Chapter 10 (Kingdom Animalia) F.Sc 1st Year Biology Helping Notes

What is importance of Acychlostoma duodenale (hook worm)? or Describe briefly about hook worm. Or What are hook worms?

Acychlostoma duodenale is commonly known as hook worm. It is a parasite of human small intestine in Asia, North Africa and Europe. It is a very dangerous because it holds the villi of intestine and sucks blood and body fluid during feeding. It produces an anticoagulant to prevent clotting of blood and after feeding leaves the wound bleeding. In children it can cause severe anaemia and retard physical and mental growth.

What is prostomium?

In annelids, the mouth is overhung by a lobed structure, the prostomium.

Differentiate between closed and open circulatory systems.

A system in which a circulatory fluid called blood flows in a network of vessels . known as blood vessels and whole blood never comes out of the vessels is called closed circulatory system e.g., annelids and chordates. While a system in which whole blood comes out of the blood vessels, bathes the body organs and then returned to the heart is called open circulatory system e.g, in arthropods. The body of annelids is metamerically segmented.

Explain or What is term metameric segmentation?

The body becomes divided transversely into a number of similar parts or segments which originate in mesoderm. The subdivisions may be indicated externally by constrictions of the body surface. Internally the segments are separated from each other by septa extending across the coelom.

What are nephridia?

In annelids excretion takes place by specialized structures called nephridia which are ciliated organs present in each segment in the body cavity.

How locomotion occurs in Annelida?

The locomotion is brought by the interaction of muscles and hydrostatic skeleton. Contraction of circular muscles produces a pressure in the coelomic fluid that forces the body to elongate. Similarly contraction of longitudinal muscles, produce a pressure in the coelomic fluid that would cause the body to widen. Most annelids possess chitinous cheatae or setae embedded in sacs (earthworm) or parapodia present in the body wall (Nereis).

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