • They are mature and dead.
  • They are compactly arranged.
  • They possess a chemical substance called suberin in their walls.
  • They do not have intercellular spaces.
  • They are thick and made up of several layers.

As the plants grow older, the outer protective tissue undergoes some changes. In the stem, the epidermis is replaced by a secondary meristem called cork cambium. It is a simple tissue which consists of rectangular cells and vacuolated protoplasts.
Cork cambium forms cork on the outer side and secondary cortex on the inner side by producing new cells on both sides.
Cork cells are compactly arranged dead cells which lack intercellular spaces. The cell walls of cork cells are thickened by a substance called suberin (fat) which makes these cells impermeable to water and gases.
Role-

  • It protects plants and prevents water loss.
  • It also protects the plants from infection and mechanical injury.
  • Cork is used as an insulator because it is light in weight and doesn’t catch fire.

 

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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.

 

Reasons

a) Meristematic tissue cells divide continuously and have a prominent nucleus and dense cytoplasm. As they are diving continuously they need not store food or waste products hence they lack vacuoles.
b) Sclerenchyma doesn’t contain intercellular spaces because its cell wall is lignified. These are densely packed and protect the plant and mechanical strength.
c) The crunchy and granular feeling upon chewing the pear fruit is because of sclerenchyma tissue. The sclerenchyma cells are of two types- fibres and sclereids. The sclereids give a crunchy feeling to the pear fruit because they provide support and harden the tissue
d) The branches of a tree move and bend freely in high wind velocity because of the presence of collenchyma which adds the property of flexibility.
e) It is difficult to pull out the husk of a coconut tree because it is made up of sclerenchyma tissues which are dead cells. This gives rigidity and stiffness.

 

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

Sol.
Types of muscles in human body

 

Skeletal Muscle- These muscles are attached to the skeleton and help in its movement.These muscles are voluntary in nature. They are also known as striated muscles because of the presence of alternate patterns of light and dark bands.
Smooth Muscle- These are non-striated, involuntary muscles controlled by the Autonomous Nervous System. It plays a role in the digestive, urinary, reproductive systems.
Cardiac Muscle- These are found only in the heart. These are involuntary muscles and help in the pumping of the blood.

 

 

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

Epithelial tissues form the outermost covering of the plant body. It acts as a protective tissue. Most organs and cavities present within the body are covered by epithelium. E.g., Skin, the lining of the mouth, the lining of blood vessels, lung alveoli, etc.
The cells of this tissue are tightly packed and form a continuous layer.  They have no intercellular spaces present between them. They are permeable and play an important role in regulating the exchange of materials between the body and the external environment and also between different parts of the body.  All types of epithelial tissue are usually separated from the underlying tissue by an extracellular fibrous basement membrane.

The different types of epithelial tissues are-

Types of epithelial tissues

Simple Squamous 

Stratified Squamous

Columnar

Ciliated Columnar

Cuboidal

Glandular

Structure

They have delicate cell lining and possess a flat thin structure

These cells are arranged in several layers

They are the column-like shape tissues

These tissues have cilia present in them

They are cube-shaped cells which are involved in absorption and secretion.

These are special gland cells that can secrete substances

Present in

Alveoli and Bowman’s capsule- nephron in kidney 

Skin 

Intestine 

Respiratory system 

Kidney tubules

Sweat glands in the skin

(1) Simple squamous epithelium
(2) Stratified squamous epithelium
(3) Columnar epithelium
(4) Ciliated columnar
(5) Cuboidal epithelium
(6) Glandular epithelium

 

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

 

The differences between sclerenchyma and parenchyma tissues are:

Parenchyma

Sclerenchyma

It consists of living cells

It consists of dead cells

It consists of thin-walled cells

Its cell walls are uniformly thickened.

The cell wall is made up of cellulose

The cell wall is made up of a complex polymer called lignin

It serves as packing tissue

It serves as mechanical tissue

It stores food and performs photosynthesis

It gives strength, and rigidity and protects from the attack of parasites.


 

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. 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

Sol.
a. Xylem and Phloem are forms of complex tissue.
b. Stomata have guard cells.
c. Cells of cork contain a chemical called Suberin.
d. Husk of coconut is made of Sclerenchyma tissue.
e. Collenchyma gives flexibility to plants.
f.Xylem and phloem.are both conducting tissues.
g. Xylem transports Water and minerals from soil.
h.Phloem transports Food fromthe  leaf to other parts of the plant

 

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Why is the epidermis important for plants?

The epidermis serves as the crucial outermost layer of plant leaves, meticulously protecting the delicate tissues beneath. This protective layer is not limited to just leaves it also extends its function to the flowers, roots, and stems of the plant, creating a comprehensive shield against environmental threats.

Importance of the Epidermis:
 
1. The epidermis plays a vital role in safeguarding the plant's internal cells from external harm. One of its key features is the waxy cuticle layer, which is secreted by the epidermis. This cuticle forms a resilient barrier that effectively minimizes water loss while offering protection against infections and pathogens, ensuring the plant remains healthy and hydrated.
 
2. The epidermis is equipped with specialized openings known as stomata, which facilitate the process of transpiration. These tiny pores allow for the exchange of gases, playing an essential role in the plant's ability to regulate moisture and maintain overall homeostasis. Through its diverse functions, the epidermis is essential for the survival and well-being of the plant in various environmental conditions.

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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 ———.

 

(a) Cork cells possess Suberin on their walls which makes them impervious to gases and water.
(b) Sieve tubes have tubular cells with perforated walls and are living in nature.
(c) Bone possesses a hard matrix composed of calcium and Phosphorus.

 

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