Section 1

Porifera

• The phylum Porifera is made up of sponges, sessile invertebrates that have no true tissues or organs. The simplest types of sponges are shaped like hollow cylinders.

• The body wall of a sponge is composed of two layers of cells that are separated by a jellylike substance called mesohyl. The body is supported by a skeleton made of spongin, spicules, or both.

• Choanocytes which line the inside of a sponge beat their flagella, thus drawing a current of water into the sponge through pores (ostia) in the body wall. Water leaves through the osculum, an opening at the top of the sponge.

• Sponges feed by filtering small organisms and organic matter out of the water that passes through their body. Nutrients are distributed through the body by amoebocytes, cells which crawl about within the body wall.

• Sponges can reproduce asexually, through budding or regeneration, and sexually, through the joining of egg and sperm. Most sponges are hermaphroditic, meaning that a single animal can produce both eggs and sperm.

Vocabulary sponge (p. 673) sessile (p. 673) choanocyte (p. 673)

ostium (p. 673) osculum (p. 673) spongin (p. 673)

spicule (p. 673) filter feeding (p. 674) amoebocyte (p. 674)

gemmule (p. 675) regeneration (p. 675) hermaphrodite (p. 675)

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