Question

Meroblastic cleavage is a division which is

• A. horizontal
• B. partial/parietal
• C. total
• D. spiral.

Answer 1

The Correct Option is B

Meroblastic cleavage is a specific type of embryonic development process that occurs in certain animals, primarily those with large amounts of yolk in their eggs. Let's understand this concept in detail and see why the correct answer is "partial/parietal".

In biology, the term "cleavage" refers to the series of cell divisions that occur immediately after the fertilization of an egg. Cleavage converts a single-celled zygote into a multicellular structure called the blastula.

There are two main types of cleavage:

1. Holoblastic Cleavage: This type involves the complete division of the egg into smaller cells, called blastomeres. It occurs in eggs with relatively small amounts of yolk, such as in amphibians, mammals, and some others.
2. Meroblastic Cleavage: In this type, the cleavage is partial or incomplete, meaning that only a part of the egg divides. This typically occurs in eggs with a large amount of yolk, such as in birds, reptiles, and fish.

Given the options:

• Horizontal: This describes the orientation of a cleavage furrow but does not specify whether the cleavage is complete or partial.
• Partial/Parietal: This accurately describes meroblastic cleavage as it only divides part of the egg, leaving the yolk undivided.
• Total: This implies a complete division, as seen in holoblastic cleavage, so it is incorrect for meroblastic cleavage.
• Spiral: This refers to the pattern of cleavage orientation and is not directly relevant to whether the cleavage is complete or partial.

Therefore, the correct answer is that meroblastic cleavage is partial/parietal, occurring in cases where the large yolk mass does not undergo cleavage.