Master DAV Class 6 Science Chapter 8: Structure and Function of the Living Organisms – Plants from the official textbook The Living World with our master examination guide. Contains complete, 100% accurate textbook solutions (Parts A through E), detailed 3-column comparative tables (Tap vs Fibrous roots, Root vs Shoot system, Venation correlations), step-by-step anatomical breakdowns, and authentic DAV Board Exam Common Question Paper PYQs (2022–23 & 2023–24) with teacher marking rubrics.
Part A: Fill in the Blanks
Carefully study the completed textbook statements with essential botanical terms emphasized:
- 1. Maize, wheat and rice are examples of fibrous roots. (Concept: Fibrous roots arise in clusters from the base of the stem without a primary taproot.)
- 2. Ginger and potato are two examples of modified stems. (Clarification: Potato is an underground stem tuber and ginger is an underground rhizome storing starch and nutrients.)
- 3. The main function of the leaf is to prepare food for the plant. (Process: Synthesizes carbohydrates through photosynthesis using green chlorophyll.)
- 4. Banyan is an example of prop roots. (Function: Pillar-like adventitious aerial roots that grow downwards into the soil to provide mechanical support to heavy horizontal branches.)
- 5. Flower is the most attractive, and colourful, part of the plant. (Biological significance: Flowers serve as the specialized organs of sexual reproduction.)
- 6. The leaves of cacti are modified into spines. (Adaptation: Drastically cuts down transpiration water loss in extreme desert heat.)
- 7. The leaf blade is also known as lamina. (Anatomy: The broad, flattened, green surface of a leaf specialized for light absorption and gas exchange.)
Part B: Write True or False for the Following Statements
Each statement is rigorously evaluated with complete scientific reasoning:
1. All plants possess the tap root system.
Answer: FALSE.
Scientific Justification: Only dicotyledonous plants (such as gram, pea, mustard) possess a tap root system. Monocotyledonous plants (such as wheat, maize, grass) possess a fibrous root system.
2. The wheat and maize plants have a fibrous root system.
Answer: TRUE.
Scientific Justification: Wheat and maize are monocots. Their primary embryonic radicle stops growing early and is replaced by a dense cluster of slender, thread-like fibrous roots originating from the base of the stem.
3. Cactus plants photosynthesise through their stems.
Answer: TRUE.
Scientific Justification: In cacti, leaves are reduced to defensive spines to prevent water loss; the fleshy green stem (phylloclade) contains chlorophyll and takes over the entire photosynthetic manufacturing of food.
4. Leaves manufacture food for themselves.
Answer: FALSE.
Scientific Justification: Leaves manufacture food for the entire plant body. The synthesized glucose is translocated through phloem vessels to the roots, stems, flowers, developing fruits, and storage organs.
5. Flower is meant for the reproduction of the plant.
Answer: TRUE.
Scientific Justification: Flowers house the male reproductive whorl (androecium) and female reproductive whorl (gynoecium) that produce gametes, facilitate pollination and fertilization, and yield seeds and fruits.
6. The pistil is the female part of a flower.
Answer: TRUE.
Scientific Justification: The pistil (or carpel) is the innermost female reproductive whorl (gynoecium) consisting of the stigma, style, and ovary.
7. Stigma and ovary have no role in reproduction of plants.
Answer: FALSE.
Scientific Justification: Both play decisive roles: the sticky stigma captures pollen grains during pollination, while the ovary contains ovules where fertilization occurs and which later matures into the fruit containing seeds.
8. Seeds store food for the future plant.
Answer: TRUE.
Scientific Justification: The cotyledons and endosperm within seeds store starch, proteins, and oils to nourish the developing baby plant (embryo) until it sprouts green leaves to perform photosynthesis.
Part C: Tick the Correct Option
1. The roots, that are consumed as food, are-
(a) Ginger and potato
(b) Radish and carrot
(c) Onion and garlic
(d) Tomato and brinjal
Correct Option: (b) Radish and carrot
Why this is correct: Radish and carrot are modified fleshy tap roots that store excess reserve food carbohydrates. (Ginger, potato, onion, and garlic are underground modified stems).
2. The plants manufacture food through the process of-
(a) Transpiration
(b) Respiration
(c) Photosynthesis
(d) Germination
Correct Option: (c) Photosynthesis
Why this is correct: Photosynthesis is the biochemical synthesis of glucose from carbon dioxide and water by chlorophyll in green leaves powered by sunlight.
3. Leaves are attached to stem at the-
(a) Internode
(b) Apex
(c) Node
(d) Root cap
Correct Option: (c) Node
Why this is correct: A node is the specific anatomical point or joint on the stem where leaves, branches, or buds originate. The interval between two successive nodes is an internode.
4. The total number of whorls, in a complete flower, is/are-
(a) Two
(b) Three
(c) Four
(d) Five
Correct Option: (c) Four
Why this is correct: A typical complete flower possesses four concentric whorls: Calyx (sepals), Corolla (petals), Androecium (stamens), and Gynoecium (carpels/pistil).
5. The reproductive organ, of a plant, is the-
(a) Root
(b) Stem
(c) Leaf
(d) Flower
Correct Option: (d) Flower
Why this is correct: Roots, stems, and leaves are vegetative organs; the flower is the specialized reproductive shoot bearing male and female sexual structures.
6. The part of the flower, that provides protection to the bud, before it blooms, is the-
(a) Petal
(b) Sepal (Calyx)
(c) Stamen
(d) Carpel
Correct Option: (b) Sepal (Calyx)
Why this is correct: Green leaf-like sepals enclose the delicate inner floral organs securely during the immature bud stage, shielding them from insects and harsh weather.
Part D: Answer the Following Questions in Brief
1. Name the two main systems of a plant.
Answer:
A typical flowering plant is divided into two primary structural systems:
1. The Root System: The underground, non-green axis that anchors the plant and absorbs water/minerals.
2. The Shoot System: The aerial, upright axis growing above the soil consisting of the stem, branches, leaves, flowers, and fruits.
2. Name the different parts of the shoot system.
Answer:
The shoot system comprises the following essential structures:
• Stem: The central upright main axis.
• Branches: Lateral offshoots arising from stem nodes.
• Leaves: Lateral green appendages specialized for food manufacture.
• Buds: Terminal (apical) and axillary growing points.
• Flowers: Reproductive structures.
• Fruits and Seeds: Ripened ovaries enclosing fertilized ovules.
3. Name different types of modified stems.
Answer:
Stems undergo distinct anatomical modifications to perform specialized functions:
1. Underground Stems for Food Storage: Tuber (Potato), Rhizome (Ginger), Bulb (Onion).
2. Stem Tendrils for Mechanical Support: Slender twining coils in Grapevine and Passion fruit.
3. Stem Thorns/Spines for Defense: Sharp woody structures in Bougainvillea and Citrus.
4. Photosynthetic Succulent Stems (Phylloclades): Green fleshy stems in Cactus for water retention and photosynthesis.
4. State the role of spines—the modified leaves.
Answer:
In xerophytic desert plants like cactus, leaves are modified into sharp, pointed spines to serve two critical biological functions:
1. Reduction of Transpiration: By drastically minimizing leaf surface area, spines prevent excessive water loss in arid environments.
2. Protection: Sharp spines act as a formidable deterrent shielding the fleshy, water-laden plant from grazing desert animals.
5. Name the different parts of a flower.
Answer:
The structural parts of a typical flower arranged in concentric whorls are:
1. Pedicel and Thalamus: The flower stalk and its swollen receptacle base.
2. Calyx (composed of Sepals): Outer protective green whorl.
3. Corolla (composed of Petals): Brightly coloured whorl to attract pollinators.
4. Androecium (composed of Stamens): Male reproductive whorl made of filament and pollen-bearing anther.
5. Gynoecium / Pistil (composed of Carpels): Female reproductive whorl made of stigma, style, and ovule-bearing ovary.
Part E: Answer the Following Questions (Long Answers)
1. State the differences between the two main systems of a plant.
Answer:
Below is the structured 3-column distinction between the Root System and Shoot System:
| Feature | Root System | Shoot System |
|---|---|---|
| Location & Growth | Underground; positively geotropic (grows towards gravity) and negatively phototropic. | Aerial; negatively geotropic and positively phototropic (grows toward sunlight). |
| Constituent Parts | Primary root, secondary lateral roots, root hairs, and root cap. | Stem, nodes, internodes, buds, leaves, flowers, and fruits. |
| Primary Functions | Firm anchorage in soil; absorption of water and dissolved mineral salts. | Conduction, photosynthesis, transpiration, and sexual reproduction. |
| Chlorophyll & Nodes | Non-green (lacks chlorophyll); devoid of nodes and internodes. | Green in young stage; distinctly divided into nodes and internodes. |
2. Define root system. Give two functions of roots.
Answer:
Definition: The descending underground axis of a plant that develops directly from the embryonic radicle of a germinating seed is termed the root system.
Two Vital Functions:
1. Anchorage: Roots spread deep and wide through soil particles, firmly binding the plant upright against wind and rainwater runoff.
2. Absorption and Conduction: Microscopic root hairs absorb capillary soil water and dissolved mineral ions, channeling them upwards into xylem vessels of the stem.
3. Define shoot system. Give two functions of the stem.
Answer:
Definition: The aerial, ascending part of the plant axis that develops from the embryonic plumule and grows upward above the ground into the atmosphere is termed the shoot system.
Two Vital Functions of the Stem:
1. Mechanical Support and Display: The stem holds branches, spreading leaves in optimal positions to receive sunlight, and displays flowers and fruits for pollination and seed dispersal.
2. Bidirectional Conduction: Transports water and dissolved minerals from roots upward to leaves via xylem, and translocates synthesized organic food from leaves downward and upward to all plant organs via phloem.
4. How is a tap root different from a fibrous root? Give one example of each type.
Answer:
The structural comparison between tap roots and fibrous roots is shown below:
| Feature | Tap Root System | Fibrous Root System |
|---|---|---|
| Origin & Structure | Develops from embryonic radicle; features one prominent, thick central primary root with smaller lateral branches. | Radicle ceases growth; replaced by a cluster of nearly identical, thin, thread-like roots from the stem base. |
| Depth of Penetration | Penetrates deeply vertical into soil layers. | Remains relatively shallow, spreading horizontally like a turf mat. |
| Leaf Venation Correlation | Always associated with leaves having reticulate venation (net-like). | Always associated with leaves having parallel venation. |
| Botanical Examples | Mustard, Pea, Gram, Mango, Carrot. | Wheat, Rice, Maize, Grasses, Bamboo. |
5. What is a leaf? Draw / describe the different parts of a leaf.
Answer:
A leaf is a flattened, thin, lateral green outgrowth developing from a node on the stem or branch, specialized for photosynthesis and transpiration.
Principal Anatomical Parts:
1. Petiole (Leaf Stalk): The cylindrical stalk that attaches the leaf blade to the stem node and positions the blade toward light.
2. Lamina (Leaf Blade): The broad, expanded green surface of the leaf where photosynthesis occurs.
3. Midrib: The prominent central vein extending from petiole to apex along the middle of the blade.
4. Veins & Veinlets: Network of rigid vascular conduits branching across the lamina to transport water/food and provide skeletal support.
5. Stomata: Microscopic pores on the epidermal surface of the blade that regulate gas exchange (CO₂/O₂) and transpiration.
6. Name any two types of stem modifications, giving one example for each type.
Answer:
1. Underground Stem for Food Storage: Stems swell beneath the soil to store reserve starch. Example: Potato tuber (bears nodes called ‘eyes’ containing buds).
2. Stem Tendril for Climbing Support: Delicate axillary buds transform into spirally coiled, sensitive threads that twine around supports. Example: Grapevine and passion fruit.
7. What are the functions of a fruit?
Answer:
A fruit is the mature, ripened ovary developed after fertilization. It performs three critical biological functions:
1. Seed Protection: Shields developing and delicate seeds from mechanical injury, desiccating climatic conditions, and fungal infections.
2. Nutrient Storage & Food: Stores sugars, vitamins, and minerals, providing nutrition to humans and wildlife (e.g., mango, apple, tomato).
3. Seed Dispersal: Fleshy, sweet pericarp attracts animals and birds, which consume the fruit and carry seeds across wide geographic distances, ensuring propagation of the species.
Value-Based Questions (VBQ) & HOTS
Value-Based Question (VBQ)
Scenario: During Van Mahotsav week at school, Ananya noticed that many potted plants on the school terrace had wilting leaves under the blazing sun. Instead of ignoring it, she organized her classmates to water the plants during early mornings and evenings and moved sensitive flowering pots under green shade nets.
(a) Identify two positive qualities displayed by Ananya:
Model Answer: Empathy towards living nature, leadership, and scientific awareness of plant physiology.
(b) Why should plants be watered in early mornings or evenings rather than bright noon?
Model Answer: In intense midday heat, high evaporation causes water to evaporate rapidly before roots can absorb it, and sudden cold water on hot soil can cause thermal stress to tender root tissues.
Higher Order Thinking Skills (HOTS)
Question: Without pulling up a plant from the soil, how can a botanist accurately determine whether it possesses a tap root system or a fibrous root system?
Model Answer: By examining the venation pattern of its leaves:
• If the leaves show reticulate venation (a complex interconnected net-like vein network, like mustard or peepal), the plant invariably possesses a tap root system.
• If the leaves show parallel venation (veins running parallel from base to tip, like grass, wheat, or banana), the plant invariably possesses a fibrous root system.
🎯 DAV Board Exam Corner: Authentic PYQs (2022–23 & 2023–24)
Below are authentic questions directly retrieved from official DAV Public Schools Half-Yearly and Annual Board Papers for Chapter 8:
Q1. [DAV Half-Yearly Board Exam 2023–24 • 1 Mark VSA]
Define the term ‘transpiration’. Which organ of the plant primarily performs it?
Model Answer: The biological process of loss of excess water in the form of water vapour from the aerial surface of a plant (mainly through stomata on leaves) is called transpiration.
Q2. [DAV Annual Board Exam 2022–23 • 2 Marks SA-I]
Name the two parts that comprise a stamen. What microscopic substance is produced in the anther?
Model Answer: A stamen consists of: (1) A slender stalk called the filament, and (2) A bilobed sac at the top called the anther.
The anther produces fine, powdery yellow grains called pollen grains containing the male gametes.
Q3. [DAV Annual Board Exam 2023–24 • 3 Marks SA-II]
Explain the structure of the female reproductive organ (Carpel/Pistil) of a flower with its three distinct parts.
Model Answer: The carpel/pistil is the female reproductive unit consisting of:
1. Stigma: The sticky terminal landing platform at the top that captures and retains pollen grains during pollination.
2. Style: The elongated slender neck that supports the stigma and conducts the pollen tube down to the ovary.
3. Ovary: The swollen basal chamber enclosing one or more ovules (egg cells). Following fertilization, the ovary matures into a fruit and ovules develop into seeds.
Q4. [DAV Annual Board Exam 2022–23 • 5 Marks Long Answer]
(a) State the relationship between leaf venation, root type, and cotyledon count in seeds.
(b) Tabulate this relationship comparing Dicotyledonous and Monocotyledonous plants with two examples of each.
Model Answer:
(a) Scientific Correlation: Flowering angiosperms exhibit an invariant structural link: plants with reticulate venation possess tap roots and two seed cotyledons, whereas plants with parallel venation possess fibrous roots and a single seed cotyledon.
(b) Comparative Summary:
| Parameter | Dicotyledonous Plants (Dicots) | Monocotyledonous Plants (Monocots) |
|---|---|---|
| Leaf Venation | Reticulate (network) | Parallel (straight lines) |
| Root System | Tap Root System | Fibrous Root System |
| Seed Cotyledons | Two cotyledons | One cotyledon |
| Examples | Gram, Pea, Mustard, Mango | Wheat, Rice, Maize, Grass |
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