Types of eggs, Biology

TYPES OF EGGS

Different species of animal has different type of eggs. They are classified on the following basis -

1.         ON THE BASIS OF AMOUNT OF YOLK

On the basis of amount of yolk eggs are 4 types -

(i) Alecithal - The yolk is almost absent. eg. Eutherian eggs

(ii) Microlecithal - They have very little amount of yolk. Romer and Balenski proposed the term oligolecithal. eg. Amphioxis and Tunicates.

(iii) Mesolecithal - They have moderate amount of yolk. eg. Amphibian, Dipnoi Fishes, Petramizon and Annelids worm.

(iv) Megalecithal / Macrolecithal / Polylecithal - They have large amount of yolk. eg. Insect, reptiles, mixine, cartilage fishes and prototherian mammals.

2.         ON THE BASIS OF DISTRIBUTION OF YOLK

On the basis of distribution of yolk eggs are 3 types &

(i) Isolecithal / Homolecithal - There is even distrubtion of the yolk in the ooplasm. eg. Alecithal and microlecithal yolk.

(ii) Telolecithal - The yolk is found in the one pole which called as vegital pole. The yolk free pole is called as an animal pole. eg fishes, emphibians, reptiles and birds. Yolk unequally distributed in the ooplasm.

(iii) Centrolecithal - The yolk is present in the center and surrounded by ooplasm. eg. Insect and hydrozoa.

3.         PRESENCE OR ABSENCE OF HARD SHELL

On the basis of presence or absence of shell the eggs are of 2 types -

(i) Cleidoic eggs - Such eggs are covered by hard shell for protection which is permeable for gases. Yolk present in sufficient quantity. eg. Reptiles and birds.

(ii) Non cleidoc egg - They are without shell and these develop in aquatic medium and uterus of female. eg. amphioxis, mammals, frog and hardmania.

764_structure of eggs.png

4.         ON THE BASIS OF DEVELOPMENT

On the basis of development eggs are of 2 types -

(i) Determinate or Mosaic Eggs

In these types of eggs before fertilization determined the different parts of embryo called the mosaic eggs.

If any part remove the eggs the related organs does not originate in the embryo.

After first cleavage both blastomere are separate than develop the half embryo. eg. Polyclade, Nimertine, Annelidsm, Molluscs and Ascidian.

(ii) Indeterminate or Regulative Eggs

Different parts determined after third cleavage, these eggs are called regulative eggs.

If two blastomere are separate after first cleavage both blstomeres developed the complete embryo.

In man twins developed due to this region.

Posted Date: 10/3/2012 8:05:52 AM | Location : United States







Related Discussions:- Types of eggs, Assignment Help, Ask Question on Types of eggs, Get Answer, Expert's Help, Types of eggs Discussions

Write discussion on Types of eggs
Your posts are moderated
Related Questions
How can we increase of total peripheral resistance?   A.  A decrease in the diameter of every arteriole.   B.  An increase of sympathetic discharge to all the smooth muscles

Q. How is the gastric mucosa protected from the acid pH of the stomach? The gastric epithelium is mucus secretory that is it produces mucus, the mucus covers the stomach wall p

Define Polysaccharides (DP: > 9) - carbohydrates? Polysaccharides are high molecular weight polymers of monosaccharide units formed by glycosidic bonding. They may be long unbr

Define the Management of Obesity? Management of obesity should be taken up with a clear understanding of the harsh realities of the problem and its outcome. It may be a frustra

Explain Unresorbable Barriers - Root Perforation MTA exhabits excellent tissue biocompatible non resorbable barrier and restorative material. It represents an extraord

Which of the following compounds results from cyclization of glucose? Select one: a. alpha-D-glucopyronose b. beta-D-glucopyronose c. alpha-D-glucofuranose d. beta-D

B l oo d Protozoan and Ricketsial Diseases T r y p a n o s o m i a si s It is also known as surra in equines and tibarsa in camel and results in intermitte

Q. What is biological control? The Biological control is a natural method to control the size of microorganism, animal or plant populations. The Biological control is based on

P o x diseases Small-pox in human beings and pox in a few animal species are closely related to each other. It is shown by the fact that the vaccine for the prevention of sma

Admission to  the Hospital The  philosophy of  childcare, whether in the home, hospital, or  other community agency, should be consistently one of concern and support for the