9. The table below lists cleavage pattern and names of species.

   Match the cleavage patterns with the species.
   (1) A- i; B- ii; C- iii; D- iv
   (2) A- ii; B- iv; C- i; D- iii
   (3) A- iv; B- i; C- iii; D- ii
   (4) A- iii; B- i; C- iv; D- ii

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Introduction

Embryogenesis begins with cleavage, the series of cell divisions after fertilization. The cleavage pattern varies widely among species and correlates with yolk distribution and egg type. This guide matches key cleavage patterns to representative species, clarifying their biological significance.

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Embryonic Cleavage Patterns and Species

1. Rotational Cleavage
   This cleavage occurs in mammals. It is holoblastic but involves a distinctive rotational second cleavage wherein one cell divides meridionally and the other equatorially.

2. Superficial Cleavage
   Observed in many insects and arthropods which have centrolecithal eggs (yolk in center). Cell division occurs only in the cytoplasm surrounding the yolk.

3. Radial Cleavage
   Common in amphibians and echinoderms, characterized by symmetrical division with cleavage planes perpendicular or parallel to the polar axis.

4. Discoidal Cleavage
   Found in birds and reptiles (teleolecithal eggs with dense yolk). Cleavage is partial and restricted to a small disc of cytoplasm at the animal pole, above the yolk.

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The Importance of Matching Cleavage Patterns

Understanding cleavage patterns helps in studying development, evolutionary adaptations, and reproductive biology. This matching also aids in comparative embryology by highlighting species-specific developmental strategies.

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Conclusion

The cleavage pattern and yolk distribution define embryonic development across species. Mammals show rotational cleavage, insects superficial, amphibians radial, and birds discoidal cleavage, forming a foundational framework for developmental biology.

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Final Answer:
(2) A- ii; B- iv; C- i; D- iii