Modes Of Nutrition In Living Organisms

Mode of nutrition means different ways by which living organisms get their nutrition for survival. Nutrition is the key to growth as nutritional elements provide energy. 

• Organisms need the energy to carry out their numerous functions.
• Nutrients supply these basic building blocks. 
• All species require food that contains carbon-based molecules because their bodies are all composed of molecules with this composition. 
• Always, outside sources are used for food and nutrients however, some organisms do produce food using outside-sourced raw materials. 
• The term nutrition comes from the word 'nutrients'. 
• A nutrient is an organic or inorganic substance required for the maintenance of life and survival of a living organism. 

Key Terms: Nutrition, Autotrophs, Animals, Photosynthesis, Food, Parasites, Organisms.

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What are Nutrients? 

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A substance that an organism takes in from its environment and uses as a source of energy is referred to as a nutrient.

• The three basic nutrients, known as macronutrients, are carbohydrates, proteins, and fats. 
• Minerals and vitamins are referred to as micronutrients as they are needed in small amounts. 
• Nutrition is the process through which an organism consumes nutrients (such as carbs, lipids, proteins, minerals, and vitamins) and uses these nutrients. 

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Modes of Nutrition 

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"Modes of nutrition," mean the ways in which an organism obtains nourishment. Every organism gets its food in a different way. Different organisms have various ways of finding and acquiring food.

All organisms can be divided into two categories according to how they receive food:

1. Autotrophic 
2. Heterotrophic

Autotrophic mode of nutrition 

Auto means "self," and troph is "nutrition." Autotrophic, thus, refers to self-nutrition. 

• When an organism uses simple inorganic substances like carbon dioxide and water to produce its own food, this is known as autotrophic nutrition 
• The green plants are autotrophic in their mode of nutrition. 
• The autotrophic way of nutrition is also about autotrophic bacteria.
• The green pigment chlorophyll, which can store solar energy, is present in autotrophic organisms. 
• Plants are a type of autotrophs as they do photosynthesis and store the energy gained from the sun. 
• Autotrophs therefore manufacture food that can be consumed by many other species, including humans.

Heterotrophic mode of nutrition

Heteros means 'others' and troph means 'nutrition'. So, the definition of heterotrophic is food gained from others. Heterotrophic nutrition is the type of nutrition in which an organism relies on other organisms for its food because it is not able to synthesize its own food from basic inorganic components like carbon dioxide and water.

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Types of Heterotrophic Nutrition

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Heterotrophs are of different subtypes. 

1. Saprotrophic nutrition
2. Parasitic nutrition
3. Holozoic nutrition

Saprotrophic Nutrition (or saprophytic Nutrition)

Saprophytic nutrition is the type of nutrition in which an organism derives its sustenance from decomposing organic materials, such as rotting bread, dead plants, and dead animals. 

• The term "saprophytes" refers to organisms that feed themselves through a saprophytic process. 
• Numerous bacteria, as well as fungi (including yeast, mushrooms, and bread moulds) are saprophytes. 
• Saprophytes are organisms that break down complex organic molecules found in dead and decaying matter and transform them into less complex substances.

Parasitic Nutrition

An organism that feeds on the body of another living thing (referred to as its host) without killing the host is said to have parasitic nutrition.

• The organism that receives food is referred to as a "parasite," and the organism whose body the food is obtained from is referred to as the "host." 
• The host provides the parasite with nourishment, but the parasite does not help the host in any way. 
• An animal or a plant could serve as the host. 
• Numerous fungi, bacteria, a few plants like Cuscuta (amarbel), and some animals like Plasmodium and roundworms are known to eat in a parasitic manner. 
• Ticks, lice, leeches, and tapeworms are some further examples of parasites.

Holozoic Nutrition

The process by which an organism ingests complex organic food elements, digests them, and then absorbs them into its body cells is known as holozoic nutrition. 

• The organism expels the portion of the food that was not digested and absorbed through the process of egestion. 
• Most animals, including humans, have a holozoic manner of nourishment. 
• In other words, the Holozoic way of nourishment is shared by several species including humans, cats, dogs, cattle, deer, tigers, lions, bears, giraffes, frogs, fish, and amoebas.

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Things to remember

• Modes of nutrition can be of different types for different living organisms.
• It can be autotrophic, heterotrophic, saprotrophic, parasitic and holozoic modes of nutrition.
• The food taken in by an organism contains a large number of nutrients like carbohydrates, fats, proteins, minerals, vitamins and water, etc. 
• A nutrient is anything that an organism consumes from its surroundings and uses as a source of energy or for the production of its component parts.
• A heterotrophic organism is a consumer which derives its nutrition from other organisms. 
• Food is created through photosynthesis using sunlight. Photosynthesis is a practice of green plants.
• Saprotrophs feed on decomposing organic materials and absorb nutrients via secreting digestive enzymes.
• Holozoic type of nutrition is found in humans, dogs, lions etc animals (carnivores and omnivores).
• Parasitic nutrition is achieved by building a parasitic relationship with the host.