Similarities between sponges and protozoa.

The simplest are acellular (having a body that does not consist of cells) organisms and constitute the simplest group of animals. They make up about 50,000 species and are found in almost every habitat where moisture is present, as well as parasites in most animals. Because of their resistant spores, some protozoa can withstand extreme temperatures and humidity. It is not surprising that they are among the most numerous animals in the world. Some protozoa share similarities with sponges, which suggests that the two groups may be related. Both of them have a cellular level of organization, they digest food in the cell; all sponges are heterotrophic, and most protozoa are also heterotrophic nerve cells.