Noteworthy Points of the Chapter:
1. Sponges exhibit cellular level of organisation. Coelenterates show tissue level of organisation.
2. In open type type of circulatory system the blood is pumped out of the heart and the cells and tissues are directly bathed in it.
3. When any longitudinal plane passing through the central axis of the body divides the organism into identical halves, it is called radial symmetry and when only one plane can divide body into identical left and right halves, it is called bilateral symmetry.
4. Animals in which the cells are arranged in two embryonic layers, an external ectoderm and an internal endoderm, are called diploblastic animals.
Click on the download below for chapter summary