Ch. 6 Tissues

Q. Make comparison between functions of tissues in plants and animals ?

A.

PLANT TISSUES	ANIMAL TISSUES
Dead supportive tissues are more abundant as compared to living tissues.	Living tissues are more common as compared to dead tissues.
They require less maintenance.	They require more maintenance.
Due to activity of meristematic tissue plants grow throughout life.	Do not show growth after reaching maturity.
Tissue organisation is meant for stationary habit for plants.	Tissue organisation is targeted towards high mobility of animals
Growth is limited to certain regions.	There is uniform growth.
Based on their dividing capacity plant tissues are classified into meristematic or permanent.	There is no demarcation of dividing tissues in animals.

Q. What are the different types of meristematic tissues? Where are the located in a plant and how do they bring about growth in plants?

A.

TYPE OF MERISTEMATIC TISSUE	LOCATION	FUNCTION
Apical	Present at the growing tips of stems and roots.	Increases length of stems and roots.
Intercalary	Present at the base of leaves and internodes on twigs.	Helps in the growth of leaves and internodes.
Lateral	Present in the sides of stems (cambium).	Increases girth of stems and roots.

Q. Why meristematic tissues lack vacuole?

A. Meristematic tissues lack vacuole because they don't need to store products and vacuole causes hindrance in cell division as it provides turgidity and rigidity to the cell.

Q. Name 2 specialised parenchymal tissues and mention their functions.
     I. Chlorenchyma- In some situations, parenchyma contains chlorophyll and performs photosynthesis.
    II. Aerenchyma- In some aquatic plants, cavities are present in parenchyma to give buoyancy to the plants and to help them float.
   

Q. Differentiate between the 2 types of plant tissues.

A.

MERISTEMATIC TISSUES	PERMANENT TISSUES
Divide continuously and help in the growth of the plant.	Do not divide. Help in protection, support, storage etc.
Lack vacuole.	Vacuole is present.
Have a dense cytoplasm.	Cytoplasm is not dense.
Nucleus is placed in the centre.	Nucleus is placed at the periphery.
Cell wall of these tissues is thin.	Cell wall of these tissues is thick.
Intercellular spaces are absent.	Intercellular spaces are present.
Contain living cells.	Contain dead cells.
These are not mature as they can divide.	These are mature.
Shape keeps on changing.	Acquire a definite shape.
Found in some regions only, like root tip, shoot tip etc.	Found almost everywhere.

Q. List 2 characteristics of cork cells which help them to function as protective tissue.

A. 1. They are dead and compactly arranged without intercellular spaces.
     2. They have a chemical called suberin in their walls that makes them impervious to gases and water.


Q. Why does the growth of a plant  occur in specific regions?

A. Growth of a plant occurs in specific regions as meristematic tissues, which are responsible for growth are localised for growth in certain regions.


Q. What are the characteristic features of meristematic tissues?

A. 1. The cells of meristematic tissue are very active.
     2. Meristems have dense cytoplasm and thin cellulose walls.
     3. They have a prominent nuclei and lack vacuoles.


Q. How do meristematic tissues form permanent tissues? What is this process termed as?

A. When meristematic tissues take up a specific role and lose their ability to divide, they form permanent tissues. This process is termed as differentiation.


Q. Is the outer layer of a branch of a tree different from the outer layer of a young stem? How?

A. As plants grow older, the outer protective tissue undergoes changes. A strip of secondary meristem replaces the epidermis of the stem cells on the outside are cut off from this layer. This forms the multilayer thick cork cell or bark of a tree.


Q. What are the various elements of phloem? Mention their functions.

A. Elements of a phloem are-
   1. SIEVE TUBE: Help in conduction of organic compounds as they perforated walls.
   2. COMPANION CELLS: Help in metabolic activities.
   3. PHLOEM PARENCHYMA: They help in storage and slow lateral conduction of food.
   4. PHLOEM FIBRES: Provide mechanical support to the phloem.


Q. Differentiate between xylem and phloem on the basis of structure and functions.

A. 

XYLEM	PHLOEM
Conducts water and minerals	Conducts food and organic compounds
Conduction is mostly unidirectional	Conduction is mostly bidirectional
Conducting channels are tracheids and vessels	Conducting channel is sieve tube
Components are tracheids, vessels, xylem parenchyma and xylem fibres	Components are sieve tubes, companion cells, phloem parenchyma and phloem fibres
3 of 4 elements are dead(except xylem parenchyma)	3 of 4 elements are living(except phloem fibres)
Also gives mechanical strength to plants	Doesn’t give mechanical strength

Q. Name the 3 types of simple permanent tissue and differentiate between them on the basis of structure, location and functions.

A. 

CRITERIA	PARENCHYMA	COLLENCHYMA	SCLERENCHYMA
Structure	Consists of living, unspecialised cells with thin cell wall and intercellular spaces.	Consists of living, elongated cells with irregularly thickened corners with less intercellular spaces.	Consists of dead, long and narrow cells with thickened cell walls due to lignum.
Location	Stems, roots, leaves, flowers and fruits.	Leaf stalks below the epidermis	Stems, around vascular bundles, veins of leaves, heard covering  of seeds and nuts
Function	Provide support, store food, give buoyancy to aquatic plants and sometimes carry out photosynthesis	Gives flexibility and support to plants	Provides strength to plants and makes them hard and stiff

Q. How is the epidermis modified to perform various functions in the following-

1. Desert plants: Their epidermis is very thick and develops a waxy coating of a waterproof chemical called cutin.

2. Aerial parts of plants: They secrete a waxy, water-resistant layer on their outer surface to prevent loss of water, mechanical injury and invasion by parasitic fungi.

3. Exchange of gases: Epidermis contains small pores called stomata for exchange of gases and also transpiration.

4. Roots: Epidermis of roots bears long hair like parts that increase the total absorption surface area.

Q. Name the connective tissue which helps in repair of tissues and where is it located?

A. Areolar tissue helps to repair tissues. It is found between skin and muscles, around blood vessels, nerves, bone marrow and space in organs.

Q. Write 2 functions of adipose tissues.

A. 1. Acts as an insulator as it stores fat.

     2. Works as a self-absorber.

Q. What is basement membrane?

A. It is an extracellular fibrous membrane which separates the epithelium from the underlying tissue.

Q. Name the different types of WBC's and a polynucleated leukocyte.

A. Types of WBC's are Neutrophil, Eosinophil, Basophil, Lymphocytes and monocytes.

Neutrophil is a polynucleated leukocyte.

Q. Where are smooth muscles found? Why are they known so?

A. They are found in the iris of the eye, bronchi of lungs. They are called smooth muscles as the entire muscle has no bone. 

Q. Where are the skeletal muscles located? Skeletal muscles are also known as striated muscles. Why?

A. These skeletal muscles show alternate and dark bounds or striations thus they are called striated muscles and are found in arms, legs, fingers etc.

Q. Give reasons-

1. Blood is known as fluid connective tissue: It is called connective tissue as it connects organs and bones via arteries and veins. It is fluid as it contains 90% water.

2. We can bend the cartilage of our wars but cannot end the bones in our arms: Cartilage can be bent because it contains proteins and sugar. Bones contain inorganic and organic substances like calcium that is why it cant be bent.

Q. What is the composition of blood plasma? Mention the functions of various blood cells.

A.  Blood plasma contains 90-95% of water and 5-10% dissolved salts. Eg: amino acids, proteins etc.

1. WBC- Fights pathogens.

2. RBC- Carries oxygen and haemoglobin.

3. Platelets- Clots blood.

Q. Write the various components of nervous systems.

A. Brain, spinal cord, nerves constitute the nervous system.

Q. Differentiate between-

1. Ligament and tendon.

LIGAMENT	TENDON
Less strength	More strength
Very little matrix	Has a lot of matrix
More flexible	Less flexible
Connects bones to bones	Connects  muscles to bones

2. Bone and cartilage.

BONE	CARTILAGE
Framework of the body	Helps in flexibility
Opaque	Translucent
Contains inorganic and organic substances	Contains proteins and sugar
Can’t be bent	Can be bent
Rigid matrix	Soft matrix
Found in skeletal framework	Found in nose, ears
Bone cells are called osteocyte	Cartilage cells are called Chondrocyte

3. Axon and dendrite.

AXON	DENDRITE
It is long uniformly thickened fibre like part of a neuron	It is the short tapering part of the neuron
It is covered with a sheath	Sheath is absent
Nissil’s granules are absent but myofibrils are present	Both Nissil’s granules and myofibrils are present

4. Voluntary and involuntary muscles.

VOLUNTARY MUSCLES	INVOLUNTARY MUSCLES
Also known as skeletal or striated muscles	Also known as unstriated or smooth muscles
Contains dark and light bands	Doesn’t contain any bands
Shape is elongated	Spindle shapes
Speed is fast	Speed is slow
Each cell is multi-nucleated	Each cell is nucleated
Attached to bones, work according to our will and are responsible for body movements	Does not work according to our will. Helps in the movement of food in the alimentary canal
Found in diaphragm, tongue etc	Found in bronchi, iris of the eye etc

Q. What are the characteristic features of the following epithelial tissues which make it suitable for the following-
1. Protective role: Stratified squamous tissues are present in many layers to prevent wear and tear.
2. Excretion and secretion: Cuboidal and glandular epithelium tissues are responsible for excretion and secretion. The columnar epithelium tissue folds inward and form a multicellular glad which secretes chemicals
3. Absorption: The columnar epithelium consists of tall cells. The nuclei are towards the base and sometimes have border containing microvilli.
4. Mechanical support: The squamous epithelium is made up of thin, flat, irregular shaped cells which fit together like floor tiles to form a compact tissue. This arrangement provides mechanical support.


Q. What is the peculiar characteristic features of connective tissues? How is the nature of the matrix related to the function of the connective tissue?

A. The matrix of connective tissue is non-living or an extracellular matrix. The proportions of the cells, fibres and intercellular substance vary depending upon the function of the connective tissue. For example, a strong connective tissue needs a greater proportion of collagen fibres and fewer cells, say tendons and ligaments. On the other hand, a connective tissue composed of mostly cells won't be very strong in adipose tissue.