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📘 Class 9 Biology – Competency & Case-Based Questions
Chapter 1: The Fundamental Unit of Life (25 Questions)
A. Competency-Based (Application/Analysis)
1. A cheek cell is observed under a microscope after staining. What differences would you expect if it were compared with a plant cell?
2. A student accidentally places onion peel in plain water and observes it under the microscope. Explain the change in the cell.
3. Why does plasma membrane act as a selectively permeable membrane? Give one example.
4. If mitochondria are removed from a cell, what cellular activities will be affected?
5. A student observes more lysosomes in the WBC compared to muscle cells. Justify.
6. Why are Golgi bodies considered the “post office” of the cell? Give an example to support your answer.
7. In which way is nucleolus different from the nucleus? Why is it important for the cell?
8. Why are chloroplasts double-membrane structures? How is this feature useful?
9. Explain why the fluid mosaic model is considered more acceptable than earlier models of plasma membrane.
10. If ribosomes of a cell stop functioning, which life process will be directly affected? Why?
B. Case-Based
11. A farmer uses excessive fertilizers. Plant cells absorb excess salts from the soil. Predict the effect on the vacuole and the cell as a whole.
12. A scientist isolates two types of cells: one has a cell wall, large vacuole, and chloroplasts; the other lacks them. Identify both types of
cells and give reasons.
13. A student notices that a raisin swells in water but shrinks in sugar solution. Explain this observation scientifically.
14. A cell is placed in a solution. After some time, the cell shrinks. What kind of solution was it? Justify with an example from daily life.
15. A patient is suffering from a disease where his lysosomes burst inside body cells. Predict the effect on those cells.
16. A slide of onion peel is prepared but the nucleus is not visible under a microscope. Suggest two reasons.
17. A boy cuts his finger while playing. Which organelles of his cells will be most active during healing? Explain.
18. A plant kept in the dark for a week shows pale leaves. Relate this observation with cell organelles.
19. A factory releases cyanide that inhibits mitochondria. Predict its impact on the factory workers’ body cells.
20. Why do prokaryotic cells divide faster than eukaryotic cells? Support your answer with structural differences.
C. Descriptive
21. “The cell is the basic structural and functional unit of life.” Justify this statement with suitable examples.
22. Describe the structure and function of the nucleus in detail.
23. Explain how diffusion and osmosis help in the survival of living organisms.
24. Draw and label the ultrastructure of a plant cell.
25. Differentiate between smooth and rough endoplasmic reticulum with diagrams.
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Chapter 2: Tissues (25 Questions)
A. Competency-Based (Application/Analysis)
26. Why is xylem lignified while phloem is not? Relate it to their functions.
27. Why does epidermis of desert plants secrete cutin? How is it advantageous?
28. A gardener observes that the stems of young plants bend easily but older stems become hard. Explain this on the basis of tissues.
29. How are cardiac muscles different from skeletal muscles in terms of function?
30. Which connective tissue stores fat in the body? Why is this tissue important for animals in cold climates?
31. Why are blood cells considered connective tissue?
32. Root hairs are extensions of epidermal cells. How does this help in absorption?
33. Why are sieve tubes in phloem kept alive, while xylem vessels are dead?
34. How does areolar tissue act as a “packing material” in the body?
35. A person has difficulty in movement due to joint injury. Which tissue might be damaged and why?
B. Case-Based
36. A farmer reports wilting of crops even when the soil is moist. Which tissue might be affected? Explain.
37. A weightlifter’s muscles swell after heavy exercise. Which type of muscle tissue is most involved and why?
38. A person with anemia is unable to carry out normal activities. Which tissue is responsible? Explain.
39. A student accidentally cuts the tip of a plant root. Predict which tissue is damaged and what effect it will have.
40. In a cactus plant, leaves are reduced to spines but photosynthesis still occurs. Which tissue helps in this?
41. A man feels pain in joints and difficulty in movement. Which connective tissue disorder could it be?
42. In drought-prone areas, plants show thickened cuticle. Which tissue modification is this?
43. A bone fracture is repaired by plaster. Which connective tissue helps in healing?
44. A child shows stunted growth and poor nutrient transport in plants. Which tissue is malfunctioning?
45. An athlete runs long distances without tiring quickly. Which muscle tissue property helps in this endurance?
C. Descriptive
46. Draw a neat diagram of phloem and label its parts. Write functions of each.
47. Differentiate between simple and complex tissues in plants with examples.
48. Explain how epithelial tissue is adapted to perform different functions in the body.
49. Write short notes on: (a) Meristematic tissue (b) Connective tissue.
50. With diagrams, describe different types of muscle tissues and their locations.
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Thanks for confirming 📘. Since you said "Yes," I’ll assume you want all 50 answers together, each in 40–50 words. This will be a long but
complete set for both chapters:
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📘 Class 9 Biology – Answers (40–50 words each)
Chapter 1: The Fundamental Unit of Life
1. Cheek cells are animal cells, so they lack a cell wall and chloroplasts, and have small vacuoles. Onion peel cells, being plant cells, have a
rigid cell wall, large vacuole, and may contain plastids. Both, however, have nucleus, cytoplasm, and plasma membrane.
2. When onion peel is placed in plain water, water enters the cell by osmosis. The vacuole swells, pressing the cytoplasm against the cell
wall. This condition is called turgidity, which maintains shape and firmness of plant cells.
3. Plasma membrane allows only certain molecules, such as oxygen and water, to pass freely, while restricting others like salts or proteins.
For example, glucose enters the cell through specific transport proteins but large molecules like starch cannot pass directly.
4. Without mitochondria, the cell cannot generate sufficient ATP through respiration. Energy-dependent processes like muscle contraction,
active transport, cell division, and biosynthesis will fail. The cell will gradually lose vitality and eventually die because no alternate efficient
source of energy exists.
5. White blood cells actively digest and destroy pathogens, requiring more hydrolytic enzymes. Lysosomes provide these enzymes for
intracellular digestion. Muscle cells mainly perform contraction and relaxation, so fewer lysosomes are needed. This explains the higher
lysosome count in WBCs.
6. Golgi bodies modify, package, and transport proteins and lipids, similar to how a post office sorts and dispatches parcels. For example,
enzymes secreted by the pancreas are packed in vesicles by Golgi apparatus before being transported outside the cell.
7. The nucleus is a membrane-bound organelle containing DNA, while nucleolus is a dense region inside the nucleus. Nucleolus mainly
synthesizes ribosomal RNA and assembles ribosomal subunits, which are essential for protein synthesis in the cytoplasm.
8. Chloroplasts have a double membrane, with the inner membrane enclosing stroma and thylakoids. This double boundary protects
chloroplast enzymes and maintains compartmentalization. It ensures efficient photosynthesis and regulates movement of molecules
necessary for glucose production.
9. The fluid mosaic model describes plasma membrane as a flexible structure with proteins embedded in a lipid bilayer. This explains
selective permeability, protein mobility, and transport better than earlier rigid models, which could not account for active transport and
dynamic properties.
10. Ribosomes synthesize proteins, which are essential for enzymes, hormones, and structural functions. Without ribosomes, no proteins
are formed, halting growth, repair, and metabolic reactions. As proteins are the building blocks of cells, absence of ribosome activity is fatal.
11. Excess salts create a hypertonic medium. Water exits the vacuole by osmosis, causing the vacuole to shrink. Plant cells lose turgidity and
become plasmolyzed. As a result, leaves wilt even though soil water appears available, because osmotic balance is disturbed.
12. The first cell with wall, vacuole, and chloroplasts is a plant cell. The second, lacking these, is an animal cell. Plant cells require cell walls
for rigidity and chloroplasts for photosynthesis, while animal cells depend on other nutrition sources.
13. A raisin swells in water because water enters its cells by endosmosis, as water concentration outside is higher. In sugar solution, water
leaves the cell by exosmosis due to higher solute concentration outside, leading to shrinking of the raisin.
14. The cell was placed in a hypertonic solution. Water moves out, causing shrinkage (plasmolysis). In daily life, pickles in concentrated salt
or sugar solutions remain preserved because bacterial cells lose water and shrink, preventing spoilage.
15. If lysosomes burst, hydrolytic enzymes leak into the cytoplasm, digesting cell components. This self-destruction causes cell death,
known as autolysis. Tissues lose function, leading to serious disease symptoms. Lysosomes are hence called “suicidal bags” of the cell.
16. The nucleus may not be visible if staining is improper or too light, making it indistinct. Another reason could be poor focusing under
microscope, or the cell is cut in such a way that the nucleus is not included.
17. During healing, ribosomes synthesize proteins for repair, while mitochondria provide ATP for energy. Golgi bodies secrete materials
needed for tissue regeneration. Lysosomes clear damaged cell debris. All these organelles coordinate to restore tissue health and structure.
18. Chloroplasts in leaves perform photosynthesis, which requires light. In darkness, chloroplasts cannot produce chlorophyll effectively,
causing leaves to appear pale. This condition is called etiolation, where leaves lose green pigment and growth is stunted due to lack of food.
19. Cyanide blocks enzymes of mitochondria, halting cellular respiration. Cells cannot produce ATP, leading to failure of essential processes
like nerve conduction and muscle contraction. Workers may collapse, as mitochondria are the powerhouse supplying continuous energy for
life activities.
20. Prokaryotic cells lack complex organelles and have a simple structure with circular DNA. They divide by binary fission, a fast process.
Eukaryotic cells undergo mitosis with multiple steps and organelle duplication, making their division slower compared to prokaryotes.
21. All living organisms are made up of cells, which perform essential life processes like respiration, excretion, and protein synthesis. For
example, muscle cells enable movement, while nerve cells conduct impulses. Thus, the cell is rightly called the structural and functional unit
of life.
22. The nucleus is a double-membrane structure with nuclear pores. It contains chromatin, nucleolus, and nucleoplasm. It regulates cell
activities, stores genetic information, and directs protein synthesis. By controlling hereditary material, it acts as the cell’s command center.
23. Diffusion allows gases like oxygen and carbon dioxide to move freely across cell membranes, essential for respiration and
photosynthesis. Osmosis maintains turgidity in plant cells, enabling support and nutrient absorption. Both processes ensure survival by
balancing cellular environment.
24. A plant cell has a rigid cell wall, plasma membrane, cytoplasm, nucleus, mitochondria, chloroplasts, large central vacuole, and Golgi
bodies. These structures work together to maintain life functions, provide energy, and support the plant structurally.
25. Rough endoplasmic reticulum (RER) has ribosomes attached and synthesizes proteins, while smooth endoplasmic reticulum (SER) lacks
ribosomes and synthesizes lipids, detoxifies drugs, and stores ions. Together, they form an interconnected transport system for
macromolecules in cells.
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Chapter 2: Tissues
26. Xylem is lignified, making it rigid and waterproof, ensuring efficient upward conduction of water under tension. Phloem lacks lignin, as it
must remain flexible and alive for translocation of sugars and nutrients. Their structures match their functions perfectly.
27. The epidermis of desert plants secretes a waxy layer of cutin to reduce water loss through transpiration. This adaptation helps plants
survive in hot, dry conditions by conserving moisture and preventing excessive evaporation from leaves and stems.
28. Young stems are flexible due to collenchyma and parenchyma tissues, which provide support while allowing growth. As plants mature,
xylem becomes lignified and sclerenchyma develops, making stems harder and woody, thereby providing mechanical strength to withstand
environmental stress.
29. Cardiac muscles are involuntary, branched, and rhythmic, ensuring continuous pumping of blood without fatigue. Skeletal muscles are
voluntary, cylindrical, and contract quickly, enabling body movements. The functional difference lies in their control and endurance, suited
to their roles.
30. Adipose tissue stores fat beneath the skin and around organs. In cold climates, stored fat provides insulation and maintains body
temperature. It also acts as an energy reserve during food scarcity, ensuring survival in harsh environments.
31. Blood is considered connective tissue because it connects different body parts by transporting oxygen, nutrients, hormones, and wastes
Like other connective tissues, it has cells (RBCs, WBCs, platelets) suspended in plasma, which acts as the matrix.
32. Root hairs are thin, tubular extensions of epidermal cells. They increase surface area for absorption of water and minerals from the soil.
Their thin walls and close contact with soil particles make absorption more efficient for plant growth.
33. Sieve tubes in phloem remain alive to allow active transport of food using companion cells. Xylem vessels are dead and lignified, as their
primary role is passive conduction of water, requiring no metabolic activity.
34. Areolar tissue fills spaces between organs, acting as packing material. It provides elasticity, supports blood vessels, and holds tissues in
place. It also helps repair tissues by providing fibroblasts and macrophages for defense and healing.
35. Injury to cartilage or ligament tissues in joints causes pain and restricted movement. Cartilage provides cushioning, while ligaments hold
bones together. Damage leads to swelling, stiffness, and loss of flexibility, directly affecting locomotion.
36. Wilting despite moist soil occurs if xylem is damaged, preventing water transport to aerial parts. Without proper conduction, leaves lose
turgidity and droop. This shows the vital role of xylem tissue in water supply and support.
37. Skeletal muscles are most involved in heavy exercise. Muscle fibers enlarge due to accumulation of lactic acid and increased blood flow.
This causes swelling and fatigue, showing the high activity of voluntary muscles during weightlifting.
38. Anemia reduces the number of red blood cells or hemoglobin, lowering oxygen transport. As a result, tissues receive less energy,
causing weakness, fatigue, and shortness of breath. This shows blood’s critical role as a connective tissue.
39. Cutting the root tip damages apical meristematic tissue. This halts cell division, stopping further elongation and growth of the root. The
plant may show stunted root development and reduced ability to absorb water and minerals.
40. In cactus, photosynthesis occurs in green stems containing chlorenchyma tissue. Leaves are reduced to spines to minimize water loss,
but the stem’s chloroplast-rich tissues perform photosynthesis, ensuring survival in desert conditions.
41. Painful joints may indicate arthritis, where cartilage in joints degenerates. Without cushioning, bones rub against each other, causing
stiffness and swelling. This connective tissue disorder severely affects movement and comfort.
42. Thick cuticle in drought areas is a modification of epidermal tissue. The waxy layer minimizes water evaporation, helping plants survive
under scarce water conditions. This is a protective adaptation against excessive transpiration.
43. During bone fracture, specialized connective tissue called osteoblasts deposit new matrix and calcium salts. With time, bone
regenerates, supported by blood vessels and cartilage. Plaster immobilizes the bone so connective tissue can repair efficiently.
44. Stunted growth may occur due to malfunctioning phloem tissue. If phloem transport of food is blocked, nutrients from leaves cannot
reach roots or growing parts. This prevents proper development of the plant despite photosynthesis.
45. Cardiac and red skeletal muscles contain abundant mitochondria, allowing aerobic respiration and sustained energy release. This
prevents fatigue, enabling athletes to run long distances. Their endurance is due to continuous ATP supply and coordinated muscle
contractions.
46. Phloem consists of sieve tubes, companion cells, phloem parenchyma, and fibers. Sieve tubes conduct food, companion cells assist in
loading sugars, parenchyma stores food, and fibers provide mechanical support. All parts work together to transport nutrients in plants.
47. Simple tissues are made of one type of cell, like parenchyma, collenchyma, and sclerenchyma, performing basic functions. Complex
tissues like xylem and phloem consist of different cells working together for conduction and transport, ensuring plant survival.
48. Epithelial tissue covers body surfaces, lining organs and cavities. Squamous epithelium enables diffusion, cuboidal epithelium aids
secretion, columnar epithelium helps absorption, and ciliated epithelium clears particles. Its variations make it adaptable for diverse
functions in the body.
49. (a) Meristematic tissue has actively dividing cells responsible for plant growth, found at root and shoot tips. (b) Connective tissue
supports and binds body parts. Examples include bone for rigidity, cartilage for cushioning, blood for transport, and adipose for fat storage.
50. Muscle tissues are of three types: Skeletal (voluntary, cylindrical, multinucleated, attached to bones), Smooth (involuntary,
spindle-shaped, in organs like stomach), and Cardiac (involuntary, branched, rhythmic, in heart). Each type performs specific movements
suited to its location.
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📘 That’s all 50 answers in 40–50 words each.
Would you like me to also prepare this in a Word/PDF file format so you can directly use it for study or printing?
