,Animals are multicellular and heterotrophic.
Animal kingdom is most diverse than the plant kingdom.
Based on the organization of the cells, there are 3 levels of organization
Cellular level of organization: Cells are arranged as loose cell aggregates. E.g. sponges
Tissue level of organization: Cells are arranged into tissues. E.g. coelenterates, ctenophores
Organ level of organization: Tissues are arranged into organs and the organs are associated to
form organ systems. Each system performs a specific physiological function. E.g. All higher
animals (from platyhelminthes to chordates).
Organ systems of different animals show complexities. For example,
The digestive system of cnidarians and platyhelminthes is incomplete (only a single opening
functioning as mouth and anus). Complete digestive system has 2 openings (mouth and anus).
Circulatory system is 2 types (open and closed).
It is the arrangement of similar body parts on 2
sides of main axis of body.
Based on symmetry, animals are 2 types:
, Symmetry is 2 types:
Radial symmetry
Bilateral symmetry
Radial symmetry: Body can be divided into 2 similar parts by any plane along oral- aboral axis
of body. E.g. some Sponges, Coelenterates, Echinoderms.
Bilateral symmetry: Body can be divided into 2 right and left halves by a section passing
through the longitudinal axis. E.g. All vertebrates and many invertebrates.
Such animal has
An upper or vertebral dorsal side
A lower ventral side
Left and right lateral sides
Anterior (cephalic) side and
Posterior (anal) side.
Animal kingdom is most diverse than the plant kingdom.
Based on the organization of the cells, there are 3 levels of organization
Cellular level of organization: Cells are arranged as loose cell aggregates. E.g. sponges
Tissue level of organization: Cells are arranged into tissues. E.g. coelenterates, ctenophores
Organ level of organization: Tissues are arranged into organs and the organs are associated to
form organ systems. Each system performs a specific physiological function. E.g. All higher
animals (from platyhelminthes to chordates).
Organ systems of different animals show complexities. For example,
The digestive system of cnidarians and platyhelminthes is incomplete (only a single opening
functioning as mouth and anus). Complete digestive system has 2 openings (mouth and anus).
Circulatory system is 2 types (open and closed).
It is the arrangement of similar body parts on 2
sides of main axis of body.
Based on symmetry, animals are 2 types:
, Symmetry is 2 types:
Radial symmetry
Bilateral symmetry
Radial symmetry: Body can be divided into 2 similar parts by any plane along oral- aboral axis
of body. E.g. some Sponges, Coelenterates, Echinoderms.
Bilateral symmetry: Body can be divided into 2 right and left halves by a section passing
through the longitudinal axis. E.g. All vertebrates and many invertebrates.
Such animal has
An upper or vertebral dorsal side
A lower ventral side
Left and right lateral sides
Anterior (cephalic) side and
Posterior (anal) side.
