It is classified on the basis of polypoid phase in the life cycle. They are classified as - hydrozoa, scyphozoa and anthozoa. The hydrozoa are also known as water animals. They are marine and occur in fresh water also. They may occur alone or in ...

These are also known as the sting cells. Their stinging nature was discovered by Aristotle. They provide the link between animals and plants. Peyssonel and Trembley grouped them as animals. Coelenterates were put together with the sponges by Leuckart. They were further divided into ...

The phylum porifera has three classes which are calcarea, hyalospongiae and demospongiae. The calcarea are also known as lime sponge. They have spicules which are calcareous in nature. They have collared flagellate cells. They are mainly marine in their habitat. The hyalospongiae are also known ...

Porifera are also known as pore bearing organisms. They are also known as sponges. The sponges were recognized by Ellis and Aristotle was the first one to identify it. They were included as animals and were given the name porifera by Robert Grant. Sometimes they ...

The nervous system consists of neurons which help in the conduction of impulse and the coordination of body functions. Sponges do not possess it. Coelenterates have primitive type of nervous system. The nervous system is ring shape and lies around the front part of alimentary ...

There are certain organisms which lose the metabolic wastes through their body by diffusion. It includes sponges, coelenterates and echinoderms. There are flame cells which help in excretion and occur in flat worms. The excretory system is unique in round worms which contains canals and ...

Respiration is mainly of two types that are aerobic and anaerobic. Aerobic respiration includes cutaneous, branchial and body surface respiration. Aerobic animals require oxygen which is utilized from air or water. Organisms like Hydra show body surface respiration. These are aquatic animals. Animals like fishes, ...

Digestive tract is defined as the path through which food travels and goes through the various processes like absorption, digestion and elimination. Animals included under coelenterates and flat worms have single opening for ingestion and egestion. This single opening is known as mouth. This type ...