Give a detailed summary of the types of nutrition seen in the living world, describing each type.
Answers
Main modes of nutrition in plants and animals are: 1. Autotrophic nutrition 2. Heterotrophic nutrition!
Plants and some bacteria have the green pigment chlorophyll to help synthesize food, while animals, fungi and other bacteria depend on other organisms for food.Based on this, there are two main modes of nutrition: autotrophic and heterotrophic.
1. Autotrophic nutrition:
The term ‘autotroph’ is derived from two Greek words—autos (self) and trophe (nutrition). In autotrophic nutrition, an organism makes its own food from simple raw materials.
Photosynthesis:
Green plants, which are autotrophic, synthesize food through the process of photosynthesis. Photosynthesis is a process by which green plants, having chlorophyll, synthesize the simple sugar (glucose) from the simple raw materials water and carbon dioxide using the energy of sunlight. Oxygen is released in this process.
Photosynthesis requires chlorophyll, carbon dioxide, water and sunlight.
1. Chlorophyll:
Chlorophylls are green pigments found in all photosynthetic organisms and are responsible for their green colour. In plants, chlorophyll is mainly found in the leaves.
2. Carbon dioxide:
Air contains about 0.03% of carbon dioxide. Terrestrial plants use atmospheric carbon dioxide in photos3mthesis. Aquatic plants use the carbon dioxide dissolved in water. Plants obtain carbon dioxide through pores called stomata present on the surfaces of leaves.
3. Water:
Water is an important raw material for photosynthesis. Plants absorb water from the soil through their root hairs. The water is then transported up to the leaves through the stem.
4. Sunlight:
Light energy is used in splitting water molecules into hydrogen and oxygen. The splitting of water in the presence of light is called photolysis.
2. Heterotrophic nutrition:
The word ‘heterotroph’ is derived from two Greek words—heteros (other) and trophe (nutrition). Unlike autotrophs, which manufacture their own food, heterotrophic organisms obtain food from other organisms. As heterotrophs depend on other organisms for their food, they are called consumers. All animals and non-green plants like fungi come under this category.
Depending upon the mode of living and the mode of intake of food, heterotrophs may be parasitic, saprophytic or holozoic.
Parasitic:
Parasitic organisms, or parasites, live on or inside other living organisms, called hosts, and obtain their food from them. The host does not get any benefit from the parasite.
Saprophytic:
Saprophytic organisms, or saprophytes, derive their food from dead organisms. They secrete enzymes that are released on food material outside their body. These enzymes break down complex food into simple forms. Common examples of saprophytes are fungi (moulds, mushrooms, yeasts) and many bacteria.
Holozoic:
In holozoic nutrition complex organic substances are ingested (taken in) without their being degraded or decomposed. After intake, such food is digested by enzymes produced within the organism.