Tag: the life cycle of animals

• Oviparous animals are that lay eggs, with little or no other embryonic development within the mother. Birds are oviparous.

• Panthera leo which is commonly known as lion belongs to the family Felidae and comes under the class Mammalia (which give birth to their young ones).

• Elephas maximus which is commonly known as Asiatic elephant belongs to the family Elephantidae and comes under the class Mammalia (which give birth to their young ones).

• Hemidactylus flaviviridis is a species of lizards which is also known as the Geko or northern house gecko which belong to the class Amphibia.

• Ornithorhynchus anatinus is also known as duck-billed platypus which is a semiaquatic egg-laying mammal.

• So, the correct answer is 'Ornithorhynchus anatinus'.

Mammalian eggs have very little yolk (microlecithal) because the embryo obtains maternal nutritional support throughout its development.

Each time the molting process is completed the cockroach will get bigger, change in color, and look more like an adult cockroach. The nymph stage of the cockroach life cycle can take anywhere from a month and a half to several years, depending on the environment, the type of cockroach, and the prevalence of cockroach disease and parasites. When the cockroach reaches its adult size it will not moult again. Many types of cockroaches will complete their transformation into adulthood with a pair of wings. Young adults may look almost exactly like a nymph, with the wings being the one characteristic that easily sets the two apart. The number of moultings in cockroach after hatching and development of a complete animal are more than 10 and they vary from one cockroach type to another.

Cockroaches are oviparous. The egg hatches at specific conditions to give birth to young ones. The eggs are carried by the mother cockroach around in a sac called an ootheca, which is attached to her abdomen. The number of eggs in each ootheca are about 16 and varies from species to species. Many female cockroaches drop or hide their ootheca shortly before the eggs are ready to hatch. Others continue to carry the hatching eggs and care for their young after they are born. But regardless of how long the mother and her eggs stay together the ootheca. 

Cleidoic eggs are laid by terrestrial animals like reptiles and birds. The egg is surrounded by a hard porous shell. Gaseous diffusion occurs through porous shell. Egg of aquatic animals is covered by a jelly coat and not by a hard shell. The shell in cleidoic eggs protects the developing embryo and also makes available an aquatic environment for development. The yolk of an egg is a source of nutrition for developing an embryo.

Reptiles and birds are terrestrial animals. They lay large yolk-rich eggs which are covered with a porous shell. As the eggs are rich in yolk they can support the development of an embryo. Hence, embryogenesis occurs outside the body of the animal inside the egg. Such yolk-rich eggs are called as macrolecithal eggs.

The yolk is a part of an egg, that feeds the developing embryo in animals. It is composed of carbohydrates (3.5%), protein (16%) and fats (phospholipids 26.5%) of total yolk. The main fatty acids present in the yolk is oleic acid, linoleic acid, palmitic acid etc. 

The process of formation of the yolk is known as vitellogenesis. These are generally used to nourish the developing embryo in oviparous animals. They are deposited during oocyte maturation for use after fertilization and are synthesized in the liver or fat bodies as a common precursor termed vitellogenin.