Nutrition and mode of nutrition
Nutrition
Nutrition is the physiological process of acquiring energy for the metabolic activities, growth or other life
processes. The organism acquired the energy from food. So, the process of obtaining food (nutrients) is
simply known as nutrition.
Mode of Nutrition: on the basis of mode of acquiring food
1. Autotrophic mode of nutrition:
It is also known as holophytic mode (plant like nutrition). Organisms can synthesize all the essential
nutrients required for them from inorganic substrates (CO2, NH3, nitrates, water etc) present in the
environments. It is of two types.
i) Phototropic nutrition: Organisms synthesize their food in the presence of sun light using
Carbon-dioxide and water as substrate. Such organisms are known as Photo-Autotrophs. Eg. Green plants
ii) Chemotropic nutrition: Organisms synthesis their organic food by the chemical reactions (Oxidation)
utilizing inorganic substrates like nitrates, Hydrogen sulphate, iron etc. such organisms are known as
chemo-autotrophs. Eg. Sulphur bacteria, Nitrobacter, Nitromonas etc.2.
2. Heterotropic mode of nutrition:
organisms cannot synthesize their food by themselves rather they depend on the food prepared by
Autotrophs (directly or indirectly). Such organisms are known as heterotrophs. According to the types of
food or mode of feeding, heterotropic nutrition are o following types
i) Holozoic nutrition: it is known as animal-like mode of nutrition. In this mode, animals feed on plants or
other animals whole or their parts for food. Such animals are free living and have the characteristics of
Ingestion, digestion, absorption, assimilation and egestion. Such animals are classified into following
types
Herbivorous: Animals which feed on plants for nutrition. Eg. Cow , goat, buffalo etc
Carnivorous: Animals which feed on other animals or animal products. Eg. Tiger, lion
Omnivorous: Animals having mixed diets (feeding on both animals and plants and their products). Eg.
Human, crow
Coprophagous: Animals feeding upon faeces of other animlals. Eg. Pig
Cannibalism: Animals feeding upon smaller animals of same species. Eg. Snakes, frog
Sanguivorous: Animals feeding upon blood. Eg. Leech, Vampire bat
ii) Saprotrophic nutrition: organisms obtain their nutrition from dead and decaying organic matter. They
are decomposers. Eg. Fungi, bacteria, earthworm etc. They includes saprophytes and saprozoic.
