Class 9 Science Chapter 6 Tissues

Key Concept: Phloem Fibres

c) Phloem tissue

[Solution Description] Phloem fibres are part of the phloem tissue, which is one of the complex tissues in plants responsible for transporting food and providing structural support.

Key Concept: Apical Meristem, Growth Mechanism

d) Elongation of the stem and roots

[Solution Description]

The apical meristem is responsible for the elongation of the plant by producing new cells at the tips of roots and shoots. When it is removed, the primary growth in length will halt because there are no more actively dividing cells to contribute to this growth. Although lateral growth can still occur due to the lateral meristem, the direct impact of removing the apical meristem is the cessation of longitudinal growth.

Key Concept: Meristematic Tissue

c) Lateral meristem

[Solution Description]

The girth of the stem or root increases due to lateral meristem, also known as cambium. Apical meristem increases the length of the stem and root, while intercalary meristem is located near the node.

Key Concept: Simple Permanent Tissue

c) Flexibility and mechanical support

[Solution Description]

The flexibility in plants is due to collenchyma tissue. It allows bending of various parts of a plant like tendrils and stems of climbers without breaking. It also provides mechanical support.

Key Concept: Concept: Types of Tissues in Plants and Animals

c) Plants have mostly dead tissues for support

[Solution Description]

The syllabus states that plants have a large quantity of supportive tissue with dead cells, while animals contain mostly living tissues. This reflects their different modes of life: plants are stationary and require structural support, whereas animals move around and consume more energy.

Key Concept: Cork Cells

b) They are dead and contain suberin

[Solution Description] Cork cells are formed from a strip of secondary meristem located in the cortex. These cells are dead, compactly arranged without intercellular spaces, and contain a substance called suberin in their walls, making them impervious to gases and water.

Key Concept: Meristematic Tissue

d) Meristematic tissue

[Solution Description]

Meristematic tissues are the tissues in plants that have the ability to divide throughout their life. These tissues are localised in specific regions such as the tips of roots and stems, contributing to the plant’s growth.

Key Concept: Epithelial Tissue

c) Ciliated columnar epithelium

[Solution Description]

The respiratory tract contains ciliated columnar epithelium. This type of epithelial tissue has hair-like projections called cilia on the outer surfaces of epithelial cells. These cilia can move, pushing mucus forward to clear it from the respiratory tract.

Key Concept: Phloem Transport

b) Leaves to other parts of the plant

[Solution Description] Phloem is responsible for the transportation of food, primarily in the form of sugars, from the leaves (where photosynthesis occurs) to other parts of the plant, such as roots, stems, and fruits.

Key Concept: Neuron Structure

c) Cell body

[Solution Description]

The nucleus of a neuron is located within the cell body. The cell body is the main part of the neuron that contains the cytoplasm and organelles, including the nucleus.

Key Concept: Cork Cells

c) To make cells impermeable to gases and water

[Solution Description]

Suberin is a substance found in the walls of cork cells. It makes these cells impervious to gases and water, providing waterproofing and protection.

Key Concept: Definition of Tissue

c) A group of cells similar in structure and function

[Solution Description] A tissue is a group of cells that are similar in structure and function, working together to achieve a specific purpose.

Key Concept: Sclerenchyma Cells

b) Dead cells with thick lignified walls

[Solution Description]

Sclerenchyma cells are characterized by being dead at maturity, having thick lignified walls, and lacking internal space. These features provide strength to the plant parts.

Key Concept: Epidermal Tissue

c) Protection

[Solution Description]

The epidermis is the outermost layer of cells in plants, forming a continuous protective layer without intercellular spaces. Its main functions include protection against water loss, mechanical injury, and invasion by parasitic fungi. It also secretes a waxy, water-resistant layer on its outer surface.

Key Concept: Neuron Structure

c) Dendrite

[Solution Description]

Dendrites are the short, branched parts of a neuron that receive signals from other neurons and transmit them toward the cell body.

Key Concept: Plant Tissues

d) Xylem

[Solution Description]

In plants, the tissue responsible for the transport of water and minerals is called xylem. Xylem is a complex tissue that consists of various elements like tracheids, vessels, xylem parenchyma, and xylem fibers. Its main function is to conduct water and dissolved minerals from the roots to the other parts of the plant.

Key Concept: Tissue Definition

c) A group of cells that are similar in structure and/or work together to achieve a particular function

[Solution Description]

A tissue is defined as a group of cells that are similar in structure and or work together to achieve a particular function. This is the basic definition provided in the syllabus.

Key Concept: Stratified Squamous Epithelium

d) Skin

[Solution Description]

Stratified squamous epithelium is composed of multiple layers of epithelial cells. It is primarily found in areas subject to wear and tear, such as the skin.

Key Concept: Phloem Function

c) Transporting food from leaves to other parts of the plant

[Solution Description]

Phloem is composed of sieve tubes, companion cells, phloem fibres, and phloem parenchyma. Its main function is to transport food from leaves to other parts of the plant.

Key Concept: Chlorenchyma

b) Chlorenchyma

[Solution Description] When parenchyma contains chlorophyll and performs photosynthesis, it is specifically referred to as chlorenchyma.

Key Concept: Stomata Function

b) Facilitating gas exchange

[Solution Description]

Stomata are small pores found in the epidermis of leaves, primarily involved in gas exchange. They allow carbon dioxide to enter the leaf for photosynthesis and oxygen to exit. Additionally, they facilitate transpiration, the loss of water vapor from the plant. Hence, their main function is facilitating gas exchange.

Key Concept: Cartilage as Connective Tissue

a) Nose, Ear, Trachea

[Solution Description]

Cartilage is present in various parts of the body such as the nose, ear, trachea, larynx, and at bone surfaces in joints. It provides smooth movement and flexibility in these areas.

Key Concept: Function of Sclerenchyma

d) Mechanical support

[Solution Description]

The primary function of sclerenchyma tissue is to provide mechanical support and rigidity to plant structures. Its thick lignified cell walls enable it to withstand various stresses, making the plant hard and stiff.

Key Concept: Structure of Xylem Vessels

b) Tubular structure

[Solution Description]

Xylem vessels are tubular structures with thick walls. This tubular nature allows them to transport water and minerals efficiently. Therefore, the correct answer is “Tubular structure.”

Key Concept: Simple Permanent Tissue

d) Store food

[Solution Description]

Parenchyma is the most common simple permanent tissue consisting of unspecialized cells with thin cell walls. Its primary function is to store food. In some cases, it can also contain chlorophyll (chlorenchyma) or have air cavities (aerenchyma) to aid in buoyancy, but its main role remains food storage.

Key Concept: Cardiac Muscles

b) Cylindrical and branched

[Solution Description]

Cardiac muscle cells are cylindrical, branched, and uninucleate. They are responsible for the rhythmic contraction and relaxation of the heart throughout life.

Key Concept: Nervous Tissue Composition

a) Axon

[Solution Description]

Neurons, which are the cells of the nervous tissue, are responsible for receiving and conducting impulses. They play a crucial role in transmitting information throughout the nervous system.

Key Concept: Muscular Tissue

b) Smooth muscle

[Solution Description]

Smooth muscle tissue is responsible for involuntary movements like breathing, digestion, and blood flow regulation. Cardiac muscle is specific to the heart, and skeletal muscles are voluntary.

Key Concept: Cutin

c) Cutin

[Solution Description]

The chemical substance that gives the waxy cuticle its waterproof quality is called cutin. Cutin is a hydrophobic polymer that helps reduce water loss from the plant surface.

Key Concept: Tissue Definition

c) A cluster of cells specialized in one function

[Solution Description]

A tissue is a group of cells that are similar in structure and work together to achieve a specific function. This allows for efficient division of labor in multi-cellular organisms.

Key Concept: Tissue Definition

c) A cluster of similar cells performing a specific function

[Solution Description]

In multicellular organisms, tissues are groups of cells that are similar in structure and work together to achieve a specific function. This grouping increases the efficiency of performing that particular function.

Key Concept: Complex Permanent Tissue

b) Phloem

[Solution Description]

Phloem is the complex tissue made up of sieve tubes, companion cells, phloem fibres, and phloem parenchyma, responsible for transporting food from leaves to other parts of the plant.

Key Concept: Composition of Cork Cells

c) Suberin

[Solution Description]

The cells of cork 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.

Key Concept: Muscular Tissue

c) Muscular tissue

[Solution Description]

Muscular tissue consists of elongated cells called muscle fibers, which are responsible for movement in the body.

Key Concept: Tissue Structure, Growth Patterns

c) Plant growth is limited to certain regions, while animal growth is uniform.

[Solution Description]

Plant growth is limited to specific regions, such as meristematic tissues, which are capable of continuous division throughout the plant’s life. These regions are localized and contribute to the plant’s ability to grow in height and width. In contrast, animals exhibit uniform cell growth across their bodies, without distinct regions dedicated solely to growth. This fundamental difference arises due to the sedentary nature of plants and the active locomotion of animals.

Key Concept: Smooth Muscles

c) Movement of food in the alimentary canal

[Solution Description] Smooth muscles, also known as involuntary or unstriated muscles, are responsible for movements that we cannot consciously control. These include the movement of food in the alimentary canal, contraction and relaxation of blood vessels, and other involuntary functions. They are found in the iris of the eye, ureters, and bronchi of the lungs.

Key Concept: Location of Collenchyma

b) Below the epidermis in leaf stalks

[Solution Description]

Collenchyma tissue is typically found just below the epidermis in leaf stalks and stems. Its location allows it to provide structural support and flexibility to these parts of the plant. It is not found in roots, flowers, or seeds.

Key Concept: Tracheids – Maturity

c) When they are mature and dead

[Solution Description]

Tracheids are functional in the xylem tissue when they are mature. At this stage, they are dead cells with thick, lignified walls, which allows them to efficiently transport water and minerals vertically throughout the plant.

Key Concept: Parenchyma, Intercellular Spaces

c) To facilitate the storage and movement of substances

[Solution Description]

Parenchyma tissue consists of loosely arranged living cells with thin cell walls. The large intercellular spaces between these cells allow for the storage of substances like air or water.

Key Concept: Cork Cells

a) Suberin

[Solution Description] Cork cells have a substance called $suberin$ in their walls, which makes them impervious to gases and water. This is a key feature of cork cells as mentioned in the syllabus.

Key Concept: Characteristics of Xylem Cells

c) They are dead cells at maturity

[Solution Description]

Tracheids and vessels are tubular structures in the xylem that facilitate the transport of water and minerals. Both have thick walls and are dead cells when they reach maturity, which allows them to perform their function efficiently.

Key Concept: Living Cells in Phloem

a) Sieve tubes, companion cells, and phloem parenchyma

[Solution Description]

The phloem consists of five types of cells: sieve cells, sieve tubes, companion cells, phloem fibres, and phloem parenchyma. Among these, all except phloem fibres are living cells.

Key Concept: Collenchyma Function

d) Provides mechanical support and flexibility

[Solution Description]

Collenchyma tissue provides flexibility and mechanical support to plant parts like stems and leaf stalks. It allows bending without breaking, which is essential for climbing plants and tendrils.

Key Concept: Complex Permanent Tissue: Phloem Components

b) Sieve tube

[Solution Description]

Phloem is composed of sieve cells, sieve tubes, companion cells, phloem fibres, and phloem parenchyma. Sieve tubes are tubular cells with perforated walls, which facilitate the transport of food from leaves to other parts of the plant.

Key Concept: Sieve Tubes Function

c) Transport food from leaves to other parts of the plant

[Solution Description]

Sieve tubes are a part of the phloem tissue in plants. Their primary function is to transport food, which is mainly sucrose, from the leaves (where it is produced through photosynthesis) to other parts of the plant such as roots, stems, and fruits.

Key Concept: Stomata and Guard Cells

b) Guard cells

[Solution Description]

Stomata are small pores found in the epidermis of leaves, enclosed by two kidney-shaped cells called guard cells. These guard cells control the opening and closing of stomata, which is essential for gas exchange and transpiration.

Key Concept: Parenchyma, Collenchyma

b) Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion.

[Solution Description]

The assertion states that parenchyma cells are thin-walled, living cells with large intercellular spaces, which is true as per the syllabus. Parenchyma cells store food and can also perform photosynthesis when they contain chlorophyll, forming chlorenchyma. The reason states that collenchyma cells are thick-walled, living cells with little intercellular space, which is also true. Collenchyma provides mechanical support and flexibility to plant parts like tendrils and stems. However, the reason does not explain why parenchyma cells have these characteristics; it merely describes another type of tissue (collenchyma). Therefore, both the assertion and reason are true, but the reason does not correctly explain the assertion.

Key Concept: Connective Tissue – Bone

d) Supporting the body

[Solution Description]

Bone is a strong and nonflexible connective tissue that forms the framework supporting the body. It anchors muscles, supports internal organs, and provides structural stability. Thus, the primary function of bone is to provide support and structure to the body.

Key Concept: Structural Organisation

d) Animals have more specialised organ systems

[Solution Description]

The structural organisation of organs and organ systems is far more specialised and localised in complex animals than in very complex plants. This reflects their different modes of life, particularly in their feeding methods and adaptation to sedentary existence versus active locomotion.

Key Concept: Cell Characteristics

b) They are dead cells with thick walls

[Solution Description]

Sclerenchyma cells are characterized by being dead at maturity, having thick cell walls due to lignin deposition, and often lacking internal space. These features contribute to their role in providing mechanical support to the plant.

Key Concept: Simple Permanent Tissue

b) Chlorenchyma

[Solution Description]

Chlorenchyma is a type of parenchyma tissue that contains chlorophyll and performs photosynthesis. It is specialized for this function and is found in the green parts of plants where photosynthesis occurs.

Key Concept: Concept: Examples of Tissues

c) Vascular tissue

[Solution Description]

In plants, vascular tissues such as xylem and phloem are examples of tissues that conduct food and water from one part of the plant to other parts. These tissues are specialised for their respective functions, contributing to the overall efficiency of the plant.

Key Concept: Simple Permanent Tissue

b) Collenchyma

[Solution Description]

The flexibility in plants is due to the presence of collenchyma tissue. Collenchyma allows bending of various parts of a plant like tendrils and stems of climbers without breaking. It also provides mechanical support. The cells of this tissue are living, elongated, and irregularly thickened at the corners.

Key Concept: Function of Sieve Tubes

c) Transporting food from leaves to other parts

[Solution Description]

Sieve tubes are tubular cells with perforated walls that facilitate the transportation of food (primarily sugars) from the leaves to other parts of the plant.

Key Concept: Complex Permanent Tissue

c) Xylem parenchyma

[Solution Description]

The xylem consists of tracheids, vessels, xylem parenchyma, and xylem fibres. Among these, the xylem parenchyma is the living component that stores food. Tracheids and vessels are involved in transporting water and minerals, while xylem fibres provide structural support.

Key Concept: Xylem fibres, structural adaptation

c) Thick lignified walls

[Solution Description]

Xylem fibres have thick lignified walls, which make them strong and rigid. This structural adaptation allows them to effectively provide mechanical support to the plant.