Evolution
Sponges are the simplest known animals. This could be due to one (possibly both) of these two things: One, sponges diverged from the evolution of animals after they lost their cell walls (found in plants) but before the development of such physiological functions as muscles, tissue, organs or nerves. Or two, sponges were originally designed to have these functions but have lost them or the genes are dormant.
Their simple design is incredibly successful however, because they are also one of the oldest known animals. There are fossils of soft bodied sponges that are 600 million years old. The Sequences for genes of ribosomal ribonucleic acid show that sponges may be closely related to the first animal to exist. The ancestors of current choanoflagellates, one celled organisms with flagellum, were also most likely the ancestors of sponges.
One of Porifera's only functions and issues is finding sufficient substrate in the right conditions (access to food, space to grow, water flow, temperature, depth, stability of sediment, etc.) and many of their evolutionary advancements appear to have stemmed from avoiding competition over these resources. In areas lacking sufficient detritus, some sponges evolved to be predatory, consuming small organisms and digesting them in mucus. Also to avoid choosing poor substrate and not getting enough water flow/microorganisms moving through ostia, some Porifera have evolved into commensalistic epizoa, attaching themselves to a larger, mobile organism. Some sponges' (around 2%) adaption to freshwater could potentially be another form of this, looking for habitat elsewhere. Another prime example of Porifera's unique adaptation and evolution is their ability to reproduce both sexually and asexually, something very few organisms can do. They also evolved to be able to change sexes, which is very unique. Their regenerative abilities certainly count as a bizarre and unique evolutionary trait, unlike no other animal. The syncytial tissue in glass sponges is most likely a derived trait, because the development of glass sponges begins with a cellular embryo.
Their simple design is incredibly successful however, because they are also one of the oldest known animals. There are fossils of soft bodied sponges that are 600 million years old. The Sequences for genes of ribosomal ribonucleic acid show that sponges may be closely related to the first animal to exist. The ancestors of current choanoflagellates, one celled organisms with flagellum, were also most likely the ancestors of sponges.
One of Porifera's only functions and issues is finding sufficient substrate in the right conditions (access to food, space to grow, water flow, temperature, depth, stability of sediment, etc.) and many of their evolutionary advancements appear to have stemmed from avoiding competition over these resources. In areas lacking sufficient detritus, some sponges evolved to be predatory, consuming small organisms and digesting them in mucus. Also to avoid choosing poor substrate and not getting enough water flow/microorganisms moving through ostia, some Porifera have evolved into commensalistic epizoa, attaching themselves to a larger, mobile organism. Some sponges' (around 2%) adaption to freshwater could potentially be another form of this, looking for habitat elsewhere. Another prime example of Porifera's unique adaptation and evolution is their ability to reproduce both sexually and asexually, something very few organisms can do. They also evolved to be able to change sexes, which is very unique. Their regenerative abilities certainly count as a bizarre and unique evolutionary trait, unlike no other animal. The syncytial tissue in glass sponges is most likely a derived trait, because the development of glass sponges begins with a cellular embryo.
Genetic Makeup
Not much is known about the genetic makeup of Porifera, but there appears to be a lot to discover. Genetic study of Porifera indicates that the four sponge classes have a surprisingly high number of genes in common with other Metazoans. Which could mean that Porifera expressed many more complex phenotypes at one point, but evolved out of doing so. It could also mean some Porifera still have the genotype for these complexities. There is also genetic evidence to prove that the classes of Porifera are quite different, more so than originally thought.