Animal characteristics include having distinct genes that control unique body plans, being heterotrophs that develop from fertilized eggs and have internal digestion and motility. Phylum Porifera includes sponges, which have spicules for structure/defense and filter feed using choanocytes and ostia. Phylum Cnidaria includes jellyfish, anemones, and corals, which have stinging nematocysts, a sac-like gut, and a diploblastic body plan. Phylum Platyhelminthes includes flatworms such as flukes and tapeworms, which have an unbranched digestive system and tissues but not complete organ systems.