Published on: Mar 4, 2016
Transcripts - Poriferans summary
SUMMARYPoriferans Anatomy and Physiology Marine habitats. These primitive multicellular animals lack true tissues or organs. There are no digestive, circulatory or nervous systems. Adults are sessile and use specialised cells called choanocytes to draw water through a system of water canals into the internal cavity called the spongocoel. Nutrients are distributed around the body by mobile cells called amoebocytes. Poriferans are Hermaphroditic: no permanent gonads, can become either egg or sperm. Poriferans have no respiratory or excretory organs; both functions occur by diffusion in individual cells. Structures Skeletons of sponges can be composed of an organic substance called sponging or they may have calcareous or siliceous skeletons composed of chambers or spicules. Sponges are not like other animals because they do not have a mouth. The tiny holes on their outer layer absorbs water in. The calls in the sponge have a variety of functions and are independent form each other then the cells of other animals. ...Sponges can contain 16,000 other animals inside of it. ...A new type of sponge is found every year. ...One of the largest sponges ever was almost 10 ft wide.
Distribution According to the article “Global Diversity of Sponges”, there are around 8,553 accepted species of Porifera, the majority of which (83%) are Demospongiae ; 8% corresponds to Hexactinellida, 8% to calcarea, and 1% to homocleromorpha.Characteristics No definite symmetry. Body Multicellular, few tissues, no organs. Cells and tissues surround a water filled space, but no true body cavity. All are sessile. Reproduce sexually or asexually, sexual reproduction either gonochoristic or hermaphroditic. No nervous system Distinct larval stage-planktonic. Lives in aquatic environments, mostly marine All are filter feeders. Often have a skeleton of spicules.Diversity and classification Poriferans have an ancient history whose first fossils appeared in Precambrian deposits at the end of the Cryogenian "Snowball Earth" period.Scientific Classification: Domain: eukaryota Kingdom: animalia Phylum: porifera Sponges are classified as as Poriferans. Three different groups of Poriferans are: Hexactinellida (glass sponges).
Demospongia (bath sponges). Calcarea (calcareous sponges. Sponges lack a gut, nervous system, and circulatory system. Pros and Cons Pros The constant activity of the sponges filtering removes bacteria, small planktonic organisms and organic particles increasing water clarity and quality, linked to live coral reef structure and facilitate its regeneration. Cons The lost of the sponges could accelerate the lost of coral reefs.Galo AlfaroErick escobar