Heterotrophic nutrition, which can be classified into the following: 

• Holozoic Nutrition– This is a kind of heterotrophic nutrition where organisms intake solid food; a method that is also called ingestive nutrition. The food consumed may be either another organism or a plant. There are three different types of holozoic organisms and are classified on the basis of the food they consume. They are- carnivores, herbivores and omnivores. 

• Saprophytic Nutrition- This is a kind of heterotrophic nutrition where organisms obtain their food sources from remains of decaying organic substances, including dead organisms, decomposed leaves and plant remains, excreta, food articles, and more—examples – Mushroom, Mold, mycorrhizal fungi, etc. 

• Parasitic Nutrition- This is the third kind of heterotrophic nutrition where an organism derives its food from another living organism. The organism that derives its food and shelter from the other organism is known as a parasite, while the organism that lends food and shelter is known as a host. Examples – Lice and Tapeworm.                  Below is a detailed explanation of each of the kinds of heterotrophic modes of nutrition and the organisms that classify under each.           

  Holozoic Nutrition

  The internal processing and ingesting of both solid and liquid food in an organism is known as holozoic nutrition. This is a step-by-step process that involves ingestion, digestion, absorption, assimilation, and excretion. 

  During this process, food that has been consumed is slowly broken down by the process of digestion into smaller organic particles. After the useful particles and food have been absorbed, the unimportant and ingested particles are eliminated from the body using the process of excretion. 

  All vertebrates classify under animals that exhibit holozoic nutrition. Apart from them, other animals exhibiting holozoic nutrition are certain unicellular organisms like the amoeba. 

  Holozoic Nutrition in Amoeba

  Amoeba is a unicellular organism that shows holozoic nutrition, and below is a breakdown of the process in which it happens.

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  • First, the amoeba encircles the food by projecting its pseudopodia, after which it uses the process of phagocytosis to engulf the food. 

  • Next is the process of digestion, which occurs when the food vacuoles of amoeba that are rich in digestive enzymes then help break the food down into smaller and easily- digestible substances. 

  • After which, the cytoplasm absorbs the digested food while leaving the undigested substances behind. The food already absorbed, on the other hand, is further utilized in the production of energy that eventually helps in the development and growth of the cell. 

  • Lastly, the process of holozoic nutrition in amoeba ends when the cell membrane ruptures to excrete the unwanted and undigested food substances. 

  Types of Holozoic Organisms

  Holozoic organisms can be classified into the following three types: 

  • Herbivores- They are animals that depend upon plants for their source of food and nutrition. Examples of herbivores include deers, elephants, cows among others. 

  • Carnivores- They are animals that feed on, consume or depend on other animals for their source of food. Examples of carnivores include tigers, wolves, lions, among others.

  • Omnivores- They are animals that can survive on other animals or plants for their source of food. Examples of omnivores are pigs, ants, raccoons, and cockroaches, among others. 

  Saprophytic Nutrition

  Saprophytic nutrition is the process of animals feeding on dead and decomposed substances or organisms for energy, food, and nutrition. Organisms that follow saprophytic nutrition are called saprophytes. Saprophytes hold a highly important position in the ecosystem since they help to keep the environment and surroundings clean, free of unwanted matter, and also help in the process of recycling nutrients. 

  Parasitic Nutrition

  Parasitic nutrition is a form of heterotrophic nutrition where an organism lives on or feeds off another living organism. Organisms living in and sourcing food from the host organism are called parasites. Parasites often derive their nutrients and energy directly from the host, something that can be harmful to the host organism’s health and may also end up killing the host.  Parasites are completely dependent on their hosts in order to survive since the host organism provides nutrition, energy, food, and shelter. 

  Parasites can be of two types, which are:

• EctoParasites : These parasites remain outside the body of the host and obtain their food and energy from the organism. Examples of ectoparasites are bed bugs, lice, ticks, and mosquitoes. 
• Endoparasites : These parasites remain inside the body of the host organism and obtain their food and energy from the host. Examples of endoparasites are tapeworm, Ascaris, Plasmodium vivax, and others.