Sponges have multiple cell types that are geared toward executing various metabolic functions. Cnidarians have outer and inner tissue layers sandwiching a noncellular mesoglea. Cnidarians possess a well-formed digestive system and carry out extracellular digestion. Cnidarians are invertebrates such as jellyfish and corals. They belong to Phylum Cnidaria. All cnidarians are aquatic. Most of them live in the ocean, but a few species live in fresh water. Cnidarians are a little more complex than sponges. Besides specialized cells, they have tissues and radial symmetry. There are more than... Show more Sponges have multiple cell types that are geared toward executing various metabolic functions. Cnidarians have outer and inner tissue layers sandwiching a noncellular mesoglea. Cnidarians possess a well-formed digestive system and carry out extracellular digestion. Cnidarians are invertebrates such as jellyfish and corals. They belong to Phylum Cnidaria. All cnidarians are aquatic. Most of them live in the ocean, but a few species live in fresh water. Cnidarians are a little more complex than sponges. Besides specialized cells, they have tissues and radial symmetry. There are more than 10,000 cnidarian species. Cnidarians can be found in almost all ocean habitats. Jellyfish, which spend most of their lives as medusae, may live virtually everywhere in the ocean. They prey on zooplankton, other invertebrates, and the eggs and larvae of fish. Corals form large colonies in shallow tropical water. They are confined to shallow water because they have a symbiotic relationship with algae that live inside of them. The algae need sunlight for photosynthesis, so corals must stay relatively close to the surface of the water for the algae to get enough light. Corals exist only as polyps. They catch plankton with their tentacles. Many corals form a hard, mineral exoskeleton. Over time, this builds up to become a coral reef. Coral reefs provide food and shelter to many other ocean organisms. Show less
Sponges have multiple cell types that are geared toward executing various metabolic functions. Cnidarians have outer and inner tissue layers sandwiching a noncellular mesoglea. Cnidarians possess a well-formed digestive system and carry out extracellular digestion.
Cnidarians are invertebrates such as jellyfish and corals. They belong to Phylum Cnidaria. All cnidarians are aquatic. Most of them live in the ocean, but a few species live in fresh water. Cnidarians are a little more complex than sponges. Besides specialized cells, they have tissues and radial symmetry. There are more than 10,000 cnidarian species. Cnidarians can be found in almost all ocean habitats. Jellyfish, which spend most of their lives as medusae, may live virtually everywhere in the ocean. They prey on zooplankton, other invertebrates, and the eggs and larvae of fish. Corals form large colonies in shallow tropical water. They are confined to shallow water because they have a symbiotic relationship with algae that live inside of them. The algae need sunlight for photosynthesis, so corals must stay relatively close to the surface of the water for the algae to get enough light. Corals exist only as polyps. They catch plankton with their tentacles. Many corals form a hard, mineral exoskeleton. Over time, this builds up to become a coral reef. Coral reefs provide food and shelter to many other ocean organisms.
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