Compare and contrast Oligochaetes and Caecilians
Oligochaetas are earthworms which belongs to phylum Annelida while Caecilians are amphibians that look like earthworm or snakes belonging to phylum Chordata order Apoda and both have similar appearances. Both classes belongs to Eumetazoa having similar characteristics like organ system level of organization, increased cephalisation , bilaterally symmetry, triploblastic tissue development and coelomate development. The difference is that Oligochaeta are protostomes while caecilians are deuterostomes hence they have different patterns of embryonic development. In Oligochaeta the blastospore develops into the mouth first forming the first opening to the embryonic gut. The blastospore undergoes spiral cleavage diagonal cell division and determinate cleavage where the developmental fate of cells are fixed early. By contrast in Caecilians, the blastospore develops into the anus first and the mouth formed from the second opening to embryonic gut. The blastospore undergoes radial cleavage which cell divisions parallel and perpendicular and also indeterminate cleavage where the developmental fate of cells fixed at later stages. Oligochaetas are detritus feeders as they feed on non living organic material from dead organisms or fecal material where as Caecilians are carnivores feed on preys like earthworm.i Both groups live in similar moist environment. Caecilians also have a more complex digestive and excretory system by having kidneys and endocrine system. The Caecilians belongs to the subphylum Vertebrata are more complex and have a higher degree of cephalisation compared to Oligochaetes. Caecilians have retain primitive features like tiny scales on their skin and have reduced eyes but developed special sensory tentacle. Caecilians have a bony endoskeleton including the vertebral column which protects the dorsal hollow nerve cord and also cranium which protects the brain. They also have a ventral heart derived from the...
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