
In a mesolecithal egg one would expect
A. Meroblastic cleavage
B. Unequal holoblastic cleavage
C. Equal holoblastic cleavage
D. None of these
Answer
502.5k+ views
1 likes
Hint: The egg is a vessel containing organic zygote in which the embryo develops until it can survive on its own, at which point the animal hatches. The egg is the product of egg cell fertilisation.
Complete Answer:
There are three types of eggs, depending on the proportion of the yolk to the ovum cytoplasm.
- Microlecithal egg: The amount of yolk in microlecithal eggs is much less than the amount of cytoplasm. These eggs are tiny in size.
- Mesolecithal eggs: Here the amount of yolk is moderate and these eggs are called mesolecithal or megalecithal (i.e. median yolk). The distribution of the yolk is obviously uneven. The shark eggs, ganoid fish, dipnoi and several amphibians are of this kind.
- Macrolecithal or polylecithal eggs: Macrolecithal eggs contain huge quantities of yolk, and the yolk is several times larger than the cytoplasm. These eggs may be huge or tiny. This type includes teleost fish eggs, gymnophiona (legless amphibians), reptiles , birds and monotremes (egg laying mammals). Cleavage, a sequence of mitotic divisions, with immense divisions. Amount of egg cytoplasm is divided into several smaller nucleated cells. These cleavage-stage cells are called blastomeres
- Holoblastic or total cleavage: When the cleavage furrows separate the whole egg. It may be:
(I) Equal: When the furrow of the cleavage cuts the egg into two equal cells. They can be radially symmetrical, bilateral, symmetrical, irregular or spirally symmetrical.
(II) Inequal: When the resulting blastomeres become inconsistent in size.
- Meroblastic cleavage: It is called meroblastic cleavage when segmentation occurs only in a small portion of the egg that results in blastoderm formation. Mesolecithal eggs have unequal holoblastic cleavage.
Thus the correct answer is option(B).
Note: Most arthropods, vertebrates (excluding live-bearing mammals) and molluscs lay eggs, while some, such as scorpions, do not.
Complete Answer:
There are three types of eggs, depending on the proportion of the yolk to the ovum cytoplasm.
- Microlecithal egg: The amount of yolk in microlecithal eggs is much less than the amount of cytoplasm. These eggs are tiny in size.
- Mesolecithal eggs: Here the amount of yolk is moderate and these eggs are called mesolecithal or megalecithal (i.e. median yolk). The distribution of the yolk is obviously uneven. The shark eggs, ganoid fish, dipnoi and several amphibians are of this kind.
- Macrolecithal or polylecithal eggs: Macrolecithal eggs contain huge quantities of yolk, and the yolk is several times larger than the cytoplasm. These eggs may be huge or tiny. This type includes teleost fish eggs, gymnophiona (legless amphibians), reptiles , birds and monotremes (egg laying mammals). Cleavage, a sequence of mitotic divisions, with immense divisions. Amount of egg cytoplasm is divided into several smaller nucleated cells. These cleavage-stage cells are called blastomeres
- Holoblastic or total cleavage: When the cleavage furrows separate the whole egg. It may be:
(I) Equal: When the furrow of the cleavage cuts the egg into two equal cells. They can be radially symmetrical, bilateral, symmetrical, irregular or spirally symmetrical.
(II) Inequal: When the resulting blastomeres become inconsistent in size.
- Meroblastic cleavage: It is called meroblastic cleavage when segmentation occurs only in a small portion of the egg that results in blastoderm formation. Mesolecithal eggs have unequal holoblastic cleavage.
Thus the correct answer is option(B).
Note: Most arthropods, vertebrates (excluding live-bearing mammals) and molluscs lay eggs, while some, such as scorpions, do not.
Recently Updated Pages
Master Class 11 Physics: Engaging Questions & Answers for Success

Master Class 11 Chemistry: Engaging Questions & Answers for Success

Master Class 11 Biology: Engaging Questions & Answers for Success

Class 11 Question and Answer - Your Ultimate Solutions Guide

Master Class 11 Business Studies: Engaging Questions & Answers for Success

Master Class 11 Computer Science: Engaging Questions & Answers for Success

Trending doubts
Explain why it is said like that Mock drill is use class 11 social science CBSE

The non protein part of an enzyme is a A Prosthetic class 11 biology CBSE

Which of the following blood vessels in the circulatory class 11 biology CBSE

What is a zygomorphic flower Give example class 11 biology CBSE

The deoxygenated blood from the hind limbs of the frog class 11 biology CBSE

What is the function of copulatory pads in the forelimbs class 11 biology CBSE
