What is centrolecithal in biology?
Centrolecithal egg is an egg in which the yolk is concentrated near the centre of the egg cell, as is the case in many of the insects. Biology.
What is telolecithal biology?
adjective Embryology. having an accumulation of yolk near the vegetal pole, as the large-yolked eggs or ova of reptiles and birds.
What is cleavage in biology?
cleavage, in embryology, the first few cellular divisions of a zygote (fertilized egg). Initially, the zygote splits along a longitudinal plane. The second division is also longitudinal, but at 90 degrees to the plane of the first. The third division is perpendicular to the first two and is equatorial in position.
What is the difference between isolecithal and telolecithal?
uniformly distributed yolk are termed isolecithal. This condition occurs in invertebrates and in all but the lowest mammals. Eggs with abundant yolk concentrated in one hemisphere of the egg are termed telolecithal.
What animals show Holoblastic cleavage?
The holoblastic type of cleavage is commonly seen in eggs containing moderate to sparse amount of yolk. Examples of animals with eggs that divide holoblastically include the amphibians, mammals, echinoderms, annelids, flatworms, nematodes, etc.
What are isolecithal eggs?
Isolecithal eggs refers to the even distribution of yolk in the cytoplasm. It occurs in organisms with very little yolk, like mammals.
What is Mesolecithal egg?
Mesolecithal eggs: The eggs which contains moderate amount of yolk, such eggs are called as ‘Mesolecithal eggs’. The mesolecithal eggs are found in Petromyzon, Dipnoi and Amphibia. 3. Macrolecithal eggs: The eggs which contains enormous (large) amount of yolk, such eggs are called as ‘Macrolecithal eggs’.
Is Hen egg telolecithal?
Birds have a telolecithal type of egg with a large and dense yolk spread throughout most of the egg, but separate from the pole of the developing embryo.
What are the 4 types of cleavage?
In the absence of a large concentration of yolk, four major cleavage types can be observed: radial holoblastic, spiral holoblastic, bilateral holoblastic, and rotational holoblastic cleavage.
What are the 5 types of cleavage?
These forms of cleavage are:
- Basal cleavage:
- Cubic cleavage:
- Octahedral cleavage:
- Prismatic cleavage:
- Pinicoidal cleavage:
- Rhombohedral cleavage.
- Conchoidal – Fracture resembling a semicircular shell, with a smooth, curved surface.
- Uneven – Fracture that leaves a rough or irregular surface.
Is chicken egg telolecithal?
Is human egg isolecithal?
In human beings, the eggs are alecithal i.e. they do not contain yolk. Mesolecithal eggs contain moderate amount of yolk e.g., frog. Microlecithal eggs contain a little amount of yolk e.g., Amphioxus. Macrolecithal eggs contain large amount of yolk e.g. birds.