In-Text Questions Answers
1. What is a tissue?
A tissue is a group of similar cells that work together to perform a specific function in an organism. This organization allows the cells to be more efficient in carrying out tasks like movement, support, or transporting nutrients.
2. What is the utility of tissues in multi-cellular organisms?
Tissues allow multi-cellular organisms to function more effectively by dividing tasks among specialized groups of cells. This specialization enables different parts of the organism to work together smoothly, improving overall survival and function.
1. Which of the two onions has longer roots? Why?
The onion in Jar 1 has longer roots because the root tips were not cut, allowing the apical meristem, which is responsible for growth, to continue functioning and promoting root elongation.
2. Do the roots continue growing even after we have removed their tips?
No, the roots in Jar 2 stop growing after their tips are removed because the apical meristem, the region responsible for cell division and growth, is cut off, preventing further root elongation.
3. Why would the tips stop growing in Jar 2 after we cut them?
The tips stop growing in Jar 2 because cutting off the root tips removes the apical meristem. This region is essential for producing new cells, so without it, the roots cannot grow any longer.
4. Can we think why they would lack vacuoles?
Meristematic cells lack vacuoles because they are actively dividing and need space for dense cytoplasm and organelles involved in cell division. Vacuoles, which store substances, are not necessary in these rapidly dividing cells.
5. Can we think of reasons why there would be so many types of cells?
There are many types of cells because different cells are specialized to perform specific functions that are necessary for the organism’s survival. This diversity allows for complex tasks to be carried out more efficiently within the organism.
6. Recall which gas is required for photosynthesis.
The gas required for photosynthesis is carbon dioxide (CO₂), which plants take in from the atmosphere to produce glucose and oxygen during the process of photosynthesis.
7. Find out the role of transpiration in plants.
Transpiration helps in the upward movement of water and minerals from the roots to the leaves, cools the plant by evaporative cooling, and maintains the flow of nutrients and water within the plant.
8. Can we think of a reason for this? (Why do desert plants have a thick waxy coating of cutin?)
Desert plants have a thick waxy coating of cutin to reduce water loss in their dry environment. This adaptation helps them conserve water by preventing excessive evaporation through the leaves.
9. Is the outer layer of a branch of a tree different from the outer layer of a young stem?
Yes, the outer layer of a branch of a tree, known as cork, is different from the outer layer of a young stem. Cork is thicker, tougher, and waterproof, providing better protection as the plant ages.
Exercise Questions Answers
1. Define the term “tissue”.
Tissue is a group of cells that are similar in structure and work together to perform a specific function within an organism. This allows the organism to carry out complex activities more efficiently.
2. How many types of elements together make up the xylem tissue? Name them.
Xylem tissue is made up of four types of elements: tracheids, vessels, xylem parenchyma, and xylem fibers. These elements work together to transport water and minerals from the roots to the rest of the plant.
3. How are simple tissues different from complex tissues in plants?
Simple tissues are composed of only one type of cell and perform a single function, such as support or storage. Complex tissues, like xylem and phloem, consist of more than one type of cell and perform multiple functions, such as transporting water, minerals, and food throughout the plant.
4. Differentiate between parenchyma, collenchyma, and sclerenchyma on the basis of their cell wall.
- Parenchyma: Cells have thin and flexible cell walls, making them suitable for storage and photosynthesis.
- Collenchyma: Cells have unevenly thickened cell walls, providing flexibility and mechanical support to growing parts of the plant.
- Sclerenchyma: Cells have thick, lignified cell walls, making them rigid and strong, providing structural support to mature plant parts.
5. What are the functions of the stomata?
Stomata are responsible for gas exchange, allowing carbon dioxide to enter the plant for photosynthesis and oxygen to exit. They also regulate water loss through transpiration, helping to maintain water balance within the plant.
6. Diagrammatically show the difference between the three types of muscle fibres.
- Striated Muscle (Skeletal Muscle): Long, cylindrical, multinucleated fibers with alternating light and dark bands.
- Smooth Muscle: Spindle-shaped, uninucleate fibers without striations, found in the walls of internal organs like the stomach and intestines.
- Cardiac Muscle: Cylindrical, branched, uninucleate fibers with striations and intercalated discs, found in the heart.
7. What is the specific function of the cardiac muscle?
The specific function of the cardiac muscle is to pump blood throughout the body by contracting and relaxing rhythmically and involuntarily, ensuring continuous blood circulation.
8. Differentiate between striated, unstriated, and cardiac muscles on the basis of their structure and site/location in the body.
- Striated Muscle (Skeletal Muscle):
- Structure: Long, cylindrical, multinucleated cells with striations.
- Location: Attached to bones, responsible for voluntary movements.
- Unstriated Muscle (Smooth Muscle):
- Structure: Spindle-shaped, uninucleate cells without striations.
- Location: Found in the walls of internal organs, controlling involuntary movements.
- Cardiac Muscle:
- Structure: Cylindrical, branched, uninucleate cells with striations and intercalated discs.
- Location: Found in the heart, responsible for involuntary rhythmic contractions.
9. Draw a labelled diagram of a neuron.
- The diagram should include the cell body, dendrites, axon, and nerve endings.
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: Epithelial tissue (specifically, stratified squamous epithelium).
- Bark of tree: Protective tissue (cork).
- Bone: Connective tissue (bone tissue).
- Lining of kidney tubule: Epithelial tissue (cuboidal epithelium).
- Vascular bundle: Complex tissue (xylem and phloem).
12. Name the regions in which parenchyma tissue is present.
Parenchyma tissue is present in various regions of the plant, including the cortex and pith of stems, the mesophyll of leaves, and the soft parts of fruits. It serves as a primary tissue for storage, photosynthesis, and healing.
13. What is the role of the epidermis in plants?
The epidermis serves as the outer protective layer of the plant. It helps in protecting the plant from water loss, mechanical injury, and infection by pathogens. The epidermis also plays a role in gas exchange and transpiration through structures like stomata.
14. How does the cork act as a protective tissue?
Cork acts as a protective tissue by forming a tough, thick, and waterproof layer on the surface of stems and roots in woody plants. The cells of cork are dead and compactly arranged, with walls that contain suberin, a substance that makes them impermeable to gases and water. This helps protect the plant from water loss, physical damage, and infections.
15. Complete the following chart:
Here’s a brief explanation of the chart you might be completing:
- Tissue Type:
- Meristematic Tissue: Cells actively divide and are found in growing regions like the tips of roots and shoots.
- Simple Permanent Tissue: Consists of one type of cell, such as parenchyma, collenchyma, and sclerenchyma.
- Complex Permanent Tissue: Made up of more than one type of cell, such as xylem (for water transport) and phloem (for food transport).