Rosenberg et al. (2007) have described coral reefs as ?the largest structures made by living creatures. Biogenic activities over millennia has lead reefs to evolve to become a complex, productive, yet fragile marine ecosystem with a biodiversity to rival that of a terrestrial rainforest (Rohwer et al. 2002, Allen and Steene, 2007). Microorganisms are critically [...]
Describe the structure, development, physiology and reproduction of Obelia medusa. What is meant by metagenesis? Explain it with reference to the life-cycle of Obelia. Define polymorphism. Illustrate it with suitable diagrams from the Order- Siphonophora. What is a coral reef? On the basis of structural organization how corals may be classified? Define economic importance of [...]
“A coral reef is a ridge or mound of lime stone the upper surface of which is near the surface of the sea and which is formed of calcium carbonate by the action of organisms chiefly corals” (Vaughan. 1917). Though the reefs are built by stony corals but other organisms such as Foraminifera, Millipora, Tubipores, [...]
Amongst the coelenterates, hydrozoans provide very good examples of polymorphism. The phenomenon is essentially for division of labour. Division of labour is first seen in the cells of Hydra where the cells are specialized to perform different functions of individual as a whole. Physiological differentiation of this type had its effect upon the morphology of [...]
Obelia is a tree-like branched, marine colonial cnidarian, growing on the surface of sea-weeds, rocks and pilings along the sea-coasts. Colonies appear like whitish or light-brown branched threads, about 30 mm. to several cms in height. The colony arises by budding from a single hydra-like individual, the buds fail to separate and after repeated budding [...]
