Modes of Nutrition

Autotrophic Nutrition

Autotrophic nutrition is the process by which organisms synthesize their own organic molecules from simple inorganic substances such as carbon dioxide and water. They can produce their own food through photosynthesis or chemosynthesis.

Photosynthesis

Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy from the sun into chemical energy in the form of glucose. It involves the following steps:

1. Light Absorption: Chlorophyll pigments in chloroplasts absorb light energy.
2. Light-dependent Reactions: Light energy is used to split water molecules, releasing oxygen and generating ATP and NADPH.
3. Light-independent Reactions (Calvin Cycle): ATP and NADPH produced in the previous step are used to convert carbon dioxide into glucose through a series of enzyme-controlled reactions.

Chemosynthesis

Chemosynthesis is the process by which certain bacteria and archaea obtain energy from the oxidation of inorganic compounds, such as hydrogen sulfide or ammonia. It occurs in environments with no sunlight, such as deep-sea hydrothermal vents. The process involves:

1. Chemical Reactions: Inorganic compounds serve as the source of energy, and the bacteria or archaea oxidize these compounds to produce ATP.
2. Carbon Fixation: The produced ATP is then used to fix carbon dioxide into organic molecules, such as sugars.

Heterotrophic Nutrition

Heterotrophic nutrition is the process by which organisms obtain organic molecules and energy from external sources. They are unable to produce their own food and depend on other organisms for nutrition. There are several types of heterotrophic nutrition:

Holozoic Nutrition

Holozoic organisms ingest solid food and then digest it internally. They have specialized structures such as a digestive system to break down complex organic molecules into simpler forms that can be absorbed and utilized.

Saprophytic Nutrition

Saprophytic organisms obtain nutrients from dead and decaying organic matter. They decompose dead plants, animals, and other organic material, releasing simple organic molecules that can be absorbed.

Parasitic Nutrition

Parasitic organisms obtain nutrients from a living host organism. They rely on the host for their nutrition and may harm or even kill the host in the process.

Symbiotic Nutrition

Symbiotic organisms form a mutually beneficial relationship with another organism, where both partners obtain nutrition. Examples include lichens (a combination of a fungus and an alga) and nitrogen-fixing bacteria in the roots of leguminous plants.