(a) Describe the general arrangement of the viscera of a named mammal.
(b) Describe the process of feeding in (i) Hydra; (ii) Amoeba.
Explanation
(a) The general arrangement of the viscera of man or rabbit shows that the diaphragm divides the trunk into two unequal parts namely, the upper chest cavity and the lower abdominal cavity. The chest cavity is enclosed or encircled by the ribs in which the lungs and the heart lie. The gullet runs down behind the mouth or buccal cavity through the whole length of the thoracic cavity, through the diaphragm. The liver lies below the diaphragm which over-laps a large portion of the stomach. The stomach leads to the small intestine which itself leads to the large intestine. The large intestine forms the caecum at one end and continues to form the rectum at the other end which finally terminates at the anus which lies at the posterior end of the trunk. Very close to the stomach are the pancreas and spleen. At the back of the abdominal cavity, we have a pair of kidneys. In male, the male part of the vasa diferensia are seen at the posterior region in close position with the bladder and ureter. In female, ovaries lie near the kidney, and the oviducts lead to the uterus or womb which is in the lower part of the abdominal cavity or behind the urinary bladder.
(b)(i)Hydra feeds mainly on small aquatic organisms.
-Food is captured by the help of nematocysts, borne on the tentacles.
-The food is then taken into the wide mouth by the tentacle.
-Here enzymes are secreted by the gland cells.
-digested extra cellularly and partially absorbed into endodermal cells.
-Here digestion is completed intra-cellularly.
(ii) Amoeba feeds on micro-organisms, e.g. diaton or organic particles. During feeding, it engulfs the food particles by forming cup shape. When the two ends of the pseudopodia touch, they fuse and enclose the food with little amount or drop of water and these form a food vacuole. The food is digested and absorbed here.