Write the main characteristics of phylum Porifera and Aves give one example of each with its diagram.
Some of the important characteristics of phylum Porifera are mentioned below. The cells of Poriferans are loosely organized. They are mostly found in marine water. Only a few are found in freshwater. They are either radially symmetrical or asymmetrical. Their body is usually cylindrical. The scleroblast secretes spicules while spongin fibres are secreted by spongioblasts. They have no organs in their body. They depict cellular grade of organization. The body comprises numerous pores known as Ostia and osculum. The central cavity is called spongocoel or atrium which opens to the outside through the osculum. They reproduce asexually by budding, and fragmentation. The nutrition is holozoic. They have neurosensory cells but are devoid of any specific nervous system. They have the power to regenerate the lost parts. The development is indirect and the cleavage is holoblastic. The exchange of respiratory gases and nitrogenous wastes occurs by the process of diffusion
