The system circulates blood to the lungs and the rest of the body and consists of arteries, veins, and capillaries.

The circulatory system or cardiovascular system

Explanation: The circulatory system allows the blood to circulate and permits oxygen, carbon dioxide, nutrients, hormones and blood from and to the cells in the body. The system consist of heart, blood and blood vessels. There are five types of blood vessels: the arterioles; the capillaries; here exchange of chemical and water takes place between blood and tissues; the arteries; it carries blood away from the heart; the venules; and the veins, which carries blood from the capillaries back to the heart.

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.

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