Circulation in Pheretima Earthworm has a system of vessels or tubes in which red blood circulates which transports oxygen, carbon dioxide, digested food and nitrogenous waste to and from the parts of the body. A transportation system, in which blood circulates always in tubes, is called a closed circulatory system. The circulatory system comprises: blood, [...]
Classification of the Phylum Annelida The term annelida has been coined from either Greek word annulus meaning small rings of French word annular meaning arranged like small single rings. They are the first coelomate animals and as regarded as metamerically segmented animals. Definition: The animal group who are triploblastic, coelomate and whose bodies are metamerically [...]
Ans. In animals, metamerism is defined as a mesodermal event resulting in serial repetition of unit subdivisions of ectoderm and mesoderm products. Endoderm is not involved in metamerism. Segmentation is not the same concept as metamerism. Segmentation can be confined only to ectodermally derived tissue, e.g., in the Cestoda tapeworms. Metamerism is far more important [...]
Ans. The reproductive organs of earthworms are positioned at different ends of their bodies, so that fertilization of the eggs is only possible when the worms are aligned in opposite directions.
Ans. When the evolutionary dynamics of invertebrates are considered, trochophore larva attracts special attention as it shows prominent similarities with some other groups of invertebrates. The affinities with other groups suggest to conclude that the animals having bilateral symmetry emerge from those of having radial symmetry. It is assumed that the trochophore represents a transitional [...]
