Class 7 English Notes Chapter 3 (The Desert) – An allienhand Hand Supplymentry Reader Book

Alright class, let's focus on Chapter 3, 'The Desert', from your 'An Alien Hand' supplementary reader. This chapter is quite important, not just for your class exams but also as it touches upon geography and biology concepts that can appear in various government exams. Pay close attention to the details.

Chapter 3: The Desert - Detailed Notes for Exam Preparation

1. What is a Desert?

• Common Misconception: Often thought of as endless stretches of sand with no rain or vegetation.
• Actual Definition: A desert is a region characterized by extremely low rainfall (arid or semi-arid), leading to sparse vegetation. Deserts are not always flat, sandy, or hot.
• Key Feature: Lack of water and vegetation.

2. Types and Characteristics:

• Hot Deserts: Like the Thar Desert in India or the Sahara in Africa. Characterized by high temperatures during the day and cooler nights.
• Cold Deserts: Like Ladakh. Characterized by extremely cold winters and cool summers. Still very dry.
• General Characteristics:
  • Aridity: Very little rainfall.
  • Extreme Temperatures: Can be very hot or very cold, often with significant temperature differences between day and night.
  • Vegetation: Sparse, consisting of plants adapted to survive dry conditions (xerophytes).
  • Water Scarcity: Water is a precious resource.

3. Desert Landscapes:

• Not Always Sand Dunes: While sand dunes are a famous feature, deserts can also be stony, rocky, or covered in pebbles.
• Oasis:
  • A fertile spot in a desert where water is found (often from underground springs or wells).
  • Appears like a green island in the middle of the desert.
  • Supports plant life and allows human settlements.

4. Adaptation of Life:

• Plants (Xerophytes):
  • Water Storage: Cacti store water in their thick stems.
  • Reduced Water Loss: Have thick, waxy skin (cuticle) to prevent transpiration (water loss). Often have spines instead of leaves.
  • Root Systems: Develop long roots that go deep in search of water or spread wide near the surface to catch any available moisture.
  • Dormancy: Some seeds remain dormant for years, sprouting only when it rains.
• Animals:
  • Water Conservation: Many desert animals get the water they need from their food (insects, plants) or metabolic processes. Some, like the camel, can drink large amounts of water at once and survive long periods without it.
  • Avoiding Heat:
    • Nocturnal: Many smaller animals are active mainly at night when it's cooler.
    • Burrowing: They live in underground burrows during the hot day.
    • Body Adaptations: Some have adaptations like large ears (Fennec fox) to radiate heat.
  • Specific Examples:
    • Gerbils: Spend the hottest part of the day in cool underground burrows.
    • Darkling Beetles: Catch drops of moisture on their legs and lift them into the air until the drops trickle down into their mouths.
    • Camel (Ship of the Desert):
      • Feet: Large, padded feet for walking on sand.
      • Hump: Stores fat, which can be converted to energy (not water directly, but metabolizing fat produces water).
      • Water: Can drink huge quantities of water; body adapted to minimize water loss (concentrated urine, dry dung, can tolerate high body temperature).
      • Eyelashes/Nostrils: Long eyelashes and closable nostrils protect against blowing sand.

5. Importance and Beauty of Deserts:

• Not Useless Land: Deserts are an important part of nature's plan.
• Unique Ecosystem: Home to a variety of plants and animals specially adapted to harsh conditions.
• Natural Beauty: Can be very beautiful – shifting sand dunes, rocky landscapes, colourful flowers (after rain), clear starry nights.
• Humidity: Even in deserts, the air contains moisture (humidity). This moisture, though not always visible as rain, nourishes some desert plants and can form dew.

6. Key Terms:

• Arid: Extremely dry.
• Sand Dunes: Hills of sand formed by the wind.
• Oasis: A fertile spot in a desert with water.
• Humidity: The amount of water vapour in the air.
• Xerophytes: Plants adapted to survive in dry conditions.
• Nocturnal: Active at night.

Multiple Choice Questions (MCQs)

Here are 10 MCQs based on the chapter. Choose the best answer.

1. According to the chapter, what is the most defining characteristic of a desert?
   a) Endless sand
   b) Extreme heat
   c) Lack of water and vegetation
   d) Presence of camels

2. An oasis is described in the chapter as:
   a) A large sand dune
   b) A place with extremely high temperatures
   c) A type of desert animal
   d) A green island with water in the middle of a desert

3. How do smaller desert animals typically cope with the extreme heat during the day?
   a) By drinking large amounts of water
   b) By staying in underground burrows
   c) By migrating to cooler areas
   d) By developing thick fur

4. Which of the following is NOT an adaptation of desert plants mentioned in the chapter?
   a) Storing water in thick stems
   b) Having long roots
   c) Having large, broad leaves to catch sunlight
   d) Having thick, waxy skin (cuticle)

5. The chapter mentions that desert air contains moisture, even if it doesn't rain often. What is this moisture called?
   a) Dew
   b) Fog
   c) Humidity
   d) Smog

6. What is stored in a camel's hump?
   a) Water
   b) Sand
   c) Fat
   d) Air

7. Why are deserts considered important and not just 'useless land'?
   a) They are rich in oil reserves.
   b) They are home to varied forms of life adapted to the conditions.
   c) They are easy places for humans to live.
   d) They receive more sunlight than other regions.

8. Darkling beetles have a unique way of obtaining water by:
   a) Digging deep wells
   b) Eating juicy plants
   c) Catching moisture drops from the air on their legs
   d) Licking dew off rocks

9. Which statement accurately reflects the common perception vs. the reality of deserts as described in the chapter?
   a) Perception: Dry and lifeless; Reality: Always hot and sandy.
   b) Perception: Endless sand; Reality: Can be rocky or pebbly, hot or cold, but always dry with sparse vegetation.
   c) Perception: Full of oases; Reality: Oases are very rare.
   d) Perception: Only camels live there; Reality: Many types of animals and plants live there.

10. What does the term 'xerophyte' refer to?
    a) A desert animal active at night
    b) A plant adapted to dry conditions
    c) A type of sand dune
    d) An underground water source

Answer Key:

1. c
2. d
3. b
4. c
5. c
6. c
7. b
8. c
9. b
10. b

Make sure you understand the adaptations of plants and animals thoroughly, as these are key concepts. Remember, deserts are diverse environments, not just sandy wastelands. Good luck with your preparation!