Question

Human eggs are
(a) Alecithal
(b) Microlecithal
(c) Mesolecithal
(d) Macrolecithal

Answer 1

Hint: Based on the amount of yolk the egg is majorly divided in four types. Nutritive substances are stored within the cytoplasm of egg within the sort of yolk or deutoplasm. This stored food is employed by the embryo for its early development.

Complete step by step answer:
Alecithal Egg is a condition when the egg contains no yolk, it is called alecithal egg. Eg. the eggs of eutherian mammals.
- Eggs are grouped into three types based on the idea of the quantity of yolk present in them.
- Alecithal Egg: When the egg contains no yolk, it's called alecithal egg.
Eg. The eggs of eutherian mammals.
- Microlecithal Egg: When the egg contains. Small or negligible amount of yolk is claimed to be microlecithal.
Eg. Amphioxus, Tunicates

- Mesolecithal Egg: In amphibian, Dipnoi and Petromyzon the quantity of yolk present is moderate and isn't high Hence these eggs also are named as mesolecithal eggs
- Macrolecithal or Megalecithal or Polylecithal Egg: When the egg contains an outsized amount of yolk it's said to be a macrolecithal or megalecithal egg. It's also called Polylecithal egg.
Eg. Reptiles, Birds, Prototheria (Monotremata) laying mammals.
- On the idea of the distribution of yolk
- Isolecithal or Homolecithal Egg: In isolecithal eggs, the little or no amount of yolk present is uniformly distributed throughout the ooplasm.
Eg. echinoderms, Amphioxus, mammals) . This condition is typically observed in eggs with little or no amount of yolk.
- Telolecithal Egg: In eggs containing moderate or large quantities of yolk, the distribution of yolk isn't uniform. lt is concentrated more towards the vegetal pole. Such a kind of egg, during which the yolk is concentrated towards one pole, is named telolecithal egg.
So, the correct answer is, ‘(a) Alecithal.’

Note:
- Chick eggs are mesolecithal or polylecithal, discoidal and cleidoic meaning yolk is present in large amounts and cytoplasm is found within the sort of a disc. This disc is understood because of the blastoderm . Beneath the blastoderm yolk is present.
- On the idea of colour and content yolk is of two types.
Yellow yolk- It have more phospholipids
White yolk – it's rich in protein and phospholipids are in fewer amounts.
- Both sorts of yolks are arranged in alternative and concentric layers. Innermost and outermost layer is of white yolk.