.png)
Chapter – 2
Nutrition in Animals
Classification based on Eating Habits: (i) Herbivorous: Animals thateat plants orplant products. Example: cow, sheep, goat,deer, elephant, kangaroo, giraffe, etc. (ii) Carnivorous: Animals that eat only flesh of other animals. They never eat plants. Example: tiger, lizard, lion, etc. (iii) Omnivorous: Animals consume plants as well as other animals as their food. Example: bear, dog, human being, etc. (iv) Parasites: Organisms that obtain their food from other animals either by living inside (endoparasites) or outside (ectoparasites) their body. Example: tapeworm and roundworm (inside body), tickand lice (outside body).(v) Scavengers: Animals which feed on the remains of dead animals preyed by predators. Example: vulture, crows, jackal, etc. Animal nutrition includes nutrient requirement, modeof intake of food andits utilisation inthe body. The humandigestive system consists of the alimentary canal and secretory glands. It consists of (i) buccal cavity, (ii) oesophagus, (iii) stomach, (iv) small intestine, (v) large intestine ending in rectum (vi) anus. The main digestive glands which secrete digestive juices are (i) the salivary glands, (ii) the liver and (iii) the pancreas.
The stomach wall and thewall of thesmall intestine alsosecrete digestive juices. The modes offeeding vary indifferent organisms.
Nutrition is a complex process involving:
(i) ingestion,
(ii) digestion,
(iii) absorption,
(a) assimilation and
(b) egestion.
Digestion of carbohydrates, like starch, begins in the buccal cavity. The digestion of protein starts in the stomach. The bile secreted from the liver, the pancreatic juice from thepancreas and thedigestive juice fromthe intestinal wallcomplete the digestion of all components of food in the smallintestine. The digested food is absorbed in the bloodvessels from thesmall intestine.
The absorbed substances are transported to different parts of the body. Water and some salts are absorbed from the undigested food in thelarge intestine.
The undigested andunabsorbed residues areexpelled out of the bodyas faeces through the anus.
The grazing animals like cows, buffaloes and deer are known as ruminants. They quickly ingest, swallow their leafy food and store it in therumen. Later, thefood
returns tothe mouth andthe animal chews it peacefully.
Amoeba ingests its foodwith the helpof its false feet or pseudopodia. The food isdigested in thefood vacuole. Itpushes out finger-like pseudopodia which engulf the prey.
Comments