Животные /english/ - реферат по прочим предметам

 

Тезисы:

  • All are marine.
  • Reproduction is predominantly sexual, with the embryo passing through a blastula phase .
  • The latter type, protozoa, was categorized as a subkingdom of Animalia.
  • What constitutes an animal, therefore, depends on the scheme followed.
  • One basic body part is the gut, which must have arisen early in the evolution of the metazoans.
  • Furthermore, they have tissues but no real organs or nerves, and they lack symmetry.
  • A nervous system is present, but no brain or head.
  • Instead, the animals exhibit radial symmetry, or symmetry around a central axis.
  • The tissues of the Radiata have only two major layers, whereas the Bilateria have three.
  • Such groups are founded on the basis of how the cells divide and how various organs are formed.
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