Class 6 Science Notes Chapter 9 (The Living Organisms and their Surroundings) – Science Book

Detailed Notes with MCQs of Chapter 9, 'The Living Organisms and their Surroundings'. This is an important chapter as it builds the foundation for understanding ecology and biodiversity, topics often touched upon in government exams. Pay close attention to the definitions and examples.

Chapter 9: The Living Organisms and their Surroundings - Detailed Notes

1. Organisms and Surroundings (Habitat):

• Habitat: The specific place or natural environment where an organism (plant or animal) lives is called its habitat. A habitat provides everything an organism needs to survive – food, water, shelter, air, and space.
• Examples: The habitat of a camel is the desert; the habitat of a fish is water (ocean, river, pond); the habitat of a lion is the grassland/forest.
• Components of a Habitat:
  • Biotic Components: All the living things in a habitat. Examples: Plants, animals, microorganisms.
  • Abiotic Components: All the non-living things in a habitat. Examples: Rocks, soil, air, water, sunlight, temperature, humidity.

2. Types of Habitats:

• Terrestrial Habitats: Habitats found on land.
  • Deserts: Characterized by very little rainfall, high temperatures during the day, and sandy soil.
  • Mountain Regions: Characterized by cold temperatures, strong winds, snowfall in winter, and rocky slopes.
  • Grasslands: Large areas dominated by grasses; receive moderate rainfall.
  • Forests: Large areas dominated by trees; can be tropical, temperate, etc. (Though Class 6 focuses more on Desert, Mountain, Grassland).
• Aquatic Habitats: Habitats found in water.
  • Oceans: Large bodies of saltwater. Organisms are adapted to saline conditions.
  • Ponds and Lakes: Smaller bodies of freshwater.
  • Rivers: Flowing freshwater bodies.

3. Adaptation:

• Definition: The presence of specific features or certain habits which enable an organism (plant or animal) to live naturally and successfully in its particular habitat is called adaptation.
• Importance: Adaptations develop over a long period through evolution and help organisms survive changes in their environment, find food, avoid predators, and reproduce.
• Acclimatisation: Short-term adjustments made by an organism to cope with changes in its immediate surroundings (e.g., adjusting to high altitude over a few days). This is not adaptation, which occurs over thousands of years.

4. Adaptations in Different Habitats:

• Desert Adaptations:
  • Camel: Long legs (keep body away from hot sand), stores fat in hump (energy reserve), thick eyelashes and closable nostrils (protection from sand), excretes concentrated urine and dry dung (conserves water).
  • Desert Animals (Rats, Snakes): Stay in burrows deep in the sand during the day to escape heat, come out at night.
  • Desert Plants (Cacti): Leaves reduced to spines (reduce water loss via transpiration, protection), stem is green and fleshy (photosynthesis, water storage), roots go very deep into the soil to absorb water.
• Mountain Adaptations:
  • Animals (Yak, Snow Leopard): Thick fur or skin (protection from cold), strong hooves (for climbing rocky slopes - e.g., mountain goat).
  • Trees: Often cone-shaped with sloping branches (snow slides off easily), needle-like leaves (reduce water loss, withstand cold).
• Grassland Adaptations:
  • Predators (Lion): Light brown colour (camouflage), eyes in front of the face (accurate location of prey), sharp claws and teeth.
  • Prey (Deer): Strong teeth (chewing hard plant stems), long ears (hear predator movements), eyes on the sides of the head (wide field of vision), fast speed (escape predators).
• Aquatic Adaptations (Oceans):
  • Fish: Streamlined body shape (reduces water resistance, easy movement), gills (absorb dissolved oxygen from water), fins (movement and balance), scales (protection).
  • Dolphins and Whales: Mammals, not fish. They breathe air through blowholes located on top of their heads. They come to the surface to breathe. They do not have gills.
• Aquatic Adaptations (Ponds and Lakes):
  • Aquatic Plants:
    • Floating: Roots not well-anchored (e.g., Water Hyacinth).
    • Fixed: Roots fixed in soil, long hollow stems, broad floating leaves (e.g., Lotus, Water Lily).
    • Submerged: Roots fixed, narrow ribbon-like leaves (bend in flowing water), entire plant under water (e.g., Hydrilla, Vallisneria). Stomata are usually absent; gas exchange occurs through the plant surface.
  • Frogs: Can live both on land (breathe through lungs) and in water (breathe through moist skin). Have webbed hind feet (help swim).

5. Characteristics of Living Organisms:

All living things share certain common characteristics that distinguish them from non-living things:

• Need Food: To get energy for growth and life processes. Plants make their own food (photosynthesis); animals depend on plants or other animals.
• Growth: All living things grow. Growth is an irreversible increase in size.
• Respiration: The process of taking in oxygen and releasing carbon dioxide to produce energy from food. (Plants also respire day and night, though photosynthesis occurs only in daylight).
  • Breathing: The mechanism by which organisms take in air and release air. Respiration is the chemical process using that oxygen.
  • Gas exchange in plants: Through tiny pores called stomata (mainly on leaves).
  • Gas exchange in earthworms: Through their moist skin.
  • Gas exchange in fish: Through gills.
• Response to Stimuli: Living things react to changes in their environment. These changes are called stimuli. Examples: Touching a hot object (stimulus) and withdrawing hand (response); Mimosa (touch-me-not) plant leaves closing when touched (stimulus and response); plants growing towards sunlight (stimulus and response).
• Excretion: Getting rid of waste products from the body. Animals excrete urine, faeces, sweat, carbon dioxide. Plants excrete waste products through transpiration (water vapour), gums, resins, and sometimes store waste in leaves that they shed.
• Reproduction: Producing new individuals of their own kind. Methods vary: laying eggs (birds, reptiles), giving birth to young ones (mammals), through seeds (most plants), through spores (ferns), through body parts like buds or cuttings (some plants like potato, rose).
• Movement: Most animals move from place to place. Plants show movement like opening/closing of flowers, growth of roots towards water, growth of stem towards light, but generally do not move from their location (locomotion).
• Definite Lifespan: All living organisms are born, grow, reproduce, and eventually die.

Important Note: Things like viruses exhibit characteristics of living things only when inside a host cell, blurring the line sometimes, but based on NCERT Class 6, the above characteristics define living organisms clearly from non-living things like chairs, tables, rocks etc.

Multiple Choice Questions (MCQs)

Here are 10 MCQs based on the chapter for your practice:

1. Which of the following is an abiotic component of a habitat?
   a) Grass
   b) Deer
   c) Sunlight
   d) Fungus

2. The specific features that enable a plant or animal to live in a particular habitat are called:
   a) Respiration
   b) Adaptation
   c) Excretion
   d) Habitat

3. Camels are well-adapted to desert life primarily because they:
   a) Have thick fur
   b) Can store large amounts of water in their hump
   c) Excrete very little water
   d) Have gills to breathe

4. Which adaptation helps mountain animals like yaks survive in the cold?
   a) Streamlined body
   b) Gills
   c) Thick fur
   d) Long legs

5. Fish breathe using:
   a) Lungs
   b) Blowholes
   c) Skin
   d) Gills

6. Which of the following is NOT a characteristic of most living things?
   a) They need food
   b) They respire
   c) They remain unchanged throughout their life
   d) They reproduce

7. Plants respond to stimuli. For example, the shoot grows towards:
   a) Water
   b) Gravity
   c) Sunlight
   d) Soil

8. Dolphins and whales breathe through:
   a) Gills
   b) Lungs via blowholes
   c) Moist skin
   d) Stomata

9. The process by which living organisms get rid of waste products is called:
   a) Respiration
   b) Reproduction
   c) Excretion
   d) Adaptation

10. Which type of aquatic plant typically has narrow, ribbon-like leaves that can bend in flowing water?
    a) Floating plants
    b) Fixed plants with broad leaves
    c) Submerged plants
    d) Desert plants

Answer Key for MCQs:

1. c) Sunlight
2. b) Adaptation
3. c) Excrete very little water (Note: Hump stores fat, not water directly, though metabolizing fat produces some water)
4. c) Thick fur
5. d) Gills
6. c) They remain unchanged throughout their life (Living things grow and change)
7. c) Sunlight
8. b) Lungs via blowholes
9. c) Excretion
10. c) Submerged plants

Study these notes thoroughly. Focus on understanding the 'why' behind each adaptation and the precise definitions of terms like habitat, adaptation, biotic, and abiotic components. Good luck with your preparation!