Samacheer Kalvi Class 9 Science Solutions Chapter 18 Organization of Tissues

I. Choose the Correct Answer:

Question 1. The tissue composed of living thin walled polyhedral cell is
(a) parenchyma
(b) sclerenchyma
(c) collenchyma
(d) none of the options
Answer: (d) none of the options
In simple words: This question asks for a specific tissue type. Since none of the listed options fit the description of living, thin-walled, polyhedral cells, "none of the options" is the correct choice. Each tissue type has distinct cell characteristics.

🎯 Exam Tip: Always double-check the definitions of tissue types. Parenchyma cells are often living and thin-walled, but their exact shape can vary; ensure your understanding of "polyhedral" is specific to their typical forms.

Question 2. The fibres consists of
(a) parenchyma
(b) sclerenchyma
(c) collenchyma
(d) none of the options
Answer: (b) sclerenchyma
In simple words: Sclerenchyma is a plant tissue known for having long, narrow cells with thick, tough walls, which are called fibres. These fibres provide strength and support to the plant.

🎯 Exam Tip: Remember that sclerenchyma is primarily a supportive tissue, and its cells are often dead at maturity, providing mechanical strength through their lignified cell walls.

Question 3. Companion cells are closely associated with
(a) sieve elements
(b) vessel elements
(c) trichomes
(d) guard cells
Answer: (a) sieve elements
In simple words: Companion cells are found next to sieve elements in plants and help them carry food. They are like helpers that keep the sieve elements alive and working because sieve elements do not have their own nucleus.

🎯 Exam Tip: Sieve elements and companion cells together form a functional unit in the phloem, crucial for nutrient transport in plants. Their close association is key to their collaborative function.

Question 4. Which of the following is a complex tissue?
(a) Parenchyma
(b) Collenchyma
(c) Xylem
(d) Sclerenchyma
Answer: (c) Xylem
In simple words: A complex tissue is made of more than one type of cell working together for a common purpose. Xylem, which carries water and minerals, is a complex tissue because it contains different types of cells like tracheids, vessels, and parenchyma.

🎯 Exam Tip: Complex tissues are essential for specialized functions in plants, unlike simple tissues which are made of only one cell type. Xylem and phloem are the two main complex tissues.

Question 5. Aerenchyma is found in
(a) epiphytes
(b) hydrophytes
(c) halophytes
(d) xerophytes
Answer: (b) hydrophytes
In simple words: Aerenchyma is a special type of tissue with large air spaces. It is commonly found in aquatic plants, called hydrophytes, to help them float and get enough air in waterlogged conditions.

🎯 Exam Tip: Aerenchyma is an adaptation that helps aquatic plants (hydrophytes) stay buoyant and allows gases to diffuse to submerged parts, which is crucial for their survival.

Question 6. Smooth muscles occur in
(a) uterus
(b) artery
(c) vein
(d) all of the options
Answer: (d) all of the options
In simple words: Smooth muscles are found in the walls of many internal organs and blood vessels in our body. They work without us thinking about it, like in the uterus during childbirth, or in arteries and veins to control blood flow.

🎯 Exam Tip: Smooth muscles are involuntary, meaning they are not under conscious control. They play vital roles in processes like digestion, blood pressure regulation, and reproduction.

Question 7. Nerve cell does not contains
(a) axon
(b) nerve endings
(c) dendrites
(d) tendons
Answer: (d) tendons
In simple words: Nerve cells, also called neurons, have parts like axons, nerve endings, and dendrites that help them send messages. Tendons, however, are made of connective tissue and link muscles to bones; they are not part of a nerve cell.

🎯 Exam Tip: Understand the basic structure of a neuron (cell body, dendrites, axon) and its role in transmitting nerve impulses. Tendons are part of the musculoskeletal system, not the nervous system.

II. Match the following.

Question 1. Match the following.

🎯 Exam Tip: For matching questions, it's helpful to identify keywords in each item and link them to their corresponding definitions or associations. Knowing the primary function or classification of each term will ensure correct pairings.

III Fill in the Blanks:

Question 1. .................... tissues provide mechanical support to organs.
Answer: Compound epithelium
In simple words: Compound epithelium tissues are made of multiple layers of cells, which makes them strong and good for protecting organs and providing structural support. This multi-layered structure gives them their supportive role.

🎯 Exam Tip: Remember that epithelial tissues are not only for lining and protection but also for mechanical support, especially when they are stratified or "compound."

Question 2. Parenchyma, Collenchyma, Sclerenchyma are .................... type of tissue.
Answer: simple
In simple words: Parenchyma, collenchyma, and sclerenchyma are all examples of simple tissues in plants. This means they are each made up of only one type of cell.

🎯 Exam Tip: Differentiate between simple tissues (one cell type) and complex tissues (multiple cell types working together). This distinction is fundamental to plant histology.

Question 3. .................... and .................... are complex issues.
Answer: Xylem, phloem
In simple words: Xylem and phloem are two types of plant tissues that are considered complex. They each have different kinds of cells working together to perform important jobs, like carrying water and food throughout the plant.

🎯 Exam Tip: Xylem and phloem are the main vascular tissues in plants, vital for transport and support. They are "complex" because they contain several cell types like vessels, tracheids, sieve tubes, and companion cells.

Question 4. Epithelial cells with cilia are found in .................... of our body
Answer: trachea
In simple words: Epithelial cells that have tiny hair-like structures called cilia are found in parts of our body like the trachea. These cilia help to move mucus and trapped particles out of the airways, keeping our lungs clean.

🎯 Exam Tip: Ciliated epithelium is commonly found in respiratory and reproductive tracts, where its function of moving substances along a surface is crucial for health.

Question 5. Lining of the small intestine is made up of ....................
Answer: columnar epithelium
In simple words: The inside lining of the small intestine is covered by a type of tissue called columnar epithelium. These tall, column-shaped cells are very good at absorbing nutrients from digested food.

🎯 Exam Tip: Columnar epithelium, especially in the intestine, often has microvilli that further increase the surface area for absorption, a key feature for its digestive function.

IV. State Whether True or False. If False, Correct the Statement:

Question 1. Epithelial tissue is protective tissue in an animal body.
Answer: False. Correct statement: Epithelium is involved in the absorption and elimination of waste.
In simple words: While epithelial tissue does provide some protection, its main jobs also include taking in (absorbing) useful things and getting rid of (eliminating) waste. So, it's not just for protection.

🎯 Exam Tip: Epithelial tissues have diverse functions depending on their location, including protection, secretion, absorption, and excretion. Always consider all roles, not just one.

Question 2. Bone and cartilage are two types of areolar connective tissue.
Answer: False. Correct statement: Bone and cartilage are two types of supportive connective tissue.
In simple words: Bone and cartilage are special tissues that help hold our body up and give it shape. They are not areolar tissue; instead, they are types of supportive connective tissue that provide structure.

🎯 Exam Tip: Connective tissues are broadly categorized. Areolar tissue is a loose connective tissue, while bone and cartilage are specialized connective tissues that fall under the "supportive" category due to their structural roles.

Question 3. Parenchyma is a simple tissue.
Answer: True.
In simple words: Yes, parenchyma is a simple plant tissue. This means it is made up of only one kind of cell, and these cells are typically involved in storage and photosynthesis.

🎯 Exam Tip: Simple tissues in plants include parenchyma, collenchyma, and sclerenchyma, each composed of a single cell type performing specific functions.

Question 4. Phloem is made up of tracheids.
Answer: False. Correct statement: Phloem is made up of sieve tubes.
In simple words: Phloem is the plant tissue that carries food, and its main working cells are called sieve tubes. Tracheids, on the other hand, are part of the xylem, which carries water.

🎯 Exam Tip: Clearly distinguish between xylem and phloem elements. Tracheids and vessel elements are characteristic of xylem, while sieve tubes and companion cells define phloem.

Question 5. Vessels are found in collenchyma.
Answer: False. Correct statement: Vessels are found in the xylem.
In simple words: Vessels are important tubes that carry water in plants and are part of the xylem tissue. Collenchyma is a different type of plant tissue that provides flexible support, and it does not contain vessels.

🎯 Exam Tip: Vessels are key components of the plant's vascular system (xylem) for water transport, whereas collenchyma is a ground tissue for support in young stems and petioles.

V. Answer Briefly:

Question 1. What are intercalary meristems? How do they differ from other meristems?
Answer: Intercalary meristems are growth tissues found between regions of permanent tissues in plants. They are part of the primary meristem, and they occur at the base of leaves (like in Pinus) or at the base of stem nodes (like in grasses). This allows for growth in specific areas, not just at the tips. They differ from other meristems because they are located in specific middle sections rather than just at the tips (apical) or along the sides (lateral).
In simple words: Intercalary meristems are special growth areas found in the middle of a plant, like at the base of leaves or stem joints. They help plants grow longer in those specific spots, unlike other growth tissues that are at the very tips or around the edges.

🎯 Exam Tip: Focus on the location of intercalary meristems (between permanent tissues) and their role in increasing length in parts like grass stems, which allows for regeneration after grazing.

Question 2. What is complex tissue? Name the various kinds of complex tissues.
Answer: Complex tissues are made of more than one type of cells that work together as a single unit. These tissues consist of parenchyma and sclerenchyma cells; however, collenchymatous cells are not present in such tissues. Common examples of complex tissues are xylem and phloem. These tissues are vital for transport and support in plants.
In simple words: Complex tissues are plant tissues that have different kinds of cells all working together for one main job. Xylem and phloem are two common types, and they help move water and food around the plant.

🎯 Exam Tip: Remember that the defining characteristic of complex tissues is the presence of multiple cell types cooperating for a shared physiological function, such as transport in plants.

Question 3. Mention the most abundant muscular tissue found in our body. State its function.
Answer: Connective tissue is the most abundant and widely distributed tissue in our body. It provides a structural framework and gives support to different tissues, helping them form organs. For example, it helps connect various parts and fills spaces, keeping everything in place.
In simple words: The most common tissue in our body is connective tissue. It builds the frame and supports different body parts, helping them to stay together and form organs.

🎯 Exam Tip: While the question asks about muscular tissue, the answer correctly identifies connective tissue as the most abundant. Ensure you clearly state the tissue type and its primary functions (framework, support, connection).

Question 4. What is skeletal connective tissue? How is it helpful in the functioning of our body?
Answer: The supporting or skeletal connective tissues form the endoskeleton of the vertebrate body. They protect various organs and help in locomotion (movement). These supportive tissues include cartilage and bone. Cartilage provides flexible support, while bone gives rigid support and protection, both essential for body function.
In simple words: Skeletal connective tissues are like the body's frame, made of cartilage and bone. They give us shape, protect our organs, and help us move around.

🎯 Exam Tip: Highlight both the structural (forming the skeleton, protection) and functional (locomotion) roles of skeletal connective tissues. Mentioning specific examples like bone and cartilage adds depth to your answer.

Question 5. Why should gametes be produced by meiosis during sexual reproduction?
Answer: Meiosis is important because it produces gametes, which are male or female germ cells. During meiosis, a germ cell divides to make four new sex cells, each with half the number of chromosomes. As a result, when two gametes (one male and one female) join during fertilization, they form an egg or zygote with the correct full number of chromosomes. This ensures that the offspring maintain the species' characteristic chromosome count across generations.
In simple words: Gametes (sex cells) are made by meiosis so they have half the usual number of chromosomes. This way, when two gametes join during reproduction, the new baby gets the right total number of chromosomes.

🎯 Exam Tip: Emphasize the crucial role of meiosis in halving the chromosome number (reductional division) to maintain genetic consistency across generations after fertilization, ensuring species stability.

Question 6. In which stage of mitosis the chromosomes align in an equatorial plate? How?
Answer: In metaphase, the duplicated chromosomes arrange themselves in the middle of the cell, forming what is called the metaphase plate. Each chromosome gets attached to a spindle fibre at its centromere. This precise alignment ensures that when the cell divides, each new cell receives an identical set of chromosomes. After this, the centromere of each chromosome divides into two, with each part associated with a chromatid.
In simple words: During mitosis, in the metaphase stage, chromosomes line up neatly in the middle of the cell. They attach to tiny fibres, getting ready to be pulled apart equally into new cells.

🎯 Exam Tip: Remember that metaphase is characterized by the clear alignment of chromosomes at the equatorial plate. This ensures accurate segregation of genetic material to daughter cells.

VI. Answer in Detail:

Question 1. What are the permanent tissues? Describe the different types of simple permanent tissues.
Answer: Permanent tissues are those in which growth has stopped, either completely or for a period. Sometimes, they can become meristematic (dividing) again partially or wholly. These tissues are fully differentiated and specialized for certain functions.

Different types of simple permanent tissue:

Simple tissue is made of uniform cells that are structurally and functionally similar. Examples include parenchyma, collenchyma, and sclerenchyma.

Parenchyma:

• Parenchyma is a simple permanent tissue composed of living cells.
• Parenchyma cells have thin walls and are oval, rounded, or polygonal in shape, with well-developed spaces between them.
• In aquatic plants, parenchyma has intercellular air spaces, and is called aerenchyma, helping with buoyancy.
• When exposed to light, parenchyma cells can develop chloroplasts and are then known as chlorenchyma, involved in photosynthesis.

Functions:

• Parenchyma can store water in many succulent and xerophytic plants.
• It also stores food reserves, helps with absorption, provides buoyancy, and performs secretion.

Collenchyma:

• Cells are elongated with walls that are unevenly thickened and not lignified. They have rectangular, oblique, or tapering ends and a persistent protoplast (living content).
• They possess thick primary walls that are not lignified.

Functions: Collenchyma provides mechanical support for growing organs, allowing flexibility without breaking.

Sclerenchyma:

• Sclerenchyma consists of cells with thick walls that are often lignified (hardened).
• Sclerenchyma cells usually do not have living protoplasts when they are mature.
• Sclerenchyma cells are grouped into (i) fibres and (ii) sclereids.

Fibres: These are elongated sclerenchymatous cells, usually with pointed ends. Their walls are lignified, making them strong. Fibres are commonly found in many plants, such as jute, providing strength to the plant body.

Sclereids:

• Sclereids are widely distributed in the plant body. They are often broad and can appear singly or in groups.
• Sclereids are isodiametric (equally dimensioned) and have lignified walls. They have prominent pits (small depressions) along their walls.
• Their central cavity (lumen) is filled with wall materials. Sclereids are also common in fruits and seeds, giving them a gritty texture.

🎯 Exam Tip: When describing permanent tissues, always mention if their cells are living or dead at maturity, the nature of their cell walls (thin/thick, lignified/non-lignified), and their primary functions. Providing an example for each tissue type can also improve your answer.

Question 2. Write about the elements of Xylem.
Answer: Xylem is a conducting tissue in plants that carries water and mineral nutrients upwards from the roots to the leaves. It also provides mechanical support to the plant body, giving it strength. Xylem is made up of different kinds of elements, which work together to perform these functions. They are:

1. xylem tracheids
2. xylem fibres
3. xylem vessels and
4. xylem parenchyma.

(i) Xylem tracheids: These are long, slender, dead cells with hard, thick, and lignified walls. Their ends are tapering, blunt, or chisel-like. They do not have living cell content (protoplast) and feature a large, empty central cavity (lumen). Tracheids help in conducting water and provide mechanical support to the plant.

(ii) Xylem fibres: These cells are elongated, lignified, and pointed at both ends. Xylem fibres help in the conduction of water and nutrients from the root to the leaf and also give mechanical support to the plant. Their strong walls contribute to the plant's overall rigidity.

(iii) Xylem vessels: These are long, cylindrical, tube-like structures with lignified walls and a wide central lumen. Like tracheids, these cells are dead and lack protoplast. They are arranged in long series, with perforated (holed) partition walls between them, making the entire structure look like a water pipe. Their main function is to transport water and minerals from the roots to the leaves, and they also provide significant mechanical strength.

(iv) Xylem parenchyma: Its cells are living and thin-walled. The main function of xylem parenchyma is to store starch and fatty substances. Unlike the other xylem elements, these cells retain their living components, playing a vital role in food reserves for the xylem.
In simple words: Xylem is like a plant's plumbing system, moving water and minerals from the roots up to the leaves. It's made of special parts: tracheids and vessels for water flow, fibres for strength, and parenchyma cells for storing food. All these parts work together to keep the plant alive and standing tall.

🎯 Exam Tip: When describing xylem elements, clarify whether each type is living or dead, the nature of its cell walls, and its specific contribution to water transport or structural support.

Question 3. List out the differences between mitosis and meiosis.
Answer:

🎯 Exam Tip: When comparing mitosis and meiosis, clearly highlight their differences in terms of purpose (growth vs. reproduction), location (somatic vs. germ cells), number of divisions, and the chromosome count and genetic similarity of daughter cells.

Intext Activities

Activity -1

Rinse your mouth with water. Using a toothpick or ice-cream stick, scrape superficial cells from the inner side of the cheek and spread them on a clean glass slide. Dry the glass slide with the scraped cells taken from the inner side of the cheek. Add two drops of methylene blue stain. Identify the cells under low and high power of the microscope.

1. Large irregularly shaped cells with cell walls.

2. Dark blue nucleus at the central part of each cell.

3. Lightly stained cytoplasm colour in each cell.

🎯 Exam Tip: For practical activities like this, note down observations systematically. Pay attention to cell shape, nucleus presence and position, and the relative staining of different cell parts.

I. Choose the Correct Answer:

Question 1. A meristematic tissue consists of
(a) immature cells that are capable of undergoing cell division.
(b) mature cells
(c) non-living cells
(d) sclerenchyma cells
Answer: (a) immature cells that are capable of undergoing cell division.
In simple words: Meristematic tissue is made of young cells that can keep dividing. These cells are special because they are always ready to grow and make new parts for the plant.

🎯 Exam Tip: Meristematic tissues are crucial for plant growth because their cells are undifferentiated and actively mitotic, enabling continuous growth and repair.

Question 2. Two long bones of the hand are dislocated in a person who met with an accident. Which among the following may be the possible reason?
(a) Tendon injury
(b) Break of skeletal muscle
(c) Ligament tear
(d) Rupture of Areolar tissue
Answer: (c) Ligament tear
In simple words: When bones get dislocated, it means they are pulled out of their normal position at a joint. This most often happens because the ligaments, which are tough bands connecting bones, have been stretched or torn.

🎯 Exam Tip: Ligaments connect bones to bones and are essential for stabilizing joints. A tear or overstretching of a ligament (sprain) is a common cause of dislocation.

Question 3. Non-striated muscles are found in
(a) blood vessels
(b) gastric glands
(c) urinary bladder
(d) all of these
Answer: (d) all of these
In simple words: Non-striated muscles, also known as smooth muscles, work automatically without us controlling them. They are found in the walls of many internal organs like blood vessels, gastric glands, and the urinary bladder, where they help with functions like moving blood or food.

🎯 Exam Tip: Remember that smooth (non-striated) muscles are involuntary and are typically found in the walls of hollow internal organs and tubes, controlling various bodily functions automatically.

Question 4. Which of the following is not found in a neuron?
(a) Sarcolemma
(b) Dendrite
(c) Myelin sheath
(d) Axon
Answer: (a) Sarcolemma
In simple words: A neuron is a nerve cell, and it has dendrites, a myelin sheath, and an axon. Sarcolemma is a term for the cell membrane of a muscle cell, not a neuron.

🎯 Exam Tip: Remember that "sarcolemma" is specific to muscle cells, helping to distinguish between cell structures of different tissue types.

Question 5. Cylindrical, unbranched multinucleated cells are
(a) striated muscle cells
(b) smooth muscles
(c) cardiac muscles
(d) None of the options
Answer: (a) striated muscle cells
In simple words: Striated muscle cells look like long cylinders, don't branch out, and have many nuclei. They are also known as skeletal muscles and help us move.

🎯 Exam Tip: Knowing the distinct characteristics of different muscle types, like their shape, branching, and number of nuclei, is key for identification.

Question 6. The matrix of the bone is rich in
(a) elastin
(b) reticular fibres
(c) collagen
(d) myosin
Answer: (c) collagen
In simple words: Bones are hard because their main supporting material, called the matrix, has a lot of calcium salts and strong collagen fibers. Collagen makes bones strong and gives them structure.

🎯 Exam Tip: Understand the primary components of bone tissue, particularly the protein fibers (collagen) and mineral salts (calcium phosphate), which contribute to its strength and rigidity.

Question 7. Which muscles act involuntarily?
(i) Striated muscles
(ii) Smooth muscles
(iii) Cardiac muscles
(iv) Skeletal muscles
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)
Answer: (b) (ii) and (iii)
In simple words: Smooth muscles work without us thinking, like in our stomach. Cardiac muscles in the heart also beat all by themselves.

🎯 Exam Tip: Differentiate between voluntary (controlled by will, like skeletal muscles) and involuntary (not controlled by will, like smooth and cardiac muscles) actions and the tissues responsible for them.

Question 8. Tendon connects
(a) cartilage with muscles
(b) bone with skeletal muscles
(c) ligament with muscles
(d) bone with bone
Answer: (b) bone with skeletal muscles
In simple words: Tendons are strong, rope-like tissues that link your muscles to your bones. This connection helps you move your body.

🎯 Exam Tip: Clearly distinguish between tendons (muscle to bone) and ligaments (bone to bone), as this is a common point of confusion.

Question 9. In a certain type of cell division, the diploid number of chromosomes is reduced to half. This kind of division occurs in
(a) testis
(b) ovary
(c) both ovary and testis
(d) all body cells
Answer: (c) both ovary and testis
In simple words: The cell division that cuts the number of chromosomes in half is called meiosis. It happens in reproductive organs like the testis and ovary to make sperm and egg cells.

🎯 Exam Tip: Understand that meiosis (reductional division) is crucial for producing gametes with half the chromosome number, ensuring genetic stability after fertilization.

Question 10. ................ is derived from the ground meristem.
(a) Cortex
(b) Epidermis
(c) Xylem
(d) Cambium
Answer: (a) Cortex
In simple words: The ground meristem is a type of plant tissue that develops into various plant parts, and the cortex is one of them. The cortex provides support and stores food in plants.

🎯 Exam Tip: Remember the primary meristems (protoderm, ground meristem, procambium) and the tissues they give rise to in plants.

Question 11. The function of phloem fibres is ................ to the plant body
(a) passage of food
(b) Store food
(c) mechanical strength
(d) preparation of food
Answer: (c) mechanical strength
In simple words: Phloem fibers are strong parts of the phloem tissue that help support the plant and make it stand upright. They add stiffness to the plant.

🎯 Exam Tip: Note that while phloem's primary role is food transport, phloem fibers specifically provide structural support to the plant.

Question 12. The ................ epithelium is also known as pavement membrane.
(a) Ciliated
(b) Squamous
(c) Cuboidal
(d) Glandular
Answer: (b) Squamous
In simple words: Squamous epithelium is made of very thin, flat cells that fit together like tiles on a floor, so it's called pavement membrane. These cells help with easy passage of substances.

🎯 Exam Tip: Associate "pavement membrane" with squamous epithelium due to its flat, tile-like cellular arrangement, which facilitates diffusion.

Question 13. Elastic structures that connect bones to bones are called ................
Answer: Ligaments
In simple words: Ligaments are tough, stretchy bands that hold bones together at joints. They are very important for joint stability.

🎯 Exam Tip: Always remember that ligaments connect bone to bone, while tendons connect muscle to bone.

Question 14. ................ is seen in unicellular animals.
(a) Mitosis
(b) meiosis
(c) Amitosis
(d) None of the options
Answer: (c) Amitosis
In simple words: Amitosis is a very simple way cells divide, often seen in one-celled animals where the nucleus just splits directly. It is a faster and less complex process than mitosis or meiosis.

🎯 Exam Tip: Understand amitosis as a direct nuclear division without spindle formation, common in simpler organisms or specialized cells.

Question 15. The disappearance of spindle fibres is seen in ................
(a) metaphase
(b) prophase
(c) anaphase
(d) telophase
Answer: (d) telophase
In simple words: During telophase, which is the last stage of cell division, the structures called spindle fibres, which helped move the chromosomes, break down and disappear. New nuclear membranes form around the separated chromosomes.

🎯 Exam Tip: Learn the key events of each phase of mitosis and meiosis, including the formation and disappearance of the spindle apparatus.

Question 16. The ................ is a single, long fiber like process that develops from the cyton.
(a) [Dummy Option]
(b) axon
(c) dendrite
(d) neurilemma
Answer: (b) axon
In simple words: The axon is a long, thin part of a nerve cell (neuron) that carries electrical signals away from the main cell body. It acts like a cable transmitting messages.

🎯 Exam Tip: Differentiate between the axon (transmits signals away from the cell body) and dendrites (receive signals toward the cell body) in a neuron.

Question 17. Bouquet stage refers to ................
(a) diakinesis
(b) leptotene
(c) zygotene
(d) pachytene
Answer: (b) leptotene
In simple words: During the leptotene stage of meiosis, the chromosomes start to look like a bouquet of flowers inside the nucleus. This is because their ends gather together at one side.

🎯 Exam Tip: Understand the unique features of each sub-stage of Prophase I in meiosis, such as the "bouquet stage" in leptotene.

Fill in the blanks :

Question 1. The ................ tissues are made up of more than one type of cells and these woks together as a unit.
Answer: complex
In simple words: Complex tissues have different kinds of cells that all work together to do one job. This makes them more specialized.

🎯 Exam Tip: Remember that "complex tissues" are distinct because they involve multiple cell types collaborating for a single function.

Question 2. The two types of skeletal connective tissues are ................ and ................
Answer: bone, cartilage
In simple words: Bone and cartilage are the main tissues that form the body's framework, helping with support and movement. They are both vital for the skeletal system.

🎯 Exam Tip: Identify bone and cartilage as the primary components of supportive connective tissue, noting their structural differences.

Question 3. Humans have 46 chromosomes. Their sperms and eggs will have ................ chromosomes each.
Answer: 23
In simple words: Human body cells have 46 chromosomes, but sperm and egg cells only have 23. This halving ensures that when they join, the new cell has the correct total of 46 chromosomes.

🎯 Exam Tip: Understand the concept of diploid (46 chromosomes in humans) and haploid (23 chromosomes in human gametes) chromosome numbers.

Question 4. During pairing of chromosomes in meiosis, the ................ chromosomes come to lie side by side.
Answer: homologous
In simple words: In meiosis, chromosomes that are similar in shape and genetic information line up together. These matching pairs are called homologous chromosomes.

🎯 Exam Tip: Focus on the pairing of homologous chromosomes in meiosis as a unique event that leads to genetic recombination and reduction in chromosome number.

Question 5. The word meristem is derived from a Greek word ................
Answer: Meristos
In simple words: The term "meristem" comes from the Greek word "meristos", which means "divisible". This name fits well because meristematic tissues are made of cells that can divide.

🎯 Exam Tip: Knowing the etymology of biological terms can often help in understanding their meaning and function.

Question 6. Cork cambium is an example of ................ meristem.
Answer: secondary
In simple words: Cork cambium helps plants grow wider and forms the protective outer bark. It's a type of secondary meristem because it adds thickness, not length.

🎯 Exam Tip: Differentiate between primary meristems (responsible for length growth) and secondary meristems (responsible for width growth) in plants.

Question 7. The meristem found at the base of internodes is called ................
Answer: intercalary meristem
In simple words: Intercalary meristems are found in the middle parts of plants, like at the base of leaves or between stem segments. They help in the lengthening of plant parts.

🎯 Exam Tip: Identify the location and function of intercalary meristems, especially in monocots, where they contribute to regrowth after grazing.

Question 8. In apple, parenchyma stores ................
Answer: sugar
In simple words: Parenchyma tissue in fruits like apples stores various nutrients, and a key one for apples is sugar. This makes the apple sweet and provides energy for the plant.

🎯 Exam Tip: Recall that parenchyma cells are versatile, often involved in storage (food, water), photosynthesis, and secretion in plants.

Question 9. Fibres are extensively longer ranging from 20 mm to 550 mm ................
Answer: corchorus capsularis (jute)
In simple words: Jute fibres are very long and strong, making them useful for many things like making ropes and fabrics. This length is a key feature of its strength.

🎯 Exam Tip: Recognize specific plant fibres, like jute, and their characteristic length, which contributes to their commercial value.

Question 10. During meiosis in pachytene, stages the paired chromosomes are called ................
Answer: bivalents
In simple words: In the pachytene stage of meiosis, the two homologous chromosomes that have paired up are called bivalents. Each bivalent has four chromatids and is where crossing over happens.

🎯 Exam Tip: Understand that bivalents are formed during the pachytene stage of meiosis I, facilitating crossing over between homologous chromosomes.

Question 11. Mitosis was discovered by ................
Answer: Flemming
In simple words: Walter Flemming was the scientist who first observed and described the process of mitosis. His work helped us understand how cells divide to grow and repair.

🎯 Exam Tip: Know the key scientists associated with major biological discoveries, like Flemming for mitosis.

Question 12. Both smooth and cardiac muscles are ................ in nature.
Answer: involuntary
In simple words: Smooth muscles and cardiac muscles work automatically without our conscious control. They perform essential functions like pumping blood and moving food through the digestive system.

🎯 Exam Tip: Reinforce the distinction between voluntary (skeletal) and involuntary (smooth, cardiac) muscle types based on conscious control.

Question 13. ................ is a non-flexible skeletal connective tissue.
Answer: Bone
In simple words: Bone is a very strong and rigid tissue that forms the main support structure of our body. It gives shape and protects organs.

🎯 Exam Tip: Compare bone (rigid) with cartilage (flexible) as the two main types of skeletal connective tissues.

Question 14. ................ acts as a fat reservoir.
Answer: Adipose tissue
In simple words: Adipose tissue is special tissue in our body that stores extra fat. This fat acts as an energy reserve and helps keep us warm.

🎯 Exam Tip: Associate adipose tissue directly with fat storage, insulation, and energy reserve functions.

Question 15. ................ epithelium is seen in sweat glands.
Answer: Cuboidal
In simple words: Cuboidal epithelium, made of cube-shaped cells, is found in glands like sweat glands. Its main job is secretion and absorption.

🎯 Exam Tip: Relate the cuboidal shape of epithelial cells to their function in secretion and absorption, commonly found in glands and kidney tubules.

Question 16. Genetic variations occur in meiosis because of ................
Answer: crossing over
In simple words: Crossing over is when parts of homologous chromosomes swap places during meiosis. This mixing creates new combinations of genes, leading to genetic variation in offspring.

🎯 Exam Tip: Emphasize crossing over as a crucial event in meiosis that increases genetic diversity among individuals of a species.

III. State whether True or false. If false, write the correct statement:

Question 1. Epithelial layer does not allow regulation of materials between the body and the external environment.
Answer: False.
Correct statement: Epithelium is involved in the absorption and elimination of waste. It carefully controls what goes into and out of the body, acting like a gatekeeper for substances.

🎯 Exam Tip: Understand that epithelial tissue forms a barrier, but it is also highly active in regulating substance exchange through processes like absorption, secretion, and excretion.

Question 2. Striated and non-striated tissues are types of epithelial tissues.
Answer: False.
Correct statement: They are types of muscular tissues. Striated and non-striated (smooth) are classifications for muscle tissues based on their appearance under a microscope.

🎯 Exam Tip: Correctly classify tissue types: epithelial, connective, muscular, and nervous. Striated and non-striated refer to muscle, not epithelium.

Question 3. Spindle formation occur in amitosis.
Answer: False.
Correct statement: Spindle formation occur in mitosis. Spindle fibers are a key part of mitosis, pulling chromosomes apart. Amitosis is a simpler cell division without spindle formation.

🎯 Exam Tip: Distinguish between the processes of mitosis (involving spindle fibers) and amitosis (direct division without spindle fibers).

Question 4. Movement of food in the alimentary canal is because of cardiac muscles.
Answer: False.
Correct statement: Movement of food in the alimentary canal is due to rhythmic contractions and relaxations of smooth muscles in the canal walls. This process is called peristalsis.

🎯 Exam Tip: Remember that peristalsis, driven by smooth muscles, is responsible for food movement in the digestive system, not cardiac muscles (which are in the heart).

Question 5. A mature RBC lacks a nucleus.
Answer: True.
In simple words: Mature red blood cells do not have a nucleus. This allows them to carry more oxygen efficiently.

🎯 Exam Tip: Note that the absence of a nucleus in mature RBCs is an adaptation for maximizing oxygen-carrying capacity.

Question 6. Excessive pulling of bones causes a sprain.
Answer: False.
Correct statement: Sprain is caused by excessive pulling of ligaments. Ligaments are tough bands that connect bones at joints, and stretching or tearing them causes a sprain.

🎯 Exam Tip: Differentiate between a sprain (ligament injury) and a strain (muscle or tendon injury).

Question 7. Glandular epithelium gives a stratified appearance.
Answer: False.
Correct statement: Compound epithelium gives a stratified appearance. Glandular epithelium is specialized for secretion, while stratified (compound) epithelium has multiple layers.

🎯 Exam Tip: Understand that "stratified" means layered, referring to multiple cell layers, a characteristic of compound epithelium, not glandular epithelium.

Question 8. Sieve cells have no companion cells.
Answer: True.
In simple words: Sieve cells, which are found in some plants, function without the help of companion cells. Companion cells are typically associated with sieve tubes in flowering plants.

🎯 Exam Tip: Differentiate between sieve cells (found in lower plants, lack companion cells) and sieve tube elements (found in angiosperms, associated with companion cells).

Question 9. Conduction can be bidirectional in phloem tissue.
Answer: True.
In simple words: Phloem tissue can move food substances in both upward and downward directions within the plant. This allows nutrients to reach all parts of the plant, from leaves to roots and vice versa.

🎯 Exam Tip: Remember that phloem facilitates bidirectional transport of organic solutes, while xylem primarily transports water and minerals unidirectionally (upward).

Question 10. White blood corpuscles contain respiratory pigment hemoglobin.
Answer: False.
Correct statement: Red blood corpuscles contain respiratory pigment hemoglobin. Hemoglobin gives red blood cells their color and is essential for carrying oxygen.

🎯 Exam Tip: Correctly associate hemoglobin with red blood cells and its role in oxygen transport, not with white blood cells.

IV. Assertion and Reason type:

Question 1. Assertion: Non-striated muscles are said to be voluntary in nature. Reason: Non-striated muscles are under the control of our will.
Answer: (d) Both Assertion and Reason are false
In simple words: Non-striated (smooth) muscles work automatically, not by our will. So, the statement that they are voluntary and under our control is incorrect.

🎯 Exam Tip: Clearly remember that non-striated muscles are involuntary, meaning their actions are not controlled consciously.

Question 2. Assertion: Materials are exchanged between epithelial and connective tissues by diffusion. Reason: Blood vessels are absent in epithelial tissue.
Answer: (a) Assertion and Reason are true and Reason is the correct explanation of Assertion
In simple words: Epithelial tissues do not have their own blood supply, so they get food and oxygen from the nearby connective tissue through diffusion. This makes the reason a good explanation for the assertion.

🎯 Exam Tip: Understand the vascular nature of tissues; epithelial tissue is avascular (lacks blood vessels), relying on diffusion from underlying connective tissue for nutrients.

V. Answer in one or two sentences :

Question 1. Name the two types of sclerenchyma cells.
Answer: The two types of sclerenchyma cells are fibres and sclereids. Both types provide rigid support to plants. They are crucial for mechanical strength in mature plant parts.

🎯 Exam Tip: Identify fibres (long, narrow) and sclereids (short, irregular) as the distinct morphological types of sclerenchyma cells, both providing mechanical support.

Question 2. Name the components of xylem and phloem.
Answer: Xylem is made of xylem tracheids, xylem fibres, xylem vessels, and xylem parenchyma. Phloem consists of sieve elements, companion cells, phloem fibres, and phloem parenchyma. These parts work together to transport water and food throughout the plant.

🎯 Exam Tip: Learn the four main components of both xylem and phloem, recognizing that these tissues are complex because they are made of more than one cell type.

Question 3. Name the tissue that connects muscle to bone in humans.
Answer: Tendons join skeletal muscles to bones in our body. They are strong, fibrous connective tissues essential for movement.

🎯 Exam Tip: Differentiate clearly between tendons (muscle to bone) and ligaments (bone to bone) to avoid confusion.

Question 4. Name the tissue that stores excess fat in our body.
Answer: Adipose tissue stores excess fat in our body. This tissue also helps to insulate the body and cushion organs.

🎯 Exam Tip: Recall that adipose tissue is specialized connective tissue, primarily functioning in energy storage, insulation, and organ protection.

Question 5. Name the connective tissue with a fluid matrix.
Answer: Blood and lymph are connective tissues with a fluid matrix. This fluid matrix allows them to circulate throughout the body, transporting substances.

🎯 Exam Tip: Remember that blood and lymph are unique connective tissues because their matrix is liquid, enabling their transport functions.

Question 6. Name the tissue present in the brain.
Answer: Nervous tissue is present in the brain. It is responsible for transmitting signals and processing information.

🎯 Exam Tip: Identify nervous tissue as the primary tissue type found in the brain, spinal cord, and nerves, specialized for communication.

Question 7. What is plate meristem?
Answer: Plate meristem consists of cells that divide in two planes. This type of division leads to an increase in the surface area of an organ, such as during leaf formation.

🎯 Exam Tip: Understand that plate meristems contribute to the growth of flat organs like leaves by adding cells in two dimensions, increasing their surface area.

Question 8. Differentiate collenchyma and sclerenchyma.
Answer:

🎯 Exam Tip: Focus on the key differences: living vs. dead cells, presence/absence of lignin, type of mechanical support (flexible vs. rigid), and typical locations in the plant.

Question 9. Mention the type of epithelium seen in alveoli of lungs.
Answer: Squamous epithelium is seen in the alveoli of lungs. Its thin, flat structure is perfect for gas exchange. These cells allow oxygen and carbon dioxide to pass through easily.

🎯 Exam Tip: Relate the simple squamous epithelium's thinness to its function in rapid diffusion and filtration, as seen in alveoli and blood vessel linings.

Question 10. Name the supportive connective tissues.
Answer: Cartilage and bone are the supportive connective tissues. They form the skeleton and provide structure and protection to the body.

🎯 Exam Tip: Recognize bone (hard, rigid) and cartilage (firm, flexible) as the two primary supportive connective tissues, each with distinct roles.

Question 11. Name the cartilage cells present in the matrix.
Answer: Chondrocytes are the cartilage cells present in the matrix. These cells produce and maintain the extracellular matrix of cartilage.

🎯 Exam Tip: Associate chondrocytes with cartilage, just as osteocytes are associated with bone. These are the main cells within their respective matrices.

Question 12. What is the role of RBC?
Answer: Red Blood Cells (RBCs) contain a respiratory pigment called hemoglobin. Hemoglobin's main role is to transport oxygen from the lungs to various tissues and carbon dioxide from tissues back to the lungs. This makes RBCs vital for breathing and energy production.

🎯 Exam Tip: Emphasize hemoglobin's role in oxygen transport as the primary function of RBCs, which is critical for cellular respiration.

Question 13. Mention the stages of meiotic Prophase -I.
Answer: The stages of meiotic Prophase-I are Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis. Each stage involves specific events of chromosome condensation and pairing. These steps ensure correct segregation of genetic material.

🎯 Exam Tip: Memorize the correct sequence and major events of the five sub-stages of Prophase I, as it is the most complex phase of meiosis.

Question 14. What is the significance of Meiosis?
Answer: Meiosis is significant because it maintains a constant number of chromosomes in a given species across generations. It does this by reducing the chromosome number by half in gametes, ensuring that fertilization restores the correct diploid number. This also introduces genetic variation.

🎯 Exam Tip: Understand that meiosis achieves two critical outcomes: reducing chromosome number by half (for sexual reproduction) and increasing genetic variation (through crossing over and independent assortment).

Question 15. Draw a shoot apex and label the meristem's parts.
Answer:In simple words: This diagram shows a plant shoot tip, which is where growth happens. The apical meristem at the very top makes the plant grow taller, while intercalary meristems help stems and leaves get longer from within. Lateral meristems, often seen as rings, help the stem grow thicker.

🎯 Exam Tip: Practice drawing and labeling the different types of meristems (apical, intercalary, lateral) and their respective locations in a plant, understanding their roles in primary and secondary growth.

VI. Short Answer Type :

Question 1. How would you differentiate meristematic and permanent tissue?
Answer:

🎯 Exam Tip: Understand that the key distinction lies in the cells' ability to divide; meristematic cells divide continuously, while permanent cells have lost this ability and have specialized roles.

Question 2. Differentiate fibres from sclereids.
Answer:

In simple words: Sclereids are typically broader cells found alone or in small groups with blunt ends and deep pits. Fibres are long, thin, thread-like cells that usually occur in bundles, have pointed ends, and narrow pits. Both provide structural support.

🎯 Exam Tip: When differentiating, always list corresponding features side-by-side to highlight the contrasts clearly and ensure all relevant points are covered.

Question 3. Which tissue is the main component of tendons and ligaments? How do they differ in function?
Answer: Dense connective tissue is the main component of tendons and ligaments. This tissue is made of many fibers and cells called fibroblasts packed closely together.
Differences in function:
a. Tendons: These are strong, cord-like structures that connect skeletal muscles to bones. They are very strong but have limited flexibility, helping to move bones when muscles contract. Tendons contain parallel bundles of collagen fibers with rows of fibroblasts between them.
b. Ligaments: These are highly elastic structures that connect bones to other bones. They are strong and help stabilize joints while allowing normal movement. Ligaments have very little matrix and are crucial for joint stability.
In simple words: Tendons connect muscles to bones, while ligaments connect bones to bones. Both are strong, but ligaments are more elastic to help with joint movement.

🎯 Exam Tip: Remember the simple mnemonic: "Tendons-Muscle-Bone" (TMB) and "Ligaments-Bone-Bone" (LBB) to quickly recall their connections, and highlight their flexibility differences.

Question 4. What are the fibres present in the connective tissue proper?
Answer: Connective tissue proper contains three main types of fibers: collagen fibers, elastin fibers, and reticular fibers (not explicitly mentioned in the source but a standard component). These are produced by fibroblast cells. Additionally, two types of loose connective tissue proper are:
Areolar tissue: This tissue has cells and fibers loosely arranged within a semi-fluid matrix. It forms a network of fine threads that crisscross, creating small spaces called areolae. It connects skin to muscles, fills spaces within organs, and surrounds muscles, blood vessels, and nerves, also helping to attach skin to underlying muscles.
Adipose tissue: This tissue is a collection of fat cells, or adipocytes, which can be spherical or oval. It acts as a fat storage area in our bodies. The matrix of adipose tissue also contains collagen fibers, elastin fibers, and fibroblast cells.
In simple words: Connective tissue has collagen and elastin fibers. Areolar tissue is loose and fills spaces, while adipose tissue stores fat.

🎯 Exam Tip: Always describe the main components (fibers, cells, matrix) of connective tissues and give clear examples of where each type is found in the body.

Question 5. How are collagen fibres organized in dense connective tissues?
Answer: In dense connective tissues, collagen fibers are packed very closely together. These tissues are strong and contain many fibers and fibroblasts.
In tendons, collagen fibers are arranged in parallel bundles. Fibroblasts are found in rows between these bundles.
In ligaments, the organization is slightly different; they contain highly elastic fibers and have very little matrix, allowing for more stretch. This organized arrangement gives dense connective tissues their great strength and ability to resist tension.
In simple words: Collagen fibers in dense connective tissues are tightly packed. In tendons, they form straight, parallel lines, while in ligaments, they are more elastic to allow for stretching.

🎯 Exam Tip: For questions about tissue organization, mention the type of fibers, their arrangement (parallel, irregular), and the cells present, as these details determine the tissue's function.

Question 6. Write one point of difference between a) Bone and cartilage b) Simple and compound epithelial tissue.
Answer:
a) Bone and cartilage:

In simple words: Bone is hard and strong, with its matrix in layers called lamellae, while cartilage is flexible and soft, with chondrocytes in its matrix. Simple epithelium has one cell layer, while compound epithelium has many layers for protection.

🎯 Exam Tip: When comparing tissues, always mention their structural arrangement (layers, matrix, cells) and primary function to get full marks.

Question 7. Why is blood considered to be a fluid connective tissue?
Answer: Blood is considered a fluid connective tissue because it connects various parts of the body and has a liquid matrix. The cells in blood are spread out within this fluid, unlike other connective tissues where cells are tightly packed.
Blood contains different types of cells, including red blood cells (erythrocytes), white blood cells (leukocytes), and platelets. These cells float within a liquid matrix called plasma. Plasma contains inorganic salts and various organic substances. Its main role as a circulating fluid is to transport nutrients throughout the body, making it a vital connective tissue with a unique fluid nature.
In simple words: Blood is fluid connective tissue because it links different body parts and its cells float in a liquid plasma, helping to move nutrients.

🎯 Exam Tip: Emphasize the fluid matrix (plasma) and the presence of various blood cells (corpuscles) as key reasons for blood being classified as fluid connective tissue.

Question 8. Give the sequence of the events occurring during prophase of mitosis.
Answer: During prophase of mitosis, several key events occur in sequence:
1. The chromosomes first become short and thick, making them clearly visible inside the nucleus.
2. The centrosome then splits into two daughter centrioles, which move to opposite poles of the cell.
3. Each centriole is surrounded by aster rays, and spindle fibers begin to appear between the two centrioles.
4. Finally, the nuclear membrane and the nucleolus gradually disappear.
These steps prepare the cell for the division of its genetic material. The chromosomes condense to avoid tangling during separation.
In simple words: In prophase, chromosomes shorten, centrioles move apart and form spindle fibers, and the nucleus covering disappears, getting ready for cell division.

🎯 Exam Tip: Listing events in a logical, chronological order is crucial for describing stages of cell division. Focus on chromosome changes, spindle formation, and nuclear envelope breakdown.

Question 9. Why is meiosis called reductional division and mitosis as equational division?
Answer: Mitosis is known as equational division because when a parent cell divides, it produces two identical daughter cells. Each daughter cell has the same amount of DNA, the same number of chromosomes, and the same genes as the original parent cell.
Meiosis, on the other hand, is called reductional division because it reduces the chromosome number by half. A diploid parent cell (2n chromosomes) produces four haploid daughter cells (n chromosomes). This reduction is vital for sexual reproduction.
In simple words: Mitosis keeps the chromosome number the same (equational), creating identical cells. Meiosis cuts the chromosome number in half (reductional), making cells for reproduction.

🎯 Exam Tip: Clearly state the outcome of each division (number of cells, chromosome count relative to parent cell) to distinguish between equational and reductional processes.

Question 10. What is terminalization?
Answer: Terminalization is a process that occurs during the diplotene stage of meiotic prophase I. In this stage, the chiasmata (points where homologous chromosomes are still joined after crossing over) start moving towards the ends of the chromosomes. This movement leads to the separation of the homologous chromosomes, preparing them for the next stage of meiosis. The chiasmata "terminalize" or move to the ends, ensuring proper segregation.
In simple words: Terminalization is when the points where chromosomes cross over move to the ends, helping the chromosomes separate properly during cell division.

🎯 Exam Tip: Connect terminalization to chiasmata and diplotene stage to show a comprehensive understanding of meiotic events.

Question 12. What is crossing over?
Answer: Crossing over is a crucial event that happens during the pachytene stage of meiotic prophase I. In this process, the chromatids of homologous chromosomes break at certain points, and then the broken segments are exchanged between them. The points where this exchange occurs are called chiasmata. This exchange of genetic material leads to new combinations of genes, increasing genetic diversity. It is a vital mechanism for evolution and variation in species.
In simple words: Crossing over is when matching chromosomes swap pieces of their genetic material during meiosis, creating new combinations of genes.

🎯 Exam Tip: Always mention the stage (pachytene), the chromosomes involved (homologous), the outcome (exchange of segments), and the significance (genetic variation) for a complete answer.

Question 13. What is bouquet stage?
Answer: The bouquet stage occurs during the leptotene stage of meiotic prophase I. In this phase, the chromosomes become visible as long, thread-like structures. They move and cluster together at one side of the nucleus, with their telomeres (ends) attaching to the nuclear envelope, forming a flower-like or "bouquet" arrangement. This arrangement helps in the alignment and pairing of homologous chromosomes later on.
In simple words: The bouquet stage is when chromosomes clump together like a flower inside the nucleus during meiosis, preparing to pair up.

🎯 Exam Tip: Describe the visual appearance (flower-like) and mention the stage (leptotene) and the purpose (facilitates homologous pairing) for a clear explanation.

Question 14. What is zygotene?
Answer: Zygotene is a stage within meiotic prophase I. During this phase, two homologous chromosomes move closer to each other and start pairing up. This precise pairing process is called synapsis, where the chromosomes align side-by-side. The paired homologous chromosomes are now called bivalents, and this close association allows for crossing over in the next stage. It is a critical step for genetic recombination.
In simple words: Zygotene is when matching chromosomes come together and pair up closely, a process called synapsis, during meiosis.

🎯 Exam Tip: Key terms to include are "homologous chromosomes," "pairing" or "synapsis," and the formation of "bivalents" to fully explain zygotene.

Question 15. Explain amitosis.
Answer: Amitosis is the simplest way a cell divides, often seen in unicellular organisms, aging cells, and cells in foetal membranes. In this process, the nucleus first elongates, and then a constriction appears in its middle. This constriction deepens until it divides the nucleus into two. Following this, the cytoplasm also divides, resulting in the formation of two daughter cells without the complex stages seen in mitosis or meiosis. It is a direct division.
In simple words: Amitosis is a simple cell division where the nucleus just pinches into two, followed by the cytoplasm, without complex steps.

🎯 Exam Tip: Highlight "simplest mode," "direct division," and the absence of complex chromosomal events to accurately describe amitosis.

Question 16. Write the salient features of the compound epithelium.
Answer: Here are the main features of compound epithelium:
1. It has more than one layer of cells, which gives it a stratified or layered appearance. Because of this, it is also known as stratified epithelial tissue.
2. Its primary role is to protect the underlying tissues from mechanical stress and chemical damage.
3. This tissue covers dry surfaces like the skin and moist surfaces such as the lining of the buccal cavity (mouth) and the pharynx (throat).
The multiple layers provide extra protection against wear and tear.
In simple words: Compound epithelium has many cell layers for protection, covering surfaces like skin and mouth lining.

🎯 Exam Tip: Focus on the "multiple layers" and "protective function" as the defining characteristics of compound epithelium.

Question 17. Write a note the significance of mitosis.
Answer: Mitosis is a fundamental cell division process with several key significances:
1. It is an equational division, meaning it produces diploid daughter cells (2n) that have an equal distribution of genetic material (DNA) identical to the parent cell.
2. In multicellular organisms, mitosis is responsible for growth, organ development, and an increase in overall body size. All these processes happen through the continuous division of cells.
3. Mitosis also plays a crucial role in repairing damaged and wounded tissues by replacing lost cells, ensuring the body maintains its integrity and function.
It is vital for the repair and regeneration of tissues throughout an organism's life.
In simple words: Mitosis helps living things grow, develop, and repair damaged parts by making new, identical cells with the same genetic information.

🎯 Exam Tip: When discussing significance, categorize the points into growth, development, and repair/regeneration to ensure a comprehensive answer.

Question 18. Draw a neuron and label the parts
Answer:

In simple words: A neuron has a central cell body with a nucleus, branch-like dendrites to receive signals, a long axon to send signals, and terminal endings that pass signals to other cells. The myelin sheath helps signals travel faster along the axon.

🎯 Exam Tip: When drawing diagrams, ensure all major parts are clearly labelled and drawn proportionally. Practice drawing each part separately to master its shape and position.

VII. Answer In Detail:

Question 1. What are meristems? Describe the distribution and functions of various types of meristems.
Answer: Meristematic tissues are groups of immature cells that can continuously divide. In plants, meristems are found in specific areas where growth occurs, such as the tips of stems and roots, developing leaves, and in structures like vascular cambium and cork cambium. These regions are crucial for a plant's development.
Based on their location in the plant, meristems are classified into three main types:
1. Apical meristem: These meristems are located at the very tips or growing points of roots and shoots. Their primary function is to increase the plant's length.
2. Intercalary meristem: Found between regions of permanent tissues, these meristems are part of the primary meristem. They are located at the base of leaves, like in Pinus, or at the base of internodes, as seen in grasses. They contribute to stem elongation and leaf growth.
3. Lateral meristem: These meristems are arranged parallel to the sides of the plant and cause an increase in the thickness or girth of the plant parts. Examples include vascular cambium and cork cambium, responsible for secondary growth.
The main function of all meristems is to produce new cells, driving both primary growth (length) and secondary growth (thickness) of the plant. Meristems are essential for the continuous growth and development of plants throughout their life cycle.

In simple words: Meristems are plant growth areas with dividing cells. Apical meristems make plants grow taller. Intercalary meristems help stems and leaves grow longer. Lateral meristems make stems grow thicker.

🎯 Exam Tip: Always remember the three types of meristems and their specific locations and functions for growth (length vs. girth) to answer questions effectively.

Question 2. Give one reason for the following: a. Blood is fluid connective tissue. b. Skeletal muscles are voluntary muscles. c. Heart muscles are involuntary in nature.
Answer:
a. Blood is fluid connective tissue: Blood is considered a fluid connective tissue because it has a liquid matrix called plasma, in which various cells like red blood cells, white blood cells, and platelets are suspended. This fluid nature allows it to circulate throughout the body, connecting different parts and transporting substances like oxygen, nutrients, hormones, and waste products. It is the only connective tissue that is completely liquid.
b. Skeletal muscles are voluntary muscles: Skeletal muscles are called voluntary muscles because their movements are under our conscious control. We can choose when and how to move these muscles, such as lifting an arm or walking. These muscles are attached to bones and help in movement and posture.
c. Heart muscles are involuntary in nature: Heart muscles (cardiac muscles) are involuntary because their contractions are not under our conscious control. The heart beats rhythmically and continuously on its own, without us having to think about it. This automatic function is essential for pumping blood throughout the body without interruption, and it is regulated by the body's autonomous nervous system.
In simple words: Blood is fluid because it moves nutrients in liquid form. Skeletal muscles are voluntary because we control them. Heart muscles are involuntary because they beat on their own without us thinking about it.

🎯 Exam Tip: For "give reason" questions, always clearly state the characteristic and then provide a concise biological explanation of "why" it possesses that characteristic.

Question 3. Explain simple epithelium and its types.
Answer: Simple epithelium is a type of epithelial tissue formed by a single layer of cells. This single layer makes it ideal for lining body cavities, ducts, and surfaces where absorption, secretion, and filtration occur. Simple epithelium is further classified into several types based on the shape of its cells:
1. Squamous epithelium:
     • These cells are thin, flat, and irregular in shape with prominent nuclei. They fit together like tiles, forming a smooth surface.
     • It is also known as pavement membrane due to its tile-like appearance.
     • Found lining the buccal cavity, alveoli of lungs, kidney tubules, and blood vessels.
     • Its main function is to protect the body from mechanical injury, drying, and germ invasion, and facilitate diffusion.

2. Cuboidal epithelium:
     • This tissue is made of a single layer of cube-shaped cells with a round nucleus located in the center.
     • It is found in places like thyroid vesicles, salivary glands, sweat glands, and exocrine pancreas.
     • Also present in the intestine and tubular parts of nephrons (kidney tubules), where microvilli increase the surface area for absorption.
     • Its primary functions are secretion and absorption.

3. Columnar epithelium:
     • Composed of a single layer of tall, slender, pillar-like cells with nuclei located at their base.
     • Primarily involved in secretion and absorption.
     • It lines organs like the stomach, gallbladder, bile duct, small intestine, and colon, forming a mucous membrane.

4. Ciliated epithelium:
     • These are specialized columnar cells that have tiny hair-like projections called cilia on their surface.
     • The cilia move in a specific direction, helping to move particles or mucus across the epithelial surface.
     • Found in the trachea (windpipe), bronchioles, kidney tubules, and fallopian tubes.

5. Glandular epithelium:
     • Epithelial cells are often modified to form specialized gland cells.
     • These gland cells are responsible for secreting chemical substances onto the epithelial surface or into the bloodstream.
     • This type of epithelium lines gastric glands, pancreatic tubules, and intestinal glands, playing a vital role in digestion and other bodily processes.

In simple words: Simple epithelium is one layer of cells. Squamous cells are flat, cuboidal are cube-shaped, and columnar are tall. Ciliated cells have tiny hairs to move things, and glandular cells make and release substances.

🎯 Exam Tip: When explaining epithelial types, always mention the cell shape, number of layers, key features (like cilia), location in the body, and primary function for each type.

Question 4. Explain the components of phloem tissue.
Answer: Phloem is a complex plant tissue that transports food (sugars) from the leaves to other parts of the plant. It is made of four main types of elements:
1. Sieve elements: These are the main conducting cells of phloem. They are long, tube-like cells arranged end-to-end. Their end walls are perforated, forming "sieve plates" that allow food to pass through. Their main function is the translocation of food from leaves to storage organs.
2. Companion cells: These are elongated cells located alongside the sieve tubes, with which they are closely associated. A companion cell can be as long as the sieve tube element it accompanies or may divide to form a series of smaller companion cells. They help sieve elements in their functions, as sieve elements lack a nucleus.
3. Phloem parenchyma: These are living cells with cytoplasm and a nucleus found within the phloem. Their primary function is to store food materials, such as starch and fats, and to carry out other metabolic activities.
4. Phloem fibers: Also known as sclerenchymatous cells, these are associated with both primary and secondary phloem. Phloem fibers are elongated, lignified (hardened by lignin), and provide mechanical strength and support to the plant body. They are non-living cells at maturity.
All these components work together to ensure efficient transport of nutrients throughout the plant.
In simple words: Phloem tissue moves food in plants using sieve elements, supported by companion cells. Phloem parenchyma stores food, and phloem fibers give strength.

🎯 Exam Tip: For complex tissues, remember to list all component cells and briefly explain the specific role of each cell type in the overall function of the tissue.

Question 5. Write a note on blood and its components.
Answer: Blood is a vital fluid connective tissue that circulates throughout the body. It connects different body parts and helps in various functions, primarily transport. Blood consists of a liquid matrix called plasma, in which different types of blood cells, also known as corpuscles, are suspended.
The main components of blood are:
1. Plasma: This is the yellowish liquid part of blood, mostly water. It contains various inorganic salts, organic substances like proteins, hormones, and nutrients. Plasma's main role is to act as the circulating fluid that transports nutrients, hormones, and waste products throughout the body.
2. Red Blood Corpuscles (Erythrocytes):
     • These cells are oval-shaped, circular, and biconcave disc-like. They are unique because they lose their nucleus when mature in mammals.
     • They contain a special respiratory pigment called hemoglobin, which is responsible for binding and transporting oxygen to tissues throughout the body.
3. White Blood Corpuscles (Leukocytes):
     • Leukocytes are larger than red blood cells and possess a distinct nucleus. They are colorless and capable of amoeboid movement, allowing them to move through tissues.
     • Their main role is in the body's defense mechanism, fighting off infections and foreign invaders.
     • White blood cells are mainly of two types: Granulocytes and Agranulocytes.
          a. Granulocytes: These have irregularly shaped nuclei and cytoplasmic granules. They include neutrophils, basophils, and eosinophils, each with specific immune functions.
          b. Agranulocytes: These lack cytoplasmic granules and include lymphocytes and monocytes, which are crucial for specific immune responses and phagocytosis.
4. Blood Platelets (Thrombocytes):
     • Platelets are minute, anucleated (lack a nucleus), fragile fragments of giant bone marrow cells called megakaryocytes.
     • They play a crucial role in blood clotting (coagulation) mechanisms, stopping blood loss from injuries.
Together, these components ensure blood effectively performs its transport, protective, and regulatory functions, maintaining the body's health.
In simple words: Blood is a fluid that carries nutrients and defends the body. It has plasma (liquid part) and three types of cells: red cells carry oxygen, white cells fight germs, and platelets help stop bleeding.

🎯 Exam Tip: When describing blood components, always include the function and a key characteristic (e.g., presence/absence of nucleus, color) for each component.

VIII. Higher Order Thinking Skills

Question 1. Identify the figure given below (Refer to the cross-section diagram of bone tissue with parts A, B, C).
Answer:
(a) The labeled parts are:
(A) Lamellae (rings)
(B) Lacunae (small spaces)
(C) Central (Haversian) canal (the middle canal)
(b) The bone tissue's matrix is rich in calcium salts and collagen fibers. These components are crucial for providing strength to the bone.
In simple words: The picture shows a bone cross-section. A, B, and C are names for its different parts. The bone's strength comes from calcium and collagen in its main material.

🎯 Exam Tip: When identifying diagrams, make sure to clearly state what the overall figure represents before labeling its individual parts. Always check for sub-questions related to composition or function after identification.

Question 2. Identify figures A and B (Refer to the diagrams of two different epithelial tissues).
(a) __________ epithelium forms the outer lining of the buccal cavity.
(b) __________ epithelium consists of cells that are tall and pillar-like.
(c) Which one allows diffusion of substances?
(d) Which is called pavement epithelium?
(e) Which epithelium lines the gastrointestinal tract and epiglottis?
Answer:
Figure A shows Squamous Epithelium.
Figure B shows Glandular Epithelium.
(a) Squamous epithelium forms the outer lining of the buccal cavity.
(b) Columnar epithelium consists of cells that are tall and pillar-like.
(c) Squamous epithelium allows diffusion of substances.
(d) Squamous epithelium is also called pavement epithelium.
(e) Columnar epithelium lines the gastrointestinal tract and epiglottis.
In simple words: Figure A is flat, thin squamous tissue, good for quick movement of things. Figure B is glandular, which means it makes and releases substances. Squamous cells are thin and flat, making them perfect for lining and diffusion. Columnar cells are tall, often found where absorption and secretion happen.

🎯 Exam Tip: Remember key features for each epithelium type: squamous for thin lining and diffusion, cuboidal for secretion and absorption, and columnar for absorption and secretion, often with cilia or microvilli.

Question 3. If cell (A) has undergone one mitotic division and another cell (B) has completed its meiotic division. The number of cells produced in A and B would be Cell A: Cell B :
Answer:
Cell A (after one mitotic division): 2 daughter cells.
Cell B (after one meiotic division): 4 daughter cells.
Mitosis produces two identical daughter cells, while meiosis creates four genetically different cells.
In simple words: Mitosis makes two new cells that are exactly the same as the first one. Meiosis makes four new cells, but they are all a bit different from the first one.

🎯 Exam Tip: Always associate mitosis with growth and repair, producing two identical diploid cells, and meiosis with sexual reproduction, producing four haploid cells with genetic variation.

Question 4. List the chromosomal events in this stage (Refer to the diagram of Mitotic Anaphase).
Answer: The stage shown is Mitotic Anaphase.
(i) During anaphase, the centromeres that hold the two chromatids together divide. After this, the two daughter chromatids from each chromosome separate and move towards opposite ends of the cell.
(ii) Spindle fibers contract, pulling the separated daughter chromosomes to their respective poles.
The movement of chromosomes towards the poles ensures that each new cell gets a complete set of genetic material.
In simple words: In this stage (anaphase), the chromosomes split in half and each half moves to opposite sides of the cell. This happens because special fibers pull them apart.

🎯 Exam Tip: For mitosis, remember the order of stages (Prophase, Metaphase, Anaphase, Telophase) and the key event in each, especially the separation of sister chromatids in anaphase.

Question 5. Identify the following relationship, similar to the example: Cuboidal : Epithelial
Cardiac :
Granulocytes :
Osteocytes :
Answer:
Cuboidal : Epithelial
Cardiac : Muscular
Granulocytes : Blood cells
Osteocytes : Bone cells
Understanding these relationships helps classify different cell types and tissues in the body.
In simple words: This question asks you to match cells or tissues to their main group. Like how cuboidal cells belong to epithelial tissue, cardiac cells belong to muscle tissue, granulocytes are a type of blood cell, and osteocytes are bone cells.

🎯 Exam Tip: When given an analogy or relationship, identify the common characteristic or classification (e.g., cell type, tissue type, location, function) between the first pair and apply it to the remaining items.

Question 6. Umbilical cord blood is collected at the time of childbirth and stored in stem cell banks. Reason out why this is done.
Answer:
• Umbilical cord blood contains stem cells, which are special cells that can divide many times without limit. They can develop into various different types of cells, tissues, and organs in the body. These are known as embryonic stem cells.
• Stem cells from cord blood can be very useful later on to treat certain diseases where cells are damaged or lost. For example, they can help with blood disorders or immune system problems.
This storage offers a future medical resource for the child or close family members.
In simple words: Umbilical cord blood is saved because it has stem cells. These cells can grow into many different kinds of body parts. They can be used later to help treat diseases by replacing damaged cells.

🎯 Exam Tip: When explaining the importance of stem cells, focus on their two key properties: self-renewal (unlimited division) and differentiation (ability to form different cell types), and provide examples of their therapeutic applications.

Question 7. How do WBC help in defence?
Answer: White Blood Cells (WBCs), also called leucocytes, help in defense by moving around like amoeba. They find and swallow foreign invaders, like bacteria or viruses, to protect the body. Some WBCs also produce antibodies to fight off infections.
In simple words: White blood cells protect our body. They can move and eat harmful germs, acting like the body's little soldiers.

🎯 Exam Tip: When asked about WBC function, emphasize their role in immunity, their phagocytic nature (engulfing pathogens), and their ability to produce antibodies.