Types of alimentary canal

Types of alimentary canal are:

1. Complete:
   In this, mouth and anus or clocal aperture are present. E.g. from Nematodes to Chordates

2. Incomplete:
   In this, only one opening i.e. mouth is present. E.g. flatworms

Body layers:

1. Diplobastic:
   Organisms having two germs layers in the body – outer ectoderm and inner endoderm. E.g. Sponges and Coelentrates

2. Triplobastic:
   Organisms having three germ layer-ectoderm, mesoderm and endoderm. E.g. flatworms to chordates

Respiratory Organs:

1. Gills in aquatic animals, tadpoles of amphibians, some mollucs and some echinoderms.
2. Tracheae in terrestrial arthropods.
3. Book lungs in arthropods.
4. Lungs in terrestrial animals.

Blood circulations:

1. Open circulatory system: Blood flows through large open spaces.

2.Cloud circulatory system: Blood flows in definite vessels in definite circuit and blood is in direct contact with the cells. E.g. annelids, vertebrates