NCERT Class 9 Science Solutions: Tissues

Question:

Parenchyma is a fundamental plant tissue found in various parts of plants. It consists of living cells with thin cell walls, involved in storage, photosynthesis, and secretion. Identifying regions where parenchyma is abundant is key.


Parenchyma tissue is present in a wide variety of plant organs and regions. These include:

1. Cortex: This is the outermost layer of cells in stems and roots, lying just inside the epidermis. Parenchyma cells in the cortex are often involved in storage of food reserves.

2. Pith: Located in the center of stems and roots, the pith is also composed primarily of parenchyma cells. It serves as a storage tissue.

3. Mesophyll of Leaves: The internal tissue of a leaf, between the upper and lower epidermis, is called the mesophyll. This region is rich in parenchyma cells, specifically chlorenchyma (a type of parenchyma containing chloroplasts), which are the primary sites of photosynthesis.

4. Flesh of Fruits: The soft, edible parts of many fruits are composed of parenchyma tissue, which is responsible for storing sugars and water.

5. Seed Cotyledons: The cotyledons (seed leaves) of many seeds are parenchymatous and serve to store food for the developing embryo.

6. Ground Tissues: Generally, parenchyma forms the bulk of the ground tissue system in plants, which includes the cortex, pith, and mesophyll.

7. Vascular Bundles: While vascular tissues (xylem and phloem) are the primary components of vascular bundles, parenchyma cells are often found associated with them, forming parenchyma sheaths or ray parenchyma in secondary growth.

Therefore, parenchyma tissue is a ubiquitous component of plant anatomy, found in stems, roots, leaves, fruits, and seeds.

Question:

The question asks about the components that make up phloem, a type of vascular tissue in plants responsible for transporting sugars. To answer this, one needs to recall the specific cell types and tissues that constitute phloem.


Phloem is a complex tissue found in vascular plants. It is primarily responsible for the translocation of soluble organic compounds, especially sugars produced during photosynthesis, from the leaves to other parts of the plant where they are needed for growth or storage. The main constituents of phloem are:

1. Sieve elements: These are the principal conducting cells. In angiosperms, they are called sieve-tube elements, which are arranged end to end to form sieve tubes. In gymnosperms and pteridophytes, they are called sieve cells. Sieve-tube elements lack a nucleus, ribosomes, and a large central vacuole at maturity, which facilitates the flow of sap. Their end walls are perforated, forming sieve plates.

2. Companion cells: These are associated with sieve-tube elements in angiosperms. They are closely connected to sieve-tube elements and are metabolically active. Companion cells play a vital role in loading and unloading sugars into the sieve-tube elements and provide metabolic support to them.

3. Phloem parenchyma: These are living cells that store food materials and other substances like resins and latex. They also help in the lateral translocation of food.

4. Phloem fibers: These are elongated, thick-walled sclerenchyma cells that provide mechanical support to the phloem tissue. They are dead at maturity.

Therefore, the constituents of phloem are sieve elements (sieve-tube elements and sieve cells), companion cells, phloem parenchyma, and phloem fibers.

Question:

The skin is a complex organ made up of several different types of tissues that work together to perform various functions like protection, sensation, and temperature regulation. Understanding the different tissue types in the body is crucial to identifying them in specific organs. The main tissue types are epithelial tissue, connective tissue, muscle tissue, and nervous tissue.


The skin is primarily composed of epithelial tissue, connective tissue, and in some layers, muscle tissue and nervous tissue. The outermost layer of the skin, the epidermis, is made of epithelial tissue (specifically, stratified squamous epithelium). Beneath the epidermis lies the dermis, which is primarily composed of connective tissue (dense irregular connective tissue). Muscle tissue (arrector pili muscles) and nervous tissue (sensory receptors) are also found within the skin. Therefore, the skin contains multiple types of tissues. However, if asked to identify the *type of tissue* in the skin as a general question, the most prominent and defining tissues are epithelial and connective tissues. Given the phrasing of the question, it’s likely looking for the major tissue types present.

The skin contains:
1. Epithelial Tissue (Epidermis): Forms the protective outer layer.
2. Connective Tissue (Dermis): Provides support, strength, and contains blood vessels, nerves, and glands.
3. Muscle Tissue (arrector pili muscles): Attached to hair follicles, causing “goosebumps”.
4. Nervous Tissue: Contains sensory receptors for touch, pain, temperature, and pressure.

Therefore, the skin is composed of a combination of epithelial tissue, connective tissue, muscle tissue, and nervous tissue.

Question:

Cardiac muscles are specialized muscle tissues found only in the heart. They are responsible for the rhythmic contraction and relaxation that pumps blood throughout the body. Understanding their unique structure and function is key to answering this question.


Here are three features of cardiac muscles:

1. Striated: Cardiac muscle fibers exhibit striations, which are alternating light and dark bands, similar to skeletal muscle. This striation is due to the organized arrangement of contractile proteins like actin and myosin.

2. Branched: Unlike skeletal muscle fibers which are generally unbranched and cylindrical, cardiac muscle fibers are branched. These branches interconnect with neighboring fibers, forming a complex network.

3. Intercalated Discs: Cardiac muscles are characterized by the presence of intercalated discs. These are specialized junctions between adjacent cardiac muscle cells. They contain gap junctions that allow for rapid communication and electrical coupling between cells, ensuring coordinated contractions, and desmosomes that provide mechanical strength and prevent cells from pulling apart during contraction.

4. Uninucleated: Each cardiac muscle cell typically contains a single, centrally located nucleus. While multinucleated cells are common in skeletal muscle, cardiac muscle cells are generally uninucleated.

5. Involuntary: Cardiac muscle contraction is involuntary, meaning it is not under conscious control. The heart beats rhythmically without us having to think about it, regulated by the intrinsic electrical system of the heart.

(Choose any three of the above points as your answer.)

Question:

Connective tissues are a diverse group of tissues that support, connect, or separate different types of tissues and organs in the body. They are characterized by having cells embedded in an extracellular matrix. This matrix can be solid, gel-like, or fluid.


The question asks to name a connective tissue that has a fluid matrix. Among the different types of connective tissues, blood is the classic example that fits this description. Blood consists of cells (red blood cells, white blood cells, and platelets) suspended in a fluid extracellular matrix called plasma. Plasma is primarily composed of water, proteins, salts, and other dissolved substances, making it fluid in nature. Therefore, blood is the connective tissue with a fluid matrix.

Detailed Solution:
1. Identify the core requirement: The question asks for a connective tissue with a fluid matrix.
2. Recall types of connective tissues: Think about the various classifications and examples of connective tissues taught in high school biology. These include loose connective tissue, dense connective tissue, adipose tissue, cartilage, bone, and blood.
3. Analyze the matrix of each type:
* Loose and dense connective tissues have a gel-like or fibrous matrix.
* Cartilage and bone have a solid, calcified matrix.
* Blood has a fluid matrix.
4. Match the description to the tissue: Based on the analysis, blood is the connective tissue characterized by a fluid matrix (plasma).
5. State the answer: The connective tissue with a fluid matrix is blood.

Question:

A neuron is a specialized cell that transmits nerve impulses. Its structure is adapted for this function, consisting of distinct parts responsible for receiving, processing, and transmitting signals.


A neuron, also known as a nerve cell, is the fundamental unit of the nervous system. It has a characteristic structure that allows it to communicate with other cells. The main parts of a neuron are:

1. Dendrites: These are branched, tree-like extensions that receive signals from other neurons and transmit them towards the cell body.

2. Cell Body (Soma): This is the central part of the neuron, containing the nucleus and other essential organelles. It processes the incoming signals.

3. Axon: This is a long, slender projection that carries nerve impulses (action potentials) away from the cell body towards other neurons, muscles, or glands.

4. Axon Terminals (Synaptic Terminals): These are the branched endings of the axon that form synapses with other cells. They release neurotransmitters, chemical messengers that transmit signals across the synapse.

5. Myelin Sheath: In many neurons, the axon is covered by a fatty insulating layer called the myelin sheath. This sheath speeds up the transmission of nerve impulses. Gaps in the myelin sheath are called Nodes of Ranvier.

In essence, a neuron resembles a tiny electrical wire with branches at either end, designed for efficient communication throughout the body.

Question:

The question asks to differentiate between parenchyma, collenchyma, and sclerenchyma based on their cell walls. This requires understanding the characteristic cell wall composition and thickness of each of these plant tissues.


The primary difference between parenchyma, collenchyma, and sclerenchyma lies in the modifications of their cell walls.

Parenchyma:
Cell Wall: Parenchyma cells have thin, primary cell walls made primarily of cellulose. These walls are typically uniform in thickness and are living at maturity.

Collenchyma:
Cell Wall: Collenchyma cells have unevenly thickened primary cell walls. The thickening is usually at the corners and is due to the deposition of extra cellulose and pectin. The cell lumen remains relatively large. These cells are also living at maturity.

Sclerenchyma:
Cell Wall: Sclerenchyma cells have thick, lignified secondary cell walls. Lignin is a rigid substance that makes the cell walls very strong and impermeable to water. The cell lumen is often very narrow or absent. These cells are typically dead at maturity.

To summarize the differentiation based on cell wall:

Parenchyma: Thin, primary cell walls, uniform thickness.
Collenchyma: Unevenly thickened primary cell walls, particularly at corners, due to cellulose and pectin.
Sclerenchyma: Thick, lignified secondary cell walls, strong and rigid.

Question:

Stomata are small pores on the surface of leaves, stems, and other organs of plants. They are surrounded by specialized cells called guard cells.


The primary functions of stomata are:

1. Gas Exchange: Stomata facilitate the exchange of gases between the plant and the atmosphere.
* Carbon Dioxide (CO2) uptake: Plants require CO2 for photosynthesis. Stomata open to allow CO2 to enter the leaf.
* Oxygen (O2) release: Oxygen is a byproduct of photosynthesis and needs to be released from the plant. Stomata allow O2 to exit.

2. Transpiration: Stomata are the main sites for transpiration, which is the process of water vapor loss from the plant, primarily through the stomatal pores.
* Water movement: Transpiration creates a “pull” that draws water from the roots up through the xylem to the leaves, helping to transport water and dissolved minerals throughout the plant.
* Cooling: Transpiration also helps to cool the plant, especially during hot weather.

3. Regulation of water loss: The guard cells surrounding the stomata can open or close them in response to environmental conditions. This regulation helps the plant to conserve water when it is scarce, while still allowing for gas exchange when necessary. For example, stomata usually close at night to reduce water loss and open during the day for photosynthesis.

Question:

The lining of kidney tubules is composed of specialized cells that perform functions like absorption and secretion. Identifying the type of tissue requires understanding the different epithelial tissues and their characteristic structures and functions. Specifically, knowledge of simple cuboidal epithelium, which lines many ducts and tubules, is crucial.


The inner lining of kidney tubules is primarily composed of simple cuboidal epithelium. This type of epithelial tissue consists of a single layer of cube-shaped cells. The cells have a relatively large, centrally located nucleus. Simple cuboidal epithelium is well-suited for the kidney tubules because its structure facilitates efficient absorption of useful substances from the filtrate and secretion of waste products into the tubule. The short diffusion distance across a single layer of cuboidal cells is advantageous for these transport processes. Other epithelial tissues like squamous, columnar, or stratified epithelia have different structures and functions and are not the primary tissue type found lining the kidney tubules.

Question:

A neuron is the basic structural and functional unit of the nervous system. It is a specialized cell responsible for transmitting nerve impulses. Key parts include the cell body (soma), dendrites, and axon.


To draw a labelled diagram of a neuron, follow these steps:
1. Draw a roughly spherical or star-shaped structure to represent the cell body (soma). This contains the nucleus and other organelles.
2. From the cell body, draw several short, branched extensions called dendrites. These receive signals from other neurons.
3. From the cell body, draw a single, long projection called the axon. This transmits signals away from the cell body.
4. The axon may be covered by a myelin sheath, which is a fatty insulating layer. Draw segments along the axon to represent this.
5. At the end of the axon, draw branched structures called axon terminals (or synaptic terminals). These connect to other neurons or effector cells.
6. Label all these parts clearly: Cell Body (Soma), Nucleus, Dendrites, Axon, Myelin Sheath, Nodes of Ranvier (gaps between myelin sheath segments), Axon Terminal.

Question:

The epidermis is the outermost protective layer of cells in plants. It’s responsible for shielding the plant from mechanical damage, preventing water loss, and facilitating gas exchange through stomata.


The epidermis forms a continuous protective covering over the entire plant body, including leaves, stems, and roots. Its primary role is to act as a barrier against physical injury and invasion by pathogens. A waxy layer called the cuticle, secreted by epidermal cells, further reduces water loss through evaporation (transpiration). In leaves and young stems, the epidermis contains specialized pores called stomata, surrounded by guard cells, which regulate the uptake of carbon dioxide for photosynthesis and the release of oxygen and water vapor. In roots, some epidermal cells are modified into root hairs, which significantly increase the surface area for absorption of water and minerals from the soil.

Question:

Plant tissues are broadly classified into meristematic and permanent tissues. Permanent tissues are further divided into simple permanent tissues (parenchyma, collenchyma, sclerenchyma) and complex permanent tissues (xylem, phloem). Sclerenchyma tissue is characterized by cells with thick, lignified secondary walls, providing mechanical support and strength. It is found in various parts of plants, including seed coats, fruit skins, and fibrous structures.


The husk of a coconut is the fibrous outer layer. This fibrous texture and toughness are characteristic features of sclerenchyma tissue. Specifically, the husk is primarily composed of sclerenchyma fibers. These cells have very thick, lignified secondary cell walls, which make them strong and rigid, ideal for providing structural support and protection, as seen in the coconut husk.

The final answer is $\boxed{\text{Sclerenchyma}}$.

Question:

Vascular bundles are the primary conducting tissues in plants, responsible for the transport of water, minerals, and sugars. They are composed of two main types of vascular tissues: xylem and phloem. Xylem primarily transports water and minerals from roots to the rest of the plant, while phloem transports organic nutrients (sugars) from leaves to other parts of the plant.


A vascular bundle in plants is a strand of conducting vessels, typically consisting of xylem and phloem. Xylem is responsible for transporting water and dissolved minerals upwards from the roots to the leaves. Phloem is responsible for transporting synthesized food materials (sugars) from the leaves to all other parts of the plant where they are needed for growth or storage. Therefore, the type of tissue in a vascular bundle is vascular tissue, specifically xylem and phloem.

Question:

Simple tissues in plants are those composed of only one type of cell. These cells are structurally and functionally similar.


The question asks to name the types of simple tissues. Simple tissues in plants are classified based on their cell type and function. There are three main types of simple tissues:
1. Parenchyma: These are living cells, typically isodiametric (equal in all dimensions), with thin primary cell walls. They are involved in storage of food, photosynthesis, and secretion.
2. Collenchyma: These are living cells, elongated and thicker at the corners. They provide mechanical support to growing plant parts.
3. Sclerenchyma: These cells are typically dead at maturity and have thick, lignified secondary cell walls. They provide strength and rigidity to mature plant parts. They are of two types: fibers and sclereids.

Question:

Plant tissues, protective tissues, cork, bark, waterproof, mechanical injury, pathogen entry.


Cork acts as a protective tissue due to its unique cellular structure and chemical composition. The cells of cork are dead at maturity and are heavily impregnated with suberin, a waxy substance. This impregnation makes the cork layer impermeable to water and gases, preventing desiccation (drying out) of the plant. The presence of suberin also makes the cork tough and resistant to mechanical injury from external forces, such as impacts or abrasion. Furthermore, the impermeable nature of cork acts as a barrier against the entry of pathogens like bacteria and fungi, thus protecting the underlying tissues from infection. The layered structure of cork, often forming the bark of trees, provides an effective defense system for the plant.

Question:

Basic definition of tissues, multi-cellular organisms, and the principle of division of labor.


In multi-cellular organisms, different groups of cells specialize to perform specific functions. These specialized groups of cells are called tissues. The utility of tissues lies in the principle of division of labor. This means that instead of each individual cell performing all life functions, different tissues are responsible for different tasks. This specialization leads to increased efficiency and complexity in the organism. For example, muscle tissues are specialized for movement, nervous tissues for communication, and epithelial tissues for protection. This division of labor allows multi-cellular organisms to carry out a wide range of complex activities, leading to better survival, growth, and reproduction.

Question:

Our bodies have specialized tissues that perform various functions. Movement is a fundamental characteristic of living organisms, and specific tissues are adapted for this purpose. Understanding the different types of tissues and their roles is crucial.


The tissue responsible for movement in our body is muscle tissue. Muscle tissue is composed of specialized cells called muscle fibers that have the ability to contract and relax, generating force that enables us to move our limbs, organs, and even substances within our bodies. There are three main types of muscle tissue: skeletal muscle (responsible for voluntary movements), smooth muscle (found in internal organs and responsible for involuntary movements), and cardiac muscle (found in the heart and responsible for pumping blood).

Question:

Cardiac muscle is a specialized type of muscle tissue found only in the heart. Its primary function is to enable the heart to pump blood throughout the body. This pumping action is achieved through rhythmic, involuntary contractions.


The specific function of cardiac muscle is to contract and relax rhythmically and involuntarily to pump blood throughout the body. This continuous pumping action is essential for delivering oxygen and nutrients to all tissues and organs and for removing waste products. Unlike skeletal muscles, which are under voluntary control, or smooth muscles, which control involuntary movements in organs like the digestive tract, cardiac muscle’s unique structure allows it to generate its own electrical impulses and maintain a steady, coordinated heartbeat.

Question:

Tissues are groups of similar cells that perform a specific function. Different types of tissues are found in the human body, each with a unique structure and role. Epithelial tissue is a type of tissue that covers surfaces, lines cavities, and forms glands.


The inner lining of our mouth is a moist surface that protects the underlying tissues and helps in processes like chewing and swallowing. This lining is made up of a type of tissue called epithelial tissue. Specifically, it is lined by stratified squamous epithelium. This type of epithelium is composed of multiple layers of flattened cells, which provides a protective barrier against abrasion and the entry of microorganisms.

Therefore, the tissue that forms the inner lining of our mouth is epithelial tissue.

Question:

Plants have specialized vascular tissues for transport. One type of vascular tissue is responsible for moving sugars produced during photosynthesis from the leaves to other parts of the plant.


The tissue that transports food in plants is called phloem. Phloem is a complex vascular tissue composed of several cell types, including sieve elements, companion cells, phloem parenchyma, and phloem fibers. Its primary function is to translocate sugars (mainly sucrose) from the source (typically the leaves) to the sinks (such as roots, fruits, seeds, and growing regions) where they are used for energy or storage. This process is known as translocation.

Question:

Apical meristem is a type of plant tissue responsible for growth in length. It is characterized by actively dividing cells. Understanding the location and function of meristematic tissues in plants is crucial.


The apical meristem is found at the tips of plant shoots and roots. These are regions of continuous cell division that contribute to the primary growth of the plant, meaning an increase in length. Specifically, shoot apical meristems are located at the apex (tip) of the stem and in the axils of leaves (forming lateral buds which can grow into branches). Root apical meristems are found at the very tip of the root.

Question:

The question asks to identify the specific type of tissue responsible for storing fat in the human body. This involves recalling the different types of connective tissues and their primary functions.


The tissue that stores fat in our body is called adipose tissue. Adipose tissue is a type of loose connective tissue made up of adipocytes, which are specialized cells for storing lipids (fats). These fat globules fill the cytoplasm of the adipocytes, pushing the nucleus to the periphery. Adipose tissue serves several important functions, including energy storage, insulation, and cushioning of organs.

Question:

The brain is a complex organ responsible for processing information and controlling bodily functions. Tissues are groups of similar cells that perform a specific function. Different parts of the body are made up of different types of tissues.


The primary tissue present in the brain is nervous tissue. Nervous tissue is specialized for rapid communication throughout the body. It is composed of two main types of cells: neurons, which transmit electrical and chemical signals, and glial cells, which support and protect neurons. Therefore, the tissue present in the brain is nervous tissue.

Question:

A tissue is a group of cells that are similar in structure and function. These cells work together to perform a specific job within an organism.


A tissue is a fundamental level of organization in multicellular organisms. It’s like a team of workers, where each worker (cell) has a specific role and they all cooperate to achieve a common goal. For example, muscle tissue is made up of muscle cells that contract to enable movement. Similarly, nervous tissue is composed of nerve cells that transmit signals. Tissues are the building blocks for organs, which in turn form organ systems.

Question:

The question asks to identify the connective tissue that forms a bridge between muscles and bones in the human body. This requires knowledge of different types of connective tissues and their functions.


The tissue that connects muscle to bone in humans is called a tendon. Tendons are strong, fibrous cords made of dense connective tissue. They are crucial for locomotion, as they transmit the force generated by muscle contractions to the bones, enabling movement of the skeletal system. Ligaments, another type of connective tissue, connect bone to bone.

Question:

Biology, Cells, Organization of Life, Tissues, Similar Cells, Common Function


A tissue is a group of similar cells, along with their intercellular substance, that are specialized to perform a specific function. These cells work together in a coordinated manner to carry out a particular task within an organism. Examples include muscle tissue for movement, nervous tissue for communication, and epithelial tissue for covering surfaces.

Question:

Xylem is a complex plant tissue responsible for water and mineral transport and mechanical support. Complex tissues are composed of different types of cells working together.


Xylem tissue is composed of four distinct types of cells, which are:
1. Tracheids
2. Vessels
3. Xylem parenchyma
4. Xylem fibers