Chapter 6: Living Organisms — Characteristics and Habitats
सजीव - विशेषताएँ एवं वासस्थान (मरुस्थल, पर्वतीय, जलीय आवास, डॉल्फ़िन एवं व्हेल के श्वसन अंग)
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- Components of Environment: Biotic components (living: plants, animals, decomposers) and Abiotic components (non-living: rocks, soil, air, water, sunlight, temperature).
- Adaptation vs Acclimatization: Adaptations (अनुकूलन) are inherited structural/behavioral changes evolved over thousands of years. Acclimatization (पर्यानुकूलन) is short-term physiological adjustment by a single organism to changing surroundings (e.g. human breathing rate increasing when traveling to high altitudes).
- Terrestrial Habitat Adaptations:
- - Desert Plants (Xerophytes/Cactus): Leaves modified into sharp spines to minimize transpiration water loss; green fleshy stem carries out photosynthesis and stores water; stem coated with thick waxy cuticle layer; root system extends deep into subterranean soil.
- - Desert Animals (Camel): Long legs lift body above blistering hot desert sand; excretes highly concentrated small amounts of urine; dung is dry; does not sweat; wide flat padded feet prevent sinking in sand.
- - Mountain Plants: Conical shape with sloping branches allows heavy snow and torrential rain to slide off effortlessly; needle-like leaves reduce freezing damage.
- - Mountain Animals: Snow leopard has dense thick fur covering body, paws, and toes; mountain goat has sturdy hooves for gripping rocky precipices.
- Aquatic Habitat Adaptations:
- - Fish: Streamlined body, slippery protective scales, gills to extract dissolved oxygen from water.
- - Whales and Dolphins: DO NOT HAVE GILLS. They are mammals that breathe atmospheric air through BLOWHOLES (nostrils) situated on top of their head. They come up to the ocean surface periodically to inhale air and can remain submerged for prolonged periods holding breath.
- - Aquatic Plants: Reduced root system functioning primarily for anchoring; long, slender, flexible stems bend with water currents; submerged leaves are ribbon-like or finely divided to allow water to flow freely without tearing.
- Trap: Whales and dolphins breathe through gills like normal fish. FALSE: Whales and dolphins have LUNGS and breathe atmospheric air through blowholes.
- Trap: Cactus photosynthesis occurs in its leaves. FALSE: Cactus leaves are reduced to spines; PHOTOSYNTHESIS IS CARRIED OUT BY ITS GREEN STEM.
- Trap: The primary function of roots in fully submerged aquatic plants is water absorption. FALSE: Water is absorbed all over the plant body; aquatic plant roots function primarily for ANCHORAGE.
NCERT Core Facts: Habitats, Biomes & Morphological Adaptations
Organism adaptations to extreme environmental stresses form staple multi-statement questions in CTET Paper 2:
1. Comparative Habitat Adaptation Matrix
| Habitat | Stress Factor | Organism | Adaptive Mechanism |
|---|---|---|---|
| Hot Desert | Aridity, water shortage, intense heat | Cactus (नागफनी) | Leaves ightarrow Spines; Green stem does photosynthesis; Thick waxy cuticle |
| Hot Desert | Scorching sand surface | Camel (ऊँट) | Padded feet; no sweat; concentrated urine; dry dung; tall legs |
| Mountain | Sub-zero cold, snow load | Pine / Deodar | Conical tree shape, sloping branches, needle-shaped leaves |
| Mountain | Icy terrain, slippery rock | Snow Leopard | Thick fur on body, paws & toes; Mountain goat has hard hooves |
| Ocean | Marine aquatic respiration | Fish | Gills absorb dissolved oxygen; streamlined body |
| Ocean | Marine aquatic respiration | Dolphin & Whale | Lungs & Blowholes (वात-छिद्र); must surface to breathe air |
| Pond / Lake | Swift underwater currents | Submerged plants | Narrow ribbon-like leaves bend with currents without tearing |
2. Adaptation vs. Acclimatization (Pedagogical Distinction)
- Adaptation (हजारों वर्षों का अनुकूलन): Genetic traits selected over millennia. A camel cannot turn into a mountain goat; a cactus cannot grow delicate leaves in a decade.
- Acclimatization (अल्पकालिक पर्यानुकूलन): Transient physiological accommodation. When a person living on plains visits Ladakh (high altitude), breathing becomes labored initially. Within days, red blood cell counts rise, breathing normalizes, and fatigue fades.
Test Your Mastery: Living Organisms — Characteristics and Habitats
Authentic CBSE exam questions tested directly from this NCERT chapter.
Which of the following aquatic organisms does NOT breathe through gills and instead inhales atmospheric air through blowholes located on top of its head?
निम्नलिखित में से कौन-सा जलीय जीव गिल्स (गलफड़ों) से सांस नहीं लेता है, बल्कि अपने सिर के ऊपर स्थित वात-छिद्रों (blowholes) से वायुमंडलीय हवा में सांस लेता है?
Read the following statements regarding desert plant adaptations: (A) Photosynthesis in these plants is usually carried out by the green fleshy stem. (B) Their leaves are either absent, very small, or present in the shape of spines. (C) Roots penetrate deeply into soil to absorb moisture. Which of the statements are TRUE?
मरुस्थलीय पौधों के अनुकूलन के संबंध में निम्नलिखित कथनों को पढ़िए: (A) इन पौधों में प्रकाश-संश्लेषण आमतौर पर हरे मांसल तने द्वारा होता है। (B) इनकी पत्तियाँ या तो अनुपस्थित होती हैं, बहुत छोटी होती हैं, या कांटों के रूप में होती हैं। (C) नमी सोखने के लिए जड़ें मिट्टी में बहुत गहराई तक जाती हैं। कौन-से कथन सत्य हैं?
How do whales and dolphins breathe if they live underwater without gills?
Whales and dolphins are mammals with lungs. They breathe atmospheric oxygen by surfacing and inhaling through blowholes on top of their heads.
Why are the leaves of a cactus modified into spines?
To reduce water loss through transpiration in extremely arid desert climates, while also protecting the juicy water-storing stem from herbivores.