NCERT Solutions Poorvi Chapter 3 Spectacular Wonders — Let us explore

Book page 150 Updated on2026-09-05

Q1.
Man-made Wonders. 1. Kallanai Dam (The Grand Anaicut) in Tamil Nadu is one of the world’s oldest dams and is still in use. The Kallanai Dam represents a significant achievement in ancient Indian hydraulic engineering. It was built by the Chola King Karikala around 150 CE. 2. Another spectacular legacy of ancient wisdom that we have is the world’s first residential university at Nalanda in Bihar. Nalanda was established much before any European university, providing higher education to thousands of students. It was declared as a UNESCO heritage site in 1980. You may visit the site given below to know more about this. 3. Hampi, a town in Karnataka, is also a UNESCO World Heritage Site. The Vittala Temple in Hampi was built in the 15th century. This temple has 56 special pillars known as the SaReGaMa pillars. When these pillars are tapped, they produce musical notes that can be heard clearly. 4. Some of the man-made wonders of modern India include the Bandra–Worli Sea Link in Mumbai; Statue of Unity in Gujarat; Bhupen Hazarika Setu (The Dhola-Sadiya Bridge) in Assam; and many more.
Answer

The four notes on this page are the man-made half of the unit's argument. Fix the facts first, then notice what they have in common.

WonderWhereThe fact to remember
Kallanai Dam (The Grand Anaicut)Tamil Nadu, on the KaveriBuilt by the Chola king Karikala around 150 CE; one of the world's oldest dams and still in use
NalandaBiharThe world's first residential university, established long before any European one; a UNESCO heritage site since 1980
The Vittala Temple, HampiKarnatakaBuilt in the 15th century; has 56 SaReGaMa pillars that give out musical notes when tapped
Modern IndiaMumbai, Gujarat, AssamThe Bandra–Worli Sea Link, the Statue of Unity, the Bhupen Hazarika Setu (Dhola–Sadiya Bridge)
What the four have in common: every one of them is still working, or was working for a very long time. A dam that has watered the Kaveri delta for nearly nineteen centuries, a university that taught for seven hundred years, pillars that still sound, bridges that carry traffic today. The page is not a list of monuments to look at; it is a list of things that were used. That is a fair definition of an engineering wonder.
Take it further: find out how the Kallanai was built — of unhewn stone laid across the river without mortar, so that flood water passes over it instead of destroying it. Compare that idea with the living root bridges of Meghalaya: both work with the water rather than against it. Then make a two-column chart, ‘Ancient wonders / Modern wonders', and add three of your own to each side.
Q2.
Some micro-planktons in the sea are bioluminescent. Have you seen any other life form that has this quality? Identify the insect given below and find out what it is called in your language. Look out for it when you visit a field or a place with a wetland.
Answer

The insect in the picture is a firefly (also called a glow-worm or lightning bug). The picture shows it resting on a leaf with the tip of its abdomen glowing yellow, and, beside it, a patch of grass at night full of tiny lights.

LanguageWhat the firefly is called
Hindiजुगनू (jugnū)
Marathiकाजवा (kājvā)
Bengaliজোনাকি (jōnāki)
Tamilமின்மினிப் பூச்சி (minmiṉip pūcci)
Teluguమిణుగురు పురుగు (miṇuguru purugu)
Malayalamമിന്നാമിനുങ്ങ് (minnāminuṅṅ)
Kannadaಮಿಂಚು ಹುಳು (miñcu huḷu)
Gujaratiઆગિયો (āgiyo)
Odiaଜୁଣୁକା (juṇukā)
Punjabiਟਟਹਿਣਾ (ṭaṭahiṇā)
Assameseজোনাকী পৰুৱা (jonākī poruwā)
Other bioluminescent life: besides the micro-planktons of Kumbalangi and the firefly, light is made by glow-worms (the wingless female firefly), some fungi that make rotting wood glow faintly in damp forests, and many deep-sea creatures — anglerfish, jellyfish, squid — that live below the reach of sunlight. In every case the light comes from a chemical reaction inside the body, which is why the chapter defines bioluminescence as “light produced inside the body of a living organism by a chemical reaction”. It is cold light: almost none of the energy is wasted as heat, which is why you can hold a firefly in your palm.
Check it yourself: fireflies flash to find a mate, and each species has its own rhythm of flashes. Go to a field or a wetland edge after the first rains, stand still for five minutes, and count the seconds between one insect's flashes. If two insects are flashing at the same interval, you are watching the same species talking. And carry no torch — bright light drowns the signal.
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