Question

6. Compare the anatomy of nemerteans and flatworms. 7. Explain the cellular mechanisms leading to ejection of the algal symbionts during coral bleaching,

Answer 1

#6) Alternative names for the phylum have included Nemertini, Nemertinea and Rhynchocoela

Nemertians anatomy had been possible by using a fossils study. They have also a number of alternative name like nemertinea and Rhynchocoela . Body had no cuticle, but contain a ciliated glandular epithelium. Ventrally located mouth. Alimentry canal parts like stomach , intestine lie midlie of body. This group have Retrating or infolded proboscis. Excretion occurs with the help of Protonephridia. CNS consist of brain and ventral nerve cords. Reproduce sexually. As far as groups are concerned, they divided into classes ; Anopla (Probocis with no dagger) and ENopola (Probocis with dagger).

Flatworms have no body cavity means aceolmates. They Lack of specialized body organ system like circulatory and respiratory system, this limited their function , so the nutrients and gaseous exchange occurs through simple diffusion. The digestive system have only one opening for intake and removal of nutreitns and digestive waste respectively. Flame cells are main organ for excretion. They are divided in two groups parasitic and non-parasitic.. Among parasitic group, Cestoda, Trematoda and Monogenea are came together. And non parasitic are Turbellarians. Except turbellarians pthers group has been proven to be monophyletic.

#7 ))

Corals are group which belong to Phylum coelenterate. They have a major diversity in bottom of Marine ecosystem. We have heard about Great Barrier Reef. Reef corals have a symbiotic relationship with green alga. They have a symbiotic relationship like Corals provide nutrients and shelter to alga in return corals get photosynthetic food. This symbiotic relation enables corals for easy survival in nutrients poor aquatic ecosystems.

Corals ecosystem degraded very fast due to the environmental changes which triggers the declining of corals numbers. A recently recorded threat in corals is Coral bleaching which has become an important issue nowadays. In this phenomenon apparent loss of green symbiotic alga or loss of photosynthetic pigments due to which coral death. Corals reef declining occurs very fast in recent decades.

Behind this horrible event environmental factors like rise in sea temperature, stress due to salinity, hot and cold stress, low wavelength or high penetrating light, certain diseases also. This all done or concluded by doing a number of experiments. The major threat which comes to reality is high temperature.

Several studies done in laboratory for know the facts behinds coral bleaching. Given heat or thermal stress to corals like 30 to 32 degree Celsius. Corals released cellular forms of green algae which are digested. It is healthy for the growing population of corals. If this corals released normal forms of green algae means without digestion or cellular forms, it will degrade the Corals. When electron microscopy has been done we get the high transmission of quantum yield because more oxygen produces due to degradation of green algae. Thermal changes are the main cause behind corals bleaching.