Obelia: A Marine Colonial Hydroid
A typical hydroid has a base, a stalk, and one or more terminal zooids. The base by which colonial hydroids […]
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March 2024
Phylum Porifera: Phylogeny and Adaptive Diversification
Sponges originated before the Cambrian period. Two groups of calcareous spongelike organisms occupied early Paleozoic reefs. The Devonian period saw
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Forms and Functions of Cnidarians
One of the most interesting—and sometimes puzzling—aspects of this phylum is the dimorphism and often polymorphism displayed by many of
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Phylum Cnidaria: The Flower of the Sea
Phylum Cnidaria (ny-dar´e-a) (Gr. knide, nettle, + L. aria [pl. suffix], like or connected with) is an interesting group of
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Global Time and Different Time Scales
Global Time There’s an old Canadian joke that goes, “Repent! The world will end at midnight!—or, 12:30 a.m. in Newfoundland.”
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Cells in Sponges
Sponge cells are loosely arranged in a gelatinous matrix called mesohyl, or mesenchyme. The mesohyl is the connective tissue of
Canal Systems in Sponges
Asconoids Asconoid sponges have the simplest organization. Water is drawn into the sponge through microscopic dermal pores by the beating
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Paramecium: A Representative Free-Living Ciliate
Paramecia are often described as slipper shaped. Paramecium caudatum is 150 to 300 µm in length and is blunt anteriorly
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Phylum Euglenozoa: A Group with Flexible Pellicle
The Euglenozoa is generally considered a monophyletic group, based on the shared persistence of the nucleoli during mitosis, and the
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Phylum Porifera: Sponges
Most animals move to search for food, but a sessile sponge draws food and water into its body instead. The
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