Reproduction and Modification in Plants — Exercise Solutions

Samacheer Kalvi Tamil Nadu State Board Class 7 Science Term 1 Chapter 5 exercise solutions. Covers MCQs, fill-in-the-blanks, true/false, match the following, assertion and reason, very short, short, detailed answers, and HOTS questions.

I. Choose the Appropriate Answer (MCQ)

Q1. Vegetative propagation by leaves takes place in (a) Bryophyllum (b) Fungi (c) Virus (d) Bacteria Answer: (a) Bryophyllum ✓ — Bryophyllum produces plantlets along leaf margins that fall off and grow into new plants.

Q2. Asexual reproduction in yeast is (a) Spore formation (b) Fragmentation (c) Pollination (d) Budding Answer: (d) Budding ✓ — Yeast reproduces asexually by forming a small bud that detaches as a new cell.

Q3. Reproductive part of a plant is (a) Root (b) Stem (c) Leaf (d) Flower Answer: (d) Flower ✓ — The flower contains androecium (male) and gynoecium (female) reproductive whorls.

Q4. Pollinators are (a) Wind (b) Water (c) Insect (d) All the above Answer: (d) All the above ✓ — Wind, water, insects, and animals all serve as agents of pollination.

Q5. Climbing roots are seen in (a) Betel (b) Black pepper (c) Both of them (d) None of them Answer: (c) Both of them ✓ — Both betel and black pepper produce adventitious roots at nodes for climbing.

Additional MCQs

Q6. ___ do not produce spores. (a) Algae (b) Fungi (c) Datura (d) Ferns Answer: (c) Datura ✓ — Datura is a flowering plant that reproduces by seeds, not spores.

Q7. ___ have the smallest seeds in the plant kingdom. (a) Coconut (b) Orchids (c) Onion (d) Pumpkin Answer: (b) Orchids ✓ — Orchid seeds are microscopic and among the smallest in the plant kingdom.

Q8. Breathing roots are seen in ___ (a) Tarpa (b) Avicennia (c) Eichhornia (d) Pisum Answer: (b) Avicennia ✓ — Avicennia is a mangrove plant with pneumatophores (breathing roots).

Q9. ___ is a parasite. (a) Cuscuta (b) Hibiscus (c) Yeast (d) Spirogyra Answer: (a) Cuscuta ✓ — Cuscuta (dodder) lacks chlorophyll and derives nutrition from host plants using haustoria.

Q10. In ___ sepal is seen on the fruit after fertilization. (a) Brinjal (b) Pumpkin (c) Onion (d) Garlic Answer: (a) Brinjal ✓ — In brinjal, the calyx persists on the fruit even after fertilization.

II. Fill in the Blanks

1. The male reproductive part of a flower is Androecium. 2. Ovary is the basal swollen part of the Gynoecium. 3. After fertilization the ovule becomes seed. 4. Breathing roots are seen in mangrove plants. 5. Onion and Garlic are examples of Bulb.

Additional Fill in the Blanks

6. The tissue in epiphytic roots is called Velamen. 7. Cactus is an example for Phylloclade. 8. Ginger and Turmeric are examples of Rhizome. 9. In Gloriosa, leaf tip is modified into a tendril. 10. Spirogyra reproduces by fragmentation.

III. True or False (with corrections)

Q1. A complete flower has four whorls. Answer: True.

Q2. The transfer of pollen to the stigma is known as pollination. Answer: True.

Q3. Conical shaped root is carrot. Answer: True.

Q4. Ginger is an underground root. Answer: False. Ginger is an underground stem (rhizome), not a root.

Q5. Leaves of Aloe vera are fleshy and store water. Answer: True.

Additional True/False

Q6. In cactus, stem is modified into spines. Answer: False. In cactus, the leaf is modified into spines; the stem is modified into a phylloclade.

Q7. Ovules fall off after fertilization. Answer: False. Style and stigma fall off after fertilization; ovules develop into seeds.

Q8. In Nepenthes, leaf is modified into a flask-shaped structure. Answer: True.

Q9. Tuber is an enlarged underground root. Answer: False. Tuber is an enlarged underground stem (e.g., potato has eyes which are buds).

Q10. Scaly leaves are seen in onion. Answer: True.

IV. Match the Following

Set 1

Set 2 (Additional)

Set 3 (Additional)

V. Assertion and Reason

Q1. Assertion: Pollination and fertilization in flowers produces fruits and seeds. Reason: After fertilization, ovary becomes fruit and ovule becomes seed. Answer: (c) Both assertion and reasoning are correct. ✓

Q2. Assertion: The example of conical root is carrot. Reason: It is an adventitious root modification. Answer: (a) Assertion is correct but reasoning is incorrect. ✓ — Carrot is a tap root modification, not adventitious.

Additional Assertion and Reason

Q3. Assertion: In potato, shoot arises from eyes. Reason: Eyes represent the buds. Answer: (c) Both correct. ✓

Q4. Assertion: In Banyan, prop roots grow horizontally from the tree. Reason: They give additional support. Answer: (b) Assertion is incorrect (prop roots grow vertically from branches, not horizontally), reasoning is correct.

Q5. Assertion: Corm is a condensed form of Bulb. Reason: It has dry and fleshy scale leaves. Answer: (d) Both incorrect. ✓ — Corm is a condensed form of rhizome, not bulb.

VI. Find the Odd One Out

Q1. Pollen, anther, ovule, filament Answer: Ovule — it belongs to the gynoecium (female part); the others (pollen, anther, filament) are parts of the androecium (male part).

Q2. Corm, Bulb, Rhizome, Sucker Answer: Sucker — it is a sub-aerial stem modification; the others are underground stem modifications.

Q3. Haustoria, Velamen, Prop Roots, Phyllode Answer: Phyllode — it is a leaf modification; the others are root modifications.

VII. Very Short Answer Questions

Q1. What are the two types of reproduction in plants? Answer: Sexual reproduction (through flowers and seeds) and asexual reproduction (vegetative propagation).

Q2. Name the two important parts of a flower. Answer: Androecium (male reproductive part) and Gynoecium (female reproductive part).

Q3. Define pollination. Answer: Transfer of pollen grains from the anther to the stigma of a flower.

Q4. What are the agents of pollination? Answer: Insects, wind, water, and animals.

Q5. Give examples for (a) Corm (b) Tuber. Answer: (a) Corm — Colocasia (b) Tuber — Potato.

Q6. What is a tendril? Answer: An elongated structure produced by the plant to help it climb efficiently. Example: In pea, the terminal leaflets are modified into tendrils.

Q7. What are thorns? Answer: Pointed, sharp structures formed from modified leaves or plant parts. They protect the plant from animals and may assist in climbing.

Additional Very Short Answers

Q8. Name the whorls of a flower. Answer: Calyx, Corolla, Androecium, and Gynoecium.

Q9. What is an inflorescence? Answer: A group of flowers arranged on a stem is called an inflorescence (e.g., sunflower).

Q10. What is fertilization? Answer: The fusion of male gamete with the female gamete to form a zygote.

Q11. Name the sub-aerial modifications of stem. Answer: Runner, stolon, sucker, and offset.

Q12. Name the underground stem modifications. Answer: Rhizome, Corm, Tuber, and Bulb.

Q13. What are sucking roots? Answer: Sucking roots (haustoria) are found in parasitic plants like Cuscuta. They penetrate host plant tissues and absorb nutrients from them.

Q14. Differentiate phyllode and phylloclade. Answer: Phyllode — petioles modified to form a leaf-like structure (e.g., Acacia). Phylloclade — stem modified to form a leaf-like structure (e.g., Cactus).

Q15. What are breathing roots (pneumatophores)? Answer: Mangrove plant roots that project above ground for gaseous exchange. They are erect, peg-like structures with numerous pores. Example: Avicennia.

VIII. Short Answer Questions

Q1. Differentiate bisexual flower from unisexual flower.

Q2. What is cross pollination? Answer: Cross pollination is the transfer of pollen grains from the anther of one flower to the stigma of another flower of the same kind or a different plant. Plants must produce pollen in larger quantities to increase pollination chances. Cross pollination introduces variations in the characteristics of new plants. Agents such as wind, water, animals, and insects facilitate it. Examples: plums, apples.

Q3. Write notes on phyllode. Answer: In Acacia auriculiformis, the petioles expand to form a leaf-like structure called a phyllode. These carry out the function of a leaf, i.e., photosynthesis. Since the true leaves are small and fall off early, the phyllode performs the role of the leaf throughout the plant's life.

Q4. Post-fertilization changes in a flower. Answer: 1. Calyx sometimes persists with the fruit 2. Petals wither and fall off 3. Androecium falls off 4. Pistil remains and develops into fruit 5. Style and stigma fall off 6. Ovary enlarges, stores food, and becomes the fruit 7. Ovules inside the ovary develop into seeds

Q5. Roots modified for mechanical support. Answer: Three types: 1. Prop roots: Grow vertically from horizontal branches for support. Example: Banyan tree. 2. Stilt roots: Adventitious roots from nodes in clusters at the stem base. Example: Sugarcane, maize. 3. Climbing roots: Roots at nodes or internodes help the plant climb. Example: Betel, black pepper.

Q6. Epiphytic roots vs. Sucking roots.

Q7. Note on phylloclade. Answer: Desert plants need to store water and minimize evaporation. In cactus, the stem becomes thick and flat to perform photosynthesis. Leaves are reduced to small spines with less surface area. This stem modification is called phylloclade. Example: Cactus (Opuntia).

Q8. Traps or insectivorous plants. Answer: These plants grow in nitrogen-deficient places. In Nepenthes, leaves are modified into a flask-like structure that attracts insects. The inner wall secretes digestive enzymes that digest insects and extract nitrogen. Example: Nepenthes (pitcher plant).

IX. Detailed Answer Questions

Q1. Write a brief account on pollination. Answer: Pollination is the transfer of pollen grains from anther to stigma. Two types exist:

(a) Self pollination: Pollen moves from the anther to the stigma of the same flower or another flower on the same plant. Less pollen quantity is needed. No new variations in characteristics are produced.

(b) Cross pollination: Pollen transfers from the anther of one flower to the stigma of another flower of the same kind or different plant. Larger pollen quantities are needed to boost pollination chances. Variations are introduced in new plants (e.g., apples, plums). Agents — wind, water, insects, animals — serve as pollinators. Wind-pollinated plants produce light pollen; insect-pollinated flowers are brightly coloured with pollen that sticks to insect bodies.

Q2. Explain the underground stems. Answer: Some stems grow underground to store food, swelling and becoming thick. Four types:

1. Rhizome: A thick underground stem with nodes, internodes, and scale leaves at nodes. Grows horizontally with irregular shape. Has buds that give rise to new stems and leaves. Examples: Ginger, Turmeric.

2. Corm: Round, flat at top and bottom. A condensed rhizome bearing one or more buds in the axils of scale leaves. Daughter plants arise from these buds. Example: Colocasia.

3. Tuber: Enlarged, spherical underground stem storing food. Has many dormant buds on its surface called "Eyes." Planting a tuber part with a bud grows a new plant. Example: Potato.

4. Bulb: Condensed, disc-like stem storing food in fleshy leaves. Has two leaf types — fleshy leaves and scaly leaves. The upper stem has a terminal bud covered by scaly leaves; inner fleshy leaves store food. Examples: Garlic, Onion.

Q3. Sub-aerial modifications of the stem. Answer: Four types of sub-aerial stem modifications for reproduction:

1. Runner: Stem grows laterally on the soil surface, breaks up and produces roots where it touches ground, giving rise to new plants. Example: Centella (Vallarai).

2. Stolon: A slender branch grows upward, then bends toward the ground. On touching ground, it gives rise to a new plant. Example: Wild strawberry.

3. Sucker: A short, weak lateral branch grows diagonally upward and directly gives rise to a new shoot. Example: Chrysanthemum.

4. Offset: A short, thick branch arises from the axial part of a leaf with thick internodes. Produces a tuft of leaves above and cluster of small roots below. Example: Eichhornia.

X. Higher Order Thinking Skills (HOTS)

Q1. Ginger is considered a stem, not a root. Why? Answer: Ginger possesses characteristics of a stem: it has scale leaves, nodes and internodes, axillary buds, and a terminal bud. Roots do not have nodes, internodes, or buds. Therefore, ginger is a modified underground stem (rhizome) that stores food, not a root.

Q2. What happens if pollen of rose is deposited on stigma of lily? Will pollen germinate? Why? Answer: No, rose pollen will not germinate on lily's stigma. Pollen is compatible only with the stigma of a flower of the same species. The stigma recognizes pollen of its own species through chemical compatibility. Pollen from a different species is rejected and does not germinate.

Q3. Parasitic plants lack leaves. Why? Answer: Parasites live on other living plants and derive nutrients from them. They are non-green and do not photosynthesize. They possess sucking roots (haustoria) to absorb nutrients directly from the host tissue. Since they do not need to produce their own food through photosynthesis, they lack leaves.

XI. Intext Activity

Activity: Flower Classification Table

XII. Complete the Table

Table 1: Plant Modifications

Table 2: Whorls of a Flower

Common Mistakes to Avoid

1. Confusing ginger with a root — Ginger is a modified underground stem (rhizome) with nodes, internodes, and buds; roots lack these features. 2. Calling potato a root — Potato is a tuber (underground stem modification) with "eyes" that are buds, not a root. 3. Equating self and cross pollination — Self pollination occurs within the same flower/plant; cross pollination requires an agent to transfer pollen between different plants. 4. Saying all flowers have both male and female parts — Unisexual flowers have only one type of reproductive organ; only bisexual flowers have both. 5. Confusing phyllode and phylloclade — Phyllode is a modified petiole (leaf part); phylloclade is a modified stem that looks like a leaf. 6. Calling breathing roots as feeding roots — Pneumatophores (breathing roots) are for gaseous exchange, not for absorbing water or nutrients from soil. 7. Mixing up prop roots and stilt roots — Prop roots grow vertically from branches (e.g., banyan); stilt roots grow from the base of the stem (e.g., maize, sugarcane).

Exam Checklist

• [ ] Can define sexual and asexual reproduction and give examples of each
• [ ] Can identify the four whorls of a flower (Calyx, Corolla, Androecium, Gynoecium)
• [ ] Can explain self pollination and cross pollination with differences
• [ ] Can describe post-fertilization changes in a flower
• [ ] Can list and explain the four types of underground stem modifications (Rhizome, Corm, Tuber, Bulb)
• [ ] Can list and explain the four sub-aerial stem modifications (Runner, Stolon, Sucker, Offset)
• [ ] Can describe root modifications for storage, support, climbing, respiration, and parasitism
• [ ] Can differentiate phyllode, phylloclade, tendril, thorn, and insectivorous traps
• [ ] Can explain why ginger is a stem and not a root
• [ ] Can distinguish epiphytic roots from sucking roots (haustoria)