MODES OF NUTRITION
There are mainly two modes of nutrition:
Autotrophic Mode of Nutrition:
- Autotrophic mode of nutrition occurs when an organism makes their own food by photosynthesis.
- The autotrophs take in food from simple inorganic materials like carbon dioxide and water present in the surroundings with the help of sunlight energy.
- Those organisms which can make their own food from carbon dioxide and water are called autotrophs.
- All the green plants are autotrophs that prepare their food by the process of photosynthesis.
- The autotrophic bacteria also obtain their food by the autotrophic mode of nutrition.
- Chlorophyll, a green pigment traps the sunlight energy. Chlorophyll is present in all the autotrophic organisms or autotrophs.
Heterotrophic Mode of Nutrition:
- Heterotrophic mode of nutrition occurs when an organism cannot make (or synthesize) its own food from simple inorganic materials like carbon dioxide and water.
- The heterotrophs depend on other organisms for its food.
- All the animals have a heterotrophic mode of nutrition.
- Most bacteria and fungi also have heterotrophic mode of nutrition.
- The non-green plants (like yeast) are also heterotrophs.
- Those organisms which cannot make their own food from inorganic substance like carbon dioxide and water, and depend on other organisms for their food are called heterotrophs.
- Humans follow the holozoic mode of nutrition.
TYPES OF HETEROTROPHIC NUTRITION
A heterotrophic organism or heterotroph obtains its food from other organisms in multiple ways. Hence, the mode of nutrition is classified into three ways:
Saprotrophic nutrition (or Saprophytic Nutrition):
- In saprotrophic nutrition, the organism obtains its food from decaying organic matter of dead plants, dead animals and rotten bread.
- In this mode of nutrition organism release some enzymes on dead and decomposing materials.
- The enzymes break down them into simple nutrients which are absorbed by the organism as food.
- For example: fungi and many bacteria are saprophytes.
- A parasite is an organism (plant or animal) which feeds on another living organism called host.
- A parasite usually harms the host.
- The host may be a plant or an animal.
- Most of the diseases which affect mankind, his domestic animals (like dogs and cattle) and his crops are caused by parasites.
- Some of the examples of Parasites are :
- The micro-organism ‘plasmodium’ causes malaria disease)
- Roundworm which causes diseases in man and domestic animals (like dogs and cattle)
- Cuscuta (amarbel) which grown on mango are also parasites.
- Some other examples of parasites are ticks, lice, leeches and tapeworms.
- In this type of nutrition organism takes in whole material and breaks it down inside the body.
- For example, animals eating grass, fruit, insects, fish etc.