NCERT Class 9 Science Chapter 6 Tissues

Chapter 6 Tissues

Intext Questions
Question 1: What is a tissue?
Answer: A group of cells that are similar in structure and work together to achieve a particular function forms tissue.

Question 2: What is the utility of tissues in multi-cellular organisms?
Answer: In unicellular organisms like Amoeba, a single cell performs all the functions of multicellular organisms like digestion, excretion, reproduction etc. But in the case of multicellular organisms, the cells are grouped to form tissues. These tissues then carry out a specific function in the body. Example: a nerve cell form nervous tissue which help in transferring messages. This is known as division of labour. Due to this division of labour, the multicellular organisms are able to perform functions effectively.

Question 3: Name types of simple tissues.
Answer: There are three types of simple tissues: Parenchyma, Collenchyma, and Sclerenchyma.

Question 4: Where is apical meristem found?
Answer: Apical meristems are situated at growing tips of stems and roots.

Question 5: Which tissue makes up the husk of coconut?
Answer: Sclerenchyma tissue makes up the husk of coconut.

Question 6: What are the constituents of phloem?
Answer: The constituents of phloem are Sieve tubes, Companion cells, Phloem parenchyma and Phloem fibres.

Question 7: Name the tissue responsible for movement in our body.
Answer: Muscular tissue is responsible for movement in our body.

Question 8: What does a neuron look like?
Answer: A neuron consists of a cell body with a nucleus and cytoplasm, from which long thin hair-like parts arise. Usually each neuron has a single long part (process), called the axon, and many short, branched parts called dendrites. An individual nerve cell may be up to a metre long. Many nerve fibres bound together by connective tissue make up a nerve.

Question 9: Give three features of cardiac muscles.
Answer: Cardiac muscles are specialised tissues that are evolved to pump blood throughout the body. Three features of cardiac muscles are
• They are cylindrical, branched and uninucleate.
• These muscles are involuntary muscles.
• They show rhythmic contraction and relaxation throughout life.

Question 10: What are the functions of areolar tissue?
Answer: Areolar connective tissue are found between the skin and muscle, around blood vessels and nerves and in bone marrow. It fills the space inside the organs, supports internal organs and helps in repair of tissue.

Exercise Questions
Question 1: Define the term “tissue”.
Answer: A group of cells that are similar in structure and work together to achieve a particular function forms tissue.

Question 2: How many types of elements together make up the xylem tissue? Name them.
Answer: 4 elements together make up the xylem tissue.
• Tracheids
• Vessels
• Xylem parenchyma
• Xylem fibres

Question 3: How are simple tissues different from complex tissues in plants?
Answer:
• Simple tissue
→ Simple tissue is made up of one type of cell.
→ Cells of this type are similar in structure and perform similar function.
→ Example: Parenchyma, Collenchyma, Sclerenchyma
• Complex tissues
→ Complex tissue is made up of more than one type of cell.
→ Different types of cell perform different functions.
→ Example: xylem, phloem

Question 4: Differentiate between parenchyma, collenchyma and sclerenchyma on the basis of their cell wall.
Answer:
• Parenchyma
→ Has thin cell wall; cells are loosely packed.
→ Cell wall is made of cellulose.
• Collenchyma
→ Has cell wall which are irregularly thickened at the corners; very little intercellular space.
→ Cell wall is mainly made up of pectin and hemicellulose.
• Sclerenchyma
→ Has cell wall which are uniformly thickened; no intercellular space is present.
→ An additional layer of cell wall is found which is composed of lignin.

Question 5: What are the functions of the stomata?
Answer: The outermost layer of the cell, epidermis, has small pores here and there which are known as stomata. They are necessary for exchanging gases with the atmosphere. Transpiration (a process in which water is lost in the form of water vapour) also takes place through stomata.

Question 6: Diagrammatically show the difference between the three types of muscle fibres.
Answer:
• Striated muscles
→ They are also called Skeletal muscles as they are mostly connected to bones and help in body movement.
→ They are voluntary muscles.
→ These cells are long, cylindrical, unbranched and multinucleate (with many nucleus).
• Smooth muscles
→ They are found in alimentary canal, the bronchi of the lungs, in the iris of the eye, and in ureters.
→ They are involuntary muscles.
→ These cells have pointed ends (spindle in shape) and are uninucleate (single nucleus).
• Cardiac muscles
→ They are found in the heart.
→ They are involuntary muscles.
→ These cells are cylindrical, branched and uninucleate.

Question 7: What is the specific function of the cardiac muscle?
Answer: Cardiac muscles cells are cylindrical, branched and uninucleate. They are involuntary muscles. They show rhythmically contraction and relaxation throughout life. Their rhythmic contraction and relaxation helps in pumping action of heart.

Question 8: Differentiate between striated, unstriated and cardiac muscles on the basis of their structure and site/location in the body.
Answer:

Question 9: Draw a labelled diagram of a neuron.
Answer:

Question 10: Name the following.
a) Tissue that forms the inner lining of our mouth.
b) Tissue that connects muscle to bone in humans.
c) Tissue that transports food in plants.
d) Tissue that stores fat in our body.
e) Connective tissue with a fluid matrix.
f) Tissue present in the brain.
Answer:
a) Tissue that forms the inner lining of our mouth: Squamous Epithelium
b) Tissue that connects muscle to bone in humans: Tendons
c) Tissue that transports food in plants: Phloem
d) Tissue that stores fat in our body: Adipose tissue
e) Connective tissue with a fluid matrix: Blood
f) Tissue present in the brain: Nervous tissue

Question 11: Identify the type of tissue in the following: skin, bark of tree, bone, lining of kidney tubule, vascular bundle.
Answer:
→ Skin: Striated squamous epithelium
→ Bark of tree: Cork (which is a protective tissue)
→ Bone: Connective tissue
→ Lining of kidney tubule: Cuboidal epithelium tissue
→ Vascular bundle: Conducting tissue

Question 12: Name the regions in which parenchyma tissue is present.
Answer: Parenchyma is found in:
• Pith of stems and roots
• When parenchyma contains chlorophyll it is known as chlorenchyma, found in green leaves.
• Parenchyma found in aquatic plants has large air cavities which enables them to float and are called aerenchyma.

Question 13: What is the role of epidermis in plants?
Answer: Epidermis performs the following function:
• It protects all the parts of the plant.
• Epidermal cells on the aerial parts of the plant often secrete a waxy, water-resistant layer on their outer surface. This aids in protection against loss of water, mechanical injury and invasion by parasitic fungi.
• Epidermal cells of the roots, whose function is water absorption, commonly bear long hair-like parts that greatly increase the total absorptive surface area.

Question 14: How does the cork act as a protective tissue?
Answer: Cork acts as a protective tissue because its cells are dead and compactly arranged without intercellular spaces. They have deposition of suberin on the walls that make them impervious to gases and water.

Question 15: Complete the following chart:

  

Answer: