Question

which of the following first apperead in
nematodes :1)brain 2)pseudometamerism 3)body cavity 4)blood vascular system ​

Answer 1

Explanation:

Nematodes are roundworms and belong to the phylum Nematoda and more than half of the identified species are parasites on plants, animals and even humans. Dracunculus medinensis ( Guinea worm) is a large, thin and threadlike nematode growing up to 1 m long was recorded by the early Egyptian physicians between 1553- 1550 BC , the information which was obtained by the German Egyptologist in 1872.

Answer 2

Option (3) Body cavity is the correct answer.

• Nematodes or roundworms belong to the phylum Nematoda also called Nemathelminthes.
• Nematodes are present in soil and feed on bacteria they play an important role in nutrient cycling.
• They are cylindrical in shape and shoe tissue level of organization.
• Their body possesses a cavity which is also called Pseudocoelom. The alimentary canal is distinct from the mouth and anus.
• They do not possess any circulatory system nor any developed respiratory system.
• They are either free-living or parasitic in nature, the parasitic nematodes cause diseases in the host.
• The body walls and muscles of nematodes are longitudinal and they possess ameboid sperm cells.
• They consist of aphids a chemosensory organ situated on the lips.

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