Diversity of Animals
Diversity of Animals The most basic type of animal is the sponge. Sponges are invertebrates and have few specialized tissues. They reproduce either asexually by budding or fragmentation or sexually, in which case they are monoecious, meaning that they are simultaneously male and female. Next are Cnidarians. These marine organisms have radial or biradial body symmetry and have two tissue layers, the outer epidermis and the inner gastrodermis, with a jelly-like layer called the mesoglea in between. Following cnidarians are flatworms. Flatworms are bilaterally symmetrical, meaning that the can be divided in half along a plane. (Bartleby) Their digestive systems are incomplete, and they also exhibit cephalization, meaning that their nervous systems are concentrated around their heads. This is the beginning of a brain. More complex than flatworms are nematodes. What sets nematodes apart from less complex organisms is that they had complete digestive systems. Next highe...