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Nutrition is an important branch of biology which studies how organisms use food to obtain energy. Nutrition is broadly classified into two types: Autotrophic Mode of Nutrition and Heterotrophic Mode of Nutrition. In this article, we will be specifically talking about the Heterotrophic Mode of Nutrition.
What is the Heterotrophic Mode of Nutrition?
Let us first understand what heterotrophs are? The word ‘Hetero’ simply means ‘other’ and ‘troph’ means ‘nutrition’. Organisms that don’t have the ability to make their own food and rely on other plants and animals are known as heterotrophs. These animals cannot make their own food like green plants.
All animals and non-photosynthetic plants come in the category of heterotrophs. In the food, chain heterotrophs are placed as secondary or tertiary consumers.
Heterotrophic nutrition is a mode of nutrition in which organisms eat other organisms in order to survive. The key difference between the autotrophic mode of nutrition and the heterotrophic mode of nutrition is that autotrophs make their own food using photosynthesis.
On the other hand, heterotrophs cannot make their own food since they don’t have chlorophyll. All heterotrophs first convert the solid food into soluble compounds.
Types of Heterotrophic Mode of Nutrition
There are three types of Heterotrophic modes of Nutrition. Let’s understand them in great detail:
Holozoic Nutrition
Holozoic Nutrition is a type of heterotrophic mode of nutrition which involves the intake of complex organic food materials into the body using the process of ingestion. This involves five steps: ingestion, digestion, absorption, assimilation and excretion. An excellent example of holozoic nutrition is humans.
In this nutrition, the food is slowly broken down into very small particles (digestion). Once the useful particles are absorbed into the body, the unimportant particles are eliminated from the body (excretion).
Holozoic nutrition is further classified into three types:
Herbivores
Herbivores are animals that only eat plants to gain energy. Examples of herbivores are cows, buffalos, deer, etc. They are commonly known as primary producers.
Carnivores
Animals that eat meat or the flesh of other animals are known as carnivores. Examples of carnivores are tigers, lions, etc. They are commonly known as predators.
Omnivores
Animals that eat either plants or animals are known as omnivores. Examples of omnivores are humans, birds, dogs, etc.
Saprophytic Nutrition
In Saprophytic Nutrition animals eat dead and decomposed substances for energy. Organisms that have a saprophytic mode of nutrition are called saprophytes. These organisms play a vital role in the ecosystem since they help to keep the environment clean.
This type of nutrition is often associated with fungi. They break the matter down into composites. For example, proteins are broken down into amino acid composites. Lipids are converted into fatty acids and glycerol. Cellulose which forms the major portion of plant cells which later forms into decaying matter gets broken into glucose.
Parasitic Nutrition
A parasite is an organism that relies on another living organism (host). A parasite offers no nutritional value to the host and only harms it. Sometimes they even kill the host. Nutrition that is derived in such a manner is called parasitic nutrition. This type of nutrition is seen in fungi, cuscuta, plasmodium, etc.
Parasites are of two types
EctoParasites
They remain outside of the body of the host and feed on them. Examples are lice, ticks, mosquitoes.
Endoparasites
They remain inside the body of the host and obtain their food. Tapeworm, ascaris are excellent examples of endoparasites.
Human Parasites are further classified into three types:
Protozoa
They are microscopic, one-celled organisms that multiply in humans and cause serious infections. Protozoa that are present in the blood or tissue of humans and gets transmitted to other humans by an arthropod vector (bite of a mosquito).
Helminths
They are large, multicellular organisms that are visible to the human eye and cannot multiple in humans.
Ectoparasites
They are blood-sucking arthropods. An excellent example of this is mosquitos.
Conclusion
As you can see a lot of organisms follow the heterotrophic mode of nutrition. Now, you may ask which type of nutrition is more important in our environment: autotrophic or heterotrophic? Actually, both modes of nutrition are extremely important to maintain ecological balance in our environment. Both of them rely on each other.
Don’t get confused between heterotrophic and autotrophic modes of nutrition. Just remember that heterotrophic nutrition is a mode of nutrition in which organisms eat other organisms in order to survive.
