In the postembryonic period of development completes the final formation of organs, occurs growth, sexual development, reproduction, aging and death

Direct and indirect development [Post-embryonic]

In the postembryonic period of development completes the final formation of organs, occurs growth, sexual development, reproduction, aging and death of the organism.

All true multicellular organisms by the type of post-embryonic development can be divided into two groups — with direct and indirect type of development.

Indirect development

Indirect development is only found in multicellular animals. These are the cases when larva appears from the egg — the germ, which in its structure is significantly different from adults, but is able to eat independently. The larva always has easier structure and the size is usually less than in the adult organism, externally it looks like their ancestors (e.g. the larva of the frog — tadpole — like a small fish). It has special larval organs, and that’s why it can lead a completely different life than the mature individuals of their own species. It does not have even rudimentary sexual organs, by which it can be set, in whom it will develop — in a female or male. Taken from http://worldofschool.org

Direct development

Direct development — is a type of development in which the newborn or hatched from an egg organism by its structure does not differ from an adult organism, because it has no specific organs or structures, but immature and has a smaller size. Its further development is associated with growth and puberty. The direct type of development is a characteristic of the most highly organized groups of vertebrates (reptiles, birds and mammals), as well as individual members of other groups of Animalia kingdom: Turbellaria and Oligochaeta, leeches, some gastropods and spiders.

Questions:
  • What is direct development?

  • Compare direct and indirect development.

  • What is the difference between indirect and direct development?