Chapter 2: Ear to Ear
कान-कान में (जरायुज एवं अंडप्रजक जंतु, बाह्य कान एवं त्वचा के बाल)
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- The Golden Rule of Animal Reproduction: Animals whose ears can be seen from the outside and have hair on their skin give birth to young ones (Viviparous / स्तनधारी). Examples: Elephant, cow, buffalo, cat, deer, human.
- Oviparous Rule: Animals that do not have external ears (have tiny pin-holes hidden under feathers or scales) and do not have hair on their skin lay eggs (Oviparous / अंडप्रजक). Examples: Birds (sparrow, crow, pigeon), lizards, snakes, crocodiles, frogs.
- Bird Auditory Anatomy: Birds have tiny ear holes on both sides of their heads, which are completely concealed beneath their feathers.
- Lizards and Crocodiles: Lizards and crocodiles have tiny ear holes on their heads that can be seen only on close inspection.
- Skin Patterns: The different patterns, stripes, and spots on the skin of various animals are caused by the color of the HAIR growing on their skin, NOT due to skin pigmentation alone.
- Trap: CBSE asks if bats lay eggs or give birth. Correct: Bats have external ears and hair on their bodies; they are mammals that give birth to young ones.
- Trap: CBSE states skin patterns are caused by skin pigments without hair. Correct: NCERT explicitly states patterns are due to the colors of the hair on the animal's skin.
- Trap: CBSE asks if birds lack ears entirely. Correct: Birds HAVE ear holes, but they are hidden under feathers.
NCERT Core Facts: Animal Ear Morphology & Viviparous vs Oviparous Classification
Class 4 Chapter 2 provides the single most reliable diagnostic rule tested in CTET Paper 1 regarding animal reproduction.
1. The Definitive NCERT Diagnostic Classification
| Category | Anatomical Criteria (Observable) | Mode of Reproduction | NCERT Animal Examples |
|---|---|---|---|
| Viviparous (जरायुज) | External visible ears AND Hair on body/skin | Give birth to living young ones | Cow, Elephant, Tiger, Deer, Buffalo, Cat, Bat, Human |
| Oviparous (अंडप्रजक) | NO visible external ears (hidden pin-holes) AND NO hair on skin (feathers/scales) | Lay eggs | Sparrow, Crow, Pigeon, Lizard, Snake, Crocodile, Frog |
2. Auditory Adaptations in Non-Mammals
- Birds: Possess tiny ear holes on both lateral sides of the skull, completely covered and insulated by plumage/feathers.
- Lizards & Crocodiles: Have small slit-like ear openings behind their eyes.
- Snakes: Have no external ear opening at all; they perceive sonic waves entirely through mechanical vibrations traveling through the ground and jaw bones.
3. High-Yield CTET Exam Trap: Skin Patterns
- NCERT Concept: If you shave off an animal's hair, its distinct pattern (like tiger stripes or zebra bands) vanishes!
- The varied patterns on the bodies of animals are due to the hair on their skin, not merely skin pigment beneath.
Test Your Mastery: Ear to Ear
Authentic CBSE exam questions tested directly from this NCERT chapter.
According to NCERT Class 4 EVS, which of the following groups of animals gives birth to young ones?
NCERT कक्षा 4 EVS के अनुसार, निम्नलिखित में से कौन सा जानवरों का समूह बच्चों को जन्म देता है?
The patterns and stripes seen on the skin of different animals are due to:
विभिन्न जानवरों की त्वचा पर दिखने वाले पैटर्न और धारियाँ किसके कारण होती हैं?
Which of the following creatures possesses ear holes hidden under feathers?
निम्नलिखित में से किस प्राणी के कान के छेद पंखों के नीचे छिपे होते हैं?
How can one tell whether an animal lays eggs or gives birth to young ones?
Animals with visible external ears and hair on their bodies give birth to live young; animals without visible external ears and without hair lay eggs.
Do birds have ears according to NCERT?
Yes, birds have tiny ear holes on both sides of their heads, hidden under their feathers.
What causes the patterns and stripes on animal skin?
The varied patterns are caused by the color and arrangement of the hair on their skin.