TISSUES - Q&A
Questions Page 61
1. What is a tissue?
A tissue is a group of cells that are similar in structure and/or work together to achieve a particular function. Examples include blood, phloem, and muscle.
2. What is the utility of tissues in multi-cellular organisms?
In multi-cellular organisms, tissues provide "division of labour". Specialized cells are grouped together to perform specific functions efficiently. For example, muscle tissues help in movement, and vascular tissues (xylem and phloem) transport water and food in plants. This organization leads to higher efficiency and survival of the organism.
Questions Page 65
1. Name types of simple tissues.
The three main types of simple tissues in plants are:
1. Parenchyma
2. Collenchyma
3. Sclerenchyma
2. Where is apical meristem found?
Apical meristem is found at the growing tips of stems and roots. Its main function is to increase the length of the stem and the root.
3. Which tissue makes up the husk of coconut?
The husk of a coconut is made up of sclerenchymatous tissue. The cells of this tissue are dead, long, and narrow with thick walls due to lignin, making the husk hard and stiff.
4. What are the constituents of phloem?
Phloem is made up of four types of elements:
1. Sieve tubes (tubular cells with perforated walls)
2. Companion cells
3. Phloem parenchyma
4. Phloem fibres
Questions Page 69
1. Name the tissue responsible for movement in our body.
The tissue responsible for movement in our body is Muscular Tissue. Muscle cells contain special contractile proteins that contract and relax to cause movement.
2. What does a neuron look like?
A neuron (nerve cell) looks like a cell with a long tail. It has a cell body (cyton) containing a nucleus and cytoplasm, from which long thin hair-like parts arise. The single long part is called the axon, and many short, branched parts are called dendrites. A single neuron can be up to a meter long.
[Image of Neuron Structure]3. Give three features of cardiac muscles.
Three features of cardiac muscles are:
1. They are involuntary (cannot be controlled by our will).
2. The cells are cylindrical, branched, and uninucleate (have a single nucleus).
3. They show rhythmic contraction and relaxation throughout life without getting fatigued.
4. What are the functions of areolar tissue?
Areolar connective tissue performs the following functions:
1. It fills the space inside the organs.
2. It supports internal organs.
3. It helps in the repair of tissues.
It is found between skin and muscles, around blood vessels and nerves, and in the bone marrow.
Exercises
1. Define the term "tissue".
A group of cells that are similar in structure and/or work together to achieve a particular function forms a tissue.
2. How many types of elements together make up the xylem tissue? Name them.
Xylem tissue is made up of four types of elements:
1. Tracheids
2. Vessels
3. Xylem parenchyma
4. Xylem fibres
3. How are simple tissues different from complex tissues in plants?
| Simple Tissues | Complex Tissues |
|---|---|
| Made up of only one type of cells. | Made up of more than one type of cells. |
| All cells look similar and perform a similar function. | Different types of cells coordinate to perform a common function. |
| Examples: Parenchyma, Collenchyma, Sclerenchyma. | Examples: Xylem, Phloem. |
4. Differentiate between parenchyma, collenchyma and sclerenchyma on the basis of their cell wall.
| Tissue | Cell Wall Characteristics |
|---|---|
| Parenchyma | Thin cell walls made of cellulose. |
| Collenchyma | Cell walls are thickened at the corners (irregularly thickened). |
| Sclerenchyma | Thick cell walls due to lignin deposition (no intercellular spaces). |
5. What are the functions of the stomata?
The main functions of stomata are:
1. Exchange of gases: They allow the exchange of gases (CO2 and O2) with the atmosphere.
2. Transpiration: They help in the loss of water in the form of water vapour from the plant.
6. Diagrammatically show the difference between the three types of muscle fibres.
(Since I cannot draw, I will describe the diagrams you should look for or draw)
1. Striated Muscles: Show long, cylindrical, unbranched fibres with alternate dark and light bands (striations). They are multinucleate.
2. Smooth Muscles: Show spindle-shaped (tapered at ends) fibres without striations. They are uninucleate.
3. Cardiac Muscles: Show cylindrical, branched fibres with faint striations. They are uninucleate.
7. What is the specific function of the cardiac muscle?
The specific function of cardiac muscle is to contract and relax rhythmically throughout life. This rhythmic contraction pumps blood to various parts of the body.
8. Differentiate between striated, unstriated and cardiac muscles on the basis of their structure and site/location in the body.
| Feature | Striated Muscle | Unstriated (Smooth) Muscle | Cardiac Muscle |
|---|---|---|---|
| Structure | Cylindrical, unbranched, multinucleate, with dark/light bands. | Spindle-shaped, unbranched, uninucleate, no bands. | Cylindrical, branched, uninucleate, faint bands. |
| Nature | Voluntary (controlled by will). | Involuntary (not controlled by will). | Involuntary. |
| Location | Attached to bones (limbs, body wall). | Walls of internal organs (stomach, intestine, bronchi, iris). | Walls of the heart only. |
9. Draw a labelled diagram of a neuron.
[Image of Labelled Neuron Diagram]
Key labels to include: Cell body (Cyton), Nucleus, Dendrites (short branches), Axon (long tail), Nerve ending.
10. Name the following.
(a) Tissue that forms the inner lining of our mouth: Squamous Epithelium
(b) Tissue that connects muscle to bone in humans: Tendon
(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
11. Identify the type of tissue in the following: skin, bark of tree, bone, lining of kidney tubule, vascular bundle.
- Skin: Stratified squamous epithelium
- Bark of tree: Cork (protective tissue)
- Bone: Connective tissue
- Lining of kidney tubule: Cuboidal epithelium
- Vascular bundle: Complex permanent tissue (Xylem and Phloem)
12. Name the regions in which parenchyma tissue is present.
Parenchyma is the most common simple permanent tissue. It is present in the soft parts of the plant such as the cortex and pith of stems and roots, leaves (mesophyll), flowers, and fruits.
13. What is the role of epidermis in plants?
The epidermis is the outermost layer of cells. Its roles include:
1. Protection: It protects all parts of the plant against loss of water, mechanical injury, and invasion by parasitic fungi.
2. Secretion: In aerial parts, it secretes a waxy, water-resistant layer called the cuticle.
3. Gas Exchange: Through stomata present in the leaf epidermis.
14. How does the cork act as a protective tissue?
Cork cells are dead and compactly arranged without intercellular spaces. They have a substance called suberin in their walls that makes them impervious to gases and water. This allows cork to protect the inner tissues from desiccation (drying out), infection, and mechanical injury.
15. Complete the following chart:
Permanent tissue
↓
Simple Complex
↓ ↓
Parenchyma Xylem
Collenchyma Phloem
Sclerenchyma