Answer to Question #267702 in Zoology for Jess

Question

1.     Coral reefs are considered one of the most diverse ecosystems on earth. The coral skeletons provide habitat and protection to a variety of marine animals. Marine animals are not only associated with the reef but also with other animals living in coral reefs. This relationship further increases the complexity of the reef system, making it more resilient.

In your essay;

i. Discuss any three (3) mutualistic relationships which exist between marine animals in a coral reef ecosystem.

ii. Corals belong to phylum Cnidarians which exhibit Polymorphism. Discuss Polymorphism in Cnidarians.

iii. Discuss three (3) types of reef-building corals.

Explain what coral bleaching is and what causes it

Answer 1

i)

Trophic mutualism occurs when both species receive a similar benefit through transfer of energy and nutrients. For example, animal-algal mutualism, such as with coral polyps and dinoflagellate algae.

When a dinoflagellate lives in a coral, it is called a zooxanthellae. The coral uses photosynthesis byproducts of the zooxanthellae as food, and the coral secretes a mucus-like substance that protects the zooxanthellae. The coral also protects the zooxanthellae from organisms that might eat it and the intense ultraviolet light that might kill it.

Defensive mutualism occurs when one species receives food and shelter in return for protecting its partner from predators. For example, with the mutualism between the sea star and the scale worm, the scale worm lives in or near the sea star's mouth. As the sea star eats, the scale worm gets leftover pieces of food. Conversely, if a predator tries to attack a sea star, the scale worm uses its sharp pincer-like jaws to bite the predator.

Complete dominance .The animal-algal mutualism that exists between a coral polyp and a zooxanthellae is an example of obligate mutualism in coral reefs.

The coral bleaching phenomenon occurs when zooxanthellae are expelled by the coral, in which case eventually the coral will die. The algae and coral relationship is so intertwined that one cannot survive without the other.

ii)

Polymorphism is the phenomenon of occurrence of the same species of the organism in more than one form with different functions. This occurrence of polymorphism guarantees well-organized division of labor between several individuals. In coelenterates different individuals get united in the form of a colony and hence polymorphism is a very important feature of this phylum.

iii)

Platform reefs can form on the continental shelf, as well as in the open ocean, in fact anywhere where the seabed rises close enough to the surface of the ocean to enable the growth of zooxanthemic, reef-forming corals

A fringing reef, also called a shore reef, is directly attached to a shore,or borders it with an intervening narrow, shallow channel or lagoon.

Barrier reefs are separated from a mainland or island shore by a deep channel or lagoon

Coral bleaching is the process when corals become white due to various stressors, such as changes in temperature, light, or nutrients.