Poriferans, Echinoderms, and Cnidarians live in the water.
Poriferans (phylum Porifera) are sponges. These aquatic, asymmetrial animals are also sessile (unlike most animals). They are simple creatures, having no tissues. They can reproduce sexually or asexually and have a porous body wall.
Phylum Echinodermata consists of starfish, sea urchins, sea cucumbers, and sand dollars. These all have spiny skin, an endoskeleton, and reproduce sexually. Interestingly, the larvae have bilateral symmetry while most "adults" have radial symmetry. Echinoderms have digestive and circulatory systems, but no excretory or respiratory systems. They move using the a hydraulic system called the water vascular system.
Jellyfish, hydra, coral, and sea anemones belong to phylum Cnidaria. Cnidarians have radial symmetry, tentacles, and two layers of tissue surrounding a central "stomach" cavity. They also have one digestive opening and a nerve network. The two body forms of cnidarians are called polyp and medusa. Polyps are sessile and reproduce asexually. Polyps include the hydra and anemone. The medusa is a free-swimming form (such as the jellyfish). Some cnidarians change from one form to the other during their lifetime, while others remain in one form for their whole lives.
Phylum Echinodermata consists of starfish, sea urchins, sea cucumbers, and sand dollars. These all have spiny skin, an endoskeleton, and reproduce sexually. Interestingly, the larvae have bilateral symmetry while most "adults" have radial symmetry. Echinoderms have digestive and circulatory systems, but no excretory or respiratory systems. They move using the a hydraulic system called the water vascular system.
Jellyfish, hydra, coral, and sea anemones belong to phylum Cnidaria. Cnidarians have radial symmetry, tentacles, and two layers of tissue surrounding a central "stomach" cavity. They also have one digestive opening and a nerve network. The two body forms of cnidarians are called polyp and medusa. Polyps are sessile and reproduce asexually. Polyps include the hydra and anemone. The medusa is a free-swimming form (such as the jellyfish). Some cnidarians change from one form to the other during their lifetime, while others remain in one form for their whole lives.
Which of these is the most complex? (Correct answer will launch you to the next page)