Class 7 Social Science Notes Chapter 10 (Life in the Deserts) – Our Environment Book
Alright class, let's focus on Chapter 10, 'Life in the Deserts'. This is an important chapter as it contrasts two extreme environments found on our planet. Understanding these helps us appreciate the adaptability of life, both plant, animal, and human. Pay close attention, as questions from this area often test your understanding of geographical locations, climate, and human-environment interaction.
Chapter 10: Life in the Deserts - Detailed Notes
1. What is a Desert?
- A desert is an arid region characterized by extremely high or low temperatures and scarce vegetation.
- Key features:
- Low Rainfall: Very little precipitation (generally less than 25 cm per year).
- Extreme Temperatures: Can be very hot or very cold.
- Sparse Vegetation: Plant life is limited and adapted to survive arid conditions.
- Depending on temperatures, deserts can be classified as Hot Deserts or Cold Deserts.
2. The Hot Desert - Sahara
- Location:
- Located in North Africa.
- It is the world's largest hot desert, covering an area of around 8.54 million sq. km.
- Touches 11 countries: Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Sudan, Tunisia, and Western Sahara.
- Landscape:
- Not just vast stretches of sand. Includes gravel plains (regs), elevated plateaus with bare rocky surfaces (hamadas), and sandy areas with dunes (ergs). Sand dunes can be very high (up to 180 meters).
- Climate:
- Scorching hot and parched dry.
- Short rainy season.
- Sky is cloudless and clear. Moisture evaporates faster than it accumulates.
- Extreme Temperature Range: Days are unbelievably hot (temperatures may soar above 50°C), while nights can be freezing cold (near 0°C).
- Flora (Plants):
- Adapted to survive heat and lack of water.
- Includes cactus, date palms, and acacia.
- Oases: Green islands with date palms surrounding a water source. The Tafilalet Oasis in Morocco is a large oasis.
- Adaptations: Long roots, waxy leaf surfaces, thorns instead of leaves to reduce water loss.
- Fauna (Animals):
- Adapted to extreme conditions.
- Includes camels, hyenas, jackals, foxes, scorpions, many varieties of snakes and lizards.
- Camel: Known as the 'ship of the desert'. Adaptations include thick skin, ability to store fat in hump (energy reserve), long eyelashes, nostrils that can close, padded feet, ability to drink large amounts of water at once and survive long periods without it.
- Many smaller animals are nocturnal (active at night) to avoid the intense heat.
- People:
- Inhabited by various groups, including the Bedouins and Tuaregs.
- These are nomadic tribes rearing livestock like goats, sheep, camels, and horses for milk, hides (for leather), hair (for mats, carpets, clothes, blankets).
- They wear heavy robes as protection against hot winds and dust.
- Oases and the Nile Valley in Egypt support settled populations. People grow date palms, rice, wheat, barley, and beans here. Egyptian cotton is world-famous.
- Impact of Modernisation: Discovery of oil and gas (in Algeria, Libya, Egypt) is transforming the region. Minerals like iron, phosphorus, manganese, and uranium are also found. Trucks are replacing camels on trade routes. Tuaregs are acting as guides for tourists. More nomads are migrating to cities for jobs.
3. The Cold Desert - Ladakh
- Location:
- Lies in the Great Himalayas, on the eastern side of the Union Territory of Ladakh (previously part of Jammu & Kashmir).
- Bounded by the Karakoram Range in the north and the Zanskar mountains in the south.
- Several rivers flow through Ladakh, Indus being the most important. These rivers form deep valleys and gorges.
- Several glaciers are found, e.g., the Gangri glacier.
- Altitude: Varies from about 3000m in Kargil to more than 8,000m in the Karakoram.
- Climate:
- Extremely cold and dry due to high altitude.
- Lies in the rain shadow of the Himalayas, receiving little rainfall (as low as 10 cm annually). The Himalayas block monsoon clouds.
- Experiences freezing winds and burning hot sunlight (you can get sunstroke and frostbite at the same time!).
- Temperatures: Summer day temperatures are just above 0°C, night temperatures well below -30°C. Winter temperatures remain below -40°C for most of the time.
- Precipitation is mainly in the form of snow.
- Flora (Plants):
- Sparse vegetation due to extreme cold and dryness.
- Scanty patches of grasses and shrubs for animals to graze.
- Groves of willows and poplars are seen in the valleys.
- During summers, fruit trees such as apples, apricots, and walnuts bloom.
- Fauna (Animals):
- Adapted to harsh cold conditions.
- Wild goats, wild sheep, yak, and special kinds of dogs.
- Animals are reared for milk, meat, and hides. Yak's milk is used to make cheese and butter. Hair of sheep and goat is used to make woollens.
- Chiru or the Tibetan antelope is an endangered species, hunted for its wool known as Shahtoosh, which is very light and warm.
- Birds: Robins, redstarts, Tibetan snowcock, raven, and hoopoe are common. Migratory birds visit during summer.
- People:
- Population is sparse. People show similarities to the people of Tibet and Central Asia.
- Inhabitants are either Muslims or Buddhists.
- Several famous Buddhist monasteries or Gompas dot the landscape, e.g., Hemis, Thiksey, Shey, and Lamayuru.
- Activities:
- Summer: People are busy cultivating barley, potatoes, peas, beans, and turnips.
- Winter: People keep themselves engaged in festivities and ceremonies.
- Women manage homes, fields, and small businesses/shops.
- Leh is the capital of Ladakh.
- Tourism: A major activity, attracting domestic and international tourists who visit gompas, treks, and witness ceremonies/festivities.
- Connectivity: Well connected by road and air. National Highway 1A connects Leh to Kashmir Valley through Zoji La Pass. Manali-Leh highway crosses four high passes (Rohtang La, Baralacha La, Lungalacha La, Tanglang La). Air travel is also common.
- People have learned to live in balance with nature, using resources carefully. Scarcity of resources like water and fuel requires reverence and care.
Multiple Choice Questions (MCQs)
Here are 10 questions to test your understanding:
-
The Sahara Desert is located in which part of Africa?
a) Southern Africa
b) Eastern Africa
c) Western Africa
d) Northern Africa -
Which of the following is NOT a characteristic feature of the Sahara Desert's climate?
a) Scorching hot days
b) Freezing cold nights
c) Heavy rainfall throughout the year
d) Dry and parched conditions -
What are the fertile green areas with water sources found in deserts called?
a) Hamadas
b) Ergs
c) Oases
d) Regs -
The Bedouins and Tuaregs are nomadic tribes primarily found in which desert?
a) Ladakh
b) Sahara
c) Gobi
d) Atacama -
Ladakh is located in the rain shadow of which mountain range?
a) Alps
b) Andes
c) Rockies
d) Himalayas -
Which important river flows through the Ladakh region?
a) Ganga
b) Brahmaputra
c) Indus
d) Yamuna -
Which animal, found in Ladakh, is reared for its milk used to make cheese and butter?
a) Camel
b) Wild Goat
c) Yak
d) Wild Sheep -
The endangered Tibetan antelope, hunted for its Shahtoosh wool, is also known as:
a) Yak
b) Chiru
c) Redstart
d) Snow Leopard -
Hemis, Thiksey, and Shey are famous ______ found in Ladakh.
a) Mountain peaks
b) Glaciers
c) Buddhist Monasteries (Gompas)
d) Rivers -
Which of the following resources has significantly transformed life in parts of the Sahara desert like Algeria, Libya, and Egypt?
a) Diamonds
b) Gold
c) Water from new rivers
d) Oil and Natural Gas
Answer Key:
- d
- c
- c
- b
- d
- c
- c
- b
- c
- d
Make sure you revise these notes thoroughly. Understanding the adaptations of flora, fauna, and human life in these extreme environments is crucial. Good luck with your preparation!