MODES OF NUTRITION
There are two major classes of nutrients in food: macronutrients and micronutrients.
1. Autotrophic Nutrition-
Autotrophs, or primary producers, are organisms that can produce their own food from natural sources like water, light energy, carbon dioxide (CO2) and chemical energy. They can feed themselves without assistance from other organisms. The term comes from “auto,” meaning “self,” and “troph,” meaning “food”. Autotrophic Nutrition is also a type of Nutrition in Plants.
Autotrophic nutrition means “self-nourishing.” Organisms that use autotrophic nutrition make their own food using simple inorganic substances like carbon dioxide, water, and mineral salts. This process typically requires an energy source – most often sunlight, leading to photoautotrophic nutrition (as seen in green plants and algae). Some organisms, however, rely on chemical reactions instead of sunlight to synthesis food, termed “chemoautotrophs” (e.g., certain bacteria).
1.1. Autotrophic Nutrition Examples
Green Plants: Classic autotrophic nutrition example; they capture sunlight through chlorophyll.
Cyan-bacteria (Blue-Green Algae): Also perform photosynthesis, fixing nitrogen too.
Algae (Green, Red, Brown): Carry out photosynthesis in aquatic environments.
Chemoautotrophic Bacteria: Found in extreme habitats, using inorganic chemicals to create their own food.
1.2. Functions of Autotrophic Nutrition
Autotrophic nutrition plays many important functions in the maintenance of an ecosystem. Some of them are mentioned below and these functions collectively highlight the vital roles that autotrophic nutrition and photosynthesis play in supporting life on earth.
Carbon Sink: Autotrophs contribute to carbon sequestration, as they store carbon in their tissues, aiding in the regulation of carbon dioxide level in the atmosphere and they also help in the proper functioning of the carbon cycle.
Nitrogen Fixation: Certain autotrophic bacteria play a role in nitrogen fixation, converting atmospheric nitrogen into a form usable by the plants, thus enriching soil fertility and maintaining proper regulation of the nitrogen cycle in the environment.
Biomass Production: Autotrophs accumulate biomass, which becomes a source of energy for herbivores and subsequently higher trophic levels in the food chain.
Energy Production: Autotrophic organisms convert light energy into chemical energy through photosynthesis, which is essential for their survival and growth.
Ecosystem Stability: Autotrophs contribute to the stability of ecosystems by maintaining energy flow and nutrient cycling, which supports the overall health of the ecosystem.
2. Heterotrophic Nutrition
Heterotrophic nutrition is known to be the mode of nutrition in which certain organisms are dependent on other organisms in order to survive. Organisms that cannot prepare their own food and have to depend on other organisms for their survival are known as heterotrophs.
2.1. Heterotrophic Nutrition Examples – Animals, fungi, and bacteria.
2.2. Functions of Heterotrophic Nutrition –
Heterotrophic nutrition is essential for the survival, growth, and functioning of numerous organisms, forming a critical component of the interconnected web of life in an ecosystem.
- Diverse Dietary Habits: Heterotrophic nutrition leads to a wide range of dietary habits among organisms, contributing to the biodiversity of an ecosystem.
- Ecological Interactions: Heterotrophic organisms play crucial roles in food chains and ecosystems, serving as prey for predators and contributing to the balance of population in an ecosystem.
- Decomposition and Nutrients Cycling: Heterotrophic organisms involved in saprophytic nutrition aid in breaking down dead organic matter, returning nutrients to the soil and ecosystem for reuse by other organisms.
- Energy Acquisition: Heterotrophic nutrition allows organisms to obtain the energy they need for various life processes, such as movement, growth, and reproduction.
- Metabolic support: The acquired nutrients are used in metabolic processes like respiration, where they are broken down to release energy that powers cellular activities.