Q.40 Amphibian eggs undergo:

1. Equal radial holoblastic cleavage
2. Unequal radial holoblastic cleavage
3. Equal radial meroblastic cleavage
4. Unequal radial meroblastic cleavage

   Amphibian eggs undergo unequal radial holoblastic cleavage.

   Cleavage Pattern Analysis

   Amphibian eggs (frog, toad) contain moderate yolk concentrated at the vegetal pole, causing slower cell division there versus faster division at the animal pole. This results in unequal blastomeres.

   Holoblastic = complete cleavage through entire egg (vs. meroblastic/discoidal in birds/reptiles).
   Radial = cleavage planes parallel/perpendicular to animal-vegetal axis (vs. spiral in mollusks).

   Option Breakdown

   • Equal radial holoblastic: Sea urchin eggs (little yolk, equal blastomeres). Wrong for amphibians.

   • Unequal radial holoblastic: Amphibian eggs – smaller animal pole blastomeres, larger vegetal ones. CORRECT.

   • Equal radial meroblastic: Not applicable (meroblastic = incomplete cleavage).

   • Unequal radial meroblastic: Teleost fish (yolk plate cleavage). Wrong.

   Cleavage Stages Visualized

   1. 2-cell: Large vegetal, small animal blastomeres

   2. 4-cell: Rectangular arrangement (not square like sea urchin)

   3. 8-cell: 4 small above, 4 large below

   4. Morula: Animal cap (small cells) over vegetal mass (large cells)​

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   Amphibian eggs undergo unequal radial holoblastic cleavage due to yolk distribution creating smaller animal pole blastomeres and larger vegetal ones. This article solves Q.40 for life sciences competitive exams.

   Yolk Distribution Determines Cleavage

   Egg Type	Yolk Amount	Cleavage Pattern
   Sea Urchin	Minimal	Equal holoblastic radial
   Amphibian	Moderate (vegetal)	Unequal holoblastic radial
   Teleost Fish	Abundant (central)	Meroblastic discoidal
   Bird/Reptile	Massive (yolk)	Meroblastic discoidal

   Amphibian Cleavage Characteristics

   Key Features:

   • Holoblastic: Complete division through egg

   • Radial: Planes ⊥// to A-V axis

   • Unequal: Animal pole (micromeres) < Vegetal pole (macromeres)

   • Slower vegetal division due to yolk impeding cytokinesis

   Visual Progression

   text

   Fertilized Egg → 2-cell (piggyback) → 4-cell (rectangle)
→ 8-cell (4small:4large) → Morula → Blastula


   Why Other Options Wrong

   Option	Example Organism	Why Not Amphibian
   Equal holoblastic	Sea urchin	No yolk gradient
   Equal meroblastic	None common	Meroblastic = incomplete
   Unequal meroblastic	Fish	Yolk prevents holoblastic

   Exam Memory Trick

   “Frog = Unequal Radial” → FUR (Frog, Unequal, Radial). Sea urchin = equal. Fish = meroblastic.