What function do the red whorls of this organism have?
Invertebrates are animals that lack a backbone.
They account for 95% of known animal species.
Fig. 33-2 Review of Animal Phylogeny
Fig. 33-3-1 Invertebrate Diversity
Calcarea and Silicea (5,500 species)
Cnidaria (10,000 species)
Acoela (400 species)
Acoel flatworms (LM)
Platyhelminthes (20,000 species)
A marine flatworm
Ectoprocta (4,500 species)
Brachiopoda (335 species)
Rotifera (1,800 species)
A rotifer (LM)
A ctenophore, or comb jelly
Ctenophora (100 species)
A placozoan (LM)
Placozoa (1 species)
Concept 33.1: Sponges are basal animals that lack true tissues
Sponges are sedentary animals from the phyla Calcarea and Silicea.
They live in both fresh and marine waters.
Sponges lack true tissues and organs.
Calcarea and Silicea
Sponges are suspension feeders - capturing food particles suspended in the water that pass through their body.
Choanocytes, flagellated collar cells, generate a water current through the sponge and ingest suspended food.
Water is drawn through pores into a cavity called the spongocoel, and out through an opening called the osculum.
Anatomy of a Sponge
Azure vase sponge (Callyspongia
Sponges consist of a noncellular mesohyl layer between two cell layers.
Amoebocytes are found in the mesohyl and play roles in digestion and structure.