In which type of nutrition, digestion of food occurs outside the body?
(a) Parasitic nutrition
(b) Symbiotic nutrition
(c) Saprotrophic nutrition
(d) Autotrophic nutrition

Answer
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Hint: In this type of nutrition, organisms feed on dead and decaying organic matter by the absorption method.

Complete step-by-step solution:
In saprotrophic nutrition, the digestion of food occurs outside the body. This type of nutrition is called extracellular digestion. In this process, organisms secret the digestive juices directly on the food to make it soluble. The digestive enzymes digest the substrate and convert it into a simpler absorbable form that gets directly absorbed by the organisms. These organisms are the important members of the nutrient recycling process and decomposition. They range from microscopic to macroscopic size. Examples of organisms in which saprotrophic nutrition occurs include Yeast, Rhizopus (bread mold), Mucor (pin mold), Agaricus (mushroom), and many bacteria. Major saprotroph group includes:
1. Bacteria: Bacteria like Spirochaeta cytophaga have the capacity to decompose cellulose through absorptive nutrition. They partially break down cellulose into intermediate molecules and facilitate the process of decomposition.
2. Water mold: Water molds are considered as some of the most important decomposers in freshwater aquatic environments. They decompose both plant and animals’ materials.
3. Fungi: Fungi are the major group of saprotrophs that decompose complex organic molecules. They decompose leaves and twigs in the organic litter found on the forest floor. The example of wood-decomposing fungi includes species of turkey tails, oyster mushrooms, and Ganoderma.

So, the correct answer is ‘Saprotrophic nutrition’.

Note: Parasitic nutrition is different from saprotrophic nutrition because parasites derive their food from living organisms and cause harm to these organisms. These living organisms are called hosts.
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