a. Open and closed circulatory system
b. Oviparity and viviparity
c. Direct and indirect development
d. Acoelomate and pseudocoelomate
e. Notochord and nerve cord
f. Polyp and medusa
(a) Blood is pumped out the heart and the cells and tissues are directly bathed in the open circulatory system whereas the closed circulatory system is circulated throughout the body with the help of series of vessels
(b) Laying of fertilized and unfertilized eggs are known as oviparous whereas giving birth to young ones is viviparous
(c) When a larval stage is absent in the development of the organism, it is direct development whereas the larval stage is present in the development of the organism which does not resemble the adult is called indirect development.
(d) The animal possessing no coelom are called coelomates whereas the body cavity lined by mesoderm instead mesoderm is present in between ectoderm and endoderm are called pseudocoelomate.
(e) The notochord is mesodermally derived rod-like structure formed on the dorsal side during embryonic development whereas the nerve cord is a solid strand of nervous tissue
(f) Polyp is a sessile and cylindrical form like Hydra whereas Medusa is an umbrella-shaped and free-swimming like jellyfish