Final answer:
Sponges are simple aquatic animals without true tissues that reproduce sexually and asexually. They are monoecious, with free-swimming larvae being their only mobile stage.
Step-by-step explanation:
Sponges , or phylum Porifera, are considered to be the simplest animals and represent an early stage of multicellularity in the animal clade. They are aquatic and mainly marine, living in close contact with water, which is essential for their feeding, gas exchange, and excretion. Sponges do not have true tissues but possess specialized cells for different functions, and they reproduce both sexually and asexually. In their sexual reproduction, sponges are (hermaphroditic) with the ability to produce both eggs and sperm. The sperm, released into the water through the monoeciousosculum, may fertilize eggs of another sponge leading to the development of a free-swimming larva, which is the only time sponges exhibit mobility, as they are sessile adults.