Theory:

Animalia:
All the multicellular eukaryotic organisms which lack cell walls belong to the kingdom Animalia.
 
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Classification of animals
  
These organisms are heterotrophic, and hence they rely on other organisms for their food. Most of the animals can move, unlike plants. They have a growth pattern by which the adult animals have a specific shape and size.
 
The majority of the animals have well-defined organ systems such as respiratory system, digestive system, excretory system etc., They also have a nervous system to respond to an external stimulus.
 
Based on the differences in their body type and design, animals are further classified.
 
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Classification of animals
Coelom
The fluid-filled body cavity found between the alimentary canal and the body wall is known as coelom.
Based on the presence of a body cavity, the animals are categorised as follows:
  • Coelomates: The animals which have a true body cavity.
  • Pseudocoelomates: The animals which have a false body cavity.
  • Acoelomates: The animals which do not have a body cavity at all.
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Types of coelom in animals
Body symmetry
The presence of body parts, in size, shape, and relative position, on opposite sides of a dividing line in the living organisms is known as body symmetry. Animals are classified  based on their body symmetry into three types. They are as follows:
  • Radial symmetry: A symmetry in which the sides exhibit regularity of parts around a central axis is known as radial symmetry.
  • Bilateral symmetry: The form of symmetry in which the opposite sides are similar
  • Asymmetry: The lack or absence of symmetry
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Types of symmetry